Good hFe values for fuzz faces?

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Coolhand78
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Good hFe values for fuzz faces?

Post by Coolhand78 »

What are some good HFe values for ge & Si fuzz faces?

Should Q1 & Q2 match or are they better being different?
Should (is it common for) the Si trannies be higher than the Ge?

I'm looking for medium to high gain or around the same gain levels of the copper sola mk1.5 for those who are familiar? Also think analog man medium to high gain sunfaces...

Thanks for your help its greatly appreciated!!!!
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PlumCrazy
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Re: Good hFe values for fuzz faces?

Post by PlumCrazy »

the FF is a very forgiving circuit. as long as you go some reasonable combo (not a combo of 40 and 500) you'll probably get sound. stay in around the 100s for classic sounds. Higher means more gain and less cleanup. If you lower the 33k to the 10K-15K range it's usually even more forgiving.
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Coolhand78
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Re: Good hFe values for fuzz faces?

Post by Coolhand78 »

thanks for the info mate, curious to know what the tinkerers around here have had success with in terms of Ge trannies and their respective hFe values?
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TheWhiteComet
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Re: Good hFe values for fuzz faces?

Post by TheWhiteComet »

I recently finished a mojo Fuzz Face build, and I auditioned several transistors before setting on a pair of CV7005 (possibly relabeled CV7006) with hfe of 77 and 117. I also tried a matched set of 82 and 83 hfe, but the difference between the two was very minor; just a hair less gain on the matched set. Combinations of ~60 & ~80 hfe also yielded similar results as the matched pair. They all sound good. I was replacing a pair of AC128 hfe of 75 and 130. I also auditioned a matched set of AC128 52 hfe, another matched in the mid 80 hfe. Similar out come with the other transistors. The lower hfe had slightly less gain, but I was expected a bigger difference. I would also say that there was a bigger difference between the two transistor types. The AC128s were a bit fuzzier, while the CV7005 was a bit less boomy in the lows, and sounded clearer.
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vanguard
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Re: Good hFe values for fuzz faces?

Post by vanguard »

Yeah, it's a real friendly circuit that way. :cheers:
https://blackstrapelectrik.com/

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Electric Warrior
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Re: Good hFe values for fuzz faces?

Post by Electric Warrior »

With germaniums leakage has as least as much influence on the bias as hfe. The Fuzz Face/MK1.5 circuit is rather forgiving as it can sound great within a wide range of voltages. And if you're outside that range you can still tweak the resistor on Q1's collector.
With silicons the voltages mostly depend on Q1's hfe. Too low and Q2C voltage gets too low, so don't use low gainers unless you want to tweak the circuit.

Matched or mismatched is a matter of taste. Try and listen.
Everything is transitional.
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