At idle, 6V6 screens pull almost no current, so there will be no voltage drop across the screen resistors.
As you turn up the volume (with signal applied!) the 6V6 starts working harder and the screens start to pull more current, and so there is more of a voltage drop across the screen resistor and (like magic
) you get a lower voltage on the screens. This is the golden egg.So if you find that you always (say) play with your amp on 5 or 6, you might want to check what this voltage "relationship" is a happy one at your chosen volume. This is achieved by being smart with your sine wave and pretty much matching its volume to your guitar's (or pedals board's) output. You then change out the screen resistors to the appropriate value to give you the voltage difference you need.
This of course, like many things is very nerdy indeed.
In THEORY, we like to see the screens at a lower value, but in reality the amp still works and it sounds ok. Perhaps you will get longer valve life, perhaps not.
Life is one big experiment
