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post #1 of 32 Old 10-28-2012, 01:01 PM - Thread Starter
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Ok,
From what I have learned over the years is that HDMI has the highest jitter of any Digital transfer. I'm not sure if thats exactly true or not but it's been said by many people in and out of the industry. So lets take that at face value and talk about it.

HDMI does pass the best sounding home theater experience I have ever heard. True HD and Master Audio sound fantastic and much better then DD and DTS standard formats. These mostly where sent over SPDIF which used a Digital coax or a Optical cable.

Now one could connect his / her Blu ray player up VIA analog and bypass the cleaner connection of a single HDMI. But the real question is does that sound better then using the HDMI?
This is something I never really did a long intensive shootout and now plan on doing so. I'm gonna reconnect my Cambridge Audio BD650 Azur with analog out and HDMI on different inputs and compare for movies.

Now lets talk about audio for music. You got SACD and DVD AUDIO which can't travel over SPDIF so using a optical or coax cable will not work. You either have to go HDMI or analog out. Ok fine , this can be compared once again. The one thing that doesn't make for a fair compare is the DAC. If one DAC is better then the other or you prefer one over the other even with jitter , I'm wondering if one will still sound better then the other? Deeper thinking will the internal DAC of the given player sound better as signal paths are shorter which could result in a jitter free environment . Much to think about when trying to get the best overall performance out of todays formats.

All this thinking or revisiting of comparing is all due to the computer audio thing. From what I have read and learned , using HDMI is the worse possible connection. I would have thought it would have been the best but due to the lack of a single pin for error correction , many issues have been discovered using HDMI as your audio out.
I'm also wondering how much it really effects the sound quality. I guess finding a Blu ray player and a AVR or Pre with the same exact DAC's might get you closer to discovering the true answers to these questions. So if we all have been listening to poor audio quality out of our HDMI outputs , imagine what it should sound like IF there was a way to get it right.
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post #2 of 32 Old 10-28-2012, 02:28 PM
 
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Originally Posted by Mantis10 View Post

Ok,
So lets take that at face value and talk about it.


Now lets talk about audio for music.
Lets not. It's been done already. Read about it instead: http://www.avsforum.com/t/1326576/usb-vs-hdmi-for-2ch-audio-to-receiver
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post #3 of 32 Old 10-28-2012, 02:54 PM
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Originally Posted by diomania View Post

Lets not. It's been done already. Read about it instead: http://www.avsforum.com/t/1326576/usb-vs-hdmi-for-2ch-audio-to-receiver
+1

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post #4 of 32 Old 10-28-2012, 02:54 PM
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Here we go 'round the mulberry bush... tongue.gif
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post #5 of 32 Old 10-28-2012, 03:59 PM
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time to cue up the "almost science" crowd... tongue.gif

mantis, it appears you may have already read some material from that crowd...

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post #6 of 32 Old 10-28-2012, 04:16 PM
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Quote:
Originally Posted by Mantis10 View Post

Ok,

All this thinking or revisiting of comparing is all due to the computer audio thing. From what I have read and learned , using HDMI is the worse possible connection. I would have thought it would have been the best but due to the lack of a single pin for error correction , many issues have been discovered using HDMI as your audio out.

HDMI isn't the worst. Analog as it is generally implemented in home audio with unbalanced RCA jacks has a lot more problems with audible noise.

Jitter is the boogey man of audio. Nobody has a boogey man living under their bed, but lots of young children are worried about it. Audible jitter is about as rare, and a lot of audiophiles including some who should know better, are worried about it.

Show me a magazine or forum post where someone was able to identify jitter due to HDMI in their audio system using a good reliable listening test...

What you can show me is bunch of people, again some who should know better who did sighted, non-level-matched, non time-synched listening evaluations and talked themselves into thinking they have heard jitter.
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post #7 of 32 Old 10-28-2012, 08:52 PM
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When I first set up my system I compared the analog and HDMI connections from my Oppo blind. Every time I thought I had it nailed, the next time I was wrong. End result was I could not tell. I am sure plenty will claim they can, but for me the convenience of HDMI works fine with no audible degradation (to me).

Have fun with your shootout. Make sure it is fair; doing blind or double-blind switching and getting everything perfectly level matched can be quite the pain.

"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley
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post #8 of 32 Old 10-29-2012, 07:01 AM - Thread Starter
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Originally Posted by diomania View Post

Lets not. It's been done already. Read about it instead: http://www.avsforum.com/t/1326576/usb-vs-hdmi-for-2ch-audio-to-receiver
Thanks for the link, it can be pretty tuff to find good links not to mention the hundreds of posts trying to find some good info.
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post #9 of 32 Old 10-29-2012, 07:05 AM - Thread Starter
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Originally Posted by Ratman View Post

Here we go 'round the mulberry bush... tongue.gif
Wasn't looking to dig up some bad feelings here , is this a sensitive topic?
Reason for me even bringing this up is I'm considering replacing my Apple TV 160g music server with a Mac Mini. I was also considering a external DAC instead of going HDMI. I wasn't going to waste the extra money IF I can get it done with HDMI into my Pre. Also considering using software on top of Itunes to correct the output issues Itunes has with locking out into one style output.
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post #10 of 32 Old 10-29-2012, 07:08 AM - Thread Starter
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Originally Posted by ccotenj View Post

time to cue up the "almost science" crowd... tongue.gif
mantis, it appears you may have already read some material from that crowd...
Crowd? I have a very open mind and don't lock into any one crowd. I would like to find the answers to my questions without having crowds argue one point or the other. Facts are facts and thats all I was looking for.
If you know something about HDMI jitter or if it's a non audio issue please you have my full attention.
I'm gonna go check out the link I was given and see what I can learn.
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post #11 of 32 Old 10-29-2012, 07:16 AM - Thread Starter
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Originally Posted by arnyk View Post

HDMI isn't the worst. Analog as it is generally implemented in home audio with unbalanced RCA jacks has a lot more problems with audible noise.
Jitter is the boogey man of audio. Nobody has a boogey man living under their bed, but lots of young children are worried about it. Audible jitter is about as rare, and a lot of audiophiles including some who should know better, are worried about it.
Show me a magazine or forum post where someone was able to identify jitter due to HDMI in their audio system using a good reliable listening test...
What you can show me is bunch of people, again some who should know better who did sighted, non-level-matched, non time-synched listening evaluations and talked themselves into thinking they have heard jitter.
Interesting. I'd like to get into that kind of conversation. Starting with analog , I know there are issues with it , but it can be passed without issues or at least any audible. I have done many listening tests with tons of different analog cables and I know once you achieve the goal correctly , your done. Keeping noise out is the key and passing the entire signal is golden. I'm not one to bash cable brands and people who think any analog cable can get the job done , I want to job done correctly so I can move down the signal chain and make it the best I can. From what I have learned over the years is once the job is done , thats it. I don't care what brand cable gets it done , just get it done.
HDMI I have seen plenty of issues with it with sync problems , extreme high failure rate , super sensitive to voltage spikes of any kind etc etc etc. But I do however love the one cable solution and would like nothing more then to use just HDMI for all signal transfers. But if it's hindering sound quality , which I'm not a fan of , I'd like alternates to get the job done correctly.

Honestly I just want to listen to my music digitally stored and hear what was recorded. However that needs to get done is what I'm after. I get really tired of all the dancing around the actual topic. I'd like to discuss it like civil people , professional or not. Experience to me is gold.
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post #12 of 32 Old 10-29-2012, 08:28 AM
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There is no evidence at all that HDMI connections produce audible levels of jitter. None. You are wasting your time thinking about it.

If you can't explain how it works, you can't say it doesn't.—The High-End Creed

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post #13 of 32 Old 10-29-2012, 08:47 AM
 
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From what I have learned over the years is that HDMI has the highest jitter of any Digital transfer.

If HDMI has enough jitter to be audible, how can it possibly carry the much higher data rate video signals?
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post #14 of 32 Old 10-29-2012, 01:58 PM
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Originally Posted by SAM64 View Post

If HDMI has enough jitter to be audible, how can it possibly carry the much higher data rate video signals?
Are you asking a question or answering it in the form of a question, Jeopardy style? smile.gif

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post #15 of 32 Old 10-29-2012, 03:03 PM
 
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Are you asking a question or answering it in the form of a question, Jeopardy style? smile.gif
Are you bored or warming up for another one of your marketing in disguise?
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post #16 of 32 Old 10-29-2012, 03:07 PM
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^^^

my guess is the latter...

op, get ready for the "almost science" i warned you about,..

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post #17 of 32 Old 10-29-2012, 08:41 PM
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I've decided I am not competent to weigh in on the audibility of jitter, but will note the data/clock path for audio and video is quite different. I am not sure the relative dynamic range nor our sensitivity to the DR of video (too long since I did any video chip design).

"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley
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post #18 of 32 Old 10-30-2012, 06:54 AM
 
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but will note the data/clock path for audio and video is quite different.

The video and audio data are multiplexed and carried by the same TMDS pairs....how are the paths 'quite different'?
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post #19 of 32 Old 10-30-2012, 07:17 AM
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Originally Posted by DonH50 View Post

I've decided I am not competent to weigh in on the audibility of jitter, but will note the data/clock path for audio and video is quite different. I am not sure the relative dynamic range nor our sensitivity to the DR of video (too long since I did any video chip design).

I'm under the impression that the sound portion of am A/V signal being transmitted over HDMI is stored in packets and transmitted digitally interleaved with video. Video is sent a scan line at a time. Digital data for control and audio are interleaved with video data within each line's time slice, generally towards the end of the data for the scan line. Back in the old days we called this the "Retrace period". Storing non-video data in the video retrace period has been around for decades.

http://www.s296576215.websitehome.co.uk/hdmi.html

" A Video Data Period has the data for one video line. During the times between lines and frames the audio is sent in the Data Island Period. Between these the control data is sent in the Control Period. "

IOW each scan line is composed of a Video Data Period, a Data Island Period, and a Control period".

So, at the physical link level the video, the audio, and the control information are sent over the identically same logical path. This path implemented by 4 sets of twisted pair operating in tandem to obtain the desired relatively high bandwidth using fairly ordinary hardware. How confusing can it get? One data stream transmitted over 4 physical paths!

The video, control and audio digital data are transmitted by a means that is similar to what we called Time Division Multiplexing (RDM) back in the old days.

The exposure here is that the audio information is packetized, and its timing is not obvious from the data. When received, the data can be accurately reclocked since we know the exact rate that the samples need to be reconstructed with. The reception process is pretty straight forward, all things considered! That hasn't kept people from doing it suboptimally on occasion. ;-)
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post #20 of 32 Old 10-30-2012, 12:39 PM
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Extra points for looping retrace into the discussion; probably most who have never fiddled with CRTs have no idea where that comes from, let alone blanking and blacker than black signals. smile.gif

I have not reviewed the HDMI spec nor do I have time now; thanks very much for the info, Arny. I was not thinking of the PHY beyond the CDR circuits. I was thinking, and have no idea right or wrong, that clock recovered from the audio bit stream is applied directly to the DAC in many implementations, and that the HDMI jitter spec (being video-centric) was higher than say AES or S/PDIF links. Video clock recovery went into a DSP and video buffer so that jitter on the video signal was less critical. That's based on foggy memory, however, and perhaps the eye is less sensitive than the ear? I do not know.

Only thing I know for sure is that in my system using my ears I could not tell HDMI from analog using musical source material. I did not try with test tones.

My opinion is that wideband random jitter is rarely if ever an issue; deterministic jitter from ISI could be a problem but of course is very implementation-dependent.

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post #21 of 32 Old 10-30-2012, 08:30 PM - Thread Starter
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Thats basically where I'm at with HDMI. If and when I hear any differences good or bad , I'll consider a different transfer means. I'm gonna test the hell out of all connections and see if there is really any audio differences. I don't need test tones or mic's , test equipment to do so. I listen with my 2 ears as they are what I'm gonna use anyway. I''ve done it thtat way since the 80's and I'll continue to do so today.

I've read all the jitter issues with HDMI and I was concerned for a minute. I'm gonna dig in deep and see what turns up. I thank you guys for the replies , keep them coming if anyone has done any testing of their own.
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post #22 of 32 Old 10-30-2012, 10:01 PM
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Ears are certainly the preferred measurement tool so you're on the right track. Just remember that it is unlikely you will obtain useful results without taking care to match levels, remove sources of bias, etc.

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post #23 of 32 Old 10-31-2012, 06:55 AM
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Quote:
Originally Posted by DonH50 View Post


My opinion is that wideband random jitter is rarely if ever an issue;

The science backs you up on that. Random jitter within reason just raises the noise floor. The actual noise floors of real world recordings aren't that tough of a bar to clear.
Quote:
deterministic jitter from ISI could be a problem but of course is very implementation-dependent.

The HDMI-related AVR jitter plots I've seen looks like very spikey or impulsive timing errors that were related to the rate at which audio packets were received. Like all jitter, it can be reduced as low as is desired by buffering and reclocking.

The two most important practical limits on reclocking and buffering are lock up time which is related to when you start receiving the signal or when the signal is interrupted, and latency or delay time.

Thinking about it - impulsive jitter may have an audibility profile that is similar to that of random jitter because they both create jitter sidebands over a wide range of frequencies. Since the energy is spread over so many frequencies the total energy can be relatively high while the individual sidebands can still remain relatively low. Due to masking the ear tends to be most sensitive when the energy is concentrated in a narrow range of frequencies.

Beyond all that, we found that the HDMI-related jitter in AVRs was still below the thresholds that were found by Dolby Labs for highly concentrated jitter at the frequencies the ear was most sensitive to. That's two strikes!
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post #24 of 32 Old 10-31-2012, 09:11 PM
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Thanks! Science I know, acoustics I sort of remember or can look up, what people hear is totally up to them. smile.gif

To your list I would add buffer depth and streaming time; if things get out of synch even a little (and they always do) you will eventually run out of buffer with a continuous data stream. SAS/PCIe etc. standards have hooks to prevent that sort of thing, I assume HDMI does as well.

"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley
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post #25 of 32 Old 11-04-2012, 11:49 PM
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Here is an article I found on jitter as i have been reading up on the topic as well. I had not seen mention of it yet. It is from 2005 so not sure what value it has now.

http://www.wolfsonmicro.com/documents/uploads/misc/en/Jitter_performance_of_spdif_digital_interface_transceivers.pdf
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post #26 of 32 Old 11-05-2012, 02:36 AM
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Originally Posted by mfilippello View Post

Here is an article I found on jitter as i have been reading up on the topic as well. I had not seen mention of it yet. It is from 2005 so not sure what value it has now.

http://www.wolfsonmicro.com/documents/uploads/misc/en/Jitter_performance_of_spdif_digital_interface_transceivers.pdf

The article primarily makes the point that the digital receiver component of a audio DAC or AVR can vastly reduce or for all practical purposes eliminate jitter that has somehow entered its input. This is of course one of the major advantages of digital audio.

Unlike an analog signal, a digital signal can become highly degraded and then be made whole again with a reasonable effort and zero audible effect on the sound quality of any music or other audio signal that it carries.
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post #27 of 32 Old 11-05-2012, 07:17 AM
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Thanks, what peaked my interest was the following points the author made. I did not know however if the subsequent charts and graphs in the article showed where that might become an issue. It seemed he was concerned about it and their products were better and designed to eliminate it. i just couldn't tell if there was anything in there worthwhile as to when it becomes bad enough to be an issue. Here are the quotes.

Jitter can introduce problems in two areas of the audio system – at the digital interface, where it can cause a loss of lock and data corruption; and at the audio converter, where sampling jitter can induce errors, distortion and out of band noise.
It is therefore very important to minimise the amount of jitter created and propagated within a digital audio system. Wolfson Microelectronics’ audio converters are highly insensitive to clock jitter, and the new family of S/PDIF transceivers exhibit excellent jitter performance, as detailed in the remainder of this paper.

and this

DIGITAL AUDIO SYSTEM RELIABILITY
Although problems in meeting electrical specifications such as input sensitivity and output level can cause errors in end applications, it has been found that marginal performance in meeting timing parameters is a much more significant contributor to system failure.
IEC-60958-3/4 and AES3 specify a range of timing parameters, including timing accuracy, intrinsic jitter, jitter tolerance, jitter transfer, phase offset and phase tolerance. While it is likely that the majority of commercially available S/PDIF transceivers will meet the necessary standards, it has been found by experimentation that merely meeting standards is not necessarily enough to guarantee overall system performance and stability.
Variations in the stringency of digital audio interface standards mean that meeting one standard does not guarantee seamless interfacing to other standards. This has been especially significant in the professional domain where many products must support multiple digital audio interface types. It will soon become more important in consumer applications where the digital home will support multiple digital sources running simultaneously, with different timing requirements.
Just as important, it has been observed that jitter, in particular, can cause a significant decrease in audio performance in both the digital domain, and perhaps more importantly, in the analogue domain when the data is eventually converted back into its native form. The effect of jitter in digital audio systems is to reduce the resolution of the audio converter, raising the noise floor significantly. Audibly, this can mean the output signal is much less clean than the original analogue signal, which results in a fuzzy, flat sound.



The reason i started looking into this was in order to know what is the best way to get linear 2ch pcm into my Anthem MRX-300. Presently I have it hooked up via HDMI which works great for bitstreaming multichannel but gives me an odd issue with the Anthem when playing back 2ch pcm from the PS3. In the Anthem, I can turn the sub on or off in the speaker config area. If, while playing two channel pcm over HDMI, I turn the sub off, the overall volume of the unit increase pretty significantly. This does not happen over optical coming from the PS3. It also does not happen over HDMI from a source other than the PS3 although I have only been able to test on my iphone using my HDMI adapter cable. Playing a video on the iphone, the anthem reads 2 channel PCM and the problem does not happen. It must be something to do with my ps3 but i'll be damned to figure out what. Happens on both my fat PS3 and a slim I borrowed.

This issue, (if anyone has any ideas) led me to look to see how optical would compare to HDMI as I assumed it would be worse. That is how I stumbled onto the topic of jitter and HDMI vs Toslink vs coax. My anthem has all 3 but my PS3 only has two;no coax. If I dual output to both HDMI and optical on my ps3, it scales the multi channel bit-stream down to 5.1. I only use 5.1 anyway, but i am not sure yet if there is a performance hit. I'm just starting to try and see if I can even tell the difference between optical vs HDMI. Blind testing is very time consuming and boring done alone. It also means the wife has to be not home smile.gif

I still don't like the fact that something is going on in the receiver and since I can not isolate it. I am not sure what effects, audible or not are getting applied or not applied by the anthems circuitry and software since obviously somethings a muck. I have no problem buying a standalone player to use for audio if it meant better sound quality. And that is where I am at now. Is it worth it? which input? how to know your making a step in the right direction before buying? and how to tell afterwards? smile.gif

Mike
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post #28 of 32 Old 11-05-2012, 12:28 PM
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It sounds like an issue with bass management as implemented by the Anthem unit. If the only difference is volume I would not worry about it (OK, it would probably vex me as well until I knew why). If you only use 5.1 then I would just hook up optical and call it done.

"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley
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post #29 of 32 Old 11-05-2012, 12:38 PM
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Originally Posted by DonH50 View Post

It sounds like an issue with bass management as implemented by the Anthem unit. If the only difference is volume I would not worry about it (OK, it would probably vex me as well until I knew why). If you only use 5.1 then I would just hook up optical and call it done.

I completely concur. There's nothing about how bass management or digital inputs work in general that could IME explain what you are observing. It's a situation that is peculiar to exactly your configuration. So, while it is fun reading generalized articles like the one you cited from Wolfson, its way too general to apply to the weirdness that you are seeing.
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post #30 of 32 Old 11-05-2012, 07:29 PM
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Originally Posted by DonH50 View Post

It sounds like an issue with bass management as implemented by the Anthem unit. If the only difference is volume I would not worry about it (OK, it would probably vex me as well until I knew why). If you only use 5.1 then I would just hook up optical and call it done.

Thats what I thought, but the unit at the store, connected to a regular bluray player, does not do this. You can slap a regular cd in the player and send the pcm track over HDMI and the unit will not increase sound level when turning of the sub in bass management. It only does this on my unit when using a PS3. At first I figured it was just my older PS3 but it did the exact same thing on a newer slim. Same source material played in the PS3 but output sent through the optical connector will experience the same issue as long as HDMI is still turned on for that input on the anthem, even if you have it only enabled for the video and have optical 1 set for audio "in". Hard to explain. Let me try this way. Each input on the anthem,(BDP, CD, SAT, AUX, ETC) allows you to individually select the input type for both video and audio separately. So for "BDP", I have video set to HDMI1 and audio set the same. This way when I play a bluray, it uses the HDMI from the ps3 for both audio and video. For the CD input, I can set the video from HDMI1 so I can see the screen of the PS3 but use OPT1 for the audio in instead. The I can configure the PS3 to output the audio track via HDMI and optical. I did this to see which way sounded better when just playing cd's. What I discovered was that if the HDMI is on at all for that input, whether the sound is coming over the HDMI cable or the optical, if the material is PCM, when I turn the sub off, the sound gets louder. Now all I have to do on the "CD" input is set "video in" to "none" or something other than HDMI and the problem goes away. I figured it was an issue with the HDMI board as it did this to me on 2 separate ps3's. Got the unit swapped and new one still does it. Tried a 3rd HDMI source (my iphone via hdmi connector) and unit behaves normally. It also behaves normally if the signal coming in from the ps3 is bitstream (dd/dts) vs pcm. It does the volume increase as well if I set the ps3 to send linear pcm multichannel over the HDMI cable vs bitstream. I know the issue has to do with the ps3 but it is present on two different generation units. So bitstream from ps3 over hdmi ok. PCM over HDMI or with HDMI active on that input at all, not ok. PCM over HDMI from something other than PS3, ok, from what I can tell.
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