Did not have much to do this morn., in a bit of pain from various old age aliments, i.e. OLD AGE! My mind went to wandering if one could. Also, what would it sound like. The idea is just for discussion. Wandering if this idea will work, and never mind the application or implementation, cost, or loss of valuable chassis real estate. Looking at some Marshall and Fender Bassman amps with 2 channels. There are times when those who own them, will jumper the two channels together, for a mix of both. I looked at the schematics and thought I might could pull this off with one input and 1 3PDT switch. You would have two modes of operation. 1). With switch in position shown, you would have V1b (bottom valve in pic. forgot to label) in dark mode (normal Channel), and V1a in bright mode (bright Channel). Different values for R3 / R5/C1 which would correspond to a dark channel. Then Switch in opposite position you would have V1a & b in parallel for a different tone. Just to throw some values out there for values, lets use R3 = 220k ohm R5/C1 at 1.5k ohm and 33u. R4 and R2 at 100k and R6/C2 at 2.7k and 22u. Then separate volume / gain pots. Which would allow for mixing in the signals. Values given are not etched in the schematic as one would have do some mad scientist experimenting. Any takers on this subject for discussion?