Why do digital cables sound different?

Even with perfect square waves there will be jitter in a clock recovery circuit, due to the stochastic nature of the bit stream. Buffering the data and reclocking with a nice stable clock avoids the jitter problem, at the expense of some relatively long term drift in average sample rates to accomodate changes in the data transmission clock rate. If done properly (i.e., large data buffer, low loop bandwidths), then the time constant would be on the order of seconds. A $49 Discman CD player with "skip free" circuitry does this. So does my Levinson 360S. Now we just have to get audio manufacturers to work on the price points in between. :-)

For some reason all of these explanations are never good enough for some people. This topic inevitably leads to a long debate. Science tries to explain an experience and often falls short. All I need to know is that I tried 5 different coax cables and they all sounded different. One was consistantly better than the others, and I bought it. Anyone who can't hear the difference needs work on their listening skill.

Hear Hear.

My experience is that there are definite differences between digital cables. I suspect it has more to do with the interface of the plugs and sockets (particularly w/ RCAs) than it does with the cable itself.

Another point: it could be that different cables have differing degrees of shielding effectiveness, and therefore, generate different levels of RFI which is coupled back into the analog electronics. P.S. Don't knock science and engineering. That's what gave you something to listen to. Empiricism has its place, but progress depends on interpreting those results in the framework of physical laws and analytical principles -- or else we'd still be riding ox carts with wooden disc wheels over stone bridges.