Bias doubler circuit

[Mars Amp Repair]

Hello all,
I have a dr103 HiWatt that needs the bias voltage increased to get the idling current of the EL34s down from 50ma to a more reasonable 35ma.
The max the diode & filter can manage even with the divider resistor to ground disconnected (which you'd never want to do) is about -46vdc which yields about 40ma per EL34. Seems a bit high to me & would like more range to play with.
The AC from the winding is about 38vdc max. I've seen a voltage doubler ckt for this type of situation somewhere...anyone seen that one?
I have in the past added a filter directly from the diode output to ground & this tends to increase the resultant output, but in this case not enough.

Thanx, glen Mars Amp Repair

[Sock Puppet]

Hi Greg,

You might try a Villard voltage doubler

http://www.kronjaeger.com/hv/hv/src/mul/ (reverse the diodes)

With a third diode at the output to isolate it and feed your filter cap/divider chain. Should work.

S.

[Steve Conner]

I second that. I used the Villard circuit when I was modding an EL34 amp to run with 6L6s and needed more bias voltage, and it seemed to work fine. I built it as shown in sock puppet's link, no need for any third diode.

[Sock Puppet]

Steve's right of course,

Sometime's I even get my coffee wrong in the morning, sorry.

S.