At a gig the other night I had a buzz coming from the amp only when the volume pot (on the guitar) was turned down. If I turned the pot up at all, the noise went away. I assumed the volume pot was bad, but I can't get it to happen again at home with the same rig. I also plugged the guitar into another amp and there is no problem. Am I correct in assuming that there was something in the electric line (refridgerator compressor, flourencent ballast, etc) that was causing this or is there something I am missing?