Re: [Harp-L] Low plate voltage on the preamp tubes?

[Dina Janzen <dlj@xxxxxx>]

I agree that reducing the plate voltage of Fender and similar amps 
warms up the sound and makes it less stiff and gainy.  I have been 
happiest with 12AX7 voltages of 100 to 110V.   It is not hard to do, 
but involves dealing with a portion of the circuit that has REAL HIGH 
voltage.  A simple way to dial in the voltage and sound is to 
temporarily replace the power supply dropping resistor feeding the 
preamp tube plates with a potentiometer, adjust the pot to taste and/or 
voltage and then insert a fixed resistor of appropriate value.  You 
might be able to find a tech that will do just this as you play and 
listen.  It turns out that increasing the value of the last power 
supply dropping resistor has little effect on the upstream (power tube) 
voltages and power tube bias.  Allen Amplification makes an guitar amp 
with switch selectable final resistance.  Seems like one could also 
control this with a suitable control panel pot.

Heck, I'll do this for anyone who drags an amp to Augusta this year.

Jim R