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Tone Bender Mk II

The Solasound Tone Bender Professional Mk II otherwise known as Vox Tone Bender Professional Mk II, Marshall Supa Fuzz, RotoSound Fuzz Box or Rangemaster Fuzz Bug. This is yet another classic fuzz. Similar to the Fuzz Face but with a third transistors tucked on at the end as an extra gain stage.

Layout and Transfer

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Image is 300 dpi.

This is a NPN version of the layout, if you build this with PNP transistors you need to reverse the electrolytic capacitors and the led.

As with most germanium circuits you probably need to adjust the bias of your transistors I've included biasing information found online below. The resistors you need to adjust are the 8.2k on Q3, the 100k on Q2 and the 10k on Q1. I had a hard time getting this to sound (first at all, then) right before I understood this. My transistors leaked a bit more and I had to lower the resistor values quite a bit before I got a sweet sounding pedal.

Components

Lots can be said about the choice of transistors for this, as well as many other circuits using germanium transistors. I choose to go with NPN germaniums to make the build as simple as possible, requiring no special treatment (read power supply).

Capacitors

ValueCount
10nF2
100nF1
4.7uF2
47uF1

Pots

ValueCount
1K Lin1
100K Log1

Resistors

ValueCount
470R1
8.2K1
10K1
100K3

Other

ValueCount
Led1
Led resistor 1
Transistors3


Gut Shot

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This image was taken before I got the biasing of my germanium transistors working correctly. That's why there's silicon transistors in there.

Transistor voltage reference
Quote:
OC75 MkII (10K on Q1 base, 47K on Q2 collector)
Battery -9.01
Q1 c -8.50 b -0.038 e 0
Q2 c -0.13 b -0.076 e 0
Q3 c -8.29 b -0.13 e -0.08

OC81D MkII #1 (100K on Q1 base, 100K on Q2 collector)
Battery -9.55
Q1 c -8.51 b -0.06 e 0
Q2 c -0.13 b -0.068 e 0
Q3 c -8.72 b -0.13 e -0.07

OC81D MkII #2 (100K on Q1 base, 100K on Q2 collector)
Battery -9.50
Q1 c -8.76 b -0.062 e 0
Q2 c -0.22 b -0.075 e 0
Q3 c -8.13 b -0.22 e -0.14

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