Hi all, I sold an amp on ebay to a gentleman on St. Paul, MN. It left my house working fine but he's indicating there's a buzz going on. Specifically, he says "The buzz is not constant though, only when I play harder at higher volumes. I know it's not the amp breaking up, because it happens dirty or clean..." Generally when I hear the word "buzz" I think "tube issue." I had him pull and then reseat each but that didn't help. He says he can't afford an amp tech but it cost me about $65 to ship. I suspect it's unlikely the repair would cost that much. So, does anybody know a good amp tech in the St. Paul area who could look this over? Also, anybody want to guess what could be doing this? Thanks.