Zenith (LG) DTT900 CECB - Page 37 - AVS Forum
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post #1081 of 2451 Old 04-24-2008, 05:59 PM
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Originally Posted by wh5916 View Post

Rex, the converter is very simple to open. Only a few screws hold the cover in place, and once they're removed the cover slides off with just a minimal amount of effort.

The part/revision number for the main board is printed in white block lettering in the upper left hand corner, if the converter is face up with the rear panel pointed towards you.

Ok, here are the numbers I see in the upper left hand corner...

LSX300-4DM
EAX39807102-0711

Hope those are the numbers you were looking for

R. B.
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post #1082 of 2451 Old 04-24-2008, 06:00 PM
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Originally Posted by mrvideo View Post

Also interesting that no one uses 8T-VSB to describe ATSC. I've only ever seen 8VSB.

Yeah, you might occasionally see a reference to it in a non abbreviated fashion as "Trellis Coded 8-Level Vestigial Sideband" though ...

Not sure, but don't think many applications, if any are using any of the various modes besides 8T-VSB - at least here in U.S. If there are any applications using some of the others, my best guess might be their useage may be quite limited. Just a guess, but Perhaps that, and since 4 letter abbreviation is shorter than 5 is why we usually see 8T-VSB referred to as 8VSB .... Heck, I usually use that abbreviation as well, even though I'm aware there is 8VSB mode possible without the trellis-coding ....

16-VSB (payoad rate= 38.57Mb/s - SNR required = 28.3db) is also accepted for use(such as for digital cable) by ATSC. However, I don't think anyone uses it, either, at least in U.S. where digital cable uses QAM, usually QAM256 I think ... Also notice that from what I can recall it seems the 16-VSB section of the newer ATSC A 53 documents are "shortened" from what they used to be ....

Which reminds me, in addition to the srignoli/Zenith paper mentioned by others ... Those interested in the details of our "DTV standard" may also want to refer to the ATSC A 53Note: A 53 Part II decribes the RF/transmission system, including 8T-VSB, or 8VSB "for short") and A54 Documents here -- Do note that E8-VSB (E-VSB) has already been added to the standard, but I don't know if anyone is actually using it, if not perhaps they're waiting for M/H or A-VSB :

http://www.atsc.org/standards/a53.html

I've found the paper here quite informative as well :

http://www.broadcast.net/~sbe1/8vsb/8vsb.htm

And then there are other "items" of interest as well, such as ATSC's A65C PSIP standard (which can be found from here, along with all other ATSC published standards :

http://www.atsc.org/standards.html


And don't forget the ATSC recommended practices (such as A74 - Receiver Performance Guidelines), which are "used" for the CECB's :

http://www.atsc.org/standards/practices.html

And lastly, the ATSC candidate standards -- perhaps we might see somthing "new" here soon, if not in the "published" standards regarding M/H (mobile handheld), A-VSB, or ATSC 2.0 :

http://www.atsc.org/standards/candidate_standards.html

Note --- there is also an interesting Zenith/Sringoli paper from the late 90's which includes lots of great info on the transmission system, results from field tests, info on receiver performance/design which used to be on ATSCForum website, as I recall that's where I had downloaded it from -- It might be somewhere on the Zenith site as well, but not sure ....

Update :

Quote:
Originally Posted by hphase View Post

Read and "learn how things work."

Excellent advice, IMO ... if only more folks would understand the wisdom of it vs. 1). "skim a little", 2.)"don't think too much about it", 3.) post ... Some posts even seem to involve the reverse order of those, or a combination of #2 and #3 "all at once", or just #3 ....

Jeff
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post #1083 of 2451 Old 04-24-2008, 06:01 PM
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Originally Posted by girdnerg View Post

I have a lot of multi-path problems and was really impressed by how much better the Insignia handles it. I've been thinking about getting the samsung to replace the tuner in my Sony tv, but didn't know how well the samsung would do. All the reading about what gen receiver is in what box doesn't really help me since I can't determine which tuner is in the tv, but a real-world comparison like yours is very helpful.

Are you saying that the samsung's reception is as good as the zenith?

Thanks,
Rob

In my case, yes. But, I only have one station that is weak, and neither box will bring it in, though both detect some signal. I tested by rotating my antenna away from some of the the strong signals and seeing when the boxes lost signal. Pretty much identical results.
I can't test for multi-path, since that's not much of an issue in my exact location.
It never hurts to try the Samsung, you can always return it if you don't like it.

Enjoying crystal clear TV for free.

http://www.fcc.gov/mb/facts/otard.html
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post #1084 of 2451 Old 04-24-2008, 06:02 PM
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Quote:
Originally Posted by mrvideo View Post

Because everyone's hearing is not the same and also because the equipment being used to provide the audio isn't the same either, the best way to test this problem is to capture some of the audio output on a computer.

Here is what I propose:

1) Connect the CECB to the line input of a computer (do not go through any other pieces of active audio equipment).
2) Capture 30 seconds of Brian Williams during NBC Nightly News. (The original audio capture that started this thread was from that broadcast).
3) Post the 30 second stereo wave file (do not compress it), or provide a link to where it can be downloaded from.
4) Provide the info as to brand and model of the unit under test.

I'll then take that audio and FFT it and post images of the result.

As a control, I'll capture audio tonight using my MyHD130a OTA card and post that as a control image.

This should help prove what is going on with these boxes.

It took some furniture moving, but I wrestled the Zenith from its normal home in the den and moved it in here temporarily this evening. An RCA to mini plug cable was used to connect it directly to my system's audio card, and Wavelab's capture function was used to create uncompressed waves.

In the interest of proving that this issue isn't simply limited to NBC Nightly News, below are links to four 30 second clips, from three different stations. Left and right tracks have not been isolated this time as different waves--these are stereo tracks, taken straight off of the Zenith DTT900 (February 2008 manufacture date, the second Zenith I've had--this one was an exchange, and is not the converter that was used to create the first clip that was posted a few weeks back). Each was edited down to roughly 30 seconds, but at no point were these files saved as anything other than waves.

Also in each zipped folder is a spectrum editor display of that folder's corresponding audio clip. The "chirping" anomaly shows in each display as sort of a band of bright turquoise, in the left channel only, above 11 Khz in all but one of these clips. In one clip, taken from the QUBO channel for kids, the turquoise banded area is oddly somewhat below 11 Khz.

Here's the first clip, NBC Nightly News (WAVY, Channel 10 in Norfolk, VA):
http://www.mediafire.com/?i2bvjsx1gyy

Here's the second clip, WAVY local news, weather excerpt:
http://www.mediafire.com/?b2mnzyddbqx

Here's the third clip, from NewsHour with Jim Lehrer (WHRO, Channel 15 in Norfolk/Hampton, VA):
http://www.mediafire.com/?xmtb52j25lv

Finally, a clip from QUBO (WPXV, Channel 49, in Norfolk, VA):
http://www.mediafire.com/?uz2zyx6zdtz

The QUBO excerpt isn't quite as audible to my own ears. For starters, much of it is music, and this issue seems more noticeable with voice. The QUBO excerpt is also different from the other three in one other respect, as mentioned above--the left channel oddity is noticeably lower in frequency, as visible on the spectrum display.
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post #1085 of 2451 Old 04-24-2008, 06:14 PM
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Originally Posted by dattier View Post

Thanks for the details; I was going to ask you for them either in a PM or in the Chicago OTA thread.

Would you mind if I quoted your post into that thread and responded there?

Feel free to post there.

R. B.
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post #1086 of 2451 Old 04-24-2008, 06:46 PM
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Quote:
Originally Posted by retromzc View Post

Ok, here are the numbers I see in the upper left hand corner...

LSX300-4DM
EAX39807102-0711

Hope those are the numbers you were looking for

Yes thanks.

I guess that means that the SoC (black thing toward the middle) reads LGDT1111D on yours?

Suppose we will have to wait for the DTT901 revision for something new, but you guys are lucky that your affiliates seem to sound OK with this box.
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post #1087 of 2451 Old 04-24-2008, 07:35 PM
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Originally Posted by retromzc View Post

Ok, here are the numbers I see in the upper left hand corner...

LSX300-4DM
EAX39807102-0711

Hope those are the numbers you were looking for

Rex, thank you. I'm more puzzled than ever by the second number, since the one on my February 2008 converter is EAX39807102-071128...unless the last couple of digits indicate some type of plant ID.
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post #1088 of 2451 Old 04-24-2008, 08:00 PM
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Quote:
Originally Posted by gerty112 View Post

Is the cable run to the other room much longer? Is there a splitter (thus signal loss) involved?

When one of my sets was getting more channels than another from the same antenna, I traced it to a higher-loss RG-59 coaxial cable going from the distribution amp/splitter to the other set.

When I replaced it with a shorter length of higher-quality RG6 cable, problem solved.

I have fringe reception and the DTT900 receives everything my Sony S3000 and EyeTV 250+ tuners do; if there is a drop out, all three drop out at the same instant, so there doesn't seem a great difference in those tuners given the same source and cabling.


Thanks for your suggestions!

I spent more time looking at the problem today and discovered a bad connection behind the wall plate. Now everything works great with the same channels as the TV.

So far I like how the Zenith box works and haven't noticed anything wrong with the sound. It has a March 2008 date on the box, and is connected to an older good quality stereo sound Zenith TV with the AV out connection. One thing I don't like is the remote because it looks and feels cheap.

On the way home I stopped at Radio Shack to look at the DS box in case the Zenith didn't work out. The salesman was utterly clueless about OTA digital. He said you don't need to buy the box right now because it will just be sitting collecting dust until Febuary. When I told him I'll use it right away and that I've already been watching digital for 1 1/2 years on my other set he seemed surprised that it was already operating. They also said they would not re-ring the initial purchase with the coupon after purchasing the box to try it out like CC will do.
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post #1089 of 2451 Old 04-24-2008, 08:24 PM
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Quote:
Originally Posted by mrvideo View Post

As a control, I'll capture audio tonight using my MyHD130a OTA card and post that as a control image.

OK, here is the control that I captured during the NBC newscast. It is 24 seconds of audio.

The wave file and PNG image of the FFT is in this zip file.

"What do you say Beckett. Wanna have a baby?" - Castle to Det. Beckett
"How Long have I been gone?" Alexis after arriving home and seeing Castle and Beckett w/ the baby - Castle - 11/25/13
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post #1090 of 2451 Old 04-24-2008, 09:03 PM
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Quote:
Originally Posted by wh5916 View Post

The QUBO excerpt isn't quite as audible to my own ears. For starters, much of it is music, and this issue seems more noticeable with voice. The QUBO excerpt is also different from the other three in one other respect, as mentioned above--the left channel oddity is noticeably lower in frequency, as visible on the spectrum display.

Thanks for doing this, members of the forum will appreciate it.

The QUBO audio was definitely annoying.

I did FFTs (which makes the problem so much easier to see) of the four audio files and placed the images in this zip file.

Now we need samples from the March dated units. All indications, so far, are the fix isn't in that box either. But that needs to be proven.

"What do you say Beckett. Wanna have a baby?" - Castle to Det. Beckett
"How Long have I been gone?" Alexis after arriving home and seeing Castle and Beckett w/ the baby - Castle - 11/25/13
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post #1091 of 2451 Old 04-24-2008, 09:06 PM
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Quote:
Originally Posted by KenL View Post

Suppose we will have to wait for the DTT901 revision for something new, but you guys are lucky that your affiliates seem to sound OK with this box.

We need audio samples

"What do you say Beckett. Wanna have a baby?" - Castle to Det. Beckett
"How Long have I been gone?" Alexis after arriving home and seeing Castle and Beckett w/ the baby - Castle - 11/25/13
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post #1092 of 2451 Old 04-24-2008, 09:28 PM
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Quote:
Originally Posted by kz1000s1 View Post

On the way home I stopped at Radio Shack to look at the DS box in case the Zenith didn't work out. The salesman was utterly clueless about OTA digital. ... They also said they would not re-ring the initial purchase with the coupon after purchasing the box to try it out like CC will do.

You really ran into some bad luck there.  When I bought my Zenith DTT900 at Radio Shack, the salesclerk understood perfectly about exchanging it for itself to use the coupon, and when I went back to do it the manager happened to take care of me, and he knew exactly how to handle it.  That salesdroid you got was a real dud.
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post #1093 of 2451 Old 04-24-2008, 11:42 PM
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Nightwatchman:
You probably are looking for fol. Sgrignoli paper (1999, so take it with a lump of salt):
http://www.zenith.com/digitalbroadca...x%20Design.pdf

And here's Zenith link to Nov2003 ATSC Seminar Tutorial (525 Vugraphs) for the UbberGeek:
http://www.zenith.com/digitalbroadca...r%20Slides.pdf
and Appendix (your gonna need some more java.....):
http://www.zenith.com/digitalbroadca...20Appendix.pdf

FYI: Zenith website entry point is:
http://www.zenith.com/index.asp?url=/digitalbroadcast/
Click on "Trade Shows and Seminars".
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post #1094 of 2451 Old 04-25-2008, 02:21 AM
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Originally Posted by justdigitalized View Post

Here is the final resolution of this problem.

I will say that LG's service was great. They mailed a pre-paid Fedex shipping label in less than 5 days and all I had to do was phone Fedex for pick-up at the house. In fact they picked up the day I called. Yesterday LG shipped me a replacement converter box. Turnaround was about a week. The box they shipped was brand new in factory packaging with a label that said, "Swap Buffer". As I had suspected this seems to be a known problem that LG is fixing by exchanging boxes only for those who complain. The constant hiss at any volume is gone but I still can only adjust the TV volume to a certain level before the speakers hiss, so a balance between box volume and TV volume must be found between loadness and hearing range - if that makes any sense. There is no TV hiss when the box is disconnected and I'm on regular TV. Other than the speaker thing I like the Zenith. Getting way more DT channels than analog and reception is great.

I will try another brand of box next and do the purchase/try/return/apply coupon routine just to make sure there are no problems.

Well actually there is NO final resolution yet. After having the replacement box for about a week now the hiss is turning out to be worse than the original. This is three bad boxes so far. Because programs are broadcast at different sound levels I find I have to increase the TV speaker volume and so I get more speaker hiss. In some cases I can hear the hiss when the program sound at a quiet moment. From reading the posts it seems a box with a March 08 build date is NOT having any speaker hiss problems? Can someone confirm this? There don't seem to be a lot of hiss complaints on this forum so either most users of this box are deaf or this area was shipped a batch of bad boxes. But even the replacement produces the hiss. I bet no one at LG even tested the returned box, they just set a replacement.

I contacted LG again but I don't have a good feeling about getting this fixed. At least I can eat up their profit in shipping charges. My recommendation for now is DON'T BUY THE DTT900.
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post #1095 of 2451 Old 04-25-2008, 05:36 AM
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Quote:
Originally Posted by mrvideo View Post

Thanks for doing this, members of the forum will appreciate it.

The QUBO audio was definitely annoying.

I did FFTs (which makes the problem so much easier to see) of the four audio files and placed the images in this zip file.

Now we need samples from the March dated units. All indications, so far, are the fix isn't in that box either. But that needs to be proven.

Thank you, I'll be downloading the images in a moment.

The QUBO audio was the only digital subchannel that I captured sound from--perhaps this explains the lower frequency where the issue was observed?

This morning, reception conditions brought in stations from Richmond VA, roughly 70 miles away, providing an opportunity to compare audio from their major affiliates with those of the Norfolk VA affiliates. Of the three major networks, all of which were airing their morning shows at the time, the left channel issue was plainly audible on both the Norfolk and Richmond affiliates.
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post #1096 of 2451 Old 04-25-2008, 05:56 AM
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Originally Posted by mrvideo View Post

OK, here is the control that I captured during the NBC newscast. It is 24 seconds of audio.

The wave file and PNG image of the FFT is in this zip file.

What a difference! If I wasn't fully convinced before that this is a problem that lies with the Zenith converter, I'm convinced now.
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post #1097 of 2451 Old 04-25-2008, 07:07 AM
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Originally Posted by kz1000s1 View Post

On the way home I stopped at Radio Shack......... They also said they would not re-ring the initial purchase with the coupon after purchasing the box to try it out like CC will do.

How about just returning it and purchase another box with the coupon? They have a 30-day satisfaction guarantee online. I doubt it would be different in store.
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post #1098 of 2451 Old 04-25-2008, 07:58 AM
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Quote:
Originally Posted by wh5916 View Post

The QUBO audio was the only digital subchannel that I captured sound from--perhaps this explains the lower frequency where the issue was observed?

It is still AC3 audio, with full audio bandwidth capabilities. You'll notice that the NBC news also had a sharp dropoff long before 20 kHz. No idea why the bandwidth is limited.

EDIT: Oops, that should be 16 kHz rolloff.

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post #1099 of 2451 Old 04-25-2008, 08:00 AM
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Quote:
Originally Posted by wh5916 View Post

What a difference! If I wasn't fully convinced before that this is a problem that lies with the Zenith converter, I'm convinced now.

Yep, major difference.

IMHO, these units should be recalled, and everyone given their coupons back, or a Zentih credit for a replacement when it finally comes out.

"What do you say Beckett. Wanna have a baby?" - Castle to Det. Beckett
"How Long have I been gone?" Alexis after arriving home and seeing Castle and Beckett w/ the baby - Castle - 11/25/13
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post #1100 of 2451 Old 04-25-2008, 09:08 AM
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Originally Posted by mrvideo View Post

Yep, major difference.

IMHO, these units should be recalled, and everyone given their coupons back, or a Zentih credit for a replacement when it finally comes out.

I haven't plugged it in yet, but in front of me is a Zenith converter, exchanged at Circuit City awhile ago. This one has a March 2008 manufacture date, but the main circuit board # and LG chip # are identical to the previous two boxes--so I'm not holding out a lot of hope.

I only see one difference--the previous two had the combination Sanyo tuner/RF modulator, and this one has an LG tuner/modulator. Very shortly, I'm going to try it out. The Sanyo's RF output was decent enough to be viewable, with minimal snow, on the portable set in this bedroom, even with a lengthy run of RF cable under the house. I hope the LG tuner/modulator will perform as well.

***update*** There's no audible difference in the replacement converter. The left channel problem was quickly spotted on a local newscast. At least there seems to be no difference in performance with the LG combination tuner/RF modulator as opposed to the Sanyo. The portable set in this bedroom is still receiving a more than decent image, with only a minor amount of visible snow, in spite of the lengthy run of RF cable that it's receiving the signal from. In terms of signal strength compared to the Sanyo, I don't see any difference either.
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post #1101 of 2451 Old 04-25-2008, 09:45 AM
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Given the level of analysis and sensitivity to sonic issues, let me as if anyone's finding an issue with missing low-end when they hear the sibilance? I have a DS DTX9900, but with same LG SoC and Sanyo tuner, and I hear the sibilance, but I really notice the low frequency loss.

mrvideo's FFTs use a linear scale, but I see significant differences at the low end; QUBO's commercial is the only one that doesn't take a dive at the left.

Any chance you can show the spectra on a log-frequency axis? It'll make the sibilance harder to see in the curve, but it will also give high's the proper (small) proportion of the spectrum.

By the way, my comparisons are to a Sony XBR970 CRT tuner with all sound (TV and DTX) output to a surround sound system, and a splitter in the antenna feed so each gets the same signal. (YEs, I swapped inputs with no change).

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post #1102 of 2451 Old 04-25-2008, 09:59 AM
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Quote:
Originally Posted by holl_ands View Post

Nightwatchman:
You probably are looking for fol. Sgrignoli paper (1999, so take it with a lump of salt):
http://www.zenith.com/digitalbroadca...x%20Design.pdf

Yes, that was it. Thanks for posting it and the add'l links. I have it archived here on a CD or DVD from when I downloaded it from ATSCforum(along with a slideshow that went along with it) years ago, but couldn't find a URL for it ...

It is old, but still interesting .... I'd especially like to see some newer comprehensive field test data like that ....

Quote:
Originally Posted by mrvideo View Post

Yep, major difference.

IMHO, these units should be recalled, and everyone given their coupons back, or a Zentih credit for a replacement when it finally comes out.

I tend to agree. It seems these days, you never know what your going to get with consumer electronics equipment, regarding issues such as this, and that's not a good thing like it is with "a box of chocolates" .... As another example, In short, I explained and detailed(examples provided in comparision to caps from ATSC TS captures from a PC based ATSC capture card) an issue involving improper black levels from the internal ATSC/QAM "source" involving two different models of recent DVD/HDD recorders(Mfg by funai) with internal ATSC receivers (including involving tests of 3 different units) In following post and the one immediately preceeding it :

http://www.avsforum.com/avs-vb/showt...5#post12876145

Also, I'm not sure if this has been mentioned before ... A comparision I tried which I found interesting regarding the Zenith DTT900 audio was using the same sources -- i.e. broadcast stations, didn't matter which one I tried and whether it was a DD 2.0 vs DD 5.1 source/etc, I didn't go through all of them in my area however) --- involving comparing the audio quality from stereo line out(RCA jacks) from the Zenith DTT900 with a (analog - RCA jacks) Stereo Line out from another STB I own, a ZenithHDV420 OTA HD receiver .. (same audio amplifier/speakers were used) ...

this was several weeks ago I did this, but Just using my subjective "ears", Oddly enough it wasn't so much "missing low-end" frequencies that I recall noticing(and including right OR left channel audio, including from any source I tried) --- in addition to easil;y apparent sibilance issues on left channel from the DTT900 (again in all cases, with all sources/station) --- It seemed to me mid-High, and High range frequencies from the audio output from the DTT900 sounded very "tinny" me in comparision to the audio from the HDV420channel ....... Perhaps the best way I can think of to describe it, Kind of like comparing digital audio sampled at 48 kHZ vs. digital audio sampled at some, significantly lower rate ...

Note these comparisons I did included music programs, and I'm not so sure this is noticable just with, for instance, Brian William's voice ....

Jeff
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post #1103 of 2451 Old 04-25-2008, 11:44 AM
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Originally Posted by fbov View Post

Any chance you can show the spectra on a log-frequency axis? It'll make the sibilance harder to see in the curve, but it will also give high's the proper (small) proportion of the spectrum.

I can do that. I didn't like the way the log images looked, as it placed the bulk of the FFT data in the low frequency range covering a majority of the display. Since the problem is with the 11 kHz area, I didn't want to display it all crunched on the right.

Small portion would be correct

Is there a problem with the low end that you are looking for?

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post #1104 of 2451 Old 04-25-2008, 12:03 PM
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Quote:
Originally Posted by Nitewatchman View Post

Note these comparisons I did included music programs, and I'm not so sure this is noticable just with, for instance, Brian William's voice ....

Even with just Brian Williams voice, the audio problem is quite audible. If you look at the waveform in an audio editing program, before doing the FFT, you could see that there was something wrong, as there was one location in the file that had a peak spike near 0db, which the rest of the audio was around -12db. When you played that section, the words used drastically tripped up the problem in the receiver.

This is a drastic design flaw that should have been caught in the lab, let alone turned into a product.

Since LG appears not want to recall these things containing their screwed up chip, the FTC should get in the loop and force the issue.

I'm getting ready to send my U.S. Senator physical mail, complete with images, reference to this thread, to try and get something done about this. People are using their CECB non-replaceable coupons on junk that they don't know is junk and just might believe what they are hearing is the way digital TV is supposed to sound like.

I only have about a month left on my two coupons. While lots of boxes have been approved, try and find all those boxes in the brick-n-mortar stores. It seems, unless I am reading the threads wrong, that the majority of boxes in the stores are based on the LG chips.

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post #1105 of 2451 Old 04-25-2008, 12:27 PM
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Quote:
Originally Posted by mrvideo View Post

Even with just Brian Williams voice, the audio problem is quite audible. If you look at the waveform in an audio editing program, before doing the FFT, you could see that there was something wrong, as there was one location in the file that had a peak spike near 0db, which the rest of the audio was around -12db. When you played that section, the words used drastically tripped up the problem in the receiver.

Yes, absolutetly. I believe in the context you used it for, You're taking the comment of mine which you quoted out of context. I wasn't referring to the so-called "sibilance" left channel issue, which is even obvious to my ears with any audio+source I've checked it with, including just Brian Williams voice.

Instead, I was talking about apparent reduced response in audible higher frequencies with the DTT900 audio in (subjective - which I noticed using my "ears" only) comparisions I had done vs. analog audio output of another model DTV receiver.

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post #1106 of 2451 Old 04-25-2008, 01:20 PM
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Quote:
Originally Posted by Nitewatchman View Post

Instead, I was talking about apparent reduced response in audible higher frequencies with the DTT900 audio in (subjective - which I noticed using my "ears" only) comparisions I had done vs. analog audio output of another model DTV receiver.

To me it would seem that the linear display mode shows higher frequency rolloff than the log display would, which would show problems at the low end a lot easier.

I noticed that the NBC Nightly news tended to roll off real quickly around 16 kHz. This would be real hard to see in log mode.

Am I way off-base somewhere?

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post #1107 of 2451 Old 04-25-2008, 01:41 PM
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Aussie comparison tests (e.g FACTS, 1998):
http://happy.emu.id.au/lab/info/digtv/files/

Brazil comparison tests (e.g. ABERT/SETS, 1999):
http://www.sbc.org.br/bibliotecadigi....php?paper=626
http://www.set.com.br/artigos/testing.pdf
http://www.itu.int/ITU-D/pdf/3888-06-en.pdf

========================================
The above reports explain why most of the world chose DVB-T
(using COFDM modulation) rather than the more "efficient" ATSC:
http://www.dvb.org/technology/fact_s...Sheet.0408.pdf
http://www.dvb.org/about_dvb/dvb_worldwide/

Obviously, there are PROs and CONS to each system:

DVB-T (COFDM):
1. Flexible modulation structure can trade off data rate/robustness.
2. Designed to works in cars, buses, trains and handheld (DVB-H).
3. Designed to work with distributed, lower power transmitters in a
Single Frequency Network (SFN)....on-channel repeaters save spectrum.
4. Apparently easier to build multi-antenna receivers with optimized,
adaptive equalized MRC (Maximal Ratio Combiner) techniques.

ATSC (8T-VSB):
1. Only waveform available at time of above tests was 8T-VSB.
2. E-VSB, A-VSB and MPH enhancements are still under development
to support mobile and handheld applications....ETD Feb2009....
3. Distributed Transmitter (DTx) enhancement in development, but
may (probably will) cause problems to older receivers.
4. Not as susceptible to impulse noise in the VHF band.
5. Was more "efficient", requiring lower power transmitters for
the "same" coverage area (at least using late-90's receivers).
6. U.S. owned the Intellectual Property (IP) rights at the time
(subsequently sold for a healthy profit to LG of Korea.)

The U.S. (and a few other countries) chose ATSC, primarily due to
being more "efficient" (and profits stayed in the good ol' USA).

More info re ATSC Choice:
http://www.atsc.org/news_information...-PerfComp.html
http://www.atsc.org/news_information...mments-eng.pdf
http://www.fcc.gov/Bureaus/Engineeri...s/dtvreprt.pdf
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post #1108 of 2451 Old 04-25-2008, 01:57 PM
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Quote:
Originally Posted by mrvideo View Post

I noticed that the NBC Nightly news tended to roll off real quickly around 16 kHz.

Is this considered a problem? How much information would you expect there to be above 15k, and would it be audible?
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post #1109 of 2451 Old 04-25-2008, 02:25 PM
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Quote:
Originally Posted by mrvideo View Post

Am I way off-base somewhere?

I'm confused concerning what exactly you are reffering to in any given case when you refer to "the audio problem" with this receiver -- Involving whether you are referring solely and specifically to the Left channel "sibilence" issue, vs. if/when you are reffering more generally to an issue(or as a seperate "issue") as it also may effect both right and left channel audio, presumably involving lack of response at certian frequencies, as compared to say, your MyTV card audio captures ...

For instance, you said :

Quote:


Even with just Brian Williams voice, the audio problem is quite audible.

What I was saying is, if you listen to a musical performance, particular frequencies/harmonics are involved which produces the timbre("unique sound") of certian specific musical insturments(harmonics and not just the fundamental frequency are involved) ---- Certian sounds involving certian frequencies involved as produced by various musical instruments, sound "tinny" and "unnatural" to me via my DTT900's line audio output, even via the RIGHT channel output vs. the same sound via. analog audio output on other DTV receivers I own .....

And, what I was saying, This issue, specifically is not really noticable to me(or more difficult to notice) while merely listening to the "timbre" of someone's, single voice, regarding the frequencies involved ... It's not like for instance, Brian Willams voice sounds like it's coming over a AM radio broadcast, or over a telephone line, but in the comparisions I noted and described, certian "musical sounds" via the DTT900 *do* sound somewhat like that(OK, not quite that bad, but) to me vs. the analog audio output of other DTV receivers I own ....

From a "listening to it" perspective, This is unlike what I will call the "distortion" heard regarding the "sibilence" issue, which can easily be heard(by my ears anyway, including via some of the audio caps posted in this thread) in left channel during "sss's" etc, including from Brian Williams voice ...

Jeff
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post #1110 of 2451 Old 04-25-2008, 02:35 PM
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Quote:
Originally Posted by wh5916 View Post

I only see one difference--the previous two had the combination Sanyo tuner/RF modulator, and this one has an LG tuner/modulator. Very shortly, I'm going to try it out. The Sanyo's RF output was decent enough to be viewable, with minimal snow, on the portable set in this bedroom, even with a lengthy run of RF cable under the house. I hope the LG tuner/modulator will perform as well.

The portable set in this bedroom is still receiving a more than decent image, with only a minor amount of visible snow, in spite of the lengthy run of RF cable that it's receiving the signal from. In terms of signal strength compared to the Sanyo, I don't see any difference either.

Are you even sure it's the digital signal you're watching? If it is, you can't be seeing snow.
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