Why do digital cables sound different?

You make a mistake if you think that just transmitting the bits accurately is all that is required. Jitter (or time-based distortion) is irrelevant when there is no need for time syncronous transmission - ie. computer communications. But in audio or video you must deal/live with time-based distortion. Don't fall for the marketing BS that says a Levinson DAC or a Discman eliminates time-based issues through buffering. And by the way, don't believe that doing away with cables eliminates the problem either - otherwise we would have stuck with the three-in-one music centres of the 60's - Bmpnyc, your dream came true forty years ago.

bmpnyc... no offense taken. If there's a physical effect, then there's a physical cause. If there's no physical cause, there can be no physical effect. Those of us with the scientific mindset seek to comprehend the linkage. Understanding the linkage is every bit as enjoyable to me as other intangibles such as "beautiful design" and "great build quality".

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.