Screen resistors as a master volume?

[jamme61]

OK not a tech and sorry if this is a stupid question. I was just reading about screen resistors and read how someone used a 100k instead of a 1k screen resistor (by mistake) and it lowered the volume of the amp. Could you use a dual gang pot as your screen resistor as a master volume? Just curious about this stuff thanks

[V2]

That would be a form of power scaling, although most PS circuits vary both plate and screen voltages.

[vibratoking]

That has been tried as well as scaling the heater voltage. I haven't tried either, but there is at least one guy here that likes heater scaling as a quick and easy way to scale the amp.

The basic idea behind 'real' power scaling, as in VVR, is that the operating point stays consistent as you scale, which helps keep the tone consistent.

[Andy Le Blanc]

Yes you can shut off a power tube with the screens, but not with the value of the screen grid resistors.

You need a voltage divider with a bleeder to grounder, before the screen resistors

like a bias supply... you drop the voltage relative to the plate, reducing the screen voltage.

But... I don't know just how practical it would be, I do know that the tone and response changes, not really what a master volume is supposed to do.

Having a variable screen voltage, within a preset range, could make a practical "dynamics" control.

[V2]

Good point - I read the OP too quickly. You'd want to scale the B+ to the screens, not vary the screen R.

[matt h]

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