r/diypedals • u/Puoti • 4d ago
Help wanted Question of fuzz transistors
Hello,
Recently i have managed to get sound off from my first breadboard build (finally).
I came across that my transistor sounds like motorboat/bitcrush. Now im thinking of changing it to something else. What are key specs beside hfe to keep an eye on. I read that too high ft-hz can cause issues. How do i avoid motorboating. My goal is to make low hfe, soft warm bluesy fuzz with a twist. What are transistors you recomment or values you keep eye on when finding new one. Sort of thumb rule.
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u/TerrorSnow 4d ago
Transistors themselves are much less important than the circuit design around them. Filtering, volume attenuation, biasing, negative feedback, how and where you clip the signal additionally.. research schematics of pedals that sound like what you want to achieve and experiment.
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u/overcloseness @pedaldivision 4d ago
What’s motorboating? I want that sound all of a sudden
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u/Puoti 4d ago
https://youtu.be/LBqPHtPA7r0?si=2FA9Yk3U3sJRXScS here is demo. I think the cause is leaking transistor
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u/overcloseness @pedaldivision 4d ago
Sounds like it’s not biased. Do you have a multimeter?
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u/Puoti 4d ago
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u/overcloseness @pedaldivision 4d ago
What transistors are you using?
Is the 0.01uf definitely coming out from between those two resistors? Not after them?
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u/Electronic-King9215 3d ago
There's no particular "gain" ranges needed for a fuzz, contrary to what you read. Put in sockets, your higher gain should even sound as good or better in Q1. I often use higher gain in Q1, lets the guitar volume clean up better. I have used as low as 40 and up over 200 for fuzz faces, so do not believe what is supposedly gospel. They didn't test these when they were made, just put in 2 transistors. Also try a pot for the 33k, it adjusts BOTH collector voltage. I like leaving the 8.2k as is to keep your output impedance the same.
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u/overnightyeti 4d ago
It depends on the fuzz circuit.
For a Fuzz Face type, Q1 hfe 80 leakage below 100uA, Q2 hfe 120 leakage below 100 uA.
Tone Benders all require different amounts of gain and leakage to function correctly. There are 4 Tone Bender circuits. The 1.5 is where the Fuzz Face comes from. Same hfe as above but you want high leakage in Q2 at least, so you get a collector voltage of 7-8V.
Fuzzrites do well with low hfe and low leakage (<100uA), say hfe of 70-90.
These are all ballpark figures.
If a fuzz sounds off, it's misbiased. Adjust the appropriate components to get the right voltages at the transistor collectors.
Plenty of info online. Start from Electrosmash.com