I know this has been discussed a LOT. I have searched a LOT and asked a few guys I trust,yet I still do not really have a solid answer. Mainly 2 different ideals from what I have gathered. Each comes up with much different numbers. 1983 2204 6550's 442 plate volts approx When biasing: #1 Treat like a 25 watt tube because that's what the circuit was meant for originally. #2 Go with 35 watt tube at about 65% max diss. I would REALLY like to know what these amps were set for from the factory. Does anybody know?? One of these two ways has to be wrong. The amp sounded killer when I got it, then for safety, I checked the bias one tube at .066 1 @ .102 (it was redplating). I turned it off! But it made me wonder if I liked the HOT setting and that's what made the amp stand out to me.