like i said, it is an unknown, just seeing what others have had.. I am connecteed with USB for axe edit ofcourse. I havent used backing tracks, but you never know, it could be the audio on the PC that is trying to play back into the axe fx, i have had that before, even when i didnt point to the axe fx to hear the PC, so i most likely will find the culprit, but just putting it out there. its only very random, so i could catch it on video even if i tried.