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hFE Ratings. Finding the sound.

Started by blewis0082, December 26, 2012, 06:19:57 PM

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blewis0082

What can I expect with diffrent hFE transistor ratings.  Im trying to pick a pair for a fuzz project I'm doing and I wanted some advice.  These will be germanium AC-128s.  I want that static, spray in your face fuzz like "Captain Fantasy" by Ween. 

What will the diffrent ratings give me?  This will help me with future projects too, I hope.

midwayfair

hfe is generally not very important. You can make a high-gain transistor sound like a low-gain one and vice versa. What is important is how you use them in the circuit. Your best bet is to locate "good" voltages for the fuzz you're building and breadboard it or use sockets on the biasing resistors (all of them -- collector, feedback, emitter) on a PCB and use a pot or try different resistors until you get the right voltages. Once you're there, you can experiment until you find the sound you want.

In general, to get a spittier fuzz, underbiasing is the easiest way to go. The fuzz will gate in that situation, rather than having a smooth decay. There are several ways of achieving this. Simply altering the bias resistor (e.g. in a fuzz face) or replacing with a pot is one way. Sagging the voltage of the entire pedal is another way if you are building something with a fixed bias (like a Bosstone).

blewis0082

Great advice.  The circuit I am building is a model of a very popular "5-knob fuzz".  The circuit has a pot for "gate" and "comp".  It is extremely versatile.  That's the main reason I picked it.  I'm pretty sure I will be able to dial it in.  I was just a little overwhelmed when picking the transistors.  I think I'm going to go with 80 hFE. 

I'm kind of learning as I go.  I don't really have alot of the technical know-how.  I've built several pedals, but I won't dare claim to know exactly what I'm doing.  Soon, I hope though. 

jeffaroo

you can shoot steve a mail at small bear and describe the sound you are going after. hes always pointed me in the right direction with fuzz. on my first order i asked for jimmy page and it was dead on tits, dead ringer what i asked for
Not enough germaniums in this world to complete my wish list !