Was playing an outdoor show with my Ampeg Reverberocket last night. The amp was cranked good n loud. I have 6V6's in it vs. 6L6's. After about an hour or so of loud rockin', I began to hear a strange, metallic, kind of ringy sound when I'd play. Almost sounds like maybe a microphonic tube. What I'm wondering is do you think the biasing for 6L6s was too hot for 6V6's at very high volumes? Did the amp blow my tubes? I noticed my clean tone began to suffer, sounding unpleasantly dirty. What could have happened?