This is my take on a Tone Bender MKII ... with a lot of changes. Back when I was working on the Mossy Sloth, I breadboarded and researched a bunch of vintage fuzzes, and the MKII was one of them. One of the main things I didn't like about the circuit is that the first stage required a leaky germanium transistor just to get a functioning pedal, so I shelved the project. Then recently I got the bug to build another fuzz I didn't have in my arsenal and decided to see about altering the MKII.
These are the changes I made:
-flipped the polarity (a given ... I don't like dealing with PNP)
-replaced the first stage with a FETzer valve (so it didn't require leakage anymore)
-added a bass cut control
-added a bias trim'
-reduced the output impedance
-added polarity protection, additional power filtering, and a reverse biased temperature stabilization diode (modern conveniences)
-Finally, I ended up using a low-gain silicon in Q3 rather than germanium. I didn't find it made a big impact on the sound (most of the distortion character comes from Q2) but it helped make a more stable circuit.
It doesn't sound exactly like a TBMKII; overall it's quite close, but I think it would be worth building for people who already like that circuit and also for people who want to get close to the MKII with fewer moving parts. The toloplogy is almost identical to the original circuit, so the same layout can also be used to build a classic MKII.