I am having an issue with my D60. It's at the tech now. He is having a hard time diagnosing. The problem is intermittent. The issue happens with vibration. It will sound great and then you'll hit a note and it will crackle/buzz. This is with the head sitting on top of the cab. You can also get it to do it if you tap the head shell when not playing. In fact, it will do it without anything plugged into it. If you turn the master down, it wont do it. Any ideas?