Why do digital cables sound different?

I wasn't trying to start a religous war here when I asked the question. I'm just confused. With analogue, it makes sense that if there is an impedence mismatch (among other things) that these factors can change the signal being transmitted. The problem is that with digital and such a short distance to move the bits, unless you have a bad cable (where you get a lot of errors), shouldn't ALL good cables move them the same way and thus represent sound the same way? With all the techie types out there involved in audio, I was thinking that someone would have already taken measurements at the sending and receiving side to see IF the digital stream is the same. Isn't it ONLY if the sreams are different, at the two ends, with various cables that there will be a difference in sound? This is fairly basic, no? There is no magic involved...and if the digital stream at the receiving end is different than at the sending end regardless of how it sounds...it is just wrong! Or am I missing something here and not understanding what's involved??? What I am interested in are the possible reasons that cables COULD sound different. My only guess so far is that a weak signal or interference makes it hard for the receiving end to distinguish what is a 0 and what is a 1... I think this was inferred by Sugarbrie It is also my understanding that the Pros use a different digital signal...and that the voltages are higher (and making the difference between a 0 and 1 more easily discernible?). Can anyone hear differences in using different cables on aes/ebu? Thanks!

I share others' puzzlement here. Differences between coax and AES/EBU are perhaps easier to accept, but when comparing two different brands of coax, what can possibly be going on? In a conversation with a leading DAC designer earlier this week, he agreed there should be no differences as long as the cables are properly designed, which includes hitting the right impendence measurements. And he added that not all cables are designed properly. (There's also the camp that contends that cable length is very important in digital cables due to relections or something.) But increasingly, the DACs do such a good job of handling all of the timing issues that cable differences should be diminishing. I think I'm just repeating what others have said, but here's my new thought: my BS detector will really start ringing if I hear a claim that some brand's digital cables have sonic properties similar to their analog interconnects and speaker cables. E.g., Cardas Lightning has the characteristic Cardas warmth and fullness, Nordost digital cable is ultra fast but lean, etc. To my mind, whatever it is that lends cables their different sonic characteristics (if you believe that), will not lend the same characteristics to digital cable except by pure, unlikely coincidence. -Dan

Danielho, again I think it is important to look at these issues from the standpoint of the message not the messenger. There simply is too much information in a musical event to encode and then decode for our existing recording and playback equipment. That is not debatable. It is the reason that even the very best systems still don't sound like the real thing. I believe that there are still many types of distortions, still unidentified, that affect a musical waveform wether in the digital or analog domain. While I realize that it is "simply" ones and zeros involved here, is it not plausible that the "code" needed to carry the information that distinguishes wether say, a saxophonist is playing a Selmer or a Yamaha instrument is so inadequate that any problem or simply difference in the way that code is transmitted would further distort the sound?I assure you those differences can be heard. I think those things would have to include cable materials and all that we don't know about why say, silver can have, generally speaking, a generally identifiable sonic quality. Why is it that I hear a certain family resemblance between the Kimber digital cable(silver) and their KCAG analog interconnect when introduced into my system? There has to be something at work here that we just don't get yet. But my ears tell me so. Happy listening!

There is a reason. The digital signal is transferred at a much higher frequency than the audio signals. At these higher frequencies, the output impedance of the transport, the characteristic impedance of the cable, and the input impedance of the DAC must be matched in order to get all of the energy sent by the transport to be absorbed by the DAC. Any mismatch in impedance will result in some energy being reflected back to the transport. This results in standing waves which distort the signal, that is, it is different than what would ideally arrive at the DAC if all was matched. Some of the enrgy is disipated in the output stage of the transport, and some in the cable. There are other cable losses such as dieletric loss and radiation loss that are minimized by a well designed cable. This area of electronic theory is called transmission line theory and will be covered in any book on basic electronic communication theory. This is an ovesimplified explanation, but my point is that this an extremely complex subject that can't be explained by statements like, " I don't see how a wire can make any difference." I taught this subject for 9 years and the more I learned the more I realized how little I knew.

Bravo Bruce, precisely my point.