Tonebender MK3

From the post

Coming after the Mk2 tonebender, the Mk3 is also a 3-transistor circuit like its predecessor, but the circuit topology is quite different. Q1 and Q2 form a darlington pair and operate as a single gain stage. Perhaps most notably, the Mk3 has had a simple “Tone” control added, which provides more tone-sculpting options than were found on a lot of fuzz pedals that came before it. The Mk3 topology is perhaps most similar to the Baldwin-Burns Buzzaround, which was a favorite of Robert Fripp of King Crimson. The Buzzaround did not have a volume control, but instead had a “Balance” control which functioned similarly to a volume control, but also had an effect on the bias of Q3. The controls on the Mk3 are less unusual, with a simple Volume control instead of Balance. On a Mk3, the “Fuzz” control works by increasing resistance into the base of Q3 when turned counter-clockwise, reducing the current that enters the base and the overall gain of the circuit. On a Buzzaround, the “Sustain” control is wired as a voltage divider controlling how much signal enters the base of Q3. The Mk3 circuit or a variant was found in a few different fuzz pedals of the era, some of which were built by Sola Sound/Colorsound - e.g. the Park Fuzz Sound, Rotosound Fuzz Box, Carlsbro Fuzz, etc. 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.