So this is kinda wierd. Every now and again my amp makes a high freq whistling like sound. If I pull the bass or treble knobs out and back in again it goes away. For some reason I think its cuz I don't have a rack yet so the amp sits on the cab rattling its poor brains out, basically I think its the pre-tubes getting vibrated kinda loose like. Maybey I am way off base here. Anybody else experiance this?