Things going smoothly Friday night with my trusty Genz Benz 600 GBE. All of the sudden there is whirly twirly feed back that if it were visible, it would look like the ghosts flying around when they opened up the ark of the covenant in the original Raiders of the Lost Ark. Everyone in the band is looking up and around collectively saying WTH?! and then silence. My amp protect light goes on and the amp shuts down and will not come out of protect. In 12 years of playing, I have owned exactly two amp heads. Both Genz Benz. Never brought a back up. Shutting down like that sucked big time. I shall forever carry two henceforth. Will take the amp in for repair, but was wondering if anyone would venture a guess as to what happened. We were playing in a basketball gym and I was playing a little louder than usual, but had plenty of "headroom" as I think I understand that term. (I was turned up to 5 on master and gain, tube control about the same). Passive G&L SB-2 though the pups are hot. Had feedback with this new bass previously in a smaller venue. Comments?