Correct, the USB cable does not carry audio. A stereo audio cable is needed.Are you running audio from your BCT15x's to your PC and if so how are you doing it? I'm trying to get audio to the PC for recording with Proscan but having a hard time. I have (2) 15x's connected with USB to Serial RS232 adapters but I'm guessing the adapter doesn't carry audio. I tried connecting from the recording jack on the 15x to the line in on the PC, but still no audio.