Anyone here have an Adjustable Bias circuit for a DC-3???

[Monsta-Tone]

Has anyone here put an adjustable bias circuit in their DC-3? I did Cathode Bias on my last one, but it really sucked the headroom out of the clean channel.

The original bias circuit is very simple and doesn't allow for a pot.

I'm just wondering if there is a simple circuit, short of adding an entire circuit, that will make this amp adjustable.

Maybe I need a beer?!?! :lol:

 

[stokes]

"The original bias circuit is very simple and doesn't allow for a pot."
Any bias supply,no matter how simple,has a resistor that sets the negative voltage supply.Find that resistor and replace it with a cermet pot of approx.twice the value.i.e. if it is a 25k resistor use a 50k pot,a 50k resistor use a 100k pot.

 

[Monsta-Tone]

I tried. There is a 33k resistor. I have a resistor wheel, and tried every value from 10 k to 1 M and the bias stayed fairly close to the same. In both cases (more or less resistance) it went up.

PM me with your email address and I'll send you the drawing. I bet another set of eyes would do the trick. Maybe I just stared at it too long.

 

[stokes]

Monsta,a look at the schem shows 2 330k resistors in series with the 33k and the 220k's.Those 330k's will have to be changed or eliminated to make any pot used in place of the 33k usable.You are going to have to do some experimenting/guessing to find the right values.I would start by replacing the 330k's with 100k's and use a 250k or 500k pot to get you in the ballpark and go from there.