For owners of the JVC 30K D-Theater HD VHS Deck only.

I've owned my 30K for well over a year. I've been very pleased with it, and have also used it with the DVE (Digital Video Essentials) test tapes, both 1080I and 720P. Not long after getting the DVE tapes, I've noticed that the 720P tape was much sharper than the 1080I tape, though both were somewhat soft, however the machine was great with the HD tapes that I have.

Once while randomly scoping the output of the 30K thru my transcoder, I noticed a loss in amplitude on the high end of the burst pattern. At first I suspected the transcoder, because I did not expect a HF roll-off be to coming from a brand new deck. Playing and poking around in the transcoder eventually lead me to the Y input, and once there, I noticed that the roll-off was coming out of the deck itself. This puzzled me, because why would this problem exist. I checked the manual for the ability to enable/disable filters or such, but all I could found was a '3DNR' button on the front panel. But this did not effect that roll-off at all:confused: . I since searched the web, and found a discussion on this same issue somewhere on the internet, but no cure. I then put the matter on hold, to look at another day. That other day came, and I'm now able to get the deck to pass every test that relates to that roll-off problem. The amplitude is now there, and the unit looks so much better. The colors are even so much better. So much so that it's like having a different machine.

One of my D-Theater tapes is X-men. X-men has always looked good, but somewhat dull in some of the darker scenes. So it was not one of my favorites. After the mod, I've since watched it several times, just to see how much detail was hiding behind that haze. The tape is now enjoyable.

If this is you, and you feel that you can do very fine soldering, here is what you'll need to get started:

- 3 each 4 ohm metal film 1% 1/8 axial lead resistors.

- 3 each FB-2 mini feriite beads - here: http://www.palomar-engineers.com/Ferrite_Beads/ferrite_beads.html

You're going to need a fine tip soldering iron and some tweazers.

We'll get back to this thread later, I'll allow time for to get the above parts.

If you're not quite skillful with soldering, and don't have the smaller soldering tools - don't try this.

Mike,
Thanks for the great post.Although I dont have X-men ,I have experienced the same phenomenon in certain dark scenes in "Castaway".I am wondering if the JVC R&D doesnt test this.

Sounds like this is going to be axial lead components, but I thought I'd share my quickie SMT Home Bench Working Jig

Holding SMT components in place with tweezers while soldering is tough to do because hands shake. Normally one would use a clamp jig or some type of adhesive solder paste to hold the part in place, but for small jobs there is a cheap, super easy solution in your tool drawer.

Take a rubber handled, needle noise plier and wrap rubber bands around the handles so they close tightly under band tension. No, you aren't going to clamp the parts in the pliers! Instead, let the pliers clamp a sewing needle so the sharp end protrudes about 1/2 inch and at right angles to the body of the pliers. The needle tip and the two ends of the plier handle now form a tripod jig that can hold a component down under the needle point. The ends of the plier handle stabilize things because they are rubberized and the jig is essentially a tripod. Just position the component and hold it in place by resting the needle tip atop the SMT component. Final position the component then touch your soldering pencil tip to the solder pad to reflow your solder.

Originally posted by navinoo
am wondering if the JVC R&D doesnt test this.

I doubt it. For the HDTV band (that also includes 720P), there's a low pass filter network used after the analog out from the DAC, before the signal to the RCA components on the rear of the unit. The 30K has far too much circuitry (IMOP) before the RCA's. The purpose of the circuitry is very similar to what's on the DAC's of PC cards, but it's much more involved here (a bit of overkill). Plus it has an IC in the line right before the RCA's. And that's not all. There several transistors (a complete circuit) right after the DAC on each of the Y,Pr,Pb lines. However, that circuit is fine.

The purpose of the low pass filters is to remove processor noise (very high switching frequencies) from the analog signal. And in doing this, it only passes freqencies below a pre-determined frequency range. This makes sense on paper (theory), but high performance video needs headroom. It needs the preset limit to be higher, therefore allowing increased headroom and not clipping the upper end of the signals bandwidth.

This is a big problem with consumer electronics, period.

The 30K has very robust filtering. So much so, it's amazing that it works well at all. The over filtering also creates a blockiness (seen by looking directly into the tubes) in the image. This is common from these circuit components (caps and coils) charging and discharging from the various changes in the signal. This is a side effect of these low pass filter networks. The low pass filtering is like a good medicine, it has many side effects. It's a shame that we can't enable or disable this feature. We should have a choice here. My doctor gave me a prescription that had so many side effects that I never took it. The side effects on the label on the prescription, were far worse than my medical issue. That was a no brainer.

Anyway, with a basic change to the circuits (there's actually two levels of change). The unit performs far beyond my best expectations for this unit.

After the change, I did not see any RF interference coming from the RCA's. And that was the REAL purpose of the low pass filtering.

Hi Mike:

Great post.

Just wondering if you had an opportunity to look inside a Directv HD10-250, you could have a field day with modifications/upgrades to both the Audio(mostly DD 5.1)/ and Video of this unit.

Lon

Nice Post Guy,
Another thing you can use effectively for SMD component placment is a dental pick - very very effective. For other uses, it can also easily lift the pins on SOIC version ICs, etc.
Vic

Absolutely Vic!

I've got a dental pick, tweezers, jeweler's loupe, and Metcal soldering iron. About the only thing you can't do with those tools is BGAs.

Cary

PS. I can't recommend the Metcal enough. Digikey carries them as well.

Thanks Cary, I'll have to look into those soldering irons - I've been using a cheap radioshack one up till now :p . I've gotten a lot of use out of it though.
Vic

Anybody found an online source for the resistors?

John, www.digikey.com and www.newark.com should have the resistors.
Vic

Oops, forgot to link the resistors:

http://www.mouser.com/index.cfm?&handler=data.listcategory&D=*4.02*&Ne=100&terms=4.02&Ntt=*4.02*&Dk=1&Ns=MfgrPartNumber%7c%7cSField&N=2708&crc=true

There's a 1/4" point to point distance for where the resistors will go. You'll also have to place the feritte on one lead of each resistor.

This will go in place of the filter network, once it's removed. The total DC resistance of the coils in the network is 4 ohms. There are two coils in series in the network, with one cap in series across one of the coils (1ohm), and the other coil has a DC resistance of 3 ohms. There's a cap to ground where the two coils connect in series. There's a total of 3 caps in each network. I tried to measure the capacitance to ground in the network. It's too high to mention, so I must be doing something wrong, or there's something that I'm not seeing.

The image is quite sharp with the changes, and I would think it should be considering what's in the networks. There was some hash on each line, and that's where the feritte comes in.

There's a second section, but we'll get to that later, and in due time, I should have my brothers camera.

I hope you continue to work on moding the JVC decks.
This makes me want to pick one up now.

thanks, MP

Mike,

Is there no end to what you're working on over there??!

Chris and I are definitely in on this one. A question if I may... The link to the resistors that you kindly provided has 2 resistors listed 270-4.02 and a 270-4.02K. Which is the animal needed?

While I'm at it, for the Ferrite beads, which stock mix? 43, 61 or 77?

Thanks!

Ted

I have my tweezers ready...

After buying my dish 921 HDTV pvr and getting all it's trouble worked out, buying some new cables and a extron I have been viewing for a week or so

I just decided to watch some dvd's tonight, they are now almost painful to watch

so based on that and this thread I just purchased a 30k from ecost and ordered a bunch of flicks, including on of my fav's "True Lies"

Mike do tell on this mod, I am a soldering novice, watchs the chance we could send our decks to you to do the mods

thanks mike, I appreciate all your work but my wallet doesn't agree :D

I figure between D-vhs and my 921 I will be set until 10 months or so when HD-dvd starts to arrive

-Gary

I've been in a legal deposition for a good part of the day, and then Doug came to help me with the HTPC.

I've been very busy here lately, but will get back to this. I'll need to simply pick the camera up from my brothers, and then we'll get back on track. The improvements are substantial, and really look good on a well tweaked machine.

BTW, in response to emails and PM's. I'm not doing mods on these, I'm only sharing the process for those who are able to do it for themselves.

no problem Mike, we understand

hey when the heck is that transcoder of yours coming???

-Gary

Go get 'em Mike!

I wonder if the newer HM5U is better than the 30k in this area. I don't have a scope for testing levels, but did find that I could not see any below-black detail over component from a 30k to my 11k with the 1080i DVE tape, while I could with the HM5U. I also get it for the HM5U over HDMI to HDMI, but not to a DVI input (there is a bug in the HM5U to DVI inputs).

--Darin

If you take all the bits and the instructions to a competent reapir shop they could probably do the mod for anyone that isn't up to it, or doesn't have the gear.

Is this high frequency filtering also true for the 40K ?

Mike could you show us a pattern on DVE 1080i after your mod that we could see on one of ours before or a pic of yours from before. Fine detailed work is no problem for me but electronics .:eek: :D

Art

Originally posted by Art Sonneborn
Is this high frequency filtering also true for the 40K ?

Mike could you show us a pattern on DVE 1080i after your mod that we could see on one of ours before or a pic of yours from before. Fine detailed work is no problem for me but electronics .:eek: :D

Art

I'll see what I can do with DVE once I get the camera.

I'm not familiar with a 40K I have the 30K. But If they share the same or similar problem, the end results could be huge on your setup.

It's a simple mod. But requires careful desoldering and soldering in a somewhat tight place. Once done, you'll probably experience the best HD image from any consumer device out there.

I'm getting an improvement in sharpness, background detail and overall image punch.

Gary, I'm working real hard on that MP-5. It's number one on my agenda!

I thought of getting a 40K for MP to play with but I think with HD DVD around the corner ny investment would be short lived. Anyone know how the 40K compares to the 30K? I have a 30K, not modded. MP, I'll bring it home. If you have the parts on hand, I have a blow torch I'm pretty handy with. Is acid core sorder OK? :)

Originally posted by mark haflich
I thought of getting a 40K for MP to play with but I think with HD DVD around the corner ny investment would be short lived. Anyone know how the 40K compares to the 30K?
I don't know about the 40K, but if you are going to get something new I think the 5U is nice. And it has the HDMI output for future use with an HDMI input projector. So, unless you are saving a bunch of money by going with the 40K, I would suggest the 5U. Or the next model up with the OTA tuner, but that is quite a bit more.

I will probably still be using my 5U after HD-DVD arrives, since I use it for recording HD from my Comcast DVR. I'll probably just use it less.

--Darin

OK. So how does the 5U compare to the $30K. My CRT only accepts analog.

Originally posted by mark haflich
OK. So how does the 5U compare to the $30K. My CRT only accepts analog.
For component, I couldn't see the below-black detail with my 30k and the DVE 1080i tape, but I could see it with the 5U and component. However, I don't know if the 5U would be better with Mike's mod or not.

The 5U also seems to be much quicker to sync and show images while fast-forwarding or rewinding and also has much faster fast-forward and rewind speeds than the 30k when tapes are stopped. The 5U feels like a more refined unit to me overall.

--Darin

I certainly would love to see if PQ could be pushed even further than it is now with the 30K. It is the best HD I have since the DirecTV HD is not nearly as sharp due to their bit starvation issues.

Art

I see some company is now ready to produce Dual Layer standard DVD/HD-DVD discs, so the companies could release a HD DVD version and a DVD version on the one disc.
The record function is what will keep the 30Ks etc. alive, I just got my unit, can't wait to get it home and try it out!

O hell no, please, I don't want 2 versions on the same disc

I am looking forward to purchased a higher standard product than what the average peeps are buying, that way product isn't decided by the stinky masses at Wal-Mart

In my opinion current dvd is ruined because of all the stuff they do for the masses like over compressing the feature for all those dumb extras and boring commentaries

I wish D-VHS would take off, all it would have took was some major releases and some companies that actually cared, like for example it's inventor JVC, do they even care about this format???

-Gary

Originally posted by Art Sonneborn
I certainly would love to see if PQ could be pushed even further than it is now with the 30K. It is the best HD I have since the DirecTV HD is not nearly as sharp due to their bit starvation issues.
I think you probably just found your next upgrade. And a pretty cheap one at that.

Too bad we don't live closer, I would take my 5U over for comparison. I'll make sure Steve Smith knows about this. Maybe he will modify his 30k and then we could compare to my unmodified 30k and the 5U on his G70.

--Darin

All right. I'll order up a 5U for MP to play with. I'll have it Friday. Thank God I get em at dealer cost.

A little over a year ago, I got into trying to understand these filter networks a lot better. I called a local FCC compliance lab trying to get info from one of their engineers, because I was told that the actual design and implementation came from the compliance side. The lab invited me out to spend a day. I learned about UL, and FCC compliance. There was one engineer there who really knew about this. He was explaining that they (the labs) tested each electronic product line to make sure that it was both FCC interference compliant and UL power supply compliant. And if the equipment failed the manufacturers would more likely follow (and pay for) their recommendations to correct the problem. I learned a ton of stuff about noise, and lowering spurious noise from the signal path. They even gave literature and booklets on this.

The filtering they referred to as low pass filtering on video cards and other electronic devices, were labeled computing devices (had a CPU’s in it). The filtering was to strip all frequencies above the useable frequency range. In this case it would be around 30 mhz of low pass for HDTV. And would be called a 30 mhz filter.

The problem here is, this filtering is more likely over-done, to avoid compliance issues. Or could be done better, but would involve more expensive circuitry and components. The filtering works well for compliance, but not too well for high performance video.

There's also another filtering or application of filtering done before the analog out connector to the device. It is called Anti-Aliasing

This filtering is usually known as such, or it could be called "reconstruction filters"

Aliasing happens when analog signals are presented in digital systems. It shows as lines and curves breaking up on edges of lines and objects. Anti-Aliasing corrects for this. However, there are disadvantages to using Anti-Aliasing. Because of the way the filtering works, it can enlarge lines and objects to make the edges and lines smoother. This can cause small text and finer detail to bloom. And we know what that does to the image.

Most likely, some designs are using the Anti-Aliasing approach. Because it is more likely to work best for compliance, as well as make the device look good on digital (Anti-Aliasing). This is all great. And perfect for the FCC and the digital products. But for high performance CRT, it can hinder the absolute BEST in image quality.

In one conversation with a top notch design engineer who is very sharp on this subject, he indicated that the consumer market has a low bar set for analog image quality. If the bar was raised, the quality could be much better, and it can be done by revisiting the filtering methods that we're presently using. I found this to be true. The industry is boasting super-bit processing, yet they roll-off (bandwidth limit) the analog signals output for best performance from digital display devices. With Digital the extra sharpness is not needed when using an analog connection.

To add, the Anti-Aliasing causes ‘blockiness’ in the image. This is a side effect of the "reconstructure filters" to correct lines and the edges of objects.

And most of the manufacturers know that the signal is rolled off, but who's putting the bandwidth in the specs anyway, and if so, how many are telling the truth?

And here's the other kicker. The compliance labs says that the CPU's are so well designed now with floating power supplies and better grounding that they rarely see an issue with analog noise. It's just that the manufacturers prefer to over-do-it. And since no one is complaining. It saves them money from down time in production. I'm told it cost big bucks when a product is flagged.

Art,
If I did not need the 30K here for a photo session, I would send it to you to see for yourself. It’s not the subtle jump in performance that’s seen when the filters are removed from a video card…

Mike,

What an excellent write-up, Mike. Makes you wonder, really.

Resistors and mini ferrite beads came in, the soldering iron and magnifying glasses are on standby waiting for instruction.....

I'm going to need some serious hand holding............. what's that smell?:D :eek:

Art

Originally posted by darinp2
I think you probably just found your next upgrade. And a pretty cheap one at that.

Too bad we don't live closer, I would take my 5U over for comparison. --Darin

Only cheap if I don't turn my house into a pile of smoldering rubble.

It would be cool if we were not so far we could have some serious HT gear fun !:cool:

Art

Originally posted by Art Sonneborn
Only cheap if I don't turn my house into a pile of smoldering rubble.

Art

I plan to take the pictures today. Once that's done, I could send you my 30K to evalaute.

If you notice a difference, I'll do the mod on your 30K for a small fee. That way you won't burn up the house and those G90's.

Hi MP, I guess making similar mods to the o/p stages of these sat boxes would show an improvement too then, Have you tryed any of these type mods on a sat box like the 6000

Art

Let me know when you get the box from Mike. As you know I am always game for a road trip to check out something COOL :D


BTW
I have been known to do some soldering and havent even burnt anything down yet:eek:

WTS, I tried bypassing the reconstruction filter (30MHz) on a Sony HD300 D* sat receiver earlier this year. The result looked a bit noisy to me and I couldn't see any benefit so I put it back. I didn't spend much time with it though so may try it again. It sounds like the JVC guys were more aggressive in their filtering though.

Cary

Hi JC, Hmmm, the filtering in the sony and the 6000 are probably similar I would think, no improvement though, interesting considering its set at 30Mhz.

Well, there's really not supposed to be any useful information in an HD signal above 30MHz and the filter is there to get rid of DAC noise. I'm guessing Mike is fixing some really over zealous filtering where Sony probably got it right.

Give it a shot though and let us know what you find.

Cary

Originally posted by mp20748
I plan to take the pictures today. Once that's done, I could send you my 30K to evalaute.

If you notice a difference, I'll do the mod on your 30K for a small fee. That way you won't burn up the house and those G90's.

Sounds fantastic ! :)

Art

Originally posted by sandbagger
Art

Let me know when you get the box from Mike. As you know I am always game for a road trip to check out something COOL :D


BTW
I have been known to do some soldering and havent even burnt anything down yet:eek:

Kevin,
The second I have it( or when it is coming) I'll let you know ! I'm really disappointed that I bought an HDTiVo only to find that the HD is not very good. I may have to dump that for a Dish system.

Art

Originally posted by Art Sonneborn
The second I have it( or when it is coming) I'll let you know ! I'm really disappointed that I bought an HDTiVo only to find that the HD is not very good. I may have to dump that for a Dish system.

It might be empty hope, but some of us are hoping that DIRECTV stops their current over-compression when NFL Sunday Ticket is over. I think that is within a month. I would at least wait until a week or two after that to see if they move things around when they no longer need to support something like 6 simultaneous NFL-HD games at times.

--Darin

Is DISH known to have a higher bitrate than DTV?

Originally posted by Ted White
Is DISH known to have a higher bitrate than DTV?

My understanding is NO..... everyone is overloaded.

The birds can only handle so much and with adding channels its a give and take.... bandwidth = channels * bitrate so more channels = less bitrate.

Its bad right now due to all the HD football ( is that even a sport).

OTA does look good most of the time. I can get ABC/NBC/CBS/UPN/FOX/WB all off a bowtie in the attic but I will be puting a short mast/bigger bowtie up come spring.

Sand that is totally incorrect, there are bitrate charts over on the programming forum

one example:
HDnet Movies on directv right now is 8-9 Mbps reduced 1280 Horz.
HDnet Movies Dish is 16-18 Mbps full 1920 Horz.

Directv is compressing and downrezzing HD to Hell and back

Guys Dish Network HD is so much better it is not even funny, I have had both for a while, I had my whole house filled with directv and bought 1000$ HD receivers, I sold my entire Directv setup because of the low quality of their HD channels, they are just unbearable to watch

One the other hand Dish Networks HD is worlds better, just recently they have started putting 3 HD channels per 8psk transponder and the quality has went down slightly mainly DiscoveryHD, but I am fairly certain that Dish will get everything fixed, Dish has always shown more respect to HD, at least in the past, I cannot gurantee what they will do in the future

Hdnet is so much better on Dish, it's not even close, HDNet and HDnet Movies are on one 8psk transponder all to their lonesome on Dish :D

I am also 99% certain that they do not downrez their HD, they send the full 1920x1088

ShowtimeHD is also much better on Dish

With good quality HD and my 921 I am really happy

I use a Barco Data 808s on 106" 1.78 screen

-Gary

Wow, I had no idea there was such a difference! What the hell am I doing with DTV??

What would a guy do with c-band? Obviously a gigantic dish, but why would a person use such a thing these days?

you're kidding me?? Am I in the stone ages or what? How do I find out more about this?

Originally posted by Gary Murrell
but I am fairly certain that Dish will get everything fixed, Dish has always shown more respect to HD, at least in the past, I cannot gurantee what they will do in the future One difference I see is that DIRECTV has invested in new satellites that will be going up and Dish hasn't done nearly as much here. I'm expecting Dish to be more cramped in the future, except that DIRECTV may use their extra space for 500 local HD channels. I just hope they give some bandwidth back to these national channels when they have some space.

I just ordered Showtime from cable last night because my local Comcast doesn't compress it (I'll be doing some testing later against DIRECTV's version) and because I can copy these to tape. The 6412 DVRs are much nicer than previous Comcast equipment I tried.

I would recommend cable over Dish if you can get a DVR and your local cable doesn't compress the HD channels.

Also, for those of us with DVRs it is hard to go back to having to work around broadcast schedules and not being able to answer the phone without missing part of a movie/show. I basically don't watch anything live anymore. Even if I catch up I pause it when they go to commercial and watch or do something else for a while.

EDIT: Typos.

--Darin

Holy **** I totally forgot about Big Useful Dish
Ted I'm living with you in the stone age, C-band totally slipped my mind

Can someplease answer me this and I mean NOW:D

Can I get these hd channels from c-band:

HDnet
HDnet Movies
Showtime HD
HBO HD
DiscoveryHD

and is there a C-band receiver with a firewire out???

I am going to look into this tonight

Ted I read posts a while ago on c-band about how many guys have drove around in the country(which is where I live) and stopped at houses that had a BUD in the yard and lots of times people tell them they can have the dish for free

Time to research this!!!!

-Gary

I wonder if there's a thread going on the sat forum. We might be better off moving it over there...

I'll have pictures tomorrow. I now have the camera....now what to these buttons do?:confused:

Great Mike

-Gary

MP. Whatever you do, do not, I repeat, do not, press the flashing red button. Remember, the sucka you just purchased is entirely digital.

Ted White asked:
> The link to the resistors that you kindly provided has 2 resistors listed 270-4.02 and a 270-4.02K. Which is the animal needed? <

270-4.02 (it's a 4 ohm resistor, not 4000 ohms).

> While I'm at it, for the Ferrite beads, which stock mix? 43, 61 or 77? <

I was hoping Mike would chime in on this one, because I don't know for sure, but the purpose of the beads is to tame (dampen) spurious hash in the desired part of the spectrum. According to the spec sheets at Fair-Rite, the stock mix #43 is best suited for taming noise in the 30-250 MHz region. #61 would be for noise starting from 200 MHz and up.

Of course, I could just be full of it. ;) I'm sure Mike will correct me if I'm wrong.

- Tim

Ted,
Most of this has been discussed on the HD forums. I have unfortunately just started researching my HD options a little better. I just noticed that 1080i on my old 7" CRT system looked better than my Faroudja , 1080p and 9" CRT (from memory). I asked around and found that it was not my imagination, that in fact DirecTV was not providing enough bandwidth for anything much better than decent DVD quality from their HD.

Art

Anyone know how well motorolla units are designed? I doubt the cable company would ever notice if you "corrected" the analog output filtering.

That's why one should watch over the air HD if available. Put up a 2 or 3 story ham radio type antenna tower if you need it plus a high gain beam with rotor and that should do the trick. My father had a beam on his house and a beam on mine will not hurt anyone. Mine is hidden in the attic.

Ferrite beads are another story. They do weird things as they age. Believe it or not they become magnetized and those little magnets can indeedy have a deleterious effect on other components in the circuit. Careful layout is required and may not be available on a modded circuit.

There is a reason why ferrite beads are eschewed by some video engineers.

Hey Mikey. There's that engineer in me surfacing again. I'll try to suppress it and just keep being glib. Remember, do not press that flashing red button.

Brian:
I assume that you're talking about the Moto 6200/6208.They have special screws to prevent people from opening the box.

security torx bits are widely available....

:D

I've taking 5 pictures so far with the camera. I transferred them to a program that came with the camera on CD: Roxio Photosuite 5. With this software, I was able to attach text to the images.

However, I'm lost as to how to get the pictures out of Photosuit 5 :confused:

I open everything in photo shop. Can you attach them through an email to me?


sonnebornortho@comcast.net

Done!

Originally posted by Art Sonneborn
I asked around and found that it was not my imagination, that in fact DirecTV was not providing enough bandwidth for anything much better than decent DVD quality from their HD.I think some of the blame rests with the HD TiVo as its image is reportedly much softer than the other HD receivers. It is one of the reasons I'm sticking with Sony's HD200 and HD300s... of course a DVR is nice as I had the SD version. For me the first provider with a (good) network enabled DVR is the winner.

Well , then is it the recording side Charles or the receiver itself ? I do know that there is actually a thread with screen shots of now on DTV and prior to September. Also there have been comments that HD net movies over Dish is like night and day compared to that seen on Direct TV iteration. I could be wrong but at least there seems to be a fair amount of corroboration for my experiences.

Art

Art,

I agree that DirecTV's handling of HD isn't great. Especially, HDNet Movies which took a big hit when Sunday Ticket started up this Fall. At the same time I have read countless posts from members stating that their new HD TiVo image is softer than their previous receiver. Since TiVo records the digital stream I'm guessing it's a tuner, decoder or whatever issue. I haven't done any direct testing myself because of the reports along with waiting for the ability to network recordings. If I hadn't read so many reports I'm pretty sure I'd have one right now... as even my wife complains about being TiVoless at times.

Art,
any luck decoding Mike's pictures?

Mike,
stock mix #43 on the ferrite beads, or something else?

- Tim

Tim,
He sent them to me but they were not acceptable in their focus. I asked that he take another set but his camera seems to be unable to focus on anything reasonably close. That's where he left it with me.

Art

Originally posted by Charles R
Art,

I agree that DirecTV's handling of HD isn't great. Especially, HDNet Movies which took a big hit when Sunday Ticket started up this Fall. At the same time I have read countless posts from members stating that their new HD TiVo image is softer than their previous receiver. Since TiVo records the digital stream I'm guessing it's a tuner, decoder or whatever issue. I haven't done any direct testing myself because of the reports along with waiting for the ability to network recordings. If I hadn't read so many reports I'm pretty sure I'd have one right now... as even my wife complains about being TiVoless at times.

I have some tapes made from HBO and HDNet movies from Dish and they are significantly better than what either my recorded or live through TiVo from Direct TV gives. I still have my old Mitsubishi so I may swap it out and look. I may have simply ****ed up.:(

Art

Originally posted by Art Sonneborn
Tim,
He sent them to me but they were not acceptable in their focus. I asked that he take another set but his camera seems to be unable to focus on anything reasonably close. That's where he left it with me.

Art

Ted and I are going to see what we can do to get some better shots.

Thanks Chris ! Are you guys in the process of doing the mod as we speak?

Art

Originally posted by Art Sonneborn
Thanks Chris ! Are you guys in the process of doing the mod as we speak?

Art

Not yet, still waiting on some parts, and further instructions from the Master of Mods, the pics will help Mike show us the way.

:)

I've sent the pictures as far as I can go to Mike for his comments.

Originally posted by VideoGrabber

Mike,
stock mix #43 on the ferrite beads, or something else?

- Tim

I'm using the 43's. They're working well for me, but may spec a tad below 30mhz. However, I'm not seeing a roll off with them.

The beads remove the hash, and the hash turns into a mist/haze on the image. The mist may not be noticed with regular viewing, but can show up as a slight haze in the lower details in black levels (wash out). There may be a better bead for this, but on my 30K I'm seeing excellent black detail (no mist or haze in black detail) with the 43's.

Chris and I are working on the pictures...

Just to keep this current, I too would like to mod my 30K . So I am very interested in those Pics.

Just a wee little bump

Hello,
Finally putting my tuppence in.
I have a 30k manual and I've been going through the signal path.
I assume that it's the LP filters FL801, FL802 and FL803 that are going to be bypassed with a 4ohm resistor with a ferrite(43 material) around one leg ? This is pins 1 and 5 of the FL.
(The FLs are part NQR0336-001x by the way).
Is the FL going to be cut out of circuit or is the 4ohms simply shorting across pin 1 and 5 ?
I ask because there is a common signal going to pin 4 on each of these FLs. This signal is labelled 1080_H into the circuit. Is this important? I wonder what the effect of this missing signal if the FL is cut out of circuit?
I hope the mod is simply shorting across pins 1 and 5.
I can't really see anything else that would affect the freq response apart from these FLs.

I'm just interested. Whatever works is fine by me.

Chris M

Originally posted by moggy
[B]Hello,
Finally putting my tuppence in.
I have a 30k manual and I've been going through the signal path. I assume that it's the LP filters FL801, FL802 and FL803 that are going to be bypassed with a 4ohm resistor with a ferrite(43 material) around one leg ?


Correct, as mentioned earlier in the thread.


This is pins 1 and 5 of the FL.
(The FLs are part NQR0336-001x by the way).
Is the FL going to be cut out of circuit or is the 4ohms simply shorting across pin 1 and 5 ?


I don't have a manual, so I have no way of knowing the pin assignments on the FL's. First the three FL's would need to be removed. Then the resistors are put in place with a bead on each of them. If the FL's pin assignment is similar to an IC, then the resistor would go to pins 1? and 4?.


I ask because there is a common signal going to pin 4 on each of these FLs. This signal is labelled 1080_H into the circuit. Is this important? I wonder what the effect of this missing signal if the FL is cut out of circuit?
I hope the mod is simply shorting across pins 1 and 5.
I can't really see anything else that would affect the freq response apart from these FLs.


Again, if the pin assignmemt is similar to an IC. The resistor would go across pins 1 and 4. The actual signal path is also 1 and 4. Pin 5 has a cap (30pf) going to pin 4. I'm thinking that pin 5 is a selectable roll-off or boost feature for the FL, and may be a feature for 720p to 1080I equalization.

The FL's have 5 pins. two are for grounding, and two for signal path. the 5th has a cap going to one of the signal path pins. There are three coils and three caps in each FL.

There are two pins on one side of the FL's, with three on the other side of the FL's. Connect the resistor to the two pins on the side that only has the two pins (that are farthest apart).


And there is something else that effects the response, but we'll get to that later on.

Originally posted by mp20748
I don't have a manual, so I have no way of knowing the pin assignments on the FL's. First the three FL's would need to be removed. Then the resistors are put in place with a bead on each of them. If the FL's pin assignment is similar to an IC, then the resistor would go to pins 1? and 4?.
Again, if the pin assignmemt is similar to an IC. The resistor would go across pins 1 and 4. The actual signal path is also 1 and 4. [/B]
Not according to the manual:
1 input
5 output
2 no connect
3 gnd
4 capacitor (1uF) to common 1080_H signal
The layout is different to anything I've seen. The pins go in a circle.
From corner of pcb, pins 1 then 5 on one side and pins 2,3,4 on the other edge of FL.
So it goes 1,5,4,3,2 clockwise.

I shall attempt to post some zipped bmps of the relevant section of the manual at www.mogford.com/audio/30k1.zip and www.mogford.com/audio/30k2.zip.
To the chap who asked me about the manual, it is a CD I bought and is of high quality. It's a protected pdf. As soon as I find where I bought it from, I'll post that info here.

Pin 5 has a cap (30pf) going to pin 4.
I'm thinking that pin 5 is a selectable roll-off or boost feature for the FL, and may be a feature for 720p to 1080I equalization. [/B]
A 30p cap across pins is not shown. Mind you, it may have been added as a mod.
Your explanation for reason of pin 5 is very plausable. If the response is now re-optimised by bypassing the FL then there is no need for a 720/1080 response switch. I think you've answered my query on this point. They possibly found it necessary to alter the filter because of the different digital quantisation noise between 1080 and 720.

The FL's have 5 pins. two are for grounding, and two for signal path. the 5th has a cap going to one of the signal path pins. [/B]
Pin 2 appears to be a N.C. Pin 4 Signal path being called 1080_H.
There are three coils and three caps in each FL. [/B]
Oh, I haven't opened up mine yet. I'll wait until the new year, later in Jan.

There are two pins on one side of the FL's, with three on the other side of the FL's. Connect the resistor to the two pins on the side that only has the two pins (that are farthest apart).[/B]
Pins 1 and 5.

And there is something else that effects the response, but we'll get to that later on. [/B]

What could that be?
There are no further response altering components after that. This assumes the output triple opamp IC7103 (BA7623F) is good enough.
Hmm, I just downloaded the datsheet for BA7623F. It doesn't quote anything better than 10MHz. Perhaps it's better than that in reality(maybe?). I'll also post the opamp datasheet at www.mogford.com/audio/ba7623f.pdf (69k)
(I do know of a better triple opamp OPA3691, gain would have to be set to 1 though.)

I look forward to hearing the info from the practical modification.

Originally posted by moggy
[B]Not according to the manual:
1 input
5 output
2 no connect
3 gnd
4 capacitor (1uF) to common 1080_H signal
The layout is different to anything I've seen. The pins go in a circle.
From corner of pcb, pins 1 then 5 on one side and pins 2,3,4 on the other edge of FL.
So it goes 1,5,4,3,2 clockwise.


Ok, that makes sense. With this unusual pin-out, it's still exactly what I have.


A 30p cap across pins is not shown. Mind you, it may have been added as a mod.


No, it's inside of the FL.


Your explanation for reason of pin 5 is very plausable. If the response is now re-optimised by bypassing the FL then there is no need for a 720/1080 response switch. I think you've answered my query on this point. They possibly found it necessary to alter the filter because of the different digital quantisation noise between 1080 and 720.


Exactly!


What could that be?
There are no further response altering components after that. This assumes the output triple opamp IC7103 (BA7623F) is good enough.
Hmm, I just downloaded the datsheet for BA7623F. It doesn't quote anything better than 10MHz. Perhaps it's better than that in reality(maybe?). I'll also post the opamp datasheet at www.mogford.com/audio/ba7623f.pdf (69k)
(I do know of a better triple opamp OPA3691, gain would have to be set to 1 though.)


Yep, you're pretty good at this- good guess. However, the OPA3691 will not substitute the BA7623...

Originally posted by mp20748
[B]Ok, that makes sense. With this unusual pin-out, it's still exactly what I have.
I hope the schematic I've posted will make it all clear to everyone.
www.mogford.com/audio/30k1.zip

No, it's inside of the FL.

Aha!! Yes, who needs that!

Yep, you're pretty good at this- good guess.
Thanks.
Fancy them using a basic SD RGB video chip for HDTV. JVC are a bit naughty.

However, the OPA3691 will not substitute the BA7623...
No it won't.
Hopefully you've found something that's pin compatible.

moggy wrote:
> I just downloaded the datsheet for BA7623F. It doesn't quote anything better than 10MHz. Perhaps it's better than that in reality(maybe?). <

You're correct that the chart on page 2 does indicate that 10 MHz performance can be down as much as 3 dB WRT 1 MHz (which would be pretty bad). But that's worst case for driving two loads. If you check out the frequency characteristic graph on page 6, you'll see that it's nominally flat to ~30 MHz.

Also, a tip. Those were very clean BMPs, but if you convert them to PNGs they'll be 12-24x smaller (smaller even than the ZIP-compressed files!), with no loss of quality.

Hopefully, Mike will have some time to jump back into this thread soon, and reveal the balance of his enhanced circuit design. Hint, hint. ;)

- Tim

Originally posted by VideoGrabber

You're correct that the chart on page 2 does indicate that 10 MHz performance can be down as much as 3 dB WRT 1 MHz (which would be pretty bad). But that's worst case for driving two loads. If you check out the frequency characteristic graph on page 6, you'll see that it's nominally flat to ~30 MHz.
- Tim

That chart is very confusing. The chip has a 10mhz (-3) bandwidth, with a 30mhz flatness (0.1) bandwidth.

Usually the flatness bandwidth is much lower than the -3DB rated:

(Intersil EL5163 = 500mhz (-3) with a flatness of 30mhz (0.1db)

-------------

The JVC is not the only consumer device with one of these Mickey Mouse IC's as line driver/buffer. The industry has finally realized that a buffer or line driver is a must after a DAC. You'll find buffers in most of the newer SAT boxes. Here's one of my favorites:

http://www.fairchildsemi.com/pf/FM/FMS6418A.html

That FMS6418 sounds very impressive for a single device (and check out the cost). It's not only a line driver, it's also a filter for the DAC's analog out. And it has selectable filtering for both HD and SDTV. So it looks very good on paper, and If I was a manufacturer, I would jump on these magic chips with both feet. And if you test them with a scope, it'll probably show exactly what you'd want to see - HOWEVER, it makes the analog out from a SAT box look like %#@! (did I spell that right?).

The industry is going after cost effective solutions to keeping their products competitive. The chip makers are selling chips with impressive specs, but are not living up to real expectations.

1920x1080P (60) is 251mhz. So a 300mhz chip should handle that with ease - wrong, you'll need at least a 600mhz chip for best performance.

I'm not an engineer, so my perspective is a little different. I'm one of the guys who has been trying to convince the manufaturers that it's not working...

Originally posted by mp20748

1920x1080P (60) is 251mhz. So a 300mhz chip should handle that with ease - wrong, you'll need at least a 600mhz chip for best performance.

The 30k is only 60i which brings the pixel frequency to about 66MHz and it's a good idea to have twice the bandwidth, ie 125MHz (like you have suggested 250MHz for 1080p).
These figures are rubbery, of course.
In practice, getting a chip to work at 600MHz is difficult. PCB and stray capacitances will generally tend to keep the frequency limit to 100-300MHz at best. 50mm of track can easily give you a couple of pF of stray capacitance.
My Sony 1292 has only 120MHz freq. response as well.

There are a few video(video as in high frequency, not video pictures) chips which are 1GHz but they almost all would have to have a small 1-5pF cap for stability which brings the response down a lot. 600MHz would be an absolute ideal situation and not practical in this circuit in my humble opinion.
I'd be happy with a 300MHz chip. Very happy actually.
Have you chosen a chip yet? or still investigating?
I'm very interested to hear what you come up with. It's a long time since I looked at hi-speed opamps. I'll try to have a look myself if I can get the time over the xmas break.
I just had a look at TI and they only have the OPA3691 (280MHz @g=1) with 16pins. Not a direct fit.

Originally posted by moggy
[B]
In practice, getting a chip to work at 600MHz is difficult. PCB and stray capacitances will generally tend to keep the frequency limit to 100-300MHz at best. 50mm of track can easily give you a couple of pF of stray capacitance.


I don't think 600mhz is really needed (for 1080P). I think we'll need far less. But when using a 300mhz chip, we're no where near the best bandwidth performance for the signal. And because it's so hard to get these chips to perform at specs, you'll need a higher bandwidth chip to get the best headroom for the usable signal. And that's what puzzles me about these designs that use, say a 30mhz chip for a 30mhz signal.


There are a few video(video as in high frequency, not video pictures) chips which are 1GHz but they almost all would have to have a small 1-5pF cap for stability which brings the response down a lot. 600MHz would be an absolute ideal situation and not practical in this circuit in my humble opinion.


For this circuit (30mhz), I would use a 100mhz chip. A 100mhz chip is very easy to tame (parasitics), and it'll provide excellent headroom for the usable signal.


Have you chosen a chip yet? or still investigating?


Actually, I'm not using a chip at all there. I removed the BA7623, and I'm by-passing that circuit with a direct path to the RCA's. I thought of using a replacement for the BA7623, but after seeing that once it was removed from the circuit, the roll-off problem decreased. And with 6' of good quality RCA cables, I had a perfect HF test pattern at the other end of the cables. So I could not see a reason for a line driver. And I would never run component beyond 6', with 3' being the best way to go.

When I started out with this, I did not have a diagram. So I used the scope along the signal path. That chip was the first thing I changed, then I arrived at the low pass filters.

Hey, Mike...
> I'm not using a chip at all there. I removed the BA7623, and I'm by-passing that circuit with a direct path to the RCA's. <

Does that mean we're essentially done then? I had thought you were going to replace the OA with the single-ended supply, with one with dual rails.

You also commented:
> (there's actually two levels of change). <
> There's a second section, but we'll get to that later, <
> And there is something else that effects the response, but we'll get to that later on. <

So the BA7623 driver was unnecessarily limiting the output BW, and the extra driver/buffer action wasn't really needed? (assuming cables are kept to reasonable lengths.)

Did you and Chris ever finish the annotated photos you were doing on this mod? I popped open one of my 30Ks the other night, and a quick look indicated that I'd need to remove one of the vertical PCBs at the backplane with the jack arrays. It wasn't immediately obvious how to do that. From your instructions and the SM info that moggy supplied, I think we're just about there. Let's wrap this puppy up for Christmas! :)

- Tim

Originally posted by VideoGrabber
[B]
Does that mean we're essentially done then? I had thought you were going to replace the OA with the single-ended supply, with one with dual rails.


I though about that, because a good line driver SHOULD definitely have dual rails.


So the BA7623 driver was unnecessarily limiting the output BW, and the extra driver/buffer action wasn't really needed? (assuming cables are kept to reasonable lengths.)


I believe the BA7623 was a good idea to help drive that castrated signal after the low pass filters.


Did you and Chris ever finish the annotated photos you were doing on this mod?


I'll check with him to see where he's at with this.


I popped open one of my 30Ks the other night, and a quick look indicated that I'd need to remove one of the vertical PCBs at the backplane with the jack arrays. It wasn't immediately obvious how to do that. From your instructions and the SM info that moggy supplied, I think we're just about there. Let's wrap this puppy up for Christmas! :)


The only thing you'll have to remove (pull out, but don't disconnect) is that metal enclosed video processor module, that is mounted to one side of the unit. The BA7623 is mounted on the rear PC board where the RCA connectors are. That chip can be removed, and jumpers ran without removing that board.

We'll rap this up in the next day or so for sure ;)

Originally posted by mp20748
I. And with 6' of good quality RCA cables, I had a perfect HF test pattern at the other end of the cables. So I could not see a reason for a line driver. And I would never run component beyond 6', with 3' being the best way to go.



Hi MiKe:

What type of cabling would you run for over 3-6 ' ?

Lon

Mike would you ever be interested in looking at the new 5u from JVC??,

IT has a brand new rock solid transport that is much improved over the original model, should be very reliable, seems to be so far since release

only problem is that some folks have said the component out is well below the quality of the 30k and 40k

heck I would be willing to send my unit to you for a while to look at if you would be interested

I know you are a busy guy, but I just thought I would ask

-Gary

Originally posted by mp20748
I don't think 600mhz is really needed (for 1080P). I think we'll need far less. But when using a 300mhz chip, we're no where near the best bandwidth performance for the signal. And because it's so hard to get these chips to perform at specs, you'll need a higher bandwidth chip to get the best headroom for the usable signal. And that's what puzzles me about these designs that use, say a 30mhz chip for a 30mhz signal.
For this circuit (30mhz), I would use a 100mhz chip. A 100mhz chip is very easy to tame (parasitics), and it'll provide excellent headroom for the usable signal.
Only 30MHz? How do you arrive at that? I calculated 66MHz. also, I thought your ATSC was about 50MHz or thereabouts anyway?
Our 1080i DVB is only 50Hz, so it's a bit less in MHz, but ATSC is about 55MHz , I thought. Correct me if I'm wrong.
Yes, I think a 100MHz chip(g=1) would be adequate but getting a 280MHz chip(g=1) is not hard.
eg. my favourite OPA3691 chip is 500MHz but at g=1 it is 280MHz with a flatness and -3dB point that are good enough for this puppy. It is dual supply but can be made to work with a single +5V supply. In fact the circuit has unused positions for resistors and caps that were most likely to be used for a dual supply chip version. Fitting a daughterboard with a 16pin SOP chip would be a pain though.

Actually, I'm not using a chip at all there. I removed the BA7623, and I'm by-passing that circuit with a direct path to the RCA's. I thought of using a replacement for the BA7623, but after seeing that once it was removed from the circuit, the roll-off problem decreased. And with 6' of good quality RCA cables, I had a perfect HF test pattern at the other end of the cables. So I could not see a reason for a line driver. And I would never run component beyond 6', with 3' being the best way to go.

When I started out with this, I did not have a diagram. So I used the scope along the signal path. That chip was the first thing I changed, then I arrived at the low pass filters. [/B]

With good quality 75ohm cable there is no reason that you can't go past 2m in length. My projector is 12m in length away, so a short length is not an option for me if I were to drive the projector directly. If the initial driving circuit has a 75ohm output then all will be ok but I doubt that an emitter driver with 150ohm is an accurate 75ohm drive.
Yes, for your short lengths, I guess you could live without it but I would check your pulse reflections on screen or by using a good cro.
HF rolloff will occur with long cable lengths, yes, but I intend to use 5 runs of RG11 to my 1292 (RGBHV) .
This leads me to the next sentence by the previous circuitous route.

The other option of course is that if you bypass the opamp as you suggest and have a transcoder as close as possible to the RCA output pins then that would suffice I believe. I, in fact, have to use my transcoder that I built that is dedicated for this machine so this might well be the easiest option. I can put the transcoder with it's inbult buffereing and good 75ohm drive only about 50mm away from the back of the 30k. Voila. I'm starting to like this idea. I just need to load the 30k with the right resistor for 1Vpp out of the 30k(or change my transcoder to have a g=1). You say it looks great with just 1m so with only 50mm it should also look great.
For others that only use component(YPrPb) then simply putting an external buffer might be the most practical method if you need cable lengths longer than about 1m. It needs to be able to handle 2Vpp and have g=1. Not too difficult.

I look forward to seeing some photos.
To help with the previous conversation I've now also put a schematic bitmap of the back panel pcb containg this opamp.
www.mogford.com/audio/ntsc-panel.png

It's all sounding rather good. I'm glad someone told me about this thread, I'd never thought that the JVC was lacking. I can't wait to see the final results.

I like to pretend I understand a lot of this stuff, but sometimes... I think i know how Raster must feel.

There are SOME brilliant people here... and some ... well not so brilliant...

Then there are those of us in the middle who benifit from the scraps of wisdom that drip off the table...

Mike, did I miss something? Is it within reasonable possibility to replace the RCAs with BNCs for component out???????? Would this give a further picture improvement?

Originally posted by Steve Bruzonsky
Mike, did I miss something? Is it within reasonable possibility to replace the RCAs with BNCs for component out???????? Would this give a further picture improvement?

If you don't mind hacking the back panel then (75ohm) BNCs are always better than RCAs. Whether you'll pick the difference is questionable.
I calculated that the disturbance caused by (say) 5mm of an RCA connector of not quite 75ohm is equal to just a fraction of a pixel in time and won't be seen in any normal HD video response of (say) 100MHz.
This is why I believe that cable is the most important aspect. It needs to be true 75ohm cable with the usual +/-2% accuracy. Cables amplify errors over much longer times (ie depends on length of cable).
Many BNC mods claim to be the bees knees but there is very little to suggest that it is the cure-all.
Mind you, I still consider that using 75ohm BNC connectors is a good idea.
I have a personal hate of putting RCA connectors on RG59, RG6 or RG11.
If using BNC, make sure they are 75ohm and not generic (50ohm).

For the JVC, it depends how hard it is to change the connectors.
Since I have to hack into it anyway it might be worthwhile. Having imported mine into Australia, I have no warranty to worry about. If it's too difficult, I'm not going to bother, the other mods are more important.

On a similar topic, I also plan to use BNC connectors for my pc graphics card, they just seem a more robust method of connection. It creates a 75ohm impedance over a much longer path and eliminates any VGA connector pertubations. However, the main reason is to eliminate the LP filter just as in this 30k example. The second reason is that BNCs can use real cable instead of that RG179/miniature coax rubbish that has to be connected to a VGA connector.
You can tell I love RG59, RG6 & RG11, can't you?
PCs can clock at a much higher rate than normal 1080i HiDef and this stuff for a pc is important. My htpc is used at 1920x1080x75Hz. That's a 190+MHz pixel clock. egads! omigosh! I may have to down grade to 50Hz if the pc mod doesn't help with full pixel resolution.
Anyway, I have digressed.

Moggy, the anti-aliasing filter for HD is set to 30MHz. The luminance sampling frequency is 74.25MHz so the filter is set to half (roughly).

Cary

Originally posted by jcmccorm
Moggy, the anti-aliasing filter for HD is set to 30MHz. The luminance sampling frequency is 74.25MHz so the filter is set to half (roughly).

Cary

Ok. Hmm.. I don't quite understand. What's the point of 1920 pixels if you only see half of it? I'll have to read up a bit more on your ATSC system.
I assume you're talking about ATSC offair HD?
This may be only a factor for analogue displays, not digital, if so then the analogue display fraternity is being dudded. I must read more to see what really happens.

If the 30k is truly 30MHz BW then 100Mhz is ample for our instance and I needn't worry about my projector showing 1920 pixels at full depth of resolution or changing the RCA connectors.
Unfortunately, the 30k manual says very little about such things.

See ya.

Originally posted by moggy

With good quality 75ohm cable there is no reason that you can't go past 2m in length. My projector is 12m in length away, so a short length is not an option for me if I were to drive the projector directly. If the initial driving circuit has a 75ohm output then all will be ok but I doubt that an emitter driver with 150ohm is an accurate 75ohm drive.
Yes, for your short lengths, I guess you could live without it but I would check your pulse reflections on screen or by using a good cro.
HF rolloff will occur with long cable lengths, yes, but I intend to use 5 runs of RG11 to my 1292 (RGBHV).

The other option of course is that if you bypass the opamp as you suggest and have a transcoder as close as possible to the RCA output pins then that would suffice I believe. I, in fact, have to use my transcoder that I built that is dedicated for this machine so this might well be the easiest option. I can put the transcoder with it's inbult buffereing and good 75ohm drive only about 50mm away from the back of the 30k. Voila. I'm starting to like this idea. I just need to load the 30k with the right resistor for 1Vpp out of the 30k(or change my transcoder to have a g=1). You say it looks great with just 1m so with only 50mm it should also look great.
For others that only use component(YPrPb) then simply putting an external buffer might be the most practical method if you need cable lengths longer than about 1m. It needs to be able to handle 2Vpp and have g=1. Not too difficult.


Because of this, I've designed a mini line driver circuit to retro replace the BA7623. It's a 1-1/2 x 2" mini board with 400 mhz bandwidth (-3db). I'll have some completed boards ready by the end of the week.

Very high quality cables are very important for best analog video performance. And the 30K deserves the absolute best. Once modded, it'll produce a superb video signal. Definitely the cleanest HD I've ever experienced from a consumer product. And that would probably explain why that emitter driver does so well. Actually, it should not do well at all driving a 75 ohm capacitive load. So that's why I've looked into adding the line driver circuit. Longer cable runs was not my main reason, I wanted a circuit that would produce and maintain true 75 ohms on any length of cable (>30"). I'll have five of the completed boards by next week.



What type of cabling would you run for over 3-6 ' ?
Lon

I'm not sure what the experts would recommend here, but from my experience. Once you exceed 6' of cable run, it should be true 75 ohm cables. And I know of very few true 75 ohm cables on the market. Belden and Granite Audio makes the only TRUE mini 75 ohm cables. Other than those two brands, I would not go below RG59 or RG6 for any other brand named cables. My preference is Belden 1505 and 1694. And If not using the best mini, I would use RG59 or RG6 even for short cable runs. Skip right over the fancy named stuff. I could tell you some real stories with some of the designer named stuff.


Mike would you ever be interested in looking at the new 5u from JVC??
-Gary

Sure. Someone sent me a HDSAT box to look at. So I'll take one more.


There are SOME brilliant people here... and some ... well not so brilliant...
Briands

Actually, I'm one of those "in the middle", I've just had some good instructors on this particular subject. I've always loved improving the quality of the signal, but it was only until I became a member of this forum, that I was able to take my troubleshooting skills to another level on this. I'm not an engineer, so I've learned from some of the best out there.
Keep your eye's open for postings from these guys:

Tom Rosback

VideoGrabber (TIM)

Jvanderwalker (Jim)

jcmccorm (Cary)

When you see their post, they come across very humble, and almost as if they'll learning from others. But for real, these guys are humble Heavy Weights. My favorites are Tom Rosback and Cary (Tom is a master at understanding and lowering noise)...and it seems we'll soon be adding Moggy to the list.


Mike, is it within reasonable possibility to replace the RCAs with BNCs for component out???????? Would this give a further picture improvement?
Steve

Not really, for short distances I can't see the need for BNC's over RCA's. Unless the goal is better grounding, and you'll always want the best grounding for un-balanced video. However, I'm thinking to add BNC's to my 30K, because I have BNC's on the MP-5. My modified 30K is the only consumer device with RCA's that could possibly benefit from BNC's.

Moggy, what do you think about a very clean 400mhz line driver?

Briands, I'm with you.

Duh, I'm waiting on the purdy pictures before opening my 40k.

Originally posted by moggy
[B]Ok. Hmm.. I don't quite understand. What's the point of 1920 pixels if you only see half of it? I'll have to read up a bit more on your ATSC system.
I assume you're talking about ATSC offair HD?
This may be only a factor for analogue displays, not digital, if so then the analogue display fraternity is being dudded. I must read more to see what really happens.

Thanks for setting me straight. Yes, 30MHz BW. But wait, there's more:
Cr & Cb are probably only 15MHz. Y is half filtered but Cr & Cb should be quarter filtered giving only 15MHz BW. It's possibly only the Y that could benefit from a new opamp. The 3 circuits are almost identical so I'm not entirely sure if it's 30/30/30 or 30/15/15. It's a moot point. It's easier to treat all 3 the same.
I'd assumed a higher clock rate(not sure why I did) which when filtered would be closer to 74MHz(my approximation of 66MHz was out) pixel rate. The use of the pixel rate as the basic luma clock rate means that yes, it needs to be filtered. Still, 30MHz is a big drop in resolution.
A digital signal to a digital display is the only option to prevent this loss, I think.

If the 30k is truly 30MHz BW then 100Mhz is ample for our instance and I needn't worry about my projector showing 1920 pixels at full depth of resolution or changing the RCA connectors.

I'll still do all this but the response increase on paper doesn't seem as dramatic as I originally thought. Having response out to only 30MHz is a bit of a downer. My hope is that the FL filters were their way of anti-aliasing or filtering and it's removal may actually be increasing this 30MHz to something much higher. Hoping......
Unfortunately I only have a 20MHz CRO so I can't measure any of this.

Mike, when you first saw this HF rolloff, do you know what the frequency was when it rolled off dramatically. I'm just interested.


Byee for now.

Originally posted by mp20748
Belden and Granite Audio makes the only TRUE mini 75 ohm cables.

Mike's only saying this cause Granite Audio has a special promotional deal (its not what you think) up through CES 2005. Click to find out. HA!

Originally posted by Steve Bruzonsky
Mike's only saying this cause Granite Audio has a special promotional deal (its not what you think) up through CES 2005. Click to find out. HA!


I could think of a few reasons her eyes are crossed :eek:

Originally posted by mp20748
Because of this, I've designed a mini line driver circuit to retro replace the BA7623. It's a 1-1/2 x 2" mini board with 400 mhz bandwidth (-3db). I'll have some completed boards ready by the end of the week.
Moggy, what do you think about a very clean 400mhz line driver?
I assume you are going to use that Intersil opamp. It seems very capable.
Your method is the best and the most flexible. From discussion elswhere 400MHz is a bit high but hey, why not.
I'll either fit a OPA3691 which I have a few of or simply use my external transcoder as the buffer(it uses OPA3691s). After the emitter driver I'll have to decide on values of the series cap and 75R if I use my transcoder. Hmm..

BTW, what do you make of the switched notch filter on the Y signal just after the FL? By previous reasoning it puts a notch in (or out) when in 1080 mode. Any idea what it's doing? A quick calc says it's a notch at 10MHz.


and it seems we'll soon be adding Moggy to the list. ]
I'm educated as an electronics engineer but I've never made it my career. I used to work in broadcast television in the analogue days as a technician and have only learnt digital tv from reading.
I first saw analogue HD in 1985, that was something! It was the marriage of Di and Charles on a small widescreen hdtv.
The advent of surround sound and digital HDTV in Australia in 2001 has re-kindled my interest. Setting up the best HT setup is a challenge. I don't have the same advantages that you guys have in the US. HD here is offair only and that's slim pickings. My D-Theater is imported at great expense. I currently work as a pcb designer for R&D at Varian Inc. here in Melbourne. That's enough about me.

My modified 30K is the only consumer device with RCA's that could possibly benefit from BNC's.]

ditto.

Originally posted by moggy
[B]Your method is the best and the most flexible. From discussion elswhere 400MHz is a bit high but hey, why not.


400mhz is a bit high, but it offers two advantages. One offering the best possible capacitive load driver. With the other dealing with the drop in bandwidth performance when operating with a single 5 volt supply.


BTW, what do you make of the switched notch filter on the Y signal just after the FL? By previous reasoning it puts a notch in (or out) when in 1080 mode. Any idea what it's doing? A quick calc says it's a notch at 10MHz.

Yep, it appears to be a low pass filter for Standard (480I/8mhz) video.

I first saw analogue HD in 1985, that was something! It was the marriage of Di and Charles on a small widescreen hdtv.


That's around the same time that I saw it at INFOCOMM at the DC Convention Center. The HDTV gear took up about as much space as a regular home refrigerator. It's amazing to see how much they've been able to miniaturize that technology.

Originally posted by mp20748
400mhz is a bit high, but it offers two advantages. One offering the best possible capacitive load driver. With the other dealing with the drop in bandwidth performance when operating with a single 5 volt supply.
Fair enough, your chip specs would tell you all this I suppose.


Yep, it appears to be a low pass filter for Standard (480I/8mhz) video.
It's a notch, not a LP filter. It's influence is only around 10MHz . Mabe there is a 10MHz clock when in 480p mode and the signal doesn't care at higher freqs??
The notch is switched by the same signal that goes to the FLs. Maybe it's not a 720/1080 switch but in fact a 480/HD switch. That makes sense now especially if the clock rate for 720p is the same as that for 1080i. I don't know for sure here.
What is the normal BW for 720p? is it the same 30MHz as 1080i?
Anyway, knowing that it is a 480/HD switch, I don't think we need be concerned with it, which is good.


That's around the same time that I saw it at INFOCOMM at the DC Convention Center. The HDTV gear took up about as much space as a regular home refrigerator. It's amazing to see how much they've been able to miniaturize that technology.

I saw it in West Berlin at the Funkschau. It was all Philips cameras, vtr and monitors. I also saw 3D television there. It whet my appetite and have been anxiously waiting for HD ever since that date. I'm also into 3D tv as well. Young minds can be easily impressed.

moggy asked:
> What is the normal BW for 720p? is it the same 30MHz as 1080i? <

Yes. Higher line rate, with lower data density per scan line.

- Tim

Originally posted by moggy
It's a notch, not a LP filter. It's influence is only around 10MHz . Mabe there is a 10MHz clock when in 480p mode and the signal doesn't care at higher freqs??


Ok, that makes sense. I had to revisit the schematic to understand this better, and yet I still can't understand blocking frequencies around 10mhz :confused:

I was thinking it was a low pass for 480I, since 480I is an option on the 30K, and there may not be anything in the FL that would allow for 480I filtering.

Anyway, I'm glad you caught it, and it's nothing to be concerned about.


Now, can someone elaborate more on why a notch filter is needed there?

Here are the pics and instructions for this mod. I haven't completed the mod, so no finished pics yet, just got all the parts. It's in PDF format, about 1.4MB.

JVC 30K Mod Doc (http://www.myhometheater.homestead.com/files/jvc30k_mod_doc.pdf)

Originally posted by VideoGrabber
moggy asked:
> What is the normal BW for 720p? is it the same 30MHz as 1080i? <

Yes. Higher line rate, with lower data density per scan line.

- Tim

Thanks.
That's why they can use the same FL filter for 720p or 1080i. It's the same 74.17582MHz luma/pixel clock rate.
Clever.

It's a pity a 150MHz clock wasn't used so that the filter could be higher and thus give us closer to the 1920 pixels BW.
DVD players use 27MHz and 54MHz clocks almost as standard.


I've also found out that 480i pixel clock is 13.5MHz. So perhaps those 10MHz notch components are to filter this out.
Perhaps they used a switched notch filter since it would suck the 10MHz(or 13.5MHz?) out with sharper filtering rather than a series LP filter which would have only a 1st or 2nd order LP action.
This would give the 480i a really nice response rather than the usual 4.5MHz for offair NTSC.
I think SD is realising it's full potential by having a typical 8MHz (or whatever)BW to play with. The menu text looks half decent too. (The ideal would be 13.5MHz BW, I think)
Why couldn't they have done something just as clever at 74MHz for HD instead of chopping it back to 30MHz? But as Mike has said, the designing engineers are very conservative to prevent EMC problems.

As you might have guessed I don't use my 30k for offair or recording. It's ONLY used for D-Theater playback. I don't even have any blank tapes or NTSC playback tapes. I have about 45 D-Theater movies.
There is no chance in Hades of there being a Region4 version of the 30k being made.
BTW, all D-VHS machines on sale here are SD only and cost A$3000. I don't think they even sell them anymore now that DVD SD recorders have come on line.
The only way to record HD is offair onto the HD of the htpc.

Tomorrow, I'm off for 3&1/2 weeks over christmas. Hooray. :) Soaking up the sun up north in Queensland. Lovely 32deg every day.:cool: Bloody humid though.
I've digressed again. I must like chatting. Oh no! :rolleyes:

Queensland???

When are you going to mod my video card then????

;)

Have a nice holiday.

Moggy, regarding the 74MHz vs 30MHz, it's that pesky Nyquist guy again. :) The sampling frequency (74.25MHz) is double the "frequency of interest" so they have to filter at half that to reconstruct the original signal.

You made an interesting point regarding analog vs digital. Are the luma and color difference data sent at 74.25MHz to the display device? (well, for DVI it's already converted to RGB, but what's the pixel clock?)

Which is not to say that engineers aren't still going to go overboard to fix or prevent EMI problems, which I'm guessing is what Mike has discovered here.

Cary

Originally posted by jcmccorm
[B]Moggy, regarding the 74MHz vs 30MHz, it's that pesky Nyquist guy again. :) The sampling frequency (74.25MHz) is double the "frequency of interest" so they have to filter at half that to reconstruct the original signal.
Yes. Unfortunately our frequency of interest or original pixel frequency is 74MHz, isn't it? They should sample at twice that but it appears they don't. It's like sampling audio at 22kHz to get 10kHz BW instead of 44kHz to get 20kHz.

You made an interesting point regarding analog vs digital. Are the luma and color difference data sent at 74.25MHz to the display device? (well, for DVI it's already converted to RGB, but what's the pixel clock?)

For digital I don't know, I assume the maximum clock rate whatever that might be.
For analogue: I found a data sheet for such a (active) filter and it had 30Mhz for luma(Y) or Green and either 30 for Blue & Red or 15MHz for Cr & Cb. I assume this was to cater for either RGB(or DVI?)(30/30/30) or difference Component(30/15/15).
Since the 30k is difference component I hazard a guess that it should be 30/15/15.
But what is the 'actual' clock for Cr & Cb coming out of the big chip? I can't guess. Hopefully it's 74MHz because if it's 37MHz then we may not be filtering Cr/Cb enough with just a ferrite.
Also, each FL is identical AFAIK so it may be 74MHz with each 2nd pixel being repeated for Cr & Cb. That scenario would be just dandy.

I guess I can muse over these things till the cows come home but knowing that Mike has made it work is probably all we need to know.
Still, it's interesting.

moggy indicated:
> Unfortunately our frequency of interest or original pixel frequency is 74MHz, isn't it? They should sample at twice that but it appears they don't. It's like sampling audio at 22kHz to get 10kHz BW instead of 44kHz to get 20kHz. <

Actually, this isn't quite correct. You missed the point of Cary's comments about Nyquist. The sampling rate (clock) of 74 MHz is already twice the highest frequency required (37 MHz). A 37 MHz signal already contains all the information to reconstruct the full 1920 pixel scan line.

Unfortunately, due to the need for filtering (for anti-aliasing and anti-imaging purposes), we need to roll off the response before we hit that 37 MHz mark, and thus can never quite achieve that full 1920 horizontal resolution, in the analog realm (without some attenuation). But we can get close.

SMPTE specifies that the output response (NOT bandwidth, which is the -3dB point) should be maintained "virtually flat" out to 30 MHz. I.e., +/-0.05 dB. The rolloff should start AFTER that point, and be down at least 12 dB at 37 MHz, and continue to roll off at a steep rate (IIRC 6th order), so that by the next octave, when you hit the sampling frequency, you're down at least 40 dB.

What this means is that image integrity (full detail, with unimpaired MTF) is maintained out to 1560 horizontal (i.e., 30 MHz), and rolls off smoothly beyond that, with the bandwidth (-3dB point) being 34 MHz (equivalent to 1770 horizontal). There can still be content all the way out to 1920, but 1770 is about the effective limit of reproduction (if everything in the source chain is perfect).

Based on some response curves generated by Oliver Klohs' analysis, the stock filtering on the JVC 30K creates a bit of peaking (a small hump of about 1 dB from around 10-18 MHz), which then starts rolling off and is down 3 dB already by 25 MHz (or 1300 horizontal). By the time you hit 30 MHz (which should be flat), response is down a full 8 dB. And 34 MHz is down more than 12 dB. This noticably impairs sharpness and fine detail, especially in the highest quality display systems, with the best source material.

There was some controversy last year when it was initially thought that the 30K was down 25! dB at 30 MHz, but it was discovered that the original 1080i test tape (as documented by dr1394) had its own 17 dB of rolloff at 30 MHz. Only 8 dB was contributed by the JVC 30K (which is still a pretty serious hit).

What Mike's clever mod promises to do is push that 1300 horizontal resolution out substantially, to 1600 or beyond. The fact that it's possible to do that without any increase in spurious noise products is impressive. And it obviates the need to use firewire to an external DAC (like those in the SIR-T165 that DO extend out flat to 30 MHz), to extract the full PQ that the JVC 30K is capable of delivering. Kudos to Mike!

- Tim

mysphyt wrote:
> Here are the pics and instructions for this mod. I haven't completed the mod, so no finished pics yet, just got all the parts. It's in PDF format, about 1.4MB. <

Thanks, Chris! Great job on integrating everything into a nice document. And seeing how far down into the guts of the machine this mod is located, I'm even more impressed with Mike's signal tracing and analytical skills.

It would be nice if the FL modules could be bypassed from the back of the PCB, without having to pry off the glued on daughtercard. At least we know where everything is located now.

- Tim

here a picture of the new D5 JVC, that works very reliable and looking at the picture does not have these filters you are bypassing. There are some caps and inductivities around this AKM Dac, but no FL parts.
I do not have a 30k any longer so I cannot compare the image quality of the new deck against the old.

http://www.myplasma.de/images/d5.jpg

btw, found one bug in this unit, seems that it outputs HDCP all the time, even if you playpack a non copy protected D-VHS HD tape ?
Anybody who can confirm this ?

Originally posted by VideoGrabber
moggy indicated:
Unfortunately our frequency of interest or original pixel frequency is 74MHz, isn't it? They should sample at twice that but it appears they don't. It's like sampling audio at 22kHz to get 10kHz BW instead of 44kHz to get 20kHz. <
Actually, this isn't quite correct. You missed the point of Cary's comments about Nyquist. The sampling rate (clock) of 74 MHz is [b]already twice the highest frequency required (37 MHz). A 37 MHz signal already contains all the information to reconstruct the full 1920 pixel scan line.

Er, sorry, no, I didn't miss the point.
I guess it comes down to what is the real spec for your HDTV. Is it 1920 pixels or 37MHz? 37MHz does not represent 1920 pixels. You say it does. How? Maybe I'm missing something here. 1920 pixels wide requires a clock every pixel to carry the information, yes or no? 2260x1088x29.97=74MHz.(approx.)
How can 37MHz be a representative of 1920 pixels?


The above is my first thoughts on the matter but I knew I must be missing something and I was, see below:

Well, I've been doing some reading and I think I have it now.
You are correct in stating that 37Mhz re-creates 1920 pixels, but not in the way I originally thought.
It seems that one white pixel followed by one black pixel is one cycle of the 37MHz.
This works if the definition of 1920 pixels is one white followed by one black pixel over the entire 1920 pixels wide.
That makes sense. This is how we have always defined resolution as I've rediscovered.

My original thinking was that we need to resolve individual white pixels followed by white pixels, ie. each pixel has information.
It's a matter of definition and I hadn't quite got it right.
Sample frequency is twice that required for 960 white pixels and 960 black pixels interleaved. This is what is defined as 1920 pixel resolution, not 1920 individual pixels.

I hope you've all been patient with me.


To view 1920 individual pixels with black between each individual pixel we would need to sample at 150MHz as a minimum. This has never been asked for AFAIK(except for silly me).
The only way to get near a "real" 1920 pixel res is to be entirely digital. This is where digital displays with HDMI or DVI will shine.

Ahh. I'm exhausted. I'm off to have a beer.

Spatz, nice closeup shot! but...
> looking at the picture does not have these filters you are bypassing... but no FL parts. <

I could be wrong, but if you look in the upper right-hand corner at the tan-colored rectangular device labeled "04 97" that looks oddly similar to the FL units, with their 3 legs on one side, and 2 on the other.

- Tim

yep, but they are filtering the signal that comes from the video head.

Bump

System Bandwidth Requirements for Video:

NTSC Broadcast and VHS: 4.2 MHz

Laser Disk: 5.3 MHz

Regular NTSC DVD: 7 (6.8) MHz

Progressive Scan NTSC DVD and 480p DTV: 13.5 MHz

1080i HDTV: 37 MHz; in practice with 22 MHz the picture is still very superb.

720p HDTV; 37 MHz.

OK Guys, why is this saying that HDTV is 37 mhz, and most (if not all) our consumer devices are clipping the bandwidth above 30 mhz?

I was told by an application engineer doing the design of my transcoder that HDTV signals did not exceed 25 mhz in bandwidth, and that is why the low pass is at 30 mhz...

:confused:

Mike

I was told by a Sencore rep that the ATSC spec for 1080i was 30mhz but to have a high enough resolution to define each pixel would require 37mhz as you have posted. So we have a conflict in the spec. Their early HD signal generators met the spec but could not display the full resolution for 1080i.

What's the rest of the mod? Or is this finished?

Mike asked:
> OK Guys, why is this saying that HDTV is 37 mhz, and most (if not all) our consumer devices are clipping the bandwidth above 30 mhz? <

Because full-bandwidth HDTV (on those occasions when it is discovered) does have content at 37 MHz, though at that point the rolloff is at least 12 dB down (wrt a 1 MHz reference point). The -3 dB point for HDTV should be 34 MHz. Both figures are due to filtering requirements (anti-aliasing and anti-imaging).

> I was told by an application engineer doing the design of my transcoder that HDTV signals did not exceed 25 mhz in bandwidth, and that is why the low pass is at 30 mhz... <

This is incorrect, at least in theory, because HDTV does extend considerally farther than that. In practice, it's probably quite true that most HDTV content does not exceed 25 MHz (an h-rez of 1300 lines).

According to Joe Kane, most telecined film transfers do not exceed 1300 lines, which I find very difficult to believe. Film definitely has content far beyond that point (Lowry has indicated the best film stock is in excess of 3000 lines, horizontal... which is why he oversamples at 4000). But perhaps Joe's comments are based on the end result of the transfer process, considering all the intermediate processing stages, in terms of final delivery.

If this was true in practice, then DirecTV viewers watching 1080i content would see no difference at all when d* drops the h-rez from 1920 down to 1280. From numerous comments here in the Forum, I've been led to believe this is not the case, and a noticable softening occurs.

- Tim

MIke asked:
> most (if not all) our consumer devices are clipping the bandwidth above 30 mhz? <

First off, I don't think it's quite accurate to say "clipping", which implies hard limiting, with a steep rolloff beyond 30 MHz. I suspect it's more likely that they just design to a 30 MHz BW, with response -3 dB at that point, and rolling off beyond. So some detail is retained even then.

As you know, it is frequently the case that consumer electronics are designed to meet the "good enough" criteria. If it's "good enough" to handle 95% of the normal needs, then that is considered adequate. Also, it's not just that many "HiDef" display devices would be hard pressed to show a difference between 1300 and 1800 lines of rez, but that a lot of HD content is sourced from 1440 rez HD cams in the first place (that's under 28 MHz).

The appropriate and comfortable design criteria (i.e., transparency), for an engineer spec'ing a product to process full BW hi-def without imposing it's own limits on the signal would be flat response out to 37 MHz. In practice, this calls for a ~50 MHz bandwidth at -3 dB. If the device is one of a number of units cascaded in a processing chain, it is advisable to extend this spec out to 100 MHz, to mitigate cumulative effects.

- Tim

Originally posted by VideoGrabber
Mike asked:
> OK Guys, why is this saying that HDTV is 37 mhz, and most (if not all) our consumer devices are clipping the bandwidth above 30 mhz? <

Because full-bandwidth HDTV (on those occasions when it is discovered) does have content at 37 MHz, though at that point the rolloff is at least 12 dB down (wrt a 1 MHz reference point). The -3 dB point for HDTV should be 34 MHz. Both figures are due to filtering requirements (anti-aliasing and anti-imaging).


> I was told by an application engineer doing the design of my transcoder that HDTV signals did not exceed 25 mhz in bandwidth, and that is why the low pass is at 30 mhz... <

This is incorrect, at least in theory, because HDTV does extend considerally farther than that. In practice, it's probably quite true that most HDTV content does not exceed 25 MHz (an h-rez of 1300 lines).


So we're not realy getting TRUE High Def? Knowing that true Hi Def is 1920 lines, and now knowing that we're probably getting 1300 or something else below 1920 lines. Why are they still considering this Hi Def, when the real essense of High Definition is in the lines of resolution?


According to Joe Kane, most telecined film transfers do not exceed 1300 lines, which I find very difficult to believe. Film definitely has content far beyond that point (Lowry has indicated the best film stock is in excess of 3000 lines, horizontal... which is why he oversamples at 4000). But perhaps Joe's comments are based on the end result of the transfer process, considering all the intermediate processing stages, in terms of final delivery.
- Tim

I'm sure Mr. kane would change his mind on this, IF he used something other than DVE....:mad:

Originally posted by VideoGrabber
MIke asked:
> most (if not all) our consumer devices are clipping the bandwidth above 30 mhz? <

First off, I don't think it's quite accurate to say "clipping", which implies hard limiting, with a steep rolloff beyond 30 MHz. I suspect it's more likely that they just design to a 30 MHz BW, with response -3 dB at that point, and rolling off beyond. So some detail is retained even then.


My bad. I forgot that you don't loose (completely) during roll-off.


As you know, it is frequently the case that consumer electronics are designed to meet the "good enough" criteria. If it's "good enough" to handle 95% of the normal needs, then that is considered adequate. Also, it's not just that many "HiDef" display devices would be hard pressed to show a difference between 1300 and 1800 lines of rez, but that a lot of HD content is sourced from 1440 rez HD cams in the first place (that's under 28 MHz).


We're being short-changed, because they think we all own HD limited digital display technology or other inferior display devices. And as such, we'll never experience the fullness of HD anyway.


The appropriate and comfortable design criteria (i.e., transparency), for an engineer spec'ing a product to process full BW hi-def without imposing it's own limits on the signal would be flat response out to 37 MHz. In practice, this calls for a ~50 MHz bandwidth at -3 dB. If the device is one of a number of units cascaded in a processing chain, it is advisable to extend this spec out to 100 MHz, to mitigate cumulative effects.
- Tim

This makes perfect sense. And it also depends on the build quality of the device. I have notes from my visit to the compliance lab. In that visit the engineer discussed "mixed signal design" and "grounding and isolation".

Mixed signal design, was when you have both analog and digital on the same PC board design, or when it's done internal in a chip. A manufacturer can design a circuit so well that the switching noise from the digital section would have very little effect on the analog section of the circuit. This is accomplished with better grounding, filtering and decoupling techniques.

I've noticed this on some of the video cards that I've worked with. There's a difference between the ATI cards and the newer Nvidia cards. The ATI cards have massive filtering from the DAC's on the analog, while the Nividia cards almost have no filtering at all. I'm puzzled by this, because both cards are operating at very high digital frequencies, yet the NVIDIA chip seems to have almost no noise on the analog. Maybe it's because NVIDIA put it's mini switching supplies far away from the analog section, whereas, ATI put it's mini switchers right near the analog. or it could have something to do with the boards design, or internal chip design itself. But for sure, it's much cleaner than anything analog I've ever saw come out of a DAC.

I've even tried to remove the filters from a few HD SAT boxes, and the noise was simply too much, inspite of the boost in sharpness. It just was not worth it.

With the JVC 30K. It's similar to the NVIDIA, in that it's almost noiseless. (BTW, these are the only two devices that I've experienced with this low noise, once the filters are removed).

The Video processor in the 30K is very well decoupled, both internal to other components as well as the rest of the deck. That section is also shielded in it's own metal shield. And they put it on the opposite side of the deck away from the switching power supply and other noise generating devices.

With full modification to the 30K, I've noticed that the detail in the background of a good quality HD D-theater tape is greatly improved. I was using U571, and was blown away by the increase in performance. especially coming from a consumer deck (30K). Everything looked tight. The text was good (clean and white), there's no edge enhancement (was expected after filter removal) at all. The image had an increase in punch and colors.

But, as you indicated. You'll need a good display to bring that out...otherwise, there may not be much benefit in modding the deck.

Thanks Tim. I greatly appreciate your expertise here. It's guys like yourself that have helped me to toggle along the way.

Originally posted by mp20748
[B]
We're being short-changed, because they think we all own HD limited digital display technology or other inferior display devices. And as such, we'll never experience the fullness of HD anyway.

Not sure what you mean with that but if done entirely digitally then there wouldn't be much loss, if any.
Yes, the analogue world is full of compromises.
I still think that multiplying the digital clock signal in the STB to 150MHz or higher would help. A clock at the frequency of concern is not a good starter. No comments on that idea?

The appropriate and comfortable design criteria (i.e., transparency), for an engineer spec'ing a product to process full BW hi-def without imposing it's own limits on the signal would be flat response out to 37 MHz. In practice, this calls for a ~50 MHz bandwidth at -3 dB. If the device is one of a number of units cascaded in a processing chain, it is advisable to extend this spec out to 100 MHz, to mitigate cumulative effects..
Not so hot, is it?
This is coming around to my original thoughts on what HD required insofar as BW is concerned and my surprise at it being specified to about 37MHz.
I guess it only goes to show that modern HD is meant for the digital world and is compromised in the analogue world.


Has anyone else modified their 30k yet?
Happy new year all.

moggy

Originally posted by moggy
Not sure what you mean with that but if done entirely digitally then there wouldn't be much loss, if any.
Yes, the analogue world is full of compromises.


Let's take a closer look at this. Can you get me the part number of the DAC used in the 30K?


Not so hot, is it?
This is coming around to my original thoughts on what HD required insofar as BW is concerned and my surprise at it being specified to about 37MHz.
I guess it only goes to show that modern HD is meant for the digital world and is compromised in the analogue world.


Yeah, and we've got to do something about this ;)

I have my line driver circuit finished. I've tested it on a video card so far. It appears that i'll have to use an inductor instead of the ferrite. I've ordered the inductors and so far, I'm surprised at what they're doing being in series on each line. I had to go that route, because there's a little HF over emphasis from the aliasing. And with the ferrites, it helps, but it's not enough. The inductors are perfect. I'm following Tim's lead on this, but with the intent of starting the roll-off at around 40mhz.

Originally posted by mp20748
[B]Let's take a closer look at this. Can you get me the part number of the DAC used in the 30K?

It's not a DAC, it's one big mother of a chip having 250pins or so with analogue outputs on pins 239,58 &61:
IC1001 JCP8037
This would be for security reasons, for sure.

Yeah, and we've got to do something about this ;)
Sorry, if I misled. I was just speaking generally about HDTV design such as STBs and other designs such as the 30k. I can't see any other way of helping the 30k apart from the mods you are suggesting.

I have my line driver circuit finished. I've tested it on a video card so far. It appears that i'll have to use an inductor instead of the ferrite. I've ordered the inductors and so far, I'm surprised at what they're doing being in series on each line. I had to go that route, because there's a little HF over emphasis from the aliasing. And with the ferrites, it helps, but it's not enough. The inductors are perfect. I'm following Tim's lead on this, but with the intent of starting the roll-off at around 40mhz.

Why is this?
The 4ohm with ferrite is in another part of the circuit .
Or are you talking about inductors on the output of the new opamp?
BTW, my thoughts are that 2 resistors are required to bias the input to +2.5V. This will load the signal a bit. Are you providing a small amount of gain in the new opamp?
I can't help much as I'm still on holidays so don't have any technical workshop at he moment. Don't come home till the 18th Jan.

Originally posted by moggy
It's not a DAC, it's one big mother of a chip having 250pins or so with analogue outputs on pins 239,58 &61:
IC1001 JCP8037
This would be for security reasons, for sure.


Thanks!


Sorry, if I misled. I was just speaking generally about HDTV design such as STBs and other designs such as the 30k. I can't see any other way of helping the 30k apart from the mods you are suggesting.


I now have a 40K that I'm playing with. It's slightly different from the 30K. It has the same FL's and 30mhz line driver, but they're in different places o the boards. So far, I've added a line driver circuit and BNC's.


Why is this?
The 4ohm with ferrite is in another part of the circuit .
Or are you talking about inductors on the output of the new opamp?
BTW, my thoughts are that 2 resistors are required to bias the input to +2.5V. This will load the signal a bit. Are you providing a small amount of gain in the new opamp?
I can't help much as I'm still on holidays so don't have any technical workshop at he moment. Don't come home till the 18th Jan.

The ferrrite works well, but it's not the best. I've found that you'll still need an inductor on the analog line after IC1001. It seems the signal needs a coil, but not at the level of what's already in there. I'm bringing the low band pass out to 40mhz by using an inductor on the mini 400mhz driver board. The signal level is maintained at 1 vpp (can be adjusted or increased by varying the value of the 4 ohm resistor). But with the inductor, a lot more of the spurious noise (not seen in the image anyway) is removed. And the low end blacks are much better, because high frequency noise (hash) effects black level.


I have a few extra mini line drivers if you'd want to play with one (no charge). I just refuse to accept 30mhz as a hi def signal.

I did some more reading on digital HD....DVI has it's issues as well.

Mike Parker just got done modding my JVC 40K, and he says its a better picture than the modded JVC 30K:

"Hey Steve,
I got another chance to check out the 40K. It's a little different from the 30K, in that it has a much better low end response. And it's very low noise. Dark movies look awesome on it.

Mike'

Originally posted by Steve Bruzonsky
he says its a better picture than the modded JVC 30K:


I won't say better than the 30K, but I will say it does better in low level detail. I think the 30K is a tad punchier though.

The 40k is very difficult to mod, and I hope to never remove another top from one of them. Neither do I have any desire to do another 30K.

is the "final" definitive MP mod for the 30k gonna be published? I've been waiting patiently.... :D

:cool:

Jim,
I think the improvements are huge. I also think the improvements would depend on your system.

On my test setup (Marquee 9500LC / MP-5 / 6' RGBHV/GN2 / 6' Component/GN2 cables).

Does your Elite have direct component in, or are you using a transcoder?

Are you willing to do some testing youyrself?

I have the best component video cables on the planet.

Originally posted by jimwhite
is the "final" definitive MP mod for the 30k gonna be published? I've been waiting patiently.... :D

:cool:

I have a feeling Mike's got side-tracked on other aspects.
The filter bypass was published but lately Mike's been talking of changing that with the use of an inductor. The opamp driver has been only mentioned as a possibility.

Has there been another problem Mike? We're waiting with bated breath :)

The filtering is the tricky bit for me because I don't have a 500MHz CRO.
Practical knowledge here is the best way. The opamp driver is straightforward but I need to know the source impedance before the driver to set the gain.


BTW, for the chap who asked me about the 30k manual, I finally found the info:
I bought it on ebay from 'memoryhungry' who uses the email memoryhungry@yahoo.ca .
I paid us$12.95 plus postage for the CD. Excellent quality disc. It's not just a scanned copy but a genuine pdf from the original CAD files.
I assume he has more copies. Please, try him first but if not successful then email me and we'll try to organise something.

Originally posted by mp20748
Jim,
I think the improvements are huge. I also think the improvements would depend on your system.

On my test setup (Marquee 9500LC / MP-5 / 6' RGBHV/GN2 / 6' Component/GN2 cables).

Does your Elite have direct component in, or are you using a transcoder?

Are you willing to do some testing youyrself?

I have the best component video cables on the planet.

if this was directed at me, I don't have an Elite.... but my setup IS component and I have the most average component cables on the planet :D I'm ready to mod away.....

:cool:

Ok, I think I'm willing to help out here. Now, "average" cables are not the best cables for this mod. You'll need to upgrade your cables first.

If you'll willing to upgrade your cables, I'm willing to loan you my 30K to evaluate (compare to your 30K). If you're able to notice the improvement, simply remove the cover, and walla - there's the mod!

Now, the absolute best cables for this is a set of component cables made up by GN2 (Paul). I call them magic cables, because they work magic on transferring the signal from the source to the device in use. This is the deal, you'll have to get a set of these cables form Paul to use for the evaluation. I would laon you a set of mines, but they have BNC's on one end. Plus you'll have to help me talk Paul into making more of these cables. I'm wanting to eaither sell them with my transcoder, or not sell my transcoder if they're not being used with it. Because he sells cables at longer lengths, short lengths cables may not be worth the hassle, because it's hard to get good money for short length of cables, unless you have a real fancy designer name.

Well, as far as I'm concerned, the cables that I've got from Paul, far out performs any thing else i've used, and i've used a set of 6' $100.00 fancy named junk.

though I surely appreciate the offer, this seems a bit over the top for me as to how to diseminate the mod..... a circuit diagram, a few photos and a description would certainly benefit the "masses" waiting here for the info !!

:cool:

Originally posted by Guy Kuo
Sounds like this is going to be axial lead components, but I thought I'd share my quickie SMT Home Bench Working Jig

Holding SMT components in place with tweezers while soldering is tough to do because hands shake.

I use a Crazy Glue pencil for small work.

Originally posted by jimwhite
though I surely appreciate the offer, this seems a bit over the top for me as to how to diseminate the mod..... a circuit diagram, a few photos and a description would certainly benefit the "masses" waiting here for the info !!Did you see mysphyt's PDF (http://www.myhometheater.homestead.com/files/jvc30k_mod_doc.pdf) in post #112 (http://www.avsforum.com/avs-vb/showthread.php?postid=4850731#post4850731)?!

Clarence,

How are you able to find all the links you post when you need one. You must have some database.:D

Bruce

I'd just re-read this thread because I bought a JVC 30K last night...

I was about to offer assembling a PDF for Mike since I'm good at taking macro pictures, authoring PDFs, and hosting instructional websites (but as I've admitted several times before, I suck at soldering). But I saw that Chris had already done a very nice job.

>> You must have some database

My feeble mind kinda works like Google... I actually know very little, but I have a knack for finding and accessing information. Which ties in nicely with my day job... visualization and data management.

Originally posted by Clarence
I'd just re-read this thread because I bought a JVC 30K last night...

I was about to offer assembling a PDF for Mike since I'm good at taking macro pictures, authoring PDFs, and hosting instructional websites (but as I've admitted several times before, I suck at soldering). But I saw that Chris had already done a very nice job.

>> You must have some database

My feeble mind kinda works like Google... I actually know very little, but I have a knack for finding and accessing information. Which ties in nicely with my day job... visualization and data management.

When it comes to soldering, I'm the best, but, when it comes to "memory".......I just forgot what the question was.........

Originally posted by Clarence
Did you see mysphyt's PDF (http://www.myhometheater.homestead.com/files/jvc30k_mod_doc.pdf) in post #112 (http://www.avsforum.com/avs-vb/showthread.php?postid=4850731#post4850731)?!


that's not the final mod!

:(

Jim,
I don't have photos of the final, but I could direct what to do from the service manual that you have.

Mike any chance you could look at a 5u deck???, i own 2 of them and might be willing to send you one for a little while

-Gary

Originally posted by mp20748
Jim,
I don't have photos of the final, but I could direct what to do from the service manual that you have.

That'd work !!! :D

Maybe I could then make it more general for any others who might be waiting.... anyone else waiting for the final mod ??

:confused:

Be aware that the frequency burst patterns on the 1080i DVE D-VHS tape
are grossly in error. Here's what's really on the tape:

The 1,2,4,6,8,10 MHz burst.
http://www.avsforum.com/avs-vb/attachment.php?s=&postid=3449273&fullpage=1

The 10,12,14,16,18,20 MHz burst.
http://www.avsforum.com/avs-vb/attachment.php?s=&postid=3449279&fullpage=1

The 20,22,24,26,28,30 MHz burst.
http://www.avsforum.com/avs-vb/attachment.php?s=&postid=3449284&fullpage=1

The original thread.
http://www.avsforum.com/avs-vb/showthread.php?s=&threadid=372713

And an approximation of the actual 30K response.
http://www.avsforum.com/avs-vb/attachment.php?s=&postid=3454358

Ron

Ron,
thanks for that link. I looked over the linked thread (briefly), and plan to look at it in more detail later.

The burst patterns were also my reference for modding the 30K. The 720P patterns were fine on the 30K before modding, with slight HF rolloff. The 1080I tape showed more of a problem before the mod. After the mod, I'm seeing an almost perfect burst with the 1080I DVE tape.
I've not had time to look at where it rolls off, but my goal is beyond 37mhz.

I'll double check this later and hopefully post a photo of the pattern using the DVE 1080I tape.

Originally posted by mp20748
I've not had time to look at where it rolls off, but my goal is beyond 37mhz.


SMPTE recommends a flat response to 30mHz for HDTV. 37mHz is not possible, that is almost one half the pixel clock and would exceed a practical Nyquist frequency for same.

Originally posted by Wendell R. Breland
SMPTE recommends a flat response to 30mHz for HDTV. 37mHz is not possible, that is almost one half the pixel clock and would exceed a practical Nyquist frequency for same.

Hello, yes I think Mike forgot for a moment that 37Mhz is the unobtainable ideal if the pixel clock is ~74MHz.

In all of this I don't really care what the MHz is. I have been hoping that Mike would simply start with no filtering and peg it back until the picture was acceptable for 1080i. The 4ohms with a ferrite on the lead is the crux of all this. I would like to know for sure if this is the final filtering mod for the 30k???
Cables, the output opamp buffer are all about assuming a flat response. The ferrite filter is the heart of the new anti-aliasing filter and I would like to know if this is the final mod? Mike? Any news MIke?

Moggy,
I'm sure I've answered your question several times in this same thread, when I had mentioned the results that I was seeing with my modded unit, and the changes that were made. You seem to put big emphasis on that single bead replacing that complex FL filter. I know, I feel ya there. However, I have been speaking from my experience only. If you've missed what I've reported on this thread previously, I've decided to not bother to repeat the same thing over and over, and also to include the 30K at my next HT gathering in February. At that gathering I plan to use a second non modded deck to use on the second input of my transcoder. And we'll use two of the same tape sources, and with a simple flip of a switch, I'll be able to show the diference between the two units under testing. So the next report on the changes to my 30K, should be posted on this thread after the gathering. And I'll let the attendees at the gathering make my case for me. I now have in my posession, a 30K, 2 -40k's and one 5U... And so that you may know, we'll be testing and evaluating several different items of equipment on that same day, and it'll be done using a very well tweaked and low noise Marquee 9500LC shot on a 72" wide screen.

Also, at this same gathering, we'll be showing an DVI to RGB external box, and several other DVI devices, to include Tim's LightSpeed. And I'll have a few surprises myself :cool:

OT: two weeks ago I stopped taking the pills, inhalers and other medical crap that the doctors told me I would probably need for a very long time or for the rest of my life. So far, I've be doing well, and can't see a need to continue to take any of it. I stopped taking it because of the side effects, so now I'm seeing things a little different (clearer), so bare with me...

The 5U is really, really cool:)

Check this out. It has a buffer chip that also has the low pass filters included in the same chip. But here's the real neat thing about this chip:

- It has adjustable cut-off frequency between 5 mhz and 37 mhz.

- It also has a filter bypass feature, that would allow you disable the filters all together.

- It also has a diagram on the chips PDF file, that shows how to add the variable feature, as well as how to bypass the filters all together - yes!

So in a day or so, i'll add an internal pot for cut-off, and an external switch on the rear for bypass...

:D

hmmmm.... can we retrofit this buffer-chip into 30k ??? with some "creative pwb" mods, of course :D

Originally posted by mp20748
Moggy,
I'm sure I've answered your question several times in this same thread................ I've decided to not bother to repeat the same thing over and over........., so bare with me...

That's your opinion but I have kept up to date with all the messages from go to woh. I think you have raised more questions then answers.
If you are saying that the final agreed mods are to be judged and finalised at your meeting then I am glad to hear it. I look forward to the results.

I mention the ferrite because that is the only actual mod that you have published in this forum but you have raised doubts about it's suitability.
I look forward to the results. I am only interested in the 30k, the other stuff does not concern me.

Last December, this was a hot topic, with a lot of anticipation. But in January it kind of fizzled out. Mike had come up with a great mod to extend the output response of the 30K, and was analyzing the effects of adding inductive filtering to augment the ferrite beads. Several folks (Moggy, Jim White, et.al.) were wondering if any final determination had been made, with specific recommended component values, or circuit mods beyond those that Chris had previously published.

On Jan26, Mike confirmed that there was a final revised mod in his comment:
> Jim, I don't have photos of the final, but I could direct what to do from the service manual that you have. <

I'm unsure if that information was conveyed via private communications or not, but on Jan27, Moggy followed up with his inquiry:
> I have been hoping that Mike would simply start with no filtering and peg it back until the picture was acceptable for 1080i. The 4ohms with a ferrite on the lead is the crux of all this. I would like to know for sure if this is the final filtering mod for the 30k??? <

Mike responded on Jan31, with:
> I'm sure I've answered your question several times in this same thread, when I had mentioned the results that I was seeing with my modded unit, and the changes that were made. You seem to put big emphasis on that single bead replacing that complex FL filter. If you've missed what I've reported on this thread previously, I've decided to not bother to repeat the same thing over and over... <

To refresh everyone's memory, Mike was exploring use of an inductor to control some HF emphasis he was seeing, and had reported on Jan03:
> I have my line driver circuit finished. I've tested it on a video card so far. It appears that i'll have to use an inductor instead of the ferrite. I've ordered the inductors and so far, I'm surprised at what they're doing being in series on each line. I had to go that route, because there's a little HF over emphasis from the aliasing. And with the ferrites, it helps, but it's not enough. The inductors are perfect. <

With a followup explanation on Jan05:
> The ferrrite works well, but it's not the best. I've found that you'll still need an inductor on the analog line after IC1001. It seems the signal needs a coil, but not at the level of what's already in there. I'm bringing the low band pass out to 40mhz by using an inductor on the mini 400mhz driver board. The signal level is maintained at 1 vpp (can be adjusted or increased by varying the value of the 4 ohm resistor). But with the inductor, a lot more of the spurious noise (not seen in the image anyway) is removed. And the low end blacks are much better, because high frequency noise (hash) effects black level. <

So, Mike had determined that an inductor was required (for best possible performance), though the basic ferrite bead mod by itself was already superior to the stock circuit. I think what folks were wondering at the time was what value of inductor had been used, and if the 400 MHz driver was a required element of the enhanced circuit design, or an optional stage for driving longer cable runs. We never did get an answer to either of those questions.

The last thing Mike indicated was that he planned to:
> ...include the 30K at my next HT gathering in February. So the next report on the changes to my 30K, should be posted on this thread after the gathering. And I'll let the attendees at the gathering make my case for me. <

And we haven't heard anything since, from Mike nor any of the attendees. Which is very unfortunate, since Mike put a lot of work into this, and it was an extremely promising mod to rectify what was (and still is) the most significant performance limitation of the JVC 30K decks, which many of us have. I'd hate to see this one die on the vine.

Frankly, I don't think we need the attendees to make Mike's case for him, because what we were looking for wasn't validation of his results (we'll take his word on that), but the final details of his circuit mods. The attendees aren't going to be able to provide that (unless Mike handed it off to one of them).

One thing I think we should keep in mind is that Mike's time is valuable and limited, and we shouldn't expect him to "gift wrap" this for us. But we do need him to reveal the pertinent details to somebody (Chris, Jim, Moggy, myself, anybody), who can then make them presentable to the community, with full credit to Mike for all the work he has done.

- Tim

Oh yeah, that was a good little project. And we did get to show off that modified 30K at the February gathering.

We're using inductors in place of those complex "FL" filters that came in the unit.
We chose inductors that would give us a 40mhz rolloff, though real HDTV is not quite out to 40mhz, we wanted to add a bit of headroom for upper end response without having too much noise in the signal.

The demo at the gathering was using the 30K to the MP-5. The The RGBHV connection to the projector was 25' of belden 1694. We looked at D-VHS DVE and U571. Not sure if the attendees remembered the showing, but we were showing low level detail in both DVE and U571. I was pointing out the very fine detail in the sub of U571, and how well the MP-5 also illuminated the very dark areas of the sub.

I had originally planned to have two 30k's present for a fair comparison, but we only had the modded one there. When I get a chance to get to my notes, I'll post the revised mod for the 30K. The 40K could also benefit from the mod. The latest JVC deck does not need the mod. It's not using that "FL" filter, and it does very well without modding, though I prefer the modded 30K over the latest model.

Originally posted by mp20748
I had originally planned to have two 30k's present for a fair comparison, but we only had the modded one there.Mike, I have an unmodded 30K if you ever need to use one for a comparison. Or better yet, if you want a fresh slate to document the mods.

I have both a 30k and 5u, but with mikes last comment I fill good with the 5u, I only use the 30k for recording anyway

-Gary

Hi

Mike thanks for all your work on this one. I can't wait to get my hands on the final mod details so I can put it into mine.

God bless...

Mark

I've been waiting patiently.
My intention was that if nothing came out of this discussion then I would eventually do my own mod and publish what I did. The problem is getting the time and having the good test gear.
All I need to know is what sort of mod is made around the FL filter, ie what value/type of inductor and whether or not to keep the buffer opamp or replace it with a higher BW one.
If you can supply the electrical info Mike, I'll be grateful.
Actual mechanical mounting details do not concern me.

All,

Any news from may 2005 ? Is there another thread opened elsewhere, where final status has been given on the 30K video bandwidth update (suitable value of the inductor and buffer keep/change) ?

Cheers

John

All,

Any news from may 2005 ? Is there another thread opened elsewhere, where final status has been given on the 30K video bandwidth update (suitable value of the inductor and buffer keep/change) ?

Cheers

John

Yes, but the best mod is much more involved than what we've looked at before.

We've since found that it's best to stay with the filtering, but to also go with better filtering over what's already in place.

The later unit (5U) has it's filtering done in a separate IC chip (not a passive filter network). And because of this, the 5U does not have the response limitations that the previous versions had.

I have a few chip filters to check out, and could also post the chip and drawings for the board later, but would rather confirm which of the two chips would be the best performers.

I have a few chip filters to check out, and could also post the chip and drawings for the board later, but would rather confirm which of the two chips would be the best performers.

Thanks for the reply Mike !
So it looks like that you should test some new chip filter refs that may be mount in replacement of FL802/803/805 original one. Those new chip filters should improve the video bandwith without the drawbacks of the initial fix (simple 4 ohms resistor with ferrite bead) . Am I right :) ?

I just have my 30K opened today and I was planned to apply your initial H/W fix ;) So better wait a bit more :D

Cheers from France

John

All,

I'm still searching about new solutions to update the 30K on its reconstruction filters. I'm wondering if we can't use the new IC from Maxim called MAX7454 (20 pin TSSOP then 6.5x6.35mm only) as a good candidate for IC7103 (BA7623) replacement...

This could be the same solution that has been used in the 5U unit, no ?

This chip is quite nice with HD/SD sectable filters (30/10MHz) through one pin control (linked to 1080_H signal ?) and embeded +6dB gain video follower. The idea will be to short pins #1 and #5 of each passive filters FL802/803/805 and then replace IC7103 located on the back panel with such device.

I should be able to get some IC for free to try this...

Please comment this idea.

John

John,

I'm not familiar with the chip you mentioned, but I'd just caution that the (30/10 MHz) selectable filtering, if that 30 MHz is -3dB as implied, will be not significantly better than what's already in the 30K units. Content that contributes to image detail is present all the way out to 37 MHz, and needs to be preserved.

- Tim

Hello Tim,

Yes, I've checked the IC datasheet : the HD passband value is -2.3dB@30MHz.
According to Mike tests (with DVE), I thought that the JVC30K discrete HD filters were far below this passband value and so replacing them with maxim device seem's to be a good solution to me.
According to Maxim DS, the HD standard passband is defined at 30MHz value and not 37MHz. That is the reason why all active HD(/SD) reconstructions filters integrated circuits available on the market have 30MHz HD passband feature and not 37MHz (the relevant standard is EIA770-3).

See also the following document : http://www.maxim-ic.com/appnotes.cfm/appnote_number/750

720p or 1080i HD standard maximal video BW are 26MHz.

John

Hello Tim,

Yes, I've checked the IC datasheet : the HD passband value is -2.3dB@30MHz.
According to Mike tests (with DVE), I thought that the JVC30K discrete HD filters were far below this passband value and so replacing them with maxim device seem's to be a good solution to me.
According to Maxim DS, the HD standard passband is defined at 30MHz value and not 37MHz. That is the reason why all active HD(/SD) reconstructions filters integrated circuits available on the market have 30MHz HD passband feature and not 37MHz (the relevant standard is EIA770-3).

See also the following document : http://www.maxim-ic.com/appnotes.cfm/appnote_number/750

720p or 1080i HD standard maximal video BW are 26MHz.

John

Well yes, but don't forget how confusing this has been for all, to include the designers/engineers on this. We were first lead to believe that 30mhz was the goal, but later found that we'll need headroom for best performance (as also mentioned in the Max document). We're now lookoing at 37 (or 36) mhz as the goal for HIGH Performance HD. And that would require flat bandwidth at/near 30mhz with filtering at or near 37mhz. So the -3db would be 36/37mhz, and no longer 30mhz.

This was also the problem with the 30K/40K and somewhat the 5U, to include 90% of the consumer HD products. The industry claims that a flatness bandwidth of 24mhz is OK, but on a High End CRT it's not. As I've indicated earlier in this thread, my goal was 37mhz - and these folk made that happen:


http://www.analog.com/en/prod/0%2C2877%2CADA4412%25252D3%2C00.htmllier

This was also the problem with the 30K/40K and somewhat the 5U, to include 90% of the consumer HD products. The industry claims that a flatness bandwidth of 24mhz is OK, but on a High End CRT it's not. As I've indicated earlier in this thread, my goal was 37mhz - and these folk made that happen:
http://www.analog.com/en/prod/0%2C2877%2CADA4412%25252D3%2C00.html

OK Mike, now it's clear to me that I've missed this important point in this discussion :o I now fully understand the goal of this requirement for high end CRT users :cool: .

So the ADA4412 device is the good candidate to replace IC7103 in the 30K as it enable video bandwidth of 37MHz@-3dB typical (and 31.5MHz@-1dB typical).

I would like to try this IC on my 30K unit since I can have samples of this chip too.

The only issue about IC7103 replacement is its location (on the back panel) in the unit which is quite far from VDACs. Usually, the filters should always been placed very close to the VDACs (so close to IC1001 JCP8037 chip). Moving the HD/SD filters at IC7103 location (at the end of the 25cm long FPC cable) may be not the right thing to do versus peformance :rolleyes:

John

HI Mike,

Your link to analog devices gives an error and says the page is not supported.


God bless


Mark

True Mark,

Mike's link has been corrected in my previous post quote and you can use this link.
John

John,
it sounds like you and Mike have figured things out pretty well. I'll add just a couple comments.

You wrote:
> Yes, I've checked the IC datasheet : the HD passband value is -2.3dB@30MHz. <

Unfortunately, that will limit you to ~1500 horizontal resolution. Which may be fine since many sources are already limited by HDCams (1440), and many telecined films at 1300 (which correlates well with your 26 MHz BW figure). Check out some previous discussion here (http://www.avsforum.com/avs-vb/showthread.php?p=4872758&&#post4872758) and here (http://www.avsforum.com/avs-vb/showthread.php?p=6403695&&#post6403695).

> According to Mike tests (with DVE), I thought that the JVC30K discrete HD filters were far below this passband value and so replacing them with maxim device seem's to be a good solution to me. <

The JVC filters are excessive, though not as egregiously so as originally thought from test results with the 1080i-test tapes. dr1394 found that 8 dB of that loss at 30 MHz was from the JVC-30K itself (with the tape contributing a massive -17 dB of the falloff), so anything that improves on that will be better. More details here (http://www.avsforum.com/avs-vb/showthread.php?postid=3450693).

> According to Maxim DS, the HD standard passband is defined at 30MHz value and not 37MHz. That is the reason why all active HD(/SD) reconstructions filters integrated circuits available on the market have 30MHz HD passband feature and not 37MHz (the relevant standard is EIA770-3). <

Not all of them. Case in point is the SIR-T165, which is flat well past 30 MHz. I don't have Mike's mod in either of my 30Ks yet, but I can sure tell the difference (on some source material) between the component outputs of the SIR-T165 processing the firewire output from the 30K, vs. the direct component outputs on the 30K itself.

Use of the AnalogDevs 4412 looks optimal, as it preserves flatness to 31.5 MHz (typical), and 26.5 MHz (worst case). The -3 dB BW is at 34 MHz worst case (and 37 MHz typical). Plus it does a nice job of rejecting out of band components and removing HF hash. So it offers the possibility of getting the maximum amount of detail possible out of the 30K (assuming it could be incorporated).

- Tim

Glad to see some activity on this topic. I REALLY do want to mod my 30k to get the best out of it.
I like your HT JohnWyman. My french is only basic but it looks good. Sony G70 is a good pj. I have a 1292 myself.
I haven't been able to add to this thread much of late. Busy extending house to give me a better HT room.
Nice to see 30k users outside of the US. Pity there are no new movies coming out. I've managed to collect about 70 movies.
Watching patiently.

Thanks for your post Tim,

With your summary, I now have a clearer view on the JVC30K issue and the post from Ron is summarize this BW limitation technical aspects very well :

the burst patterns on DVE were delivering full amplitude for all frequencies including 30 MHz. However, in reality the bursts are attenuated. The 30 MHz burst is -17 dB down on the tape. So when he measured -25 dB at 30 MHz, -17 dB is from the tape itself which means that -8 dB is the actual response of the component output.

It appear also that the Samy SIR-T165 unit have far better component output BW flatness than the 30/40K (according to Olivier's plots in PDF). Could be interresting to analyse its components outputs schematic :cool:

To conclude, the maximum gain we can offer to the 30K/40K units seem's to be 8dB @ 30MHz. And the ADA4412 IC could help to achieve this goal. However, I'm still unsure that tweaking the 30K/40K units with such mod can make the JVC units as good as the Samy :confused:

I've ordered some ADA ICs and plan to make a small PCB to hold it in the replacement of passive filters in the JVC (close to IC1001 Vdacs outputs) and connect the RCA component plugs directly from Analog device IC outputs with RG179B/U coaxials to have optimal output impedance respect.

John

Glad to see some activity on this topic. I REALLY do want to mod my 30k to get the best out of it.
I like your HT JohnWyman. My french is only basic but it looks good. Sony G70 is a good pj. I have a 1292 myself.
I haven't been able to add to this thread much of late. Busy extending house to give me a better HT room.
Nice to see 30k users outside of the US. Pity there are no new movies coming out. I've managed to collect about 70 movies.
Watching patiently.
Hi Moggy :)

I knew Melbourne quite well since I've been working out there for 6 month in the 90' (in a company called AKYMAN where I was an H/W POS designer).

Thanks for your comment on my HT, that's kind :) Yes I'm quite proud of it since I did all the stuff by myself (one year long work :eek: ). I know you PJ quite well since I have some friends in France that own these 1292 to watch 1080i HD. Also, I going to tweak this unit too.

It's true that no much DVHS movies in Europe :D Appart from a dedicated HTPC, this is still the only device to play/record HD material on the market till now :rolleyes:

Cheers

John

P.S. Just for fun, here is a link of my last design : adding a DVI(HDCP) input to Sony CRT projectors. http://www.cinetson.org/phpBB2/viewtopic.php?t=4030&postdays=0&postorder=asc&&start=360
I did the same for Barco CRT too : http://www.cinetson.org/phpBB2/viewtopic.php?t=8779&postdays=0&postorder=asc&&start=178

Hello Tim,

I'm currently studying the ADA4412-3 datasheet and found that its filter section is able to filter Y/Pb/Pr in HD mode with different BW :

F_SEL_A F_SEL_B Y Cutoff Pb Cutoff Pr Cutoff
0 0 36MHz 36MHz 36MHz
0 1 36MHz 18MHz 18MHz

Is there interrest to use 36MHz cutoff filter setting for Pb/Pr signals ?
I'm wondering this because usually, those components output have horizontal resolution half of the luma component one ;)

John

Just finished the schematic of the JVC update with the use of AD chip :
JVC 30K/40K video filters update schematic (http://johnhwman.chez-alice.fr/JVC30K/Update.tif)
This schematic is quite obvious and the update requires low count components

- The IC inputs are directly linked to JVC HD/SD video processing board with very short wires from J1.
- It is powered by the JVC power called "AL5V" on the JVC schematics (60mA max)
- The "1080_L" signal is derivated from "1080_H" signal (inverted by Q836 on the JVC MB) to change the polarity of the signal to be compatible with AD IC video BW selection (36MHz in HD and 9MHz in SD mode)
- The IC outputs are feed directly to the JVC back panel RCA plugs with RG179B/U 2.5mm diameter 75 ohms coaxials (BA7623F-X IC will not be use anymore).
- The coupling is DC on both inputs and outputs for better signal integrity.
- The IC size is very small : 9x6mm :eek: , so the PCB
- Because of the IC video Gain x2, R818/R830/R842 (current to voltage conv.) on the MB must be updated with there values divided by 2 factor (135R/75R/75R)

I'm gonna start the PCB layout (which is very simple :) )

John

John,

sorry for the delayed response.

> Is there interrest to use 36MHz cutoff filter setting for Pb/Pr signals ? <

Not really. 18 MHz would be the appropriate setting, in this case.

> I'm wondering this because usually, those components output have horizontal resolution half of the luma component one <

That's correct, for consumer-grade equipment running 4:2:2 or 4:2:0. Unless you're running pro 4:4:4, the half-bandwidth chroma setting (0:1) for 18 MHz BW is preferred, since it reduces chroma noise and hash outside the bandpass.

The new circuit looks good, and seems promising. Keep us updated on its performance. I'd offer to check it for you, but my spectrum analyzer tops out at a bit over 40 MHz, so any spurious high-end products wouldn't be visible (at least not directly... I could check for any components that "wrapped" back into the bandpass to see if any were above the -80 dB noise floor of my analyzer).

I think my other "spectrum analyzer" can go quite a bit higher, but it's an FFT-based DSO with 350 MHz BW, and getting all the sampling settings right for maximum BW results from the FFT is something I'd have to do some reading on first, since I've never done more than "play" with it so far, and there's some fairly complicated interactions based on those settings (max 400 MS/s, single channel, one-shot; 10GS/s repetitive).

- Tim

Now who wants to do the same thing for my laserdisc player? :D

Just finished the schematic of the JVC update with the use of AD chip :
JVC 30K/40K video filters update schematic (http://johnhwman.chez-alice.fr/JVC30K/Update.tif)
This schematic is quite obvious and the update requires low count components

- The IC inputs are directly linked to JVC HD/SD video processing board with very short wires from J1.
- It is powered by the JVC power called "AL5V" on the JVC schematics (60mA max)
- The "1080_L" signal is derivated from "1080_H" signal (inverted by Q836 on the JVC MB) to change the polarity of the signal to be compatible with AD IC video BW selection (36MHz in HD and 9MHz in SD mode)
- The IC outputs are feed directly to the JVC back panel RCA plugs with RG179B/U 2.5mm diameter 75 ohms coaxials (BA7623F-X IC will not be use anymore).
- The coupling is DC on both inputs and outputs for better signal integrity.
- The IC size is very small : 9x6mm :eek: , so the PCB
- Because of the IC video Gain x2, R818/R830/R842 (current to voltage conv.) on the MB must be updated with there values divided by 2 factor (135R/75R/75R)

I'm gonna start the PCB layout (which is very simple :) )

John

Good Job John!

I have a few of the chips on order as well, and have been waiting for them for weeks. I'll test one here, and will also get one off to Tim for testing.

Good Job John!
I have a few of the chips on order as well, and have been waiting for them for weeks. I'll test one here, and will also get one off to Tim for testing.
Thanks Mike ;)
I've also ordered some AD ICs as samples but it will take some weeks to get'em (I should have them by the end of this year :p ).
If you want (and for Tim too), I can provide some PCBs for you tests, then this will ease the implementation of the chip inside the JVC unit.
As soon as I'll get some PCB, I'll send them to you ;) .

John

Hi Tim,Not really. 18 MHz would be the appropriate setting, in this case. That's correct, for consumer-grade equipment running 4:2:2 or 4:2:0. Unless you're running pro 4:4:4, the half-bandwidth chroma setting (0:1) for 18 MHz BW is preferred, since it reduces chroma noise and hash outside the bandpass.
Fine, I should update the schematic to reflect the BW change between Y and Pr/Pb.
The new circuit looks good, and seems promising. Keep us updated on its performance. I'd offer to check it for you, but my spectrum analyzer tops out at a bit over 40 MHz, so any spurious high-end products wouldn't be visible (at least not directly... I could check for any components that "wrapped" back into the bandpass to see if any were above the -80 dB noise floor of my analyzer). I think my other "spectrum analyzer" can go quite a bit higher, but it's an FFT-based DSO with 350 MHz BW, and getting all the sampling settings right for maximum BW results from the FFT is something I'd have to do some reading on first, since I've never done more than "play" with it so far, and there's some fairly complicated interactions based on those settings (max 400 MS/s, single channel, one-shot; 10GS/s repetitive).
Your tools can be good enough to check the JVC video BW after the update. I may check the update too if I can have access to Tektronix HD5000 video test equipment in my company. The only thing I missed is the DVHS DVE test tape :o ...
John

John,
> If you want (and for Tim too), I can provide some PCBs for you tests, then this will ease the implementation of the chip inside the JVC unit. <

It would be good if the PCBs came from somewhere, since I have no time to do them myself (plus, it would be redundent effort).

> Your tools can be good enough to check the JVC video BW after the update. <

Yes, I think you're right. The critical region will be to see how 26-37 MHz fares, and I can go to 40.2 MHz directly. I had just been thinking about looking for 74.5 MHz residuals.

> I may check the update too if I can have access to Tektronix HD5000 video test equipment in my company. The only thing I missed is the DVHS DVE test tape <

Nice gear! My spectrum analyzer does have a precision tracking generator, so I'm OK in the bandpass without the DVE tape. In fact, with a -17 dB rolloff, I don't think the tape (the 1080i variant) is a good test source anyway. The FFT from the DSO should reveal products outside the bandpass to at least 100 MHz, and I have a 0-300 MHz generator I can inject a signal from to see if there's any foldover (spurious products) inside the bandpass.

- Tim

Thanks for the answer Tim,

Always good to know that we can test the tweak with differents tests rigs to be able to check the increase of the video BW with confidence.

I've passed some time to probe the HD_DEC video outputs of the 30K with a good oscilloscope (500MHz analog). I've discovered that there is two different VDAC option inside the unit :

- One is with the use of IC1001 (JCP8037) HD_DEC internal VDAC (COMPY/COMPCR/COMPCB signals),
- One with an external video DAC optionnal IC (IC801=JCP8029 not populated in my unit) a small 80-pin LQFP package chips.

I've checked the PCB and found that COMPY/COMPCR/COMPCB signals from HD_DEC VDACs are all in Unity Gain (x1) with Sync. measured at 316mV. That's a good new since there is no need to change the current to voltage conversion resistors (R1021/R1022/R1023) on the PCB to add the tweak :D Hope the use of HD-DEC internal VDACs is also major in your units :rolleyes: ...

I've also checked the "1080_H" signal states :

Playing 480i tape -> "1080_H" = 0V
Playing 480p/720p/1080i tapes -> "1080_H" = 3.3V
Then Q836 is inverting the polarity of this signal ("1080_L") with 10.5V amplitude.

Just another information : The MPEG2 HD transport stream is decrypted through a specific JVC IC (JCP8044) but unfortunatly, the decrypted TS buses (links to IC1201/IC1001/IC601 BGA) are buried in the inner layers of the digital circuit board : no access in any case for security reason :(

I've updated the schematic to reflect the change of Pr/Pb bandwith to 18MHz(HD)/9MHz(SD) and "1080_L" amplitude.

John

Hello,

Just finished the CAD layout of the JVC video BW update :
JVC 30K/40K video filters update PCB layout (http://johnhwman.chez-alice.fr/JVC30K/Layout.tif)

- The PCB size is less than 38x22mm,
- The PCB is 0.8mm thick and dual layer,
- Three 220uF 10V Ecaps have been added to the Y/Pr/Pb output to supress the DC component prior to be outputed to RCAs (AC coupling is decreasing AD IC power),
- The most PCB area is used to hold the three RG179B/U coxial terminaison,
- The "solder side" of the layout is filled with a complete ground plane with no tracks cuts,
- ADA4412-3 IC power decoupling is very good,
- Video paths are optimal, so the video signal integrity should be maximal,
- PCB mount / fix is still under study.

John

Looks great John (being a pcb designer myself).
I have to admit though that I will probably just solder 3x RG179 cables directly to the board for simplicity. This depends on assembly layout though.
Great stuff.

Hi Moggy,

Thanks again for your help on this project. The JVC30K schematic was helpfull for me !

About RG179B/U footprints on the PCB : it's indeed direct solder of the coaxial on the PCB (tip inside a throug hole pad and shield lay down on the sqare pad and soldered on it). This solution is cost and size effective. This also ensure 75 ohms impedance continuity between the coxial and the PCB (no impedance break).

The next question is how much of this PCB should I make ?

John

Count on me for 2 PCB
Thanks
Mauro

Just wondering ...

How about ending the three coax. with 75Z BNCs and put these BNCs somewhere on the back panel of the unit :rolleyes: ?

Then, we should be able to A/B compare between original filtered (RCA) and new filtered (BNC) Y/Pr/Pb outputs :D ...

John

JohnHWman inquired:
> The next question is how much of this PCB should I make ? <

Perhaps just a couple in the first batch for inital testing?

I have two of the JVC-30K decks and one 40K myself, and I think once the implementation is validated, there are many here in the Forum with these decks that would love to benefit from what should be a very noticable improvement. Those running D-Theater tapes in particular should see a night and day difference on good displays. So a second run in quantity, once people are made aware of it, would be justified.

- Tim

now who is gonna come up with a DTS mod?:D

Hmm, I sold my deck after it died, now I am tempted again.

Anyone tried plugging a laserdisc into the composite input on the JVCs - from memory they had a great comb filter - anyone know much about that side of them?

I would be interested in one for my JVC30K.

Perhaps just a couple in the first batch for inital testing?
This makes sense Tim,
However, for the PCB manufacturing, because of its size, the tooling cost is quite heavy for two PCBs only. I think that it would be better to count on 5 to 10 units in first batch (the PCB cost excluding tooling is quite cheap).
John

Dok

the JVC decks do indeed have a top notch 3D 2/4mb Comb Filter, great stuff

Only guys with LD's in their theater would talk about this stuff eh!! ;)

I keep my LD spinning for rare music LD's like Santana and Malmsteen stuff and all sorts of other LD only goodies

I am thru with D-VHS, but I would love to compare a modified 30k to the 5u using HDMI output, the later is the best damn HDTV image I have ever seen and boy have I been thru HDTV devices and decoders

-Gary

Hey Gary,

It amuses me when people are "done with D-vhs" when any other recordable, archivable HD media is 3-5 yrs out. Sure 200 hr HD dvrs give some room to work with, but I stil love my t-165 and 30k for hd recording.

God bless...

Mark

Hmm, maybe I should pick one up just to use as the input for my LD player - they are cheap enough now.

This makes sense Tim,
However, for the PCB manufacturing, because of its size, the tooling cost is quite heavy for two PCBs only. I think that it would be better to count on 5 to 10 units in first batch (the PCB cost excluding tooling is quite cheap).
John

I found another potentially good chip for testing (THS7303):

http://focus.ti.com/docs/prod/folders/print/ths7303.html

I have three of these on order, and they'll be here soon. I'm also going to draw out three boards for them, and we'll also share these to look at.

Hi Mike,

The TI part -3db point is only 35hz, so wouldn't that be 2 MHZ below ideal of 37mhz to let all detail through? The AD part -3db is 36 mhz right?

God bless...

Mark

htguy,

no, not really. Part of your confusion is that 35, 36, or 37 MHz are "hard" points. We're dealing with analog, and it's all part of the curve.

SMPTE recommendations put the -3 dB rolloff point at 34 MHz. As long as that's maintained, you're in good shape. As far as letting "all the detail through" at 37 MHz, that's never running at full amplitude at that point anyway. By the time you reach 37 MHz, you could be 6-12 dB down, and still have some detail come through at 1920 (with reduced MTF). But it is true that 34 MHz amplitude (@50% MTF) is only maintained out to ~1780 horizontal, in the best-case scenario. (And that's far better than 30K owners are currently getting.)

- Tim

I found another potentially good chip for testing (THS7303):
http://focus.ti.com/docs/prod/folders/print/ths7303.html
I have three of these on order, and they'll be here soon. I'm also going to draw out three boards for them, and we'll also share these to look at.
Yes Mark, seem's quite good one

However, it has 2:1 mux input which is useless for the application. It is also I²C protocol driven : that's make the implementation more difficult since you need a microcontroler to setup the chip operation within the JVC unit.

The 190MHz Bypass mode is interresting to see.

John

Just a small update on the project :

Just received today two ADA4412-3 chip samples for free.

Now I could launch PCBs manufacturing.

John

Here we are :cool:

Just finished populate two samples of the JVC30K/40K video BW fix :
http://johnhwman.chez-alice.fr/JVC30K/Proto1.jpg
http://johnhwman.chez-alice.fr/JVC30K/Proto2.jpg

- The PCB size is less than 38x22mm,
- The PCB is dual layer (bottom layer is 100% ground plane),
- The most PCB area is used to hold the three green RG179B/U silver coaxial terminaisons on the right side of the pictures,
- ADA4412-3 IC power decoupling is very good,
- Video paths are optimal, so the video signal integrity should be maximal,
- PCB mount / fix is using a simple dual side 2mm thick smooth scotch tape located on the bottom side.

Now I can start to modify my JVC 30K to integrate this small update and test it. I will post some pictures of the mod. integration in this thread to help DIY people.

I can provide some samples for only the BOM cost of $20 for people who want to test it (Mike, Tim ??). These samples will be without the AD chip mounted because I've got only two samples of this device so far on hands.

Moggy will got one too for free since he helped me in designing this ;)

John

Beautiful baby ! That's a work of art.

I can provide some samples for only the BOM cost of $20 for people who want to test it (Mike, Tim ??). These samples will be without the AD chip mounted because I've got only two samples of this device so far on hands. Very nice work.

I've got two JVC 30K's...

I'll volunteer to install your sample and do an A/B comparison with MP at next month's open house on my G90.

Looks great. Look forward to hearing the results.

What is really needed to make me buy one of these machines, is an PAL to NTSC HD video input converter so I can record off air PAL HD signals onto an NTSC D-vhs machine.

Anyone got one in their cupboard they want to sell?

I'm close to finish the PCB mount inside the 30K. This job is not as easy as expected first and requires some care due to the size of the components footprints on the JVC digital PCB :rolleyes: .

I'll post later the pictures of my job to let you evaluate the tricky stuff ...

Clarence, are you familiar with electronic parts soldering ? The installation of the sample require thin iron pin, thin solder, one magnifier and steady hands :o .

John

IS the firewire data streams to the D-vhs the same regardless of where the source material is NTSC 1080i or PAL 1080i. Is there a difference or are they the same?

Beautiful job on the PCB's.... my congratulations :D

I'm very interested in putting one in each of my 30K's.... I deal all the time with Analog Devices at work so getting the parts should be easy (in fact, I worked as a sales engineer for ADI back in the 80's).... AND I have access to a lady who solders such boards as a vocation.... she just happens to be my wife :D

let me know how I can get a pair...

:cool:

Clarence, are you familiar with electronic parts soldering ? The installation of the sample require thin iron pin, thin solder, one magnifier and steady hands :o .I'd go across town to Mike Parker's shop for that.

IS the firewire data streams to the D-vhs the same regardless of where the source material is NTSC 1080i or PAL 1080i. Is there a difference or are they the same?
Hi Graham,

Even the 1080i US mode is 60Hz frame rate and 1080i Australia mode is 50Hz frame rate, I assume that Firewire digital data should stay the same since they are MPEG2 MPHL Y/Pr/Pb datas ...

But maybe because of the frame rate difference, there may be some clock difference in the data stream, anyway ...

John

Just fire-up the modded JVC30K on my lab and all seem's OK (oscilloscope checking only).

I'll test it on my G90 tonight.

Here is a summary of people who are interrested to do the JVC video bandwidth tweak :

Since I've made 10 PCB for testing purpose and I keep two for me, I would sort the people in the following order :

1- Moggy
2- mp20748
3- VideoGrabber
4- Clarence
5-6 jimwhite (2)
7- Frank D
8- Plexi47

Since I only got two samples of the main ADI IC, the PCB I should send will be fully components populated (including wires and coax.) but without the ADA4412-3 IC mounted. So you should buy and solder it by yourself, I apologize :o

Is this sounds OK :rolleyes: ?

John

John, are you planning on selling this mod if it tests OK? If so, how much?

Dave

Hi Dave,

First, we must be sure that this mod. is making the DVHS JVC player video BW better than the with original JVC filters. Then, I may consider selling this update but only for people that are aware of the soldering process difficulties ...

Then, maybe I can make some of these for... let's say $60 to pay the handwork most than the BOM...

Let's first test it with different people !

John

Sounds good. You can combine s/h for mine with Mike's. Or Mike's with mine. I can paypal to cover materials and postage.

Is this the op amp:
http://www.analog.com/en/prod/0,2877,ADA4412-3,00.html
qty 1000 for $1.59
http://www.digchip.com/datasheets/new_parts/200508/1087322.php

Jim, can you get <1000 qty?

Hi,

Just a note on using the ADA4412, BBlue has already done up a board(many months ago) and used it in a Dish 6000 sat box and really wasn't sure if it was an improvement over the stock filters with an improved output amp. It was/is that close so it must do a decent job none the less. I have compared it in a stock 6000 with an improved output amp to one with the 4412 in it and its hard to tell as one is on Bell and one is on Dish and I'm not sure if its the provider quality difference sometimes or the content quality or the circuit changes.

Here we are again...

Here is some pictures of the mod. DIY step by step process. Some of the pictures are shown in the thread, some other are available for downloading to avoid too much page loading time ...

Warning : Do this mod. at your own risk :o

First of all, unplug the deck from main and place it on a clean working desk.

1°) JVC HM-DH30000U DVHS player digital board oppening :
http://johnhwman.chez-alice.fr/JVC30K/Unmount.jpg
http://johnhwman.chez-alice.fr/JVC30K/Open.jpg

2°) The pads locations for the wiring and resistances removing :
http://johnhwman.chez-alice.fr/JVC30K/Pads_location.jpg

3°) Module view with dedicated lenghts pre-cutted wires :
http://johnhwman.chez-alice.fr/JVC30K/Module.jpg

4°) AL5V/Y/Pb/Pr/1080L signals soldering pass closer views :

AL5V and GND_AL5V wiring closer view (http://johnhwman.chez-alice.fr/JVC30K/AL5V.jpg)
Y wiring closer view (http://johnhwman.chez-alice.fr/JVC30K/Y.jpg)
Pb wiring closer view (http://johnhwman.chez-alice.fr/JVC30K/Pb.jpg)
Pr wiring closer view (http://johnhwman.chez-alice.fr/JVC30K/Pr.jpg)
1080L and GND_1080L wiring closer view (http://johnhwman.chez-alice.fr/JVC30K/1080L.jpg)

Next post to follow ;)

5°) R816/R840/R828 resistors removal :

To avoid parasitic capacitance of the previous JVc analog filters, we should remove three resistors on the board.

Those resistances are shifted (to the left) to be soldered on one pad only (this ensure that the resistor can be saved in place for backwiring if needed)

R816 removal closer view (http://johnhwman.chez-alice.fr/JVC30K/R816.jpg)
R828 removal closer view (http://johnhwman.chez-alice.fr/JVC30K/R828.jpg)

R840 removal picture is not available but should be shifted as well as the two others.

6°) Wiring completion general view :
http://johnhwman.chez-alice.fr/JVC30K/Wired.jpg

7°) Digital board can closing procedure :
http://johnhwman.chez-alice.fr/JVC30K/Open_can.jpg
http://johnhwman.chez-alice.fr/JVC30K/Coax_pass.jpg

Next post to follow ...

http://johnhwman.chez-alice.fr/JVC30K/Before_placed.jpg
http://johnhwman.chez-alice.fr/JVC30K/Placed.jpg

Can cover closed, module is sticked in place and coaxials outputed through shield holes (http://johnhwman.chez-alice.fr/JVC30K/Can_closed.jpg)

8°) Back panel board update procedure :

First remove the three R7121/R7122/R7123 75R resistors to avoid previous JVC video followers influence :
http://johnhwman.chez-alice.fr/JVC30K/75R_locations.jpg
Remove R7121 SMD resistor by shifting it to the left. Tireup the through holes R7122/R7123 resistors from one side :
http://johnhwman.chez-alice.fr/JVC30K/TH_75R_loc.jpg

Next post to follow ...

Then solder the three coaxials cable as shown :
http://johnhwman.chez-alice.fr/JVC30K/Coax_soldered.jpg

Closer view of the coax. ends solders (http://johnhwman.chez-alice.fr/JVC30K/Coax_closer.jpg)

9°) Final assembly and cables fix :
http://johnhwman.chez-alice.fr/JVC30K/Wiring2.jpg
http://johnhwman.chez-alice.fr/JVC30K/Wiring1.jpg

That's it ! Test it fastly by applying the main on the unit and check that all is OK (VFD display should lit).

Just close the JVC deck cover back in place and put the 4x silver + 1x black screws in place.

Enjoy !

John

This is so Cool.. :)

John, you can ship Clarence's to me. And that way I could have him drop his decks off and I'll get them installed before his next gathering.

Holy Macro, batman, thems some close-ups!

Nice pics! Now if I can just get rid of the dreaded "Calibrating" message I might be able to record something.

I've tested the modded JVC unit in my HT yesterday night.

Even, my G90 isn't completely adjusted (MG focus not yet finished), the image displayed is great especially in the sharpness aspect :eek: (tested with Gladiator 1080i)

S/N ratio is also very good now especially with dark scenes (Blade 2 1080i)

Unfortunatly, because I've got only one JVC unit available, I can't do A/B compare. Clarence can do it and report.

I do not have DVE tape too, so cannot check the BW HF atten. aspect improvment with the oscilloscope :(

Later

John

Hi John,

Nice work!

John,

this is really a class act, and your step-by-step photo instructions are exemplary. Superb job!

> I can provide some samples for only the BOM cost of $20 for people who want to test it (Mike, Tim ??). These samples will be without the AD chip mounted because I've got only two samples of this device so far on hands. <

That sounds very generous... thanks!

> I do not have DVE tape too, so cannot check the BW HF atten. aspect improvment with the oscilloscope <

You shouldn't need the tape. In fact, you wouldn't really want the 1080i DVE tape anyway, since its rolloff is worse than the JVC 30K default output circuits. Grab Ron's (dr1394) excellent HD test patterns, described here (http://www.avsforum.com/avs-vb/showthread.php?t=570937), play back the transport streams on your PC, and send them via firewire to your JVC 30K and monitor the component outs.

WTS commented:
> Just a note on using the ADA4412, BBlue has already done up a board(many months ago) and used it in a Dish 6000 sat box and really wasn't sure if it was an improvement over the stock filters with an improved output amp. It was/is that close so it must do a decent job none the less. <

I don't know how good the 6000 was to start with, but you really can't conclude anything if the source signal (from e*) has already been filtered to start with.

- Tim

[QUOTE=VideoGrabber]John,

I don't know how good the 6000 was to start with, but you really can't conclude anything if the source signal (from e*) has already been filtered to start with.


What you think the original filters were left in, yeah okay, not qiute that stupid thanks. The 4412 was connected directly after the loaded DAC.

Walt,
> What you think the original filters were left in, yeah okay, not qiute that stupid thanks. <

Huh? Why the animosity? :confused: Did I kick your dog, or something? This is just totally out of left field.

I wasn't maligning you in any way. I said "if the source signal (from e*) has already been filtered..." and thought the implied "...by e*" was obvious enough that it didn't need to be explicitly stated. What other "source signal" is there?

It's well known that e* not only filters but manipulates their source signal in a number of ways prior to transmission. If they've already degraded the signal enough, you could make the output stage of the 6000 even worse and still not notice any difference. Likewise, making it better wouldn't net any perceptible improvement either. An enhanced output stage can only preserve quality that's there to begin with.

This kind of BS attitude makes me wonder why I spend my time here. I'd apologize for the misunderstanding, if I could conceive of any way it could be interpreted in a disparaging manner. I thought we were having a cordial and professional engineering-level discussion.

- Tim

Walt,
> What you think the original filters were left in, yeah okay, not qiute that stupid thanks. <

Huh? Why the animosity? :confused: Did I kick your dog, or something? This is just totally out of left field.

I wasn't maligning you in any way. I said "if the source signal (from e*) has already been filtered..." and thought the implied "...by e*" was obvious enough that it didn't need to be explicitly stated. What other "source signal" is there?

It's well known that e* not only filters but manipulates their source signal in a number of ways prior to transmission. If they've already degraded the signal enough, you could make the output stage of the 6000 even worse and still not notice any difference. Likewise, making it better wouldn't net any perceptible improvement either. An enhanced output stage can only preserve quality that's there to begin with.

This kind of BS attitude makes me wonder why I spend my time here. I'd apologize for the misunderstanding, if I could conceive of any way it could be interpreted in a disparaging manner. I thought we were having a cordial and professional engineering-level discussion.

- Tim

totally untrue, the 6000's output is total garbage, the newer receivers like the 942 totally destroy the 6000 output(total night and day difference), the 6000 is severly filtered and looks downright awful compared to the 921 or 942

also

Dish Networks HD(excluding the 15 Voom channels, due to fibre problems) is true 1920x1080i HDTV

including:

HDNet
HDNet Movies
Showtime
HBO
PPV
TNT
Discovery
Universal HD
Demo channels
CBS West

the 6000 could be improved by leaps and bounds and Dish's HD signal is the best out there from sat providers(compared to Directv's 100% 1280x1080i HD-Lite garbage)

-Gary

totally untrue, the 6000's output is total garbage, the newer receivers like the 942 totally destroy the 6000 output(total night and day difference), the 6000 is severly filtered and looks downright awful compared to the 921 or 942

also

Dish Networks HD(excluding the 15 Voom channels, due to fibre problems) is true 1920x1080i HDTV

including:

HDNet
HDNet Movies
Showtime
HBO
PPV
TNT
Discovery
Universal HD
Demo channels
CBS West

the 6000 could be improved by leaps and bounds and Dish's HD signal is the best out there from sat providers(compared to Directv's 100% 1280x1080i HD-Lite garbage)

-Gary

Hey Gary,

Haven't seen you posting in here for a while. How do you like the Mits??

I couldn't be happier with mine. Probably the best television I ever laid eyes on.

Cliff

What you think the original filters were left in, yeah okay, not qiute that stupid thanks. The 4412 was connected directly after the loaded DAC.
Sorry, you're wrong WTS, the VDAC output are not driving the original filters any more since R816/R840/R828 resistors were removed.

Also the original 75 ohms driver IC located on the back panel was disconnected from the Y/Pr/Pb signal paths by the removing of R7121/R7122/R7123 (75R) resistors.

You should have carefully read the step by step procedure ...

John

Hi Videograbber,

Yes and I apologize if I came across the wrong way, it just sounded like you were trying to say the guy who did the original mod and myself didn't have a clue what we were doing because we would have left the original filters in so how would we be able to tell.

Ah, John, not sure what you're talking about, I was referring to the 6000 and not the JVC deck.

Sorry I jumped into your private thread here boys and yes you're right Tim, sometimes I wonder why I come here with all the BS too, thats the reason another long time member(BBlue) left too.

You know Videograbber, sometimes I'd have to agree with you


Gary, now do you know the 6000's output is over filtered, have looked at the filters in the 6000, do you know the design of them etc.

Actually I like coming here and have met alot of great people on this site, but sometimes I can do without some of the crap thats for sure, everybody's an expert and sometimes I'm no different I guess.

I have been hanging out over on the HDTV and Video Processor forums for a while now
Cliff the Mits is treating me very well, Thanks:), I had him fully calibrated to d6500 by CraigR and now have a perfect color decoder :), along with many a mods to reduce all sorts of ringing and such
pretty much a reference display that is more pleasing than my previous tweaked Barco 808s

now if I could get someone like Mike to mod the neck cards(the bandwidth of the Mits 65813 is around 30 Mhz :() then this baby could really really shine and I mean shine bright

1080i scan lines at 12 feet is unreal

The Mits 65813 is the last of the Elite High End CRT RPTV's :(

Walter I am not a EE so I have no way of knowing specifics, but one look at the 6000 paired beside the newer Dish 942 shows a MAJOR difference

no reason to own the 6000 anymore anyway, the 921 has RGBHV output and can be had for 200$ :) and it destroy's the 6000 in picture quality

be careful though Dish going to mpeg4 means these receivers are on their last legs, so only the new guys like the 211 411 and 622 (all have Component and HDMI output, but no RGBHV)
but my display above has a Digital HDCP input so everything is golden, thats one thing I don't miss about the Barco

-Gary

now if I could get someone like Mike to mod the neck cards(the bandwidth of the Mits 65813 is around 30 Mhz :() then this baby could really really shine and I mean shine bright
-Gary

I thought about you some days ago. I too have a Mitsubishi, but it's not the one you guys have. One thing I can say about it for sure, it definitely needs RG59 cables for the best image, if going analog. I too notice some noise, and as soon as i can get around to it, I'm cleaning it up. Already, i see some things that i can improve on.. ;)

Hi Gary,

Yes I was just thinking the same thing as I was reading your post that Dish is claiming that in about a year from now all their present IRDs(mpeg2) will not work. Kinda hard to imagine they could replace 13 million IRDs in a year.
Do you know what video DAC is in the 921, have you ever had the lid off it before, I wonder if its the THS8135A. If you get curious sometime maybe pop off the lid and have a look. So they sell for $200 now, whats it(921) going to be worth in a year when you can't use it, maybe I can use it up here as I don't think ours is switching over to Mpeg4 anytime soon, if you're looking to dump it let me know.

I thought about you some days ago. I too have a Mitsubishi, but it's not the one you guys have. One thing I can say about it for sure, it definitely needs RG59 cables for the best image, if going analog. I too notice some noise, and as soon as i can get around to it, I'm cleaning it up. Already, i see some things that i can improve on.. ;)

Holy Crap Mike, sweet!!
the Mits are very noisy, that is a complaint I have seen even some Joe 6 Packs complain about, it has to be pretty bad ;)

the Mits are also attenuating the signal pretty bad, the set is giving around 1275 horizontal lines on a 1920x1080i test pattern

the 9 inch tubes in my 65813 could really shine with some image cleanup mods, I betcha they could easily do at least 1450 to 1500 lines if the signal wasn't getting trashed

all this and they still look superb

Mike I could probably get a lot of folks together that would be interested in stuff for these Mits

-Gary

Also Walter, Dish will not activate any of the current mpeg2 receivers any longer :(

only one way you can activate a mpeg2 receiver on your account:

if you currently had a mpeg2 HD receiver AND the 9.99 HDTV pack active on your account prior to Feb 1st 2005

if you didn't meet that then you can only acticate a 211 411 or 622 now, Dish is so stupid

-Gary

Back on the original JVC subject ...

The 8 prototypes are now OK for shipping to :

1- Moggy
2-3 mp20748 & Clarence
4- VideoGrabber
5-6 jimwhite (2)
7- Frank D
8- Plexi47

Please contact me by PM to give me the shipping address (Plexi47 already made it).

Remember : the PCB I'll send will be fully components populated (including wires and coax.) but without the ADA4412-3 IC mounted. So you should buy and solder it by yourself, I apologize :o .

Later

John

Remember : the PCB I'll send will be fully components populated (including wires and coax.) but without the ADA4412-3 IC mounted. So you should buy and solder it by yourself, I apologize :o .



WOW, what a great deal. It's already pre stuffed with the most difficult components... the chip is cake.

Excellent work John. thanks big time

Please contact me by PM to give me the shipping address
Thanks John.

Mike, did you send him your address for ours?

Thanks John.

Mike, did you send him your address for ours?


Yeah, we're good!

Yeah Mike,

Got your Paypal money for your module on 3rd of Feb. but still haven't got Clarence's one... :o

Modules to be shipped tomorrow morning as expected :cool:

John

John, what's your paypal address? Send mine to Mike's address... he's already got the chips and I'll take my 30K's to his workshop so he can do the soldering.

No problem Clarence,

That's what I was planning to do.

I MPed you about the paypal infos.

Later

John

Moggy, MP20748, Clarence, VideoGrabber, jimwhite and plexi47 mods were shipped today.

All shipments were made using Registered letters with signatures required to be safe.

Take your time to install the mod and test it deeply !

John

"All shipments were made using Registered letters with signatures required "

arrrgghhhh :eek:..... now I'll have to make a special Saturday morning trip to the Post Office.... nobody's home during the day except the pets.... :(

"All shipments were made using Registered letters with signatures required "

arrrgghhhh :eek:..... now I'll have to make a special Saturday morning trip to the Post Office.... nobody's home during the day except the pets.... :(

Then let yours go back, I'll take it. :D

"arrrgghhhh :eek:..... now I'll have to make a special Saturday morning trip to the Post Office.... nobody's home during the day except the pets.... :(
Then, teach your pets to sign for u :D

Sorry for the trouble :o

John

Just received the board.
Congrats to John for the impressive layout and realization.
Now I've to find a source for the chip :rolleyes:
John any hint here in Europe?

Mauro