Variable Voltage Regulator
Methods to control the power output in a musical instrument amplifier have been around
for a long time. The first patent that I have found for regulating power was filed in
October of 1979. Patent number 4,286,492 was granted on 9/1/1981. It was invented by
Guy P. Claret and he called it his “Control for Electronic Amplifiers”
“A circuit which allows for simultaneous control of the bias voltages applied to the
screen grids and control grids of output tubes while maintaining the ratio of said voltages
there by providing a method for selectively varying a single plate characteristic (Power
Output) of a tetrode / pentode vacuum tube”
Over the next couple of decades other people came out with different ways to vary the
voltages in a guitar amp to change the power level of the amplifier. Both Kevin
O’Connor and Dave Zimmerman came up with other ways to modify the power supplies
in guitar amplifiers to make the power output from an amp variable.
The VVR is a simple circuit that when installed in a musical instrument amplifier will
make the B+ voltage and Bias voltage variable from 100% power to a minimum power
level which is selectable by changing resistor values.