Shadow detail/gamma enhancement for the analog sources - Page 7 - AVS Forum
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post #181 of 492 Old 10-01-2005, 08:49 PM
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I hate to lumber into this delicately technical thread with a blunt observation, but there are likely tons of people out here who would love to have what this is, but don't fully understand WHAT it is !
Is this a device which goes between source and projector to give physical gamma control ??
If so, then I'm sure every crt projector owner would be interested.
I would, my buddy with a G90 and a Marquee would, another buddy with a few 9500LC's would be interested, but so far, every thing I've read in this thread has been pretty technical.
Where do I sign up for a little gamma box for $35. ?
I have a few NEC ISS switchers, if I could add something to that to provide gamma control, I would LOVE that.
I'm available with my several NEC ISS switchers for beta testing if anyone is making something...
Somebody post a picture of the thing, made up and connected.
A screen shot of its effect would be great too...
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post #182 of 492 Old 10-02-2005, 04:19 AM
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Quote:
Originally Posted by gn2
I hate to lumber into this delicately technical thread with a blunt observation, but there are likely tons of people out here who would love to have what this is, but don't fully understand WHAT it is !
Is this a device which goes between source and projector to give physical gamma control ??
If so, then I'm sure every crt projector owner would be interested.
I would, my buddy with a G90 and a Marquee would, another buddy with a few 9500LC's would be interested, but so far, every thing I've read in this thread has been pretty technical.
Where do I sign up for a little gamma box for $35. ?
I have a few NEC ISS switchers, if I could add something to that to provide gamma control, I would LOVE that.
I'm available with my several NEC ISS switchers for beta testing if anyone is making something...
Somebody post a picture of the thing, made up and connected.
A screen shot of its effect would be great too...
Yes on the physical gamma correction observation. The folks with the G90s may not need this device as the recent model, super-high-end scalers have multipoint gamma.

The cost on the existing design is _not_ $35.00... the bare board is $33.00 and the components and asembly cost will probably at least triple that.
I've got access to a VERY HIGH-END manufacturing site that could stuff a board like this for a few dollars (plus parts cost) BUT the volumes on this will never be high enough for them to even consider this. I've still not seen any respondants here that know of some in-between sized shop that would consider making twenty or thirty of these.
I've got a friend-of-a-friend guy I'm keeping in my pocket who does small volume board stuffing in Michigan. If there is enough interest I may contact him.

I'm working on a smaller, likely SMT version which I intend to be a bit of a universally packagable card... it'll have HD15F _and_ through-hole (for soldering coax) inputs and outputs and at least two power inputs. VGA connectors and power regulators would be optional, depending on whether the installation requires them, and it's my intention to make the card piggyback on an ISS input card, or match the width of the ISS rails so it can sit next to an ISS input card.
I'm not feeling ambitious enough to make this card fit an ISS exactly (with the correct header connector on the back and filler/input plate on the front... Besides, I want this thing to work within a Sony PC-127x switcher also.

And, since I desperately need a few good transcoders, I intend to make this theoretical uber-tse card have that input option, also. Very likely I'll have jumpers or solderstraps to bypass the transcoder-and-linedriver section

Right now I'm evaluating a low-to-mid cost schematic capture program that the average hobbyist in this community can afford (Eagle by CADSoft) hoping that the maintainence of this design will be picked up by others. I, of course, will be releasing everything just as tse has released his brilliant work.
In the way of learning Eagle, I'm redrawing tse's original 2 layer thru-hole design with HD15F VGA connectors. I should be able to push this out this week or next.

As for an ETA on the uber-tse board, I'd estimate weeks at best. There's a lot of conflict for my time lately.

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post #183 of 492 Old 10-02-2005, 06:28 AM
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Quote:
Originally Posted by picree
Sure Chris...assuming we don't need that third one.
Thanks - only if you find you have one spare, of course. No rush, I wouldn't get around to it for a while anyway.

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post #184 of 492 Old 10-02-2005, 01:41 PM - Thread Starter
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Quote:
Originally Posted by picree
I may not be the most experienced in this thread but I can't wait for you guys to decide what to do. Just ordered 3 for $33 from 4pcb.com this afternoon. Best deal I saw.

tse-I may have a few questions about testing/setup and power supplies. I'll PM you if that's OK.

Picree
Picree,

Which revision board did you order? The Rev B artwork is good to go. Rev A will require a jumper to ground pin 5 of the LT1213s. The first Rev will need the Rev A jumpers as well as a jumper to ground pin 1 of the LM311.

Any questions happily answered.

tse
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post #185 of 492 Old 10-02-2005, 02:04 PM - Thread Starter
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Quote:
Originally Posted by jtnfoley
tse (sorry to be a PITA) how about source files? The odds are very good I'll be incorporating your circuit into a larger project (which will also be opensourced and shared here) and I'd like to avoid redrawing.
Which application? I've got PCAD, Protel, PADS, TinyCAD, and another couple of freeware schematic capture apps from board makers.

The schematic capture is with Orcad. They have a demo available on their web site.

The PCB layout is PIA software from www.waldherr.com . There is a demo available there, but you can't do much more than view and print the files.

 

AVS_GAM_DCR_SCH_RevB.zip 23.89453125k . file

 

AVS_GAM_DCR_PCB_RevB.zip 18.21484375k . file
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post #186 of 492 Old 10-02-2005, 07:01 PM
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I used the Rev B. artwork. Thanks.

I'm drawing up a set of questions but will try to do it all in one shot to make it easier for you. Mostly about the IC selections.

Picree
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post #187 of 492 Old 10-02-2005, 08:01 PM
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tse-In doing a take-off I noticed that the schematics only have a total of 5 100 ohm resistors but the silkscreen shows 9.....did I miss something?

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post #188 of 492 Old 10-03-2005, 05:17 PM - Thread Starter
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Nope, I did. Good thing you guys are around to keep me straight. Correct schematics attached.
LL
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post #189 of 492 Old 10-03-2005, 05:31 PM
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Thank you sir. Everything else seems to add up...143 parts on the board and 143 parts on the schematics.
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post #190 of 492 Old 10-03-2005, 08:40 PM - Thread Starter
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Parts list with catalog numbers. Everything ending with -nd is from Digi-Key. All others are Newark. Some searching around could probably save some money but I used the least expensive parts that were easy to find. The LT1213s are terribly expensive and I am looking for cheaper parts.

 

AVS_GAM_DCR_PList_RevB.txt 2.34375k . file
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post #191 of 492 Old 10-04-2005, 09:17 AM
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tse-OMG! :eek:

Is it possible for you to make this ANY easier??? I was in the process of running these down and making a similar list. This is greatly appreciated! Hopefully, those in this thread will find this easy enough that several of these will be made up and tested with different setups!
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post #192 of 492 Old 10-04-2005, 09:20 AM
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Quote:
Originally Posted by picree
tse-OMG! :eek:

Is it possible for you to make this ANY easier???
Someone build the damn box and sell it to us lazy folk!

Dave
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post #193 of 492 Old 10-04-2005, 09:50 AM
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Quote:
Originally Posted by Person99
Someone build the damn box and sell it to us lazy folk!

Dave

:D :D :D :D
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post #194 of 492 Old 10-04-2005, 10:03 AM
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Quote:
Originally Posted by Person99
Someone build the damn box and sell it to us lazy folk!

Dave
Or those of us without the skills to build one. :eek: ;)

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post #195 of 492 Old 10-04-2005, 10:21 AM
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tse-Are C3, C4, and C5 on the Video circuit now 22 uF instead of 10 uF?
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post #196 of 492 Old 10-04-2005, 01:12 PM
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According to a DigiKey tech a couple of alternatives for the LT1213's might be:

DigiKey part no 296-10464-5-ND $2.13 ea

or

DigiKey part no AD823AN-ND $5.00 ea

I have no idea if these meet the specs. tse-any thoughts?
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post #197 of 492 Old 10-05-2005, 06:01 AM
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Quote:
Originally Posted by Person99
Someone build the damn box and sell it to us lazy folk!

Dave
For the non-DIY fraternity keep an eye on this thread:

http://www.avsforum.com/avs-vb/showthread.php?t=588046

Cheers :)

Russ

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post #198 of 492 Old 10-05-2005, 07:46 AM
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FYI to the group-this DIY option from tse prices out almost right at $100 not including any BNC jumpers and any required power supply. I sourced all parts as listed by tse above (DigiKey mostly and Newark). The boards came from 4pcb.com...the 3 for $99 option.

Cost breakdown-round #s:

Circuit board $40
The LT1213 op-amps $20
The BNC connectors $15
Everything else $25
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post #199 of 492 Old 10-05-2005, 07:56 AM
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tse
Would you have a gamma curve graph you could post? Even a hand drawn one is fine by me. I'm interested it comparing it to Benny's mate's design. Is this a black box design? Meaning there's input and output but no on switch, no adjustment knob, etc.? Are there any internal adjustment pots?

picree
Thanks for the price break down. For the BJC jumpers, I assume you mean the short BNC cables needed to hook this thing up. Also, does this include the cost of a case? Now I just need to find me an EE student to build one. :D

Aubrey
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post #200 of 492 Old 10-05-2005, 08:03 AM
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PAW-

BNC jumpers-yes...the four short cables needed to go between this board and the CRT input or scaler output depending upon which end its connected to.

The cost is without a case or the jumpers or a power supply.
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post #201 of 492 Old 10-05-2005, 08:16 AM
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Any comment on S/N for the unit... Like I said previosly, I like the idea of gamma correction, but I'm not excited about putting something in the signal chain that is going to introduce noise.

Brian
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post #202 of 492 Old 10-05-2005, 08:44 AM - Thread Starter
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The caps were originally going to be 10uF but I ran across some 22uF for cheap so I used those. Their value isn't critical and either would work.

The 10uF NP cap used at the input is more critical and some changing of loop compensation might be needed if changed in value.

I haven't tried these but they look good from a spec sheet point of view. MC33077POS-ND for $1.30 ea from Digi-Key. A possible sub for the expensive LT1213s.
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post #203 of 492 Old 10-05-2005, 10:27 AM - Thread Starter
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[quote=PAW]tse
Would you have a gamma curve graph you could post? Even a hand drawn one is fine by me. I'm interested it comparing it to Benny's mate's design. Is this a black box design? Meaning there's input and output but no on switch, no adjustment knob, etc.? Are there any internal adjustment pots?


Attached are curves with two different resistor values in the circuit. There could be pots but I don't think it would be easy to get all three colors to track. By changing fixed 1% resistors in each circuit the tracking will be good. A wide range of responces are possible but it would require changing resitor values.

The R=2.4K curve looks pretty good to me. The other would have the dark details look like you were using night vision equipment.
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post #204 of 492 Old 10-05-2005, 12:01 PM
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OK... soooo.... are we going to be able to get the PCB?? What's the plan on that?

Marc

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post #205 of 492 Old 10-05-2005, 12:08 PM
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Quote:
Originally Posted by Tinman
OK... soooo.... are we going to be able to get the PCB?? What's the plan on that?

Marc
I believe tse has done his part in engineering, debugging, and testing this circuit. I'm in the process of creating a smaller board with VGA HD15F inputs and outputs and incorporating an optional transcoder. (My effort will take weeks at my current pace.)

The community (subscribers to this thread, at least) should arrange a bulk buy and order the boards in quantity.



Picree, care to answer the call? ;)

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post #206 of 492 Old 10-05-2005, 12:30 PM
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Sorry, I already ordered a set of three bds from 4pcb.com last wk. I'm using two (one BNC and one I hope to wire up to VGA) and my neighbor agreed to take one. With shipping they were $38/bd.

Getting three together was easy enough. And the diff in $ wasn't too bad. I think the next price break was something like QTY 10 (was that about $23/bd?)...in case I did something wrong I really didn't want to risk messing up ten (I've never ordered from 4PCB before)....

Uploading the Rev B files posted above to 4pcb.com was very easy. A larger bulk order of 10-20 bds should be by someone with a little more experience than me just in case anything comes up. :)

If someone ran out ALL the cost savings ideas here (bulk buy, cheaper op-amps, VGA instead of BNC) the cost would be about $60/bd. To me that's close to $100..and I can start on it NOW!..although I'm not rich...I'm impatient! ;)
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post #207 of 492 Old 10-05-2005, 12:48 PM
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There's another inexpensive op-amp option, but I'm too EE-ignorant to know whether it's appropriate for this application. A 3 channel package by National Semiconductor that's marketed as an RGB buffer (the recommended mate to their LMH1251MT transcoder that I hope to use...)
http://www.national.com/pf/LM/LMH6739.html

Related question for tse and the rest of the "real" EE's here... Since the LMH1251MT transcoder can't source much current, National recomends the 6739 buffer. But, it requires a different power supply (10V nominal) than the 1251 or anything in the tse gamma circuit.
Is the tse gamma circuit sufficiently high in impedence to keep the 1251 happy? If I'm reading the spec right, the 1251 chip can only source three mA (per color and per sync pin, apparently.)

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post #208 of 492 Old 10-05-2005, 02:57 PM
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tse and Benny
I'm trying to compare you gamma curve graphs (Benny's is in post #100 of this thread) and I'm confused. Unfortunately, I don't profess to being anything close to an EE. :eek:

tse
- What should the horizontal axis's units of measurement be?
- Why are there two units of measure on the vertical axis?
- In the actual graphed lines, what do the horizontal sections mean?

Benny
- What are the horizontal and vertical units of measurement?
- This is not graph related but I know the gamma correction is adjustable. Is it a single adjustment or an adjustment for each color (RGB)?

tse and Benny
tse's 2.4K graph looks pretty similar to Benny's red line in his graph. The "hump" in Benny's red line looks to be a little thicker and higher up the graph. I assume this means that Benny's box produces more gamma correction and higher up in the IRE range? I also noticed that tse correction curve tapers off quicker. I guess this means less correction higher in the IRE range? Benny I understand a secondary benefit of your box is to boost the entire range. To help PJs that want a slightly stronger signal.

Thanks for entertaining my questions.

Aubrey
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post #209 of 492 Old 10-05-2005, 03:07 PM
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Benny's adjust the whole gamma curve. The same as if you have gamma in a DVD player and adjust it +1, +2, etc. tse's is designed to address a very specific CRT "problem". tse is remapping the gamma primarily in the lower IRE such that a black out screen can be absolutely pitch black and you can still have excellent shadow detail in the lower IRE range. He only effects the upper portion of the curve for a natural transition.

At least, that's my take. :)

Dave
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post #210 of 492 Old 10-05-2005, 07:06 PM - Thread Starter
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Quote:
Originally Posted by Person99
Benny's adjust the whole gamma curve. The same as if you have gamma in a DVD player and adjust it +1, +2, etc. tse's is designed to address a very specific CRT "problem". tse is remapping the gamma primarily in the lower IRE such that a black out screen can be absolutely pitch black and you can still have excellent shadow detail in the lower IRE range. He only effects the upper portion of the curve for a natural transition.

At least, that's my take. :)

Dave
You have it exactly right. I am only interested in boosting the dark image detail to the point where you can set your brightness control for black output with black input and still see detail in the shadow areas.
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