hFE Question: +/-, How Much Makes A Difference?

[railhead]

This is just a kind of general question, just for kicks, and it popped into my head as I was testing a batch of 2369s.

Let's say my goal fuzz hFEs are 75 and 150. At what point, plus or minus, will I be able to hear the difference in a higher or lower range? Like, can a human really hear the difference an 80/160 combo would make? A 70/145? A 75/170, etc., etc.?

Thoughts? Experiences?

[John Lyons]

It really depends on the circuit.
If you are close to a target HFe I'd say that you will get something that sounds "right"
The problem is that HFe targets are not very common for a lot of circuits.
Usually you can be safe in that very old circuits used lower gain devices...
Some circuit don't matter much though...

How's that for vaugue 

john]

[railhead]

Heh, no prob.

I accidentally left out the word "fuzz" in my post, which has now been modified.

[railhead]

Anyone else? RG?

[DougH]

It depends on the circuit. A well-designed discrete transistor circuit will not depend on hfe to establish its "sound". In a well-designed circuit,  bias, gain, and other circuit parameters will be independent of transistor hfe. Unfortunately, some old fuzz circuits were poorly designed and their performance flaps in the breeze depending on what transistor is used, what day of the week it is, if there is sunspot activity and what the weather forecast for next week looks like. Over time these circuits have been replicated and derived from so much by people who really don't understand simple discrete transistor circuit design that mythologies about the significance of hfe and transistor type have been formed, passed from one generation to the next, reinforced, and subsequently accepted as fact by the masses who really don't understand simple discrete transistor circuit design. (Was it Hitler who claimed if a lie is repeated often enough people will accept it as fact?)

Again, it depends on the circuit...

[railhead]

I'm referring to the basic Fuzz Face circuit. I can only tell a difference if I'm using a massively higher hFE tranny in Q1, so I was just wondering what "the math" or science would be as far as where the threshold of hFE tonal difference lies.

[Paul Perry (Frostwave)]

"the math" would be a real nightmare.
Because the whole thing is depending on exploiting non-linear parts of the transistor characteristics.
And no two transistors are the same - particularly Ge transistors.
As for how to interpret the likely audible consequences.. I doubt anyone could go there & come back alive!

The only rule: use sockets.

[DougH]

"the math" would be a real nightmare.
Because the whole thing is depending on exploiting non-linear parts of the transistor characteristics.
And no two transistors are the same - particularly Ge transistors.

Not to mention the particular guitar pickup, tone and volume control setup which hangs off the input and has a major effect on the sound as well.

[railhead]

Yeah, what you guys are saying is pretty much my experience. I have 100 2369s, and about 25% are 60-65 hFE, and the rest are right at the 75 hFE I like -- but I haven't had a chance to socket them and compare them side-by-side yet. My assumption is that I'll be hard pressed to hear the difference between a 60 hFE in Q1 vs a 75 hFE in Q1 using the same playing setup, etc.

[petemoore]

  How soon does 'that' hit a 'parameter'...
  Even low gain transistors can be 'tuned' to produce high gain FF sound, Use high output HB's as source, and bump the gain up.
  Anyway that's my 2c on what I think we're talking about.
  I like the sound of a high gain FF almost enough to have one.
  Instead I found that reducing the Hfe [especially at Q1] below a certain level, much more effectively turns my guitar volume into a gain control, The Si ~Axis Face is my go-to treble booster [guitar volume @<8, gain knob set on 'low burn' {85%..], it's not as good as my higher gain Ge FF for high gain.
  Try a bit of Q1E resistor, see AMZ, YAFF.

[Gus]

http://www.diystompboxes.com/pedals/gusFuzzFace.gif

Aron do you have a date this was posted at your site?

note the Q1 collector resistor value

[railhead]

  How soon does 'that' hit a 'parameter'...
  Even low gain transistors can be 'tuned' to produce high gain FF sound, Use high output HB's as source, and bump the gain up.
  Anyway that's my 2c on what I think we're talking about.
  I like the sound of a high gain FF almost enough to have one.
  Instead I found that reducing the Hfe [especially at Q1] below a certain level, much more effectively turns my guitar volume into a gain control, The Si ~Axis Face is my go-to treble booster [guitar volume @<8, gain knob set on 'low burn' {85%..], it's not as good as my higher gain Ge FF for high gain.
  Try a bit of Q1E resistor, see AMZ, YAFF.

Using the guitar vol as a gain control is one of the reasons why I'm loving using 2369s.