Cathode bias el34 design

[stevesamps]

Hello folks I have an amp on the bench I would like to try cathode bias el34
right now I have a hammond 270-fx SS recto and I took a look at the matchless clubman, they have 2 individual resistors 270 ohm 15W
I installed a 150 ohm 25 watt shared resistor, think this will be a good start?
I also would like to add perhaps a 100 ohm 5 watt in series on a switch for 6l6
I have built quite a few 6l6 amps with 250 10W like the old fenders
just never did this for 34's would be cool to have it switchable..

Steve

[Enzo]

I would suggest, instead of series, think parallel. Set up the basic resistor for 6L6, then calculate what parallel resistance would be needed to drop it down to EL34 levels. Yes, electrically 200 ohms is 200 ohms, and the amp doesn't care how you got there. But for reliability, I like switching a parallel element in and out - the basic path remains hard wired. If the switch were to fail, you are stuck in 6L6 mode. Ok for 6L6 and cold for EL34. In the series method, switch fails and the amp doesn't work.