liverpool (or cathode bias) bias resistor question

[pinkmarkos]

hey guys- I built a Liverpool recently and I am wondering if it is dissipating too much power for each EL84. I calculated the dissipatiopn wattage for each tube at 13.75 watts, which I know is supposed to be 12 watts max. My calcualtions included accounting for the screen current as well. The bias resistors now are 130 ohms- If I just change the bias resistors to 150 ohms, or even 200 ohms to reduce the dissipation, do I also need to change the power tube bypass caps and/or the screen resistors as well?
FYI- plate voltage 331 VDC, cathode voltage 6 VDC, screen voltage 327 VDC.
How about lowering the B+ voltage to the plates? I have another high gain amp using 2 EL84s that has a 7/15 watt switch which lowers the B+ to the power tubes, and I like the way the 7 watt setting sounds. Has anyone tried something similar to this? I want to try to get the amp down to about 8-10 watts each tube if possible, but not reduce the B+ to the preamp. Any suggestions would be much appreciated. Thanks- Mark

[Andy Le Blanc]

Use different value bias resistors, dont worry about the screen grid resistors
your not changing supply voltage. You might want to try different values of
bypass cap, to taste, but the bypass cap is not critical to changing the operating point of the tube.
If you haven't yet, now would be a good time to
make a full page blow up of your tubes Ip Ep , plate family static characteristic
curves, and plot the plate maximum dissipation boundary, and locate your
operating point(s) and load line(s) so you can "see" what your doing.

[pinkmarkos]

Andy Leblanc- Thanks for your response. Just wanted to make sure I was doing things the right way Mark