Mad Bean Pedals TONEBENDER User manual

Tonebender
FX TYPE: Fuzz
© 2017 madbeanpedals
2.05” W x 1.275” H
Terms of Use: You are free to use purchased circuit boards for both DIY and small commercial operations. You may not offer these PCBs for resale or
as part of a “kit” in a commercial fashion. Peer to peer re-sale is, of course, okay.

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R1 100k C1 10n D1 1N5817
R2 470k C2 4u7
R3 10k C3 100n Q1 - Q3 Si
R4 2k7 C4 4u7
R5 100R C5 100n T2 100k
R6 100k C6 100uF T3 25k
R7 220R C7 100n
R8 1k VOL 100kA
R9 4k7 FUZZ 1kC
RPD 1M
Trimmers
Pots
B.O.M.
Resistors Caps Diodes
Transistors
V
alue QTY Type Rating
100R 1 Metal / Carbon Film 1/4W
220R 1 Metal / Carbon Film 1/4W
1k 1 Metal / Carbon Film 1/4W
2k7 1 Metal / Carbon Film 1/4W
4k7 1 Metal / Carbon Film 1/4W
10k 1 Metal / Carbon Film 1/4W
100k 2 Metal / Carbon Film 1/4W
470k 1 Metal / Carbon Film 1/4W
1M 1 Metal / Carbon Film 1/4W
10n 1 Film 16v min.
100n 3 Film 16v min.
4u7 2 Electrolytic 16v min.
100uF 1 Electrolytic 16v min.
1N5817 1
Si 3 NPN Silicon
100k 1 Bourns 3362P
25k 1 Bourns 3362P
100kA 1 PCB Right Angle 16mm
1kC 1 PCB Right Angle 16mm
Shopping List

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1590B Drill Guide
4.43”W x 6.47”H
Bypass LED can be soldered directly to the PCB for external mounting.

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Overview
2017 Changes: Reworked the layout for centralized I/O pads. Removed cap between Q3 collector and base (mostly not
needed).
This project is a silicon version of the Tonebender fuzz, most closely comparing to the Coloursound®
Mark ii™. There are many variations of Tonebenders using both germanium and silicon transistors
with different tweaks and values. This project is a great “middle of the road” version. And, it is nothing
less than an absolute Wall of Fuzz. So, have fun!
Notes
•C5 listed as 10n on some schematics. I prefer 100n in this spot for extra bass.
•Q1 – Q3: There are many NPN transistors that will work in the Tonebender. Generally, you
want to stick to the lower gains especially for Q1 and Q2. Good ones to use for Q1-Q3 are
2n3904, 2n2222a, BL182, 2n3565, BC108 and 109. You can try higher gain transistors on Q3
such as the 2N5088 or BC459B or C. Pinouts will vary with some of these transistors. The
pinout on the PCB for Q1 – Q3 is the identical to the 2n3904 (C-B-E).
•T3 is to set the bias on the collector of Q3. Using your DMM, place the black lead to ground
and the red lead on the “TP3” pad. Adjust T3 until you get a reading of about 4.5v. Lower
values (between 3.5-4.5v will result a more compressed and squishy sound).
•T2 is purely for experimentation. Usually this is a fixed value resistor of 47k. So, start with the
trimpot set halfway up for general bias. You can then experiment with the bias point to find
your optimal fuzz tone using TP2 to monitor changes to Q2’s bias voltage.
•RPD is an optional pull-down resistor not used on most of the classic Tonebender circuits. It is
not necessary for the circuit to function but can prevent “popping” from bypass switching. You
can socket this resistor to see if you need it or not.

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