Not sure there is a difference that matters, other than when one wants to view the cable as a [ame=http://en.wikipedia.org/wiki/Transmission_line]Transmission line[/ame] and "load" the devices on either end "properly" (explanation for this statement left off, since it is outside the scope of this thread -- we're talking getting really nitpicky here). Mic cables are designed for particularly long runs of particularly low-level signals, and are (particularly) shielded, so should be able to handle anything you throw at them. (I.E. They are usually used in more demanding situations than interconnects/audio cables would be.)