SP/DIF Digital Out - How 'Good' Is It?
Nov 1, 2008 at 6:22 PM Thread Starter Post #1 of 4

Jo6Pak

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I have read many threads about the varying quality of the internal DAC circuitry in stand-alone CD/DVD players, but I have not seen anything addressing the variance, if any, of optical/coaxial digital output signals. Surely they must vary by manufacturer as well. Or is digital 'digital' and thats it? I know, 1s and 0s, but there must be good, bad and mediocre ways to form these bitstreams, no?

Somebody in the know (seriously, in the know, not opinion) please enlighten me as I have several players around here and I want to make sure I'm using the best quality source I own when I feed it to my DAC. By the way, none of them are high-end (all are off the shelf Sony, Marantz, Philips, Toshiba, Yamaha, etc).

THANKS!
 
Nov 1, 2008 at 6:35 PM Post #2 of 4

audioengr

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S/PDIF output designs vary a lot from one device to the next. CD players generally have very slow rise-times and the output impedance is not correct, even brand names like Sony. I have modded dozens of different transports and computer audio devices, so I have first-hand knowledge of this.

The problem here, like with most digital audio, is jitter.

D/A converters need two things:

1) accurate data - data errors are actually rare
2) accurate timing at the digital level - not music timing - innaccuracies are call "jitter"

Because of the slow edge-rates on most consumer gear (this way to insure passing FCC emissions testing), it is necessary to use a 1.5M digital cable length to avoid reflections and the resulting jitter. Here is white-paper I wrote for PSOnline on the subject:
spdif

Unfortunately, there are only a handful of designers in the audio industry that can design a really good-sounding, low-jitter S/PDIF interface. This is why I was able to make so much money modding Transports over the last 7 years. I dont do this anymore BTW. Computer Audio is superior, so I have abandoned transports.

Steve N.
Empirical Audio
 
Nov 2, 2008 at 2:03 AM Post #3 of 4

bordins

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It has been discovered for 20 years in the audiophile community that the S/PDIF signal can affect the sounds. I've compared various S/PDIF sources and found such differences.

Even using a PC as the transport and the same DAC, S/PDIF outputs of different sound cards produce different sonics. Cheap internal sound cards typically sound worse than decent external ones.

I've compared M-Audio Audiophile USB, Creative Live! 24-bit USB, Creative Audigy2 PCI, and on-board optical S/PDIF. The M-Audio produces the best sound, very musical due to lower jitter, while the Creative Live! USB is the worst. Surprisingly, my Philips universal DVD player's S/PDIF output is very very good, a lot better than on-board S/PDIF.

My observation confirms there exists the effects of S/PDIF signalling. However, you need a sensitive or high-resolution audio system to be able to detect these variations.

Changing the S/PDIF cable also has an effect. Pick a cable of any length that matches your system components and listening preferences, but long cables are generally sensitive to interferences and introduce delay.
jecklinsmile.gif

 
Nov 2, 2008 at 6:42 PM Post #4 of 4

Jo6Pak

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Thanks for the advice. It would appear that its not something I need to worry about, given my very run-of-the-mill gear...
 

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