ediots:idc:
There may be a difference due to jitter or the timing of the signal. However, that is not fully tested. There is conflicting testing as to how audible jitter is and at what level it becomes audible. I do not know of any blind tests that have established whether or not there is an audible difference.
Over very long distances,100s of feet, there can be a difference due to signal loss.
By USB specification max length of cable is about 16 feet. After that you need an usb hub and then you can add another 16 feet cable.
Several DAC makers say that they are recloking data which is received from usb connection, and, if I understand correctly, then jitter is not a problem anymore.
I think, but not sure about it, that usb isn't just stream of electrical signal like spdif. This connections comes from computer world, there is data exchange protocols, there just isn't easy way how to lose data. Is something lost, transfer is repeated.
I remember in a previous thread on USB cables that forum members were running lengths up to 50 feet without apparent problems.
I don't know if jitter is a problem or not and between asynch, synch and adaptive clocking, I am sure all DACs can actually cope with it. It could be a red herring which has no connection with sound quality at all, but since audiophiles raised it as a potential issue, cable and DAC makers have 'addressed' it.
I am firmly in the feel good camp. If you feel good about buying an audiophile cable, do so as mood enhancement makes music sound better.