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Topic: DVD Audio or SACD ? (Read 64577 times) previous topic - next topic
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DVD Audio or SACD ?

Reply #125 –
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Hi Nika,
since reconstruction filter "headroom" isn't part of any DAC specification I know of, it's hard to know the performance in that respect. After I read your post I called Prism (my DAC brand) to ask about their specs and although they couldn't give numbers ("would have to look that up") they assured me that their reconstruction filter has been designed with "quite some" margin for overloads.
Do you know of any test or (AES?) specification that can help to quantify DAC overload performance ? I'd love to know the limits of my DAC.
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Kees,

I don't know of any specification that is recognized regarding reconstruction filter headroom.  As for a test, you would have to be pretty smart about it, but you could certainly create an artificial signal for testing purposes.  The easiest one would be a 1/4 sampling rate sine wave wherein you create it such that the samples end up at .707, .707, -.707, -.707 FS repeatedly throughout (sampling the sine wave halfway between zero and peak throughout).  If you normalize the samples then the signal will exceed full scale by about 3dB, and if the signal is clipping the filters then this would be easy to identify on test equipment on the back end.

So:  create a digital signal of FS, FS, -FS, -FS (repeat ad nauseum) and this represents a 11.025kHz sine wave with the samples normalized at full scale.  How does this look coming out of the DAC?  Is it an 11.025kHz sine wave or is it a mess?  Now start turning that down.  What you see on your scope will probably change in other ways than just amplitude.  By the time you get down to 3dB of attenuation you should see a pure sine wave.

My guess is that the folks at Prism will tell you that they have "tons of headroom" on their filters, but they are only speaking about the analog filters.  The digital filters that are built on to the converter chips they have almost no control over.  I doubt they have any more headroom there than the chips have inherently - which you'd have to speak to the chip designer about (good luck). 

I hope this helps?
Nika

DVD Audio or SACD ?

Reply #126 –
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So:  create a digital signal of FS, FS, -FS, -FS (repeat ad nauseum) and this represents a 11.025kHz sine wave with the samples normalized at full scale.  How does this look coming out of the DAC?  Is it an 11.025kHz sine wave or is it a mess?
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Aha, I think you've helped pinning down the reason for my confusion.
During my 20 years with digital audio, I've never allowed the digital signal of my (cd-)masters to reach FS completely. Overload indicators are set to 1 sample at 16 bit.
I'm still trying to find out how DAC overload can occur with signals that have never (nowhere in the signal-path, not even inside the dsp) reached FS.
Lowering overall level by say 0.01dB to avoid overload indication is a nono IMO since it doesn't remove clipping.
From what I understood, a DAC can still overload "between samples" with some signals (probably  with lots of high freq. content), even when the signal never reaches FS.
In your FS, FS, -FS, -FS example, you're proposing to create a distorted (by definition, at least in my vocabulary) signal to start with. I have no doubt that this might result in audible distortion.

ps: if this is getting off topic too much I wouldn't mind a new thread.

DVD Audio or SACD ?

Reply #127 –
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Aha, I think you've helped pinning down the reason for my confusion.
During my 20 years with digital audio, I've never allowed the digital signal of my (cd-)masters to reach FS completely. Overload indicators are set to 1 sample at 16 bit.


Doesn't matter.  Set it as I said except .01dB lower.  You now have FS(-1 LSB) FS(-1LSB), -FS(+1 LSB), -FS(+1LSB) etc. yet your waveform is still exceeding full scale by 3dB, and this is a "legal, legitimate" waveform - a sine wave at 11.025kHz.

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I'm still trying to find out how DAC overload can occur with signals that have never (nowhere in the signal-path, not even inside the dsp) reached FS.


Go to http://www.cadenzarecording.com/papers and read the paper on "traditional peak meters."  There are graphics and whatnot that explain.

Cheers!
Nika

DVD Audio or SACD ?

Reply #128 –
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Doesn't matter.  Set it as I said except .01dB lower.  You now have FS(-1 LSB) FS(-1LSB), -FS(+1 LSB), -FS(+1LSB) etc. yet your waveform is still exceeding full scale by 3dB, and this is a "legal, legitimate" waveform - a sine wave at 11.025kHz.
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I've tried the test and didn't hear strange things. But then, to my not so young ears there is no difference between a 11.025 kHz sine wave and a ditto square wave. So if there's only harmonic distortion, I won't hear it. When I have some time I should take a look at the spectrum of the analog output of the DAC. Perhaps there's something visable but inaudible.

DVD Audio or SACD ?

Reply #129 –
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Listen to the remastered Dark Side of The Moon on SACD/CD Hybrid, it was engineered by the ORIGINAL engineer and both recordings thus should be from the same source material. This to me provides an obvious win for SACD, as its' clarity and accuracy in representing the original audio is far greater than that of CD.


Careful.  Just because it was mastered by the same engineer does not in any way mean it was mastered the same.  It is virtually impossible to do so.  First, the mastering tools available for the DSD environment are different from those available for PCM.  Second, traditional PCM mastering involves normalizing and limiting in ways that are actually illegal in the SACD scarlet book - the disk would be rejected.  The result is that mastering engineers on SACD are actually forced to use less compression and allow more dynamics.  It is not to say that the PCM mastering engineer couldn't do the same, but they don't HAVE to, so they don't.

The result is that SACD disks often use more dynamic range, have less compression, and sound that way.  But they don't have to...

Nika
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I understand this, that is why I referenced the Dark Side of The Moon Hybrid. Both layers are 30th anniversary remasters done by the original engineer.
Multi-Channel aside, compare the two 2 channel recordings.

The reason I referenced the CD was to address earlier posts by people who try to use the "scientific limitations of the human ear" to excuse the fact that they are unable to distinguish between CD and SACD.
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Your example is *useless* for addressing that issue.  The two layers opf Dark Side have *clearly* been remastered *very* differently.  This is obvious from visible inspection of the waveforms, as well as objective measurement of same.  I've done this at home, and so has John Atkinson of Stereophile.  This means that using two different A/D transfer chains for the analog output -- Atkinson's being *far* more high-end than mine -- we were both able to see that the two layers are mastered differently.  My own experience in doing the same comparison on other hybrid SACDs, btw, is that some CD layers *do* look extremely like the SACD layer (e.g., the Rollling Stones hybrids).  DSotM's isn't one of them.

[a href="http://www.stereophile.com/news/11649/]http://www.stereophile.com/news/11649/[/url]

With the mastering of the two layers being this different, you can't separate that effect, from any supposed difference between the *formats*.

Scientific evidence for *audible* difference of SACD/DVD-A/Redbook CD distribution formats *qua formats* simply has not been forthcoming, either from the industry or anywhere else.

DVD Audio or SACD ?

Reply #130 –
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The CD version is purposely designed to be bad/different in this case, as compared to the SACD version. The dynamics were squashed so that they could increase loudness as far as possible. But, many CDs seem to be designed to be purposely bad these days. Not a problem with the format. A problem with the morons mastering to the format.

-Chris
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From what I read on prosound forums, it's more a problem of moron producers/musicians demanding
entry into the loudness wars...and mastering engineers (who are hired hands, in the end) doing the job they're paid to do.

That Krall CD waveform doesn't look that bad, really , compared to lots of the stuff out there that's close to solid-brick green.

DVD Audio or SACD ?

Reply #131 –
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If they think that louder is better, why would they make CD louder if they want SACD to sound better ??


Great question. I'd say it's because it's not easy to queue up SACD and CD tracks togther quickly.  But it's quite easy to queue up multiple CD tracks (changers have been around for decades, and now of course we have lossy format players in abundance).  Also, SACD's afaik don't tend to get much radio play.  So it's the 'competition' between CDs, not between CD and SACD tracks, that has producers and musicians worrying that their mixes aren't 'punchy;' enough.

DVD Audio or SACD ?

Reply #132 –
There's another reason for the SACD being quiter...

The DSD signal on SACD is always at digital full scale - that's the nature of DSD.

However, you can't put information in the audio band at a level comparable to digital full scale because it would make the whole DSD conversion process go unstable. You might just get a ~1MHz square wave with absolutely no audio information modulated onto it at all, or something equally unpleasant and unrelated to the original audio. So you keep well away from digital full scale.

How "loud" SACDs appear at the analogue outputs relative to a standard CD depends on how the DAC is calibrated, but for DSD encoding, Sony suggest using 75% modulation as the limit, and not one that you should be aiming to hit.

For these reasons, brick wall limiting is pointless and useless for SACD, unless you want that "sound". Plus (I think) Sony have some control over what is release on SACD, and in an attempt to make the format "sound good" in the ears of consumers, they try to ensure only high quality recordings are released on SACD.

Cheers,
David.

DVD Audio or SACD ?

Reply #133 –
Actually, before each release, all the DSD track are verified in Japan. The dynamic of the high frequencies being limited, they want to be sure that it won't be distorted.

DVD Audio or SACD ?

Reply #135 –
This study does not seem to reach any conclusion that either is "better", only that under rare conditions they can be perceptively different. It would have been a lot more interesting to me if it had compared either one to 44.1/16.