Have not tried the cable on another source. I will give that a try, but I am beginning to think that it is not the issue. I swapped the connection to the computer to use a S/PDIF to RCA cable in to the Video inputs, in lieu of the USB. I am getting the same left channel drops and volume changes.

Just checked another source via the AUX and am getting the same channel drops there. It would appear to be the RR2150. I do not think that it can be blamed on the speaker wire, and that is the only other variable in the chain.

Darn.