Bias Circuit

[populartsl]

I'm building a new amp which I want to use EL34s or 6L6s.

What is the best negative voltage to work from before the voltage divider for each

Cheers

[thetragichero]

EDIT: didn't understand what you were asking at first. -50v ish should be sufficient


got a transformer already or one in mind? if you've got a bias tap work from that. if not then you're stuck working from the ht winding. how are you developing the ht voltage? full wave rectifier? Diode with the cathode towards the transformer should be good enough. if it's a bridge then you've got some experimenting to do

really i just copy from other schematics that use a similar transformer

[pdf64]

I'm building a new amp which I want to use EL34s or 6L6s.

What is the best negative voltage to work from before the voltage divider for each

Cheers

More info essential! Need to know what your expected / intended screen grid voltage, and plate/cathode current, at idle is.
Then just look at the triode connected plate characteristic chart and see what control grid voltage is required to achieve that plate voltage and current; then increase it by 10-20% to account for use of non bogey tubes. Hey presto, that's the most bias voltage you'll probably require.
eg see p3 of https://tubedata.altanatubes.com.br/she ... /6L6GC.pdf and p8 of https://tubedata.altanatubes.com.br/she ... e/EL34.pdf