the amp maker doesn't want to have power tube failer to deal with during the warranty period; this I understand. I guess what I'm really wondering is if all amps sound better biased even a little hotter than when they're new? I have read how amps "sounded great biased hot but then they had to back down the bias because they noticed some "red plating" in one or more of the tubes. "but boy did it sound good" is the usual comment. Recently read this about a Bogner 101b as well. What's the general consensus? Thanks.