Question about audio quality - HDMI x Optical - AVS Forum
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post #1 of 16 Old 08-23-2012, 09:21 AM - Thread Starter
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Hello there,

I would like to hear from the most experienced folks about this question. I have a Pioneer BDP-440 blu-ray player connected to a Yamaha RX-V471 receiver using HDMI cable. I heard that to have better audio results it would be better to connect them thru an optical cable (digital). Is this correct? I want to use them to listen SACDs, blu-rays and DVD's.

I appreciate any advice. Thanks.
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post #2 of 16 Old 08-23-2012, 10:36 AM
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No, S/PDIF can't pass Multi Channel HD audio.
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post #3 of 16 Old 08-23-2012, 12:30 PM
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Quote:
Originally Posted by William View Post

No, S/PDIF can't pass Multi Channel HD audio.

The remaining critical question is whether or not that would make an audible difference.
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post #4 of 16 Old 08-23-2012, 01:19 PM
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Some HDMI implementations supposedly have much higher jitter values than digital (optical or coax) connections. Some people claim to be able to hear a difference when listening to audio which has a significant amount of jitter (for some values of "significant" wink.gif ). (I can't.)

If you want, you could connect your Blu-ray player to your receiver using both their HDMI connections (using the receiver's Blu-ray input) and their digital optical connections (using the receiver's CD input), and compare the two when listening to a high quality CD. Maybe you'll be able to hear a difference and maybe you won't. If there is any difference, it will be extremely subtle and your personal "expectation bias" is more likely to be the cause instead of any real effect.

There are many things to take into account when you do such a comparison in order to make sure it's fair to both types of connections. A major one is to make sure both receiver inputs are reproducing the CD's audio at exactly the same volume.

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post #5 of 16 Old 08-23-2012, 05:40 PM
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Hi Caballe,

Pardon me if I seem to get into too much detail.

HDMI, as a medium, has no jitter. If there is jitter from an HDMI source, it is completely the fault of the receiver. That is because the audio over HDMI is completely devoid of timing - the audio is sent over HDMI as data during the video retrace intervals, and it is up to the receiver to reconstruct the timing. So if you could hear any jitter, it is caused by poor timing in the receiver.

On the other hand, an S/PDIF optical connection does have bit-timing over the connection, and this timing, if passed all the way through to the DAC chip and is used by the DAC to reconstruct the audio, can have some jitter. However, few receivers use the optical connection's timing directly (those days are over). Rather, they resample the audio data with their own internal clock to drive the DAC.

Not surprisingly, the clock that the receiver uses to render the audio over HDMI would be the same clock it uses to render the audio over S/PDIF. So most receivers will have identical jitter, no matter which source you use.
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post #6 of 16 Old 08-24-2012, 03:38 AM
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Quote:
Originally Posted by MarkHotchkiss View Post

Hi Caballe,
Not surprisingly, the clock that the receiver uses to render the audio over HDMI would be the same clock it uses to render the audio over S/PDIF. So most receivers will have identical jitter, no matter which source you use.

A contrary view might be found in the Miller Labs tests of several AVRs in 2010:

For example http://www.milleraudioresearch.com/download2010/reports/sep10/pioneer_sclx83_digital.html (requires free registration for userid and password to access):

48kHz/24-bit PCM Jitter
Total correlated Jitter (re. -3dBFs into 60000ohm)
573 psec (Left Channel)
578 psec (Right Channel)

HDMI - Jitter at 48kFs (PQLS Off; MCACC Off)
Total correlated Jitter (re. -3dBFs) =
1582 psec (Left Channel)
1582 psec (Right Channel)

HDMI - Jitter at 48kFs (PQLS Off; MCACC On)
Total correlated Jitter (re. -3dBFs) =
1461 psec (Left Channel)
1460 psec (Right Channel)

HDMI - Jitter at 48kFs (PQLS on; MCACC Off)
Total correlated Jitter (re. -3dBFs) =
366 psec (Left Channel)
365 psec (Right Channel)

There's something more complex going on under the hood!
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post #7 of 16 Old 08-24-2012, 03:39 AM
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Quote:
Originally Posted by arnyk View Post

A contrary view might be found in the Miller Labs tests of several AVRs in 2010:
For example http://www.milleraudioresearch.com/download2010/reports/sep10/pioneer_sclx83_digital.html (requires free registration for userid and password to access):
48kHz/24-bit PCM Jitter
Total correlated Jitter (re. -3dBFs into 60000ohm)
573 psec (Left Channel)
578 psec (Right Channel)
HDMI - Jitter at 48kFs (PQLS Off; MCACC Off)
Total correlated Jitter (re. -3dBFs) =
1582 psec (Left Channel)
1582 psec (Right Channel)
HDMI - Jitter at 48kFs (PQLS Off; MCACC On)
Total correlated Jitter (re. -3dBFs) =
1461 psec (Left Channel)
1460 psec (Right Channel)
HDMI - Jitter at 48kFs (PQLS on; MCACC Off)
Total correlated Jitter (re. -3dBFs) =
366 psec (Left Channel)
365 psec (Right Channel)
There's something more complex going on under the hood!

That all said, there is no reliable evidence that any of this makes an audible difference.
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post #8 of 16 Old 08-24-2012, 04:08 AM
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Quote:
Originally Posted by arnyk View Post

The remaining critical question is whether or not that would make an audible difference.
HDMI may or may not subjectively sound better than HDMI but HDMI is objectively superior to S/PDIF when passing multi-channle HD audio. So why should the OP run another wire and switch to a technically inferior S/PDIF source just because he/she MAY or MAY NOT be able to tell the difference?wink.gif
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post #9 of 16 Old 08-24-2012, 04:33 AM
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Quote:
Originally Posted by William View Post

HDMI may or may not subjectively sound better than HDMI but HDMI is objectively superior to S/PDIF when passing multi-channle HD audio. So why should the OP run another wire and switch to a technically inferior S/PDIF source just because he/she MAY or MAY NOT be able to tell the difference?wink.gif

Quit trying to make sense! ;-)
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post #10 of 16 Old 08-24-2012, 08:20 AM
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The OriginalPoster can use that extra connection to discover the (lack of) audible difference for himself.

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post #11 of 16 Old 08-24-2012, 02:53 PM
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Quote:
Originally Posted by arnyk View Post

A contrary view might be found in the Miller Labs tests of several AVRs in 2010:

For example http://www.milleraudioresearch.com/download2010/reports/sep10/pioneer_sclx83_digital.html

There's something more complex going on under the hood!
Thanks for the link Arny - I will investigate.

I don't yet know what PQLS is yet, but it appears to improve HDMI jitter by a factor of four when it is on.

There is something more complex, at least under that hood.
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post #12 of 16 Old 08-24-2012, 07:07 PM
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Quote:
Originally Posted by MarkHotchkiss View Post

Thanks for the link Arny - I will investigate.
Here is an article I wrote on this topic which encapsulates the same data from Paul's plus some other related bits: http://www.madronadigital.com/Library/DigitalAudioJitter.html. Paul's site only has measurements and no explanation.
Quote:
I don't yet know what PQLS is yet, but it appears to improve HDMI jitter by a factor of four when it is on.
PQLS is Pioneer's technology that puts the target -- the DAC -- in charge of the timing. Usually the source is the timing master and hence the reason jitter gets induced into the receiver (explained in the article). PQLS fixes this broken architecture by making the DAC clcok the master and the source slaved to that. Result is immediate improvement in jitter as whatever contributions there are from the source get sharply reduced (system activity caused by HDMI still can lead to jitter locally in the receiver). Same solution works in PCs in the form of "asynchronous USB" where the DAC once again is the master as opposed to USB transmitter.

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"Insist on Quality Engineering"

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post #13 of 16 Old 08-24-2012, 08:00 PM
 
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Quote:
Originally Posted by amirm View Post

Here is an article I wrote on this topic which encapsulates the same data from Paul's plus some other related bits:

Paul's site only has measurements and no explanation.
Neither does that link you posted (again). At least no explanation relevant to audio section of this forum when you dodge an important question:
Quote:
Originally Posted by amirm's link 
“yes but… is it audible?” As unfair as it might be, I am going to punt that question.
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post #14 of 16 Old 08-25-2012, 12:44 AM
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Quote:
Originally Posted by amirm View Post

Here is an article I wrote on this topic which encapsulates the same data from Paul's plus some other related bits: http://www.madronadigital.com/Library/DigitalAudioJitter.html. Paul's site only has measurements and no explanation.
Thanks for the link, Amir. I have it in the queue right behind Arny's link.
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post #15 of 16 Old 08-25-2012, 08:01 AM
 
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Quote:
Originally Posted by MarkHotchkiss View Post

Thanks for the link, Amir. I have it in the queue right behind Arny's link.
Try this instead, it has amirm's link content and the breakdown of what those things mean: http://www.avsforum.com/t/1326576/usb-vs-hdmi-for-2ch-audio-to-receiver
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post #16 of 16 Old 08-25-2012, 01:31 PM
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Thanks Diomania,

I have yet to peruse any of those links, but I think I have determined why some (maybe most) AVRs have HDMI jitter issues. I will post further . . .
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