I've been looking a lot lately about fixed value tone stacks that would work with my Harvard/5F2 type builds. With some guidance from a ChasingTone article and some Blackface studying, I added a Blackface tone stack to my College Dropout (Harvard based with parallel inputs). It's temporary because I actually had drilled and set eyelets on a small square of board that's sitting on top of the guts-up chassis on my bench, and wired it in with longer leads just to try things out. Right now, the bass & mid are set values, and the treble is adjustable. I really thought I'd come up with something unique until I got to comparing schematics and layouts and realized I built a 2-knob AA964 Princeton... The idea was a basic mid-level Blackface tone hardwired into it with some level of adjustment to fine tune it with just a volume/tone setup. It does work. It also kills a lot of gain, and I've already got TWO 25uf bypass stages in this, and 2x 12ax7 tubes in it. I've never played a non-reverb Princeton before, so I don't know what to compare it to in output, but it definitely takes a hit. The parallel input is really the only reason I'm still messing with it, however, I'm not happy with the pots in it right now. I have grown to prefer linear pots on my 2-knob amps, and this is from when I still had CTS audio pots. The only real output is when the knob is at 9 or above, and when I measured it, 80% of the adjustment is covered by the last 25% of the turn. I think a linear pot would help get things up to a working level sooner and then fine tune the last half of the dial. Anyway, biased at 65% right now, my Tele stays clean & fat all the up to 12 on the dial. I haven't tried any pedals yet, but I imagine it would love them. The tone stack calculator download has been great in seeing what I have and where to go. I didn't have exact values I wanted for a copy + paste Blackface tone stack so it's taken some playing around. I haven't played with the NFB at all to dirty it up, and it definitely likes a hotter bias now. I only have a 5y3 rectifier on hand at the moment, but I want to try out a 5u4. A gz34 will just take it hotter than I want to have it I think. The mid value is 2x or more from standard Fender, but I was experimenting trying to get the output up to a more reasonable level. There's still some more tweaking to do after getting the calculator app to visualize everything, but it's all a step in the right direction I was wanting to go. I may disconnect the NFB next time just to see what happens. Here is my Nashville Tele through a Legend 1058 in a small Blues Jr sized pine cab. The "reverb" is the echo from my concrete shop floor.