Tonebender MK2

From the post

The Tonebender Mk2 Professional is perhaps the most iconic of all Tonebenders, and one of the most legendary fuzz pedals in history. Most famously used by Jimmy Page on the early Zeppelin albums, the Mk2 tends to be fuzzier than the Fuzz Face and the similar “Tonebender Mk1.5” with an additional gain stage in front of the circuit topology used in the latter circuits. It can have some gating, but ideally tends to have a long, singing sustain. The Tonebender Mk2 can be sensitive to which transistors are used. Three OC41s are included in the BoM below, but you may need a larger batch of transistors you can try out in the circuit. Original units used different resistor values in two locations, which can have an effect on the transistor bias. One option for tuning the circuit is to try out the different original values that Mk2s used to find the best bias while staying true to the original units. In the below layout drawing, the optional value changes are shown in parentheses, and the resistors to tweak are highlighted in violet. This is a PNP build and uses battery power only. With no LED indicator, this pedal will last a very long time on battery power. If you would like to build this pedal with a DC jack, please see our PNP "Positive Ground" Pedal Considerations tech article. See Figure 4 in our Guitar Pedal Footswitch and Jack Wiring article for the recommended footswitch and I/O wiring.