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Digital Source Comparison - An audible difference?

I'm trying to compare with my own ears the difference that people hear, or claim to hear, between digital sources. I realize that it's entirely possible that my system isn't quite to the level where difference are audible but it's pretty simple to do a comparison.

Source 1: Pioneer Elite PD-D6-J SACD Player (on Nordost Sort Kones)
Source 2: Integra CDC-3.4 CD Player (multi-disk)

My plan would be to use two Toslink cables since the Integra is already connected using one and it's fairly easy to obtain another one.

Considering the rest of my system includes an Integra 50.1 AVR, Focal Chorus 836v speakers, and DIY Cat5 speaker cables, would you predict that I will hear a difference?

There is a distinct difference between the two CD players using analog connections, but if they are reduced to being transports that rely on the DAC in the AVR will there still be a difference?
mceljo
dhl93449
455 posts
 
I presume you are talking about 44.1K/16 bit native output from the players. For that frequency and bit depth I doubt if toslink will show any difference with coax, assuming you use glass fiber toslink and not plastic optical fiber.

If upsampled digital output from the players is used, all bets are off. I did this with a CA 840c (feeding a Bryston BDA-1) and found significant loss in sound quality when using the upsampled outputs (up to 24 bit/192K)of the 840. This was compared to the 840 alone feeding the same pre-amp/amp as the Bryston. At the high frequencies and bit depth the toslink would not allow the Bryston DACs to lock, whereas coax did. When I sent native 16 bit/44.1 KHz from the 840 to the Bryston, sound quality improved significantly.
mceljo OP
1,357 posts
 
Al - I can understand the concept of reflections in a digial cable, but is there concrete evidence that these reflections will actually cause an error in the transmitted data? Can the reflections actually cause the "pulses" to be outside of the acceptable range? I would assume that the DAC is looking for specified ranges with some tolerance applied.
almarg's avatar
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almarg
9,670 posts
 
Hi Mceljo,

Assuming that the impedance mismatches are within limits that are not totally unreasonable (such as might occur if the connection of the shield in a coaxial cable were broken), the resulting reflections will not cause any errors whatsoever in the digital data as received by the dac.

The issue is that the waveform distortion caused by reflections, in combination with noise that will invariably be riding on the signal to some degree, will result in small but significant fluctuations in the TIMING at which the dac senses the transitions between bit intervals. That is what the term "jitter" refers to. Depending on the jitter rejection capabilities of the dac, that can and often will have audible consequences, even though all the bits will be correct. See this paper for further explanation.

Best regards,
-- Al
mceljo OP
1,357 posts
 
Al,

I passed the two main links along to an EE friend of mine that's my sounding board for all things electrical. Here's part of his response.

"Those are the first articles you've sent me where I completely agree with everything written. This guy is obviously a well-educated electrical engineer.

How noticeable corrections to these factors will be, I do not know. I don't believe that crystal oscillators used in today's computer equipment are much farther off timing-wise than a belt-driven turntable."

In any case, he generally give me a list of things he considers to be "bunk" in the things that I pass along.
mceljo OP
1,357 posts
 
Al,

On a somewhat related question to the information in the links. Do you think jitter is a significant contributer to the difference in sound that I get between my Onkyo iPod dock and Ethernet connected Pandora Radio? The other obvious factor is the difference in DACs that are being used. Pandora is using 128 MP3 files and it takes at least the Applelosses on the iPod to sound consistently and sometimes even that doesn't sound as good.

I find myself turning off the iPod because it just sounds subpar, but Pandora runs for hours at a time.
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