Home Forums General DIY Pedal Discussion American Fuzz Transistor (answered)

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  • #4023
    Big O

    I have been playing around with my American Fuzz pedal by substituting different transistors for Q1-3.  I know the circuit is a modified Fuzz Not Wrong circuit, with an extra gain stage after the fuzz control.  The circuit is similar to to a former commercially available pedal made by the cat something people except for the transisitors used (2N2222 in the original circuit) and 2 different caps at the Q2 stage.  The Guitarpcb version exhanges the 2N2222’s for 2N5088’s with the 2 different value caps in the Q2 stage.

    My pedal just was not knarly enough for me, not having enough grit compared to similar Fuzz Not Wrong pedals I have heard.  So I auditioned 2N222’s (the transistors used with the first versions of the American Fuzz) as well as 2N3904’s in all three Q positions in all the possible various combinations, which took some time.  I settled with a 2N2222 at Q1 and the 2N5088’s at Q2 and Q3 as the best combo for my ears.  The 2N5088’s at Q1, Q2 and Q3 had more of a smoother distortion than a more raspy fuzz, almost overdrive like with the fuzz control all the way down.  The 2N3904’s had HFE’s around 215, the 2N222’s HFE’s were around 430 and the 2N5088’s had HFE’s around 500, all measured with my digital multimeter (not sure how accurate theses are, but pretty consistent for the different type of transistors).

    My question is does it really matter what NPN transistors are used at Q1, Q2 or Q3, and what are the ideal HFE’s at Q1, Q2 and Q3?  Has anyone else experimented with the transistors in the American Fuzz?  I figured that the 3rd gain stage transistor really didn’t matter except for the overall volume of the pedal, but changes at Q1 and Q2 might make a difference. I know that some of the older fuzz circuits were based around low gain (low HFE) transistors such as the FF.  Beyond this, my understanding of the ideal transistors for a fuzz circuit is somewhat limited.  Any explanation of what may be ideal might help.



    I’m of the opinion, (and all that follows is my opinion based on 40 plus years experience), that transistor selection is left to ears of the builder. I’m not that familiar with the “American Fuzz”, though it seems a common topology. “Ideal hFE’s” for specific transistor usage is just one of those “builder’s ears” things. The problem with “ideal” components is that they are so often ear-dependent changing drastically from builder to builder. The inconsistencies of germanium are why they got left in the dust with regards to mass production. Even silicon transistors bear inconsistencies – depending on the manufacturer; some manufacturers have excellent (tolerance) or quality control and others do not.

    Fundamentally, if a builder is doing one or two “identical” pedals, it’s all extremely subjective or ear-based for getting the best “sound” out of a pedal. If the builder is approaching multiple builds of identical pedals, then this forum is not the correct venue to address the controls of quality so required to assure consistent, quality results.

    At the hobbyist level, I find little reward in discussing the actual selection of components for any specific build outside of an academically controlled environment. There exists too little of what levels of awareness\knowledge\experience the other participants possess and discussing how to test specific values and parameters of specific components is simply a matter of academic referencing.

    In any case, I hope you don’t get too mired in the imperfections of component manufacture so exposed by the science of electronics. Rather, I hope you find what I consider a joyful experience in the exploration of the possibilities that (component-swapping) can bring.


    +1 Cybercow!  Well said!

    The question was does it really matter what transistors are used.

    I think the post was answered by stating that he has found the sound that he likes with a particular set of transistors.  After all, this whole pedal making experience is about finding the “sound” that lurks in everyone’s own ears.  The minute we start changing a circuit design or substituting different components and values we have strayed away from whatever “original” design there was.

    Thanks for the question and welcome to the forum.


    I found this site to be an excellent resource for these types of questions that lead to experimentation. Electrosmash.com

    There are many (sites and videos) that explore topics of transistors and chips so one could spend a great deal of time discovering a great deal of contradictory information so it is quite true as Mark pointed out that beauty is in the eye of the beholder and discovery is probably the most fun.

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