If this would get more responses in amps feel free to switch it. I jsut didnt know if a guitar amp was kosher there or not. Anyway. Crate blue voodoo 4 6l6 and 4 12ax7 tubes. Started feeding back something fierce and gets worse . Thought it was a ground in the guitar . Fixed that. Sounds microphonic to. But doenst feed back onc lean channel. Should we just switch preamp tubes for new ones? suggestions?