Why do digital cables sound different?

Redkiwi - you're right that having time synchonization requirements makes the environment more demanding. However, as long as you have 1) a redundancy scheme and 2) sufficient resources above and beyond the demands of the basic application to support the redundancy scheme, then you can effectively eliminate the time synchronous demands. The Levinson DAC / Discman buffering doesn't eliminate it because there's still no redundancy - if they send the data and it's not received correctly, there's no recovering the lost data. But if I have a 100Mbit ethernet connection and have to keep up with only the bandwidth necessary for CD playback, I can send / resend the data dozens of times if need be and still keep up. If I can transfer files across a LAN perfectly accurately at 10Mbit/sec, I should be able to transfer music "files" perfectly at a rate of 1.5Mbit/sec. If current transport /DAC interconnect technology can't perform this same feat, we should demand better.

First of all, the different digital interfaces have different bandwidth. Within a single intrface type, even slight imperfections can cause signal loss. Only ATT optical has enough bandwidth to handle all the dat correctly. Yes this lame by todays standards, but it was leading edge 20 years ago.

I would like to reply to your question. No, No, No, No, No, No!!!!! There is simply no way that any digital cable can color or change the sound of a system. While there are physical reasons why analog cables (interconnects, speaker cables etc.) can have an effect on sound quality it is beyond the laws of physical possibility for a digital cable to have an effect. The D/A in your equipment could care less if the 0111001111 bit stream came from a piece of copper or fiberoptic material. I understand that audio is very subjective but one must be careful when opening one's mouth. Consider the ramifications of someone taking what you are saying as gospel and purchasing an expensive cable what there is no physical possibility the cable will effect the sound one bit.

Bruce, cut the crap! We are not talking about frequencies in the GHz region. These are simple logic levels moving at less than a MHz. I have been a digital designer for 20 years and have never heard such garbage. I there is any effect at all it would result from delay caused by capacitance in the cable not by excessive standing waves. If I knew what the impedance of the DAC was, I bet we would would see very little return loss if we swept the cable on a network analyzer even up to 50 MHz. Sorry to burst your bubble but you are way off base.

With all due respect, and I respect your 20 year experience as a digital designer, my 25 years as a professional musician tell me very loudly and clearly that I hear these differences. What's more, they aren't all that subtle in many cases. My musical colleagues (those that care about these things )also hear them. Is it not more productive and potentially enlightening to consider as plausible what the ears of those who use them for a living hear. I hate to break your bubble, but I assure you that the subtleties (subtle variations in timbre, pitch, time etc. ) that a musician has to be sensitive to playing in say a Brahms clarinet trio are far more subtle in absolute terms than the oftentimes obvious diifferences that are heard between cables, including digital. By the way, digitally recorded music to many colleagues of mine still does't "swing" the way it should and certainly not as well as good analogue. The groove or "fun factor" is diminished; not catastrophically but diminished none the less. I would like to respectfully encourage all of us to do more listening without focusing on the technical aspects of the sound. "Hearing" is not only what takes place in our ears, but letting that go on to touch us emotionally. Then that in turn frees us to "hear" more, and the cycle continues. There is infinitely more to hear/experience in most good music than most think. I remember that years ago when I first started reading the mags a couple of reviewers were fond of pointing out in their description of the prowess (or lack thereof)of various very expensive components, that these components were somehow to be praised for allowing the listener to "hear that the instrument being played was an English horn and not an oboe". This is almost laughable, I assure you that the difference in timbre between these two instruments is so obvious, that they can be easily heard over the lamest grocery store sound system. Then why bother? Because there is so much more than most imagine. I point all of this out only to encourage the cynics to consider the possibility that they are missing out on a whole lot of fun in their listening by letting technical issues dictate what and how much they should be able to hear. Happy listening.