Build - Pedal Project: Tonebender MK2

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.

Figure 1: Turret board layout of the Tonebender MK2.

Figure 1: Turret board layout of the Tonebender MK2.

See Figure 4 in our Guitar Pedal Footswitch and Jack Wiring article for the recommended footswitch and I/O wiring.

Figure 2: Tonebender MK2 Schematic

Figure 2: Tonebender MK2 Schematic

Parts List

ValueQtySKUType
Capacitors
100 nF1C-MKT-D1-400Film cap
10 nF2C-MKT-D01-400Film cap
50 µF1C-BC-47-100Electrolytic
5 µF2C-BC-4D7-63Electrolytic
Potentiometers
100k Audio1R-VAM100KA-SSVolume Control
1k Linear1R-VAM1KL-SSAttack Control
Resistors
100 kΩ1R-I100KCarbon Comp Resistor
10 kΩ2R-I10KCarbon Comp Resistor
470R1R-I470Carbon Comp Resistor
47 kΩ1R-I47KCarbon Comp Resistor
8.2 kΩ1R-I8D2KCarbon Comp Resistor
Semiconductors
OC413P-Q2N404Germanium transistor
Other Items
2x101P-HTBW-2X10Board
Black 1590BB1P-H1590BBBKEnclosure
Carling DPDT1P-H497Footswitch
Greencell 9V1S-9V-GCELLBattery
Rigid battery snap1P-BATC-SN-1SBattery snap
Mono jack1W-SC-111XOutput jack
Phenolic chickenhead knob2P-K460Knob
Stereo jack1W-SC-112BXInput jack
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