EL34 Bias Question- 69 Super Bass

[finalapproach2]

Seeking guidance! Just bought a 69 Super Bass, installed new set of Mullards (EL34s/CV4004), did some checks: 484V Plate voltage, -40 bias voltage, 42 milliamp draw on pin 8 (Cathode I think) of all 4 power tubes. Amp sounds great, but those tubes seem very hot. Are these measurements over the often states 70% tube output? One fella alleged that whatever the current draw is on the cathode pin 8, is actually less at the plate. If so, this "appears" to be about a 69.5% tube output. If untrue, another calculation resulted in 82% tube output (yikes). It sure sounds nice though...

 

[EADGBE]

I believe I like 34-36 mA on each EL34. So yes your measurements seem a little high. Be very careful when probing the insides of a live amp.

 

[yladrd61]

Most EL 34 screens draw approx 4 ma current at idle 25W / 484 VDC = 0.0516528926 x 0.736 = 0.038016529 + .004 = .042016529 so you are running around 73.6 % of max dissipation about 18.4 watts per tube.
I usually run them at around 65% which would be about 37 ma cathode current.

 

[Maggot Brain]

these guys are on the money /\

Might want to back her off a hair.

 

[Norfolk Martin]

42 ma total cathode current is a bit hot compared to how I usually set EL34s with that sort of plate voltage I go for 36-38.