What transistor hFE(s) for a high gain Fuzz Face?

[Nocaster Cat]

Subject says it all, what hFE measurements and Q positions would be considered high gain for a Fuzz Face? Thanks in advance!

[ubersam]

There's a discussion over @ fsb about the EJF1 which supposedly uses higher h_FEtransistors. BC183s with h_FE ratings of ~200 for Q1 and ~500 for Q2. I'm currently breadboarding that, but with BC109s of the same rating while I wait for some BC183s.

[LucifersTrip]

you've gotta be a little clearer on what you mean by high gain....and whether it's silicon or germanium.

[Nocaster Cat]

you've gotta be a little clearer on what you mean by high gain....and whether it's silicon or germanium.

Sorry, germanium à la Analogman's high gain Sunface.

[Jazznoise]

What have you got?

There's something to be said for the Darlington approach mentioned in the other thread on the front page. Just means it uses twice as many trannies!

[Nocaster Cat]

What have you got?

There's something to be said for the Darlington approach mentioned in the other thread on the front page. Just means it uses twice as many trannies!

I have a bunch of germaniums that fall outside the "mojo range" so I'm not looking to make a Darlington pair.

[LucifersTrip]

you've gotta be a little clearer on what you mean by high gain....and whether it's silicon or germanium.

Sorry, germanium à la Analogman's high gain Sunface.

according to what i've read, the standard Sunface uses low gain transistors ~ 40-60 hfe, so it's possible that the high gain ones might be what is considered standard, ~ 70 - 130 ...just a guess

I really doubt that he uses upwards of 150 hfe, but who knows.

If I remember right, the Sunface also has a 50K trim at the input, a 1uF instead of the 2.2uF and a 250K vol pot

[GermaniumTransistors]

150 HFE and upwards for a germanium transistor sounds like the definition of 'high gain', regarding a germanium fuzz face that is...  You start gets significant distortion and a compressed sound.

[Kesh]

OP, do you mean the hfe (current gain) of the transistors, or the overall voltage gain (essentially volume gain) of the pedal as a whole?

[pinkjimiphoton]

if building a "high gain" ge fuzzface, you can go up to around 300hfe and be fine. but it won't sound or react like a normal fuzzface. it will be almost an octave pedal.
the fuzzface ccct really doesn't seem to care for high gain transistors, it becomes a run of the mill fuzz instead of the classic sounding face.
the LOUDEST face i built actually was pretty stock ff, with much lower gain transistors...around 80 and 130 hfe. the quietest, is probably the liberal komrade variant, with 300-500hfe (ish) which is very saturated sounding with great sustain, but not as much output as the lower gain transistors..i mean, once you square a wave off, it can't really get squarer!

ymmv...you can put pretty much anything in there, but biasing them will start to get a bit tricky. if you have transistors you prefer, breadboard it and use trimmers for all the resistors and find what works best.

[midwayfair]

if building a "high gain" ge fuzzface, you can go up to around 300hfe and be fine. but it won't sound or react like a normal fuzzface. it will be almost an octave pedal.
the fuzzface ccct really doesn't seem to care for high gain transistors, it becomes a run of the mill fuzz instead of the classic sounding face.
the LOUDEST face i built actually was pretty stock ff, with much lower gain transistors...around 80 and 130 hfe.

This is my experience as well. I use 50-60 for my FFs (at least in Q1) and they are SHOCKINGLY loud, regardless of the size of that 470R ...

OP:
Keep in mind that having higher gain transistors doesn't necessarily mean a different sound if you don't want it to. It just means a little experimentation to get there. You can tweak the collector and emitter resistors, change the total voltage of the pedal or the bias, add stick series resistors between stages (this is what a pregain trim is, essentially), adjust feedback resistor sizes, etc. Luciferstrip had a thread recently on tweaking the Knight Fuzz that you could use as a template for adjusting ANY fuzz to taste. I highly recommend searching for it.

[pinkjimiphoton]

+1

[LucifersTrip]

yes...I think the biggest misconception with fuzzes & transistors in general is that higher hfe transistors mean louder volume and more fuzz.

but the main thing higher hfe transistors will do is just give you a different tone.

In the FF, the volume and fuzz can be controlled easily with the 330/470, varying the voltage on Q2C, the size of the volume pot, etc...but there will probably be some tonal changes, of course.

[mac]

The problem with high gain germs is that in most cases more hfe mean more leakage. And a germ darlington pair multiplies leakage x gain... so biasing close to the standard values if leakage is high can be problematic...
and don't forget to check the weather channel before a show!     

The key is to get a good germ for Q1, because bias and thermal runaway depend on Q1. I don't know about those russian germs but there are nice japanese transistors that can do the job, like Matsushita 2SB176 and Toshiba 2SB56.

mac

[pinkjimiphoton]

i love how it censored matshushita.

indeed, the prob with a leaky tranny in q1 cannot be understated. a "high gain" ge may sound good there...IF the ambient temp is always constant, you can get away with it.
but here in the northeast usa, it changes too much...and the things will either not work, or fart, or just stare at ya like...wtf?

i will look into the suggested trannies, too...thanks mac!

but in the end, i think (again) the heaviest sounds in a FF seem to come from low gain trannys...high gain sounds more like an octave up with crummy matching, at least to my ears.

speaking of which, proper matching of gain in a pair of trannys in an octave type fuzz makes a huge diff..

when dino sent me a matched set of trannys for my superfuzz clone, the octave became STARTLING and is there in both setting now, which is totally hip!!

[Gus]

The hfe you read on a DMM etc might/will not be what the hfe is in circuit

Look up the spec for transistors you use in a FF like circuit if you can find the hfe vs collector current you might note how it changes with collector current.

How do you know the collector current you should test at if possible?  Ohms law the voltage across the collector resistors of a known good build  divided by the resistance value.  Also note the C to E voltage.

There are other places in the circuit that affect the bias besides the collector resistor values

The emitter resistor value at Q2 and Q1 (if you have one at that stage)

The feedback resistor from Q2 emitter to Q1 base this is part of Q1 bias AND the interaction of Q1 open loop gain vs closed loop gain.   Closed loop is the feedback resistor value divided by the guitar/ cable circuit before the ff like circuit along with the open loop gain of Q1, also note Q1 open loop gain can change with the transistor being closer to saturation or cutoff.  Examine the pinch control of a certain circuit.

I adjust resistor values for different transistors used to adjust the circuit to what I want.

[mac]

but here in the northeast usa, it changes too much...and the things will either not work, or fart, or just stare at ya like...wtf?

It's the same thing here... sea weather 
Finally I opted for a BD237-AC187K hybrid.

mac