NPN Silicon Tonebender Mk2

[Big O]

Is such a thing possible?  Why yes!

How does it sound?  Nearly identical to the PNP Ge Tonebenders I have, a BYOC Mk2 built in 2006 and a Ramble FX Twin Bender.  The main difference is that the Si Mk2 cleans up with the fuzz knob near zero unlike the other two Germanium pedals, which still have a bit of fuzziness with the fuzz knob near zero.  The circuit works fine with medium gain NPN Silicon Transistors.

I had a Mk2 PCB that I acquired many years ago that could accommodate a NPN Si version or a PNP Ge version of the fuzz.  Due to the topology of the GPCB PUTB, I couldn’t adapt it to the NPN Si version, and I didn’t have the need for a charge pump.  As per my usual pedal building method, I modded my build to have an External Bias Control and modify the switch and board wiring by using a GPCB 3PDT Wiring Board.  The external bias tends to be helpful on a lot of fuzzes.  Since this is not a full GPCB build, I did not post this in the “Show Off Your Build” section of the forum.

It should be noted that the Mk2 Tonebender circuit is basically a Fuzz Face with an extra pre-gain transistor stage before/in front of the standard FF 2 transistor circuit configuration.  You can see this on the GPCB GBOF docs for the “Neck Beard” build which uses 2 GBOF boards.  Interestingly, the GPCB “Hot Chilicon/Sriracha Fuzz” circuit is really a NPN Si Mk2 Tonebender with an extra 4th transistor stage after the dual transistor FF portion of the circuit.  Many fuzz pedals incorporate the FF topology somewhere in the circuit, with or without additional transistor gain stages (Deep Trip BOG Fuzz, Mk2 Tonebenders, etc.)

External Cover with External Bias Control on Right Side of Enclosure

Gutshot showing GPCB 3PDT Wiring Board, one of the best GPCB Utility Boards Ever!

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