how much does bias float

Hey guys I just put in some new JJ powertubes in my tweed vibrolux clone(5f11), should the bias be fluctationg when I am playing loudly and really digging in?

I have the bias set for 21mA for each tube but when I am playing I can watch the number on meter go way way up. I also notice when I engage the tremelo it goes up and down but I belive it's a bias something tremelo circuit. I don't know the proper lingo, sorry. So should the bias vary? When idle it come's back down to around 21 to what I set it at. Thanks all

by definition, the bias you set is the Idle current (ie no signal). When you are playing - you have your foot on the gas, and lots of power going to the wheels, or rather, Speaker. Current must therefore increase.

Makes perfect sense and kind of figured that but I've never looked before so it had to be asked. Thanks bdgregory