Hi Dave,

The clean channel is somewhat sterile. I think it's the 6L6 running at too high plate voltage. One of the problems with this amp is the hum level. I added a choke capacitor filter to the 6L6 plate supply  but with hindsight I think there's a better solution. With the high voltage the 6L6 can't be biased for proper class A operation. If instead of adding an LC filter you add an RC filter the hum will be reduced and the 6L6 plate voltage lowered for more normal class A operation. If you get the voltage to below 400V it should bias OK with an EL34 (or 6V6 if the PT gets too hot with the EL34). An EL34 will sound more VOX/Marshall especially if you change the tone stack 0.1u/0.047u caps to 0.022u. I have a homebrew amp like that. It was a push pull amp I converted to single ended. It has an EL34 in one power tube socket and a 6V6 in the other with a switch to select between them. I'll send you the schematic.

It should be possible to make the clean channel sound good but I'm not sure about the distortion channel. I didn't have much luck with that but I did manage to tame it a bit. I mostly used the clean channel. I wanted it to go from clean to distortion by using the guitar vol pot but it didn't have enough gain to do that. With my Strat/Tele it was always clean even with the guitar and amp vol pots on 10. You can fix that by increasing the value of R18 to give the clean channel more gain. The pull mid boost didn't sound good either so I disconnected it and used the switch to add a 10k in series with the existing 6k8 mid resistor for a more subtle mid boost.

Cheers,
Dave H.