I checked the manual but it doesn't say - is it recommended to change the Power Grid while the amp is in "Play" mode? Standby? or powered off? Does it matter? I was just wondering as I don't want to take the chance of damaging something.
Doesn't matter, as far as I know. I change it all the time in play mode. It will make a bit of noise if I am changing it on the channel that I am playing through, but that never gave me any problems. I suppose if you really want to be on the safe side, throw it in standby.
I assume they would have put a warning in the manual if it was really a problem to do.