Here is the schematic I’m working on. It’s subject to change but I think this will be the general idea. I’m trying to keep it an 18 Watt Marshall sort of thing.
It a cascaded first tube, just real basic with a coupling cap and volume knob.
The tone control might look a little different but it is Marshall in origin. That tone control is from the Marshall 2046 Specialist. It’s a little off the beaten track Marshall model that, apparently had quality issues but it’s tone control works pretty well and sounds good. Here is the Specialist schematic.
The other thing I’m experimenting with is the PPIMV. I was trying to make the master volume sound better as it is turned down. I got the idea to look into what guitar players were doing to improve the sound of guitar volume knobs as they are turned down. I saw that adding a resistor and cap in series was a popular mod. So that’s what i tried and it sounds really good. I’ll probably leave the master volume alone.
Probably the main thing I’m looking to tweak is the split load resistors on the second stage. I feel like I need to fine tune how much to drive the phase inverter and output tubes.