42-43 VDC at bias test points for EL34. 55 VDC for 6L6's
here is something I read but since i have not been educated on the matter, not sure if it is true. I just go by the MANUFACTURERS manual on my XXX.
An update 10/09/07 We just measured the bias on a XXX in the EL34 mode and with the bias set at 42 volts using the factory test points (Peavey recommends 42.5) the bias was a whopping 57mA which is over 100% of dissipation! You will burn up your tubes with all but the coldest grades of EL34's or KT77's. With the bias set to 45 volts at the factory test points the bias went way down to a very acceptable 37mA. So in this particular amp a variation of only 3 volts at the factory test points made an incredible 20mA difference in bias!!
you can go to http://www.eurotubes.com/euro-k.htm
I have always been told that as long as your switch located next to the bias pot is correct for the tubes installed (6l6 for 6l6 or el34 for el34) then you really cannot hurt your amp by adjusting the bias knob either extreme. Just go by what sounds right to you. You might just go thru tubes faster.?? I have done both schools of thought on this - when i went by what sounds good to me, I then hooked up to the bias test points & my 6L6's were actually reading about 51 VDC, so from what i understand, from the statement above is that now that the bias is set at 51 VDC, my tubes are running actually hotter than at the
recommended 55 VDC.... but then i thought well i should just do what peavey recommends and go to 55 VDC, so i did.