Calculate voltage for output tubes

[fossilshark]

How do i calculate the right bias voltage for 2 el34s running in push pull 50 watts. The bias current is 41ma theyre a matched pair.

[Glenn]

Hi Fossil - I have used this and there are bias tables for some output tube types including EL34's

http://www.tedweber.com/webervst/tubes1/calcbias.htm

hope this helps

[pompeiisneaks]

Yup absolutely dig that weber calculator.

Also if you look, you'll need the plate voltage as well to see what is 'optimal' for that plate voltage.

~Phil

[sluckey]

How do i calculate the right bias voltage for 2 el34s running in push pull 50 watts. The bias current is 41ma theyre a matched pair.

The right bias voltage??? Do you mean the negative bias voltage that will be applied to the control grids? If so, you don't calculate it. You build the bias voltage supply and make it adjustable between -35v and -50v.

[PRR]

You need a pre-guess for design.

Figure Screen voltage, divided by Mu(g2).

For 6V6 6L6 EL34 6550 KT66 KT88 and friends, Mu(g2) is about 10. EL84 and a few other high-gain tubes, Mu(g2) is about 18.

So: 6L6, say 360V on screens. 360/10 is 36V.

You need a bit more than that to Cut-OFF the tube.

You need about half (maybe 0.6) of that to run the tube HOT.

So you would rig a bias supply and trim to go say -40V to -20V.