This system controls the power supply voltage of your tube amp so that you can control the power output. See this great website there : http://www.hallamplification.com
Here are a few SPICE simulation to see the effect of the VVR on the voltage.
R2 and R3 form a 1Meg linear potentiometer (I use two separate resistors R2 and R3 for the SPICE simulations). I simulate current consumption with I1 (40mA) and I2 (10mA). Of course, it’s not a real power supply, that would need more filtering stages for preamp …
Quite full voltage (let’s say attenuator pot to 0) :
Mid voltage attenuation :
Max voltage attenuation :
My implementation on EZ board :
Tests (roots !) :