[Audio_Empire[_2_]]

On Saturday, July 27, 2013 8:59:47 AM UTC-7, Andrew Haley wrote:
Audio_Empire wrote:

In article ,

Andrew Haley wrote:



Audio_Empire wrote:



This is all fine and good, and perhaps you can even hear "some*"

difference, but it still doesn't alter the fact that the Oppo in

question still uses the same SabreDac 32 which converts DSD to LPCM

before playing it,



I don't think so: according to their white paper, they feed the DSD

data into their anti-imaging filter, which runs at a very high

frequency. There's no suggestion that they downsample it to LPCM

first; or do you have some other information?



They use the SabreDAC 32. It converts DSD to LPCM. My information comes

from the Oppo Technical guy.



Hmm. Must be true, then. Under the circumstances, I think I'll go by

the ESS white paper. But even if it does, there's no reason to

suspect that doing so will cause any audible damage.



Why would downsampling to LPCM do any harm, anyway? All the damage

has been done already during the DSD encoding.



Damage? What damage?



Single-bit sigma-delta converters are inherently unstable.



Whether it's during analogue to digital conversion or shortening the

wordlength from PCM, you must add dither to linearize the process.

The problem with single-bit sigma-delta (aka DSD) is that it is

impossible to add enough dither without overloading the modulator.

(There wouldn't have been any problem if the designers of DSD had used

two-bit sigma-delta instead of one-bit.) DSD-wide (i.e. 8-bit

sigma-delta) solves the problem, but you still have to go down from

wide to 1-bit to maks a SACD, and the problem recurs. This was proven

by Vanderkooy and Lip****z in their clasic paper. [1]



There was a rather feeble reply from Philips, but no attempt to rebut

Vanderkooy and Lip****z's proof. And it is a real mathematical proof,

the most reliable indication of truth there is.



These days, the highest-quality audio converters use multi-bit

sigma-delta modulators. (The one in the Sabre DAC is probably six

bits wide, although the white paper is rather vague about that.)



For these reasons, I suspect that if you want to convert DSD to

analogue (and remove high-frequency spuriae) there isn't any better

way to do it. As usual, I'm happy to be proved wrong by some real

evdence.

Thanks for the clarification. I'm going to have to run over to Oppo US
headquarters and talk with their technical guy again (they're about a
mile from here). What you say makes sense and the white paper
certainly points at what you say being correct.


On the other hand, it still doesn't alter the fact that my Sony XA777ES
player provides the best sounding SACD and Red Book playback I've
ever heard.