Letting my guitarist use my old Fender Ultimate Chorus and my old Ibanez guitar, apparently the pickups are microphonic and resulted in some ear piercing runaway feedback a couple of times. We got it under control enough to play for a bit, I plan on potting the pickups in the guitar tomorrow. But I'm worried about the amp. Could this have damaged the amp or the speakers. They seemed to sound fine afterward but the drummer kept making comments about how he thought the amp was about to die. Albeit it is not a great amp but it sounded like normal to me.