Why do digital cables sound different?

Redkiwi, I am not a designer of digital audio playback devices but I thought that the data sent to the DAC is asynchronis. If that is true where are the timing errors? Is the data clocked from the transport to the DAC or is it really asynchronis? I do not know, but if it is asynch, then the statement about arriving with perfect timing does not make sense to me. Is it the timing between bits that you are talking about? If that is the case, how can the cable change the timing between the bits or even cause jitter?

Redkiwi, even if jitter did cause a problem, I do not think it would manifest itself in harmonically related distortions. I can't see it causeing either higher or lower order distortions.

WOW, this is a MUCH better response than I'd anticipated when I asked the first question. Thanks to everyone for the feedback. The wide spectrum of expertise in this forum is astounding! Now to stir the pot a little... Through this discussion, we have some idea of what may be going on within the cable and the interaction of the cable and sending/receiving mechanisms. However, what is the difference in the sound that is perceived? This is my thinking...If the stream is just 1's and 0's...what happens when there is degradation? How does it manifests itself? There seems to be a few phenomena that could occur...scrambled bits, missing bits, signal too low (too hight), timing errors, etc. To me, errors in the data stream would sound like dropouts/static, even wrong notes, etc. and not the same type of subtle differences as in analogue cable. However, there are reports of more bass, the highs being too bright, etc. There are even reports of digital cables with the "family" sound of the company's analogue cables. How can this be possible? As well, if not bits are lost, what difference does timing errors make? Isn't part of the reconstitution of sound at the receiving end, reclocking the signal? Sorry for so many questions, however this thread has been very interesting and educational! Thanks everyone!

It is asynchronous, and it's fixed rate. In a "normal" setup, sender and receiver each have their own clocks that are supposed to work identically. I've never studied the CD interface, so somebody who has can correct me if I mis-state something, but in typical asynchronous communications, each byte has a "start" bit and a "stop" bit surrounding the eight bits of data, so timing errors would have to be severe enough to cause problems from the time the start bit occurs to the time the stop bit arrives. Since it's a fixed data rate, it takes just as many bits to transmit high frequencies as low frequencies, so the chance of error should be the same. In any case, I can't see any way that the cable would make a difference in the ultimate delivery of the bits based on timing errors as long as it's the usual "good working condition".

Or, I have no idea of what I'm talking about and would love to understand it with you, Danielho. I definitely don't have any idea how a DAC works electrically, certainly not on the analog side - to me, the problem is broken down into "chunks" where getting the samples delivered to the input of the DAC is separate from what the DAC does with that sample - I'm assuming that with a known stream of samples, the DAC will produce a known output. -Kirk