Tone Bender (with DC inverter)

The Tone Bender is one of the most iconic fuzz effects from the 60s. The PCB is designed to include a built-in voltage inverter, allowing it to run on negative ground and be daisy-chained with your other pedals from the same power supply.
Steps
  1. Overview
  2. Designators and components
  3. PCB assembly
  4. Enclosure and wiring
  5. Drilling template
Categories
Tayda Electronics Kits, DIY Projects, DIY Guitar Effects
Created by DHEA
Status: Active
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Designators and components Step 2 of 5

COMPONENT LIST

PCB
PCB          TONE BENDER (WITH DC INVERTER) PCB       

Capacitors
C1    10n       10NF 100V 5% POLYESTER FILM BOX TYPE CAPACITOR
C2    4.7u      4.7UF 50V ELECTROLYTIC CAPACITOR 5X11MM
C3    100n     100NF 100V 5% POLYESTER FILM BOX TYPE CAPACITOR
C4    10n       10NF 100V 5% POLYESTER FILM BOX TYPE CAPACITOR
C5    4.7u      4.7UF 50V ELECTROLYTIC CAPACITOR 5X11MM
C6    100u     100UF 35V 105C RADIAL ELECTROLYTIC CAPACITOR 6X11MM  
C7    10u       10UF 50V 105C ALUMINUM ELECTROLYTIC CAPACITOR 5X11MM
C8    10u       10UF 50V 105C ALUMINUM ELECTROLYTIC CAPACITOR 5X11MM

Transistors        
Q1       PNP   2N3906 / NPN  2N3904, BC108 or BC109
Q2       PNP   2N3906 / NPN  2N3904, BC108 or BC109
Sockets        40 PIN DIP SIP IC SOCKETS ADAPTOR SOLDER TYPE

IC
U1      TC1044SCPA   TC1044SCPA TC1044 VOLTAGE REGULATOR IC

DIODES
D1      1N4001    1N4001 DIODE 1A 50V
D2      1N4001    1N4001 DIODE 1A 50V

Resistors
R1     1M        1M OHM 1/4W 1% METAL FILM RESISTOR (Optional)
R2     100k     100K OHM 1/4W 1% METAL FILM RESISTOR
R3     10k       10K OHM 1/4W 1% METAL FILM RESISTOR
R4     100k     100K OHM 1/4W 1% METAL FILM RESISTOR
R5     470       470 OHM 1/4W 1% METAL FILM RESISTOR
BIASQ2    100k        100K OHM TRIMMER POTENTIOMETER
BIASQ3    10k          10K OHM TRIMMER POTENTIOMETER

Potentiometers
VOL          100k-A    100K OHM LOGARITHMIC TAPER POTENTIOMETER
FUZZ        1k-B        1K OHM LINEAR TAPER POTENTIOMETER

 

PCB

 

PCB SCHEMATIC

 

INPUT IMPEDANCE

For a classic Tone Bender build, omit resistor R1. The resulting low input impedance interacts with passive pickups to attenuate high frequencies, smoothing the fuzz effect and making the circuit highly responsive to the guitar's volume knob.

The 1MΩ resistor at R1 acts as a pull-down resistor. Adding this resistor helps eliminate "switching pop" noise when engaging the effect and prevents high frequency attenuation.

 

PNP/NPN VERSION

The PCB is designed to build both positive and negative grounds. To create the positive-ground (PNP transistor) version, simply place a jumper over the PNP/NPN pads as shown below.

 

For the NPN version, flip the polarity of electrolytic capacitors C2 and C5, and there is no need to mount C7, C8, D2, and U1. Make the jumper over the PNP/NPN pads as shown below.

 

PNP AND NPN TRANSISTORS

The original Tonebender uses germanium transistors (AC128). Select the gain for each transistor within the following ranges:

Q1: β = 70-90
Q2: β = 50-70
Q3: β = 110-130

For the PNP silicon version, use 2N3906.

For NPN silicon version, use 2N3904, BC108 or BC109.

 

BIASING THE CIRCUIT

Use the trimmers to bias the circuit by measuring the voltage at the Bias pads with a voltmeter. First, adjust the Bias2 trimmer until the voltage is between –0.5 V and –1.75 V. Then, adjust Bias3 until the voltage is between –7.5 V and –8.5 V. Keep in mind that if you are using germanium transistors, the voltage will be affected by temperature.

 

 

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