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Marshall JCM800 Footswitchable Solo Boost
Because this was the original 1983 Marshall JCM800 2203 amp, I didn’t want to change to much, and I wanted, that all changes are reversable easy.
The logic is simple, I add another master volume knob, and relay to switch between two masters .
Installing Master Volume
I replace LOW input with 250K alpha pot and glued it on the side.
I add relay to switch between two master volumes
And I use one of the speaker outputs to control relay with footswitch.