Plexi with solo volume pot?

[Ledvedder5150]

I've built a 1987 with a ppimv. I'm looking for a way to possible add a 2nd footswitchable "solo master" pot. Does anyone have any information on such a mod? I've heard that Splawn uses to do it to their modded Marshalls. I've also heard something about adding an additional 250k pot in line with the high treble volume pot, which can be brought in or out of the circuit?

Any help/info would be awesome!

[Roe]

It wont work if you crank the amp, but if you don't the best solution is to use two 500ka stereo pots in parallell for the larmar. then switch betweent the two pots

[bepone]

how i understood, it is needed gain for solo? not volume? so if needed gain it is possible in parallel withe some preamp gain pot, or after treble pot to PI, master volume with relay bypass