Propolis Fuzz transistor question

[krupdb8]

I am pretty new to building pedals and trying to learn more about circuits and schematics.

The Propolis Fuzz requires four 2N2222 transistors. I have four of the TO-18 metal can 2N2222 for the board and they all measured in the range of 70-80 hfe using a DCA55. They work fine and sound good, but don't have the extreme biting fuzz I was expecting from this board. I should be able to try any 2222, including plastic TO-92 P2N2222 or PN2222A, right? In fact, any NPN BJT might work in this circuit? Are there other specs I need to consider for a particular transistor to work well in this circuit?

Also, is there any need or benefit of "matching" the transistors in this circiut, like by hfe? My guess, looking at the schematic, is there is no need to "match" the hfe of the four. Swapping the transistors around might make slight differences due to different hfe ratings and pushing higher or lower gain into the next stage, but probably not noticeable. If it's true that "matching" transistors does nothing for this circuit, what is an example of a circuit where matching transistors is needed or desired for best results?

Thx!
Ken

 

[Feral Feline]

You should know that not all 2222 variants are the same.


Firstly, mind the pinout:

Secondly, there are other differences that may or may not affect the performance of a circuit;
There's a good deal of info charting the differences here:

PN2222/PN2222A VS 2N2222/2N2222A Differences (Solved)

2N2222 is one of the most popular and commonly used transistors in electronics projects. But there are many variants of this transistor in the market, mainly

www.etechnophiles.com

I doubt it matters too much for the Propolis.

What does matter, is what and when to match!
For this type of Octave Fuzz (any SuperFuzz derivative where the octave-generating transistors "face each other") to get more bite/octave-up:
match Propolis' Q3 & Q4 as closely as possible.

For more on the why and where-for of transistor-based octave fuzz check out Aion's RIFT PDF, read the "Fine Tuning the Octave" section.


You can try 2N2913 for Q3 & Q4 as well as...

I'd try 2N3904 since I've got a ton and might better be able to find a match and they're in a similar gain range to the spec'd 2N2222.

I'd also try a matched set of:

2N2219
2N3053
2N3392 also works in the same hFE range.
BC337 is often used in place of 2N2222 as is
BC547

Try your luck with:
2N4401
C945 (has more gain than a 2N2222)
BC107


Whatever you try, get the datasheet for the specific type and manufacturer you've got and
MIND THE PINOUT!

 

[krupdb8]

Fantastic info, thanks Feral!

 

[neiltheseal]

What does matter, is what and when to match!
For this type of Octave Fuzz (any SuperFuzz derivative where the octave-generating transistors "face each other") to get more bite/octave-up:
match Propolis' Q3 & Q4 as closely as possible.

When you say "match them as closely as possible" do you mean the HFE of these two should be as close as possible?

 

[Feral Feline]

When you say "match them as closely as possible" do you mean the HFE of these two should be as close as possible?

Yes, I believe that's all that's required, match the hFE.

Somebody with more intimate knowledge of the inner-workings of transistors might be able to be more specific with "turn-off time" and "collector and emitter cut-off currents or whatever — my knowledge of these things is just enough to get me and others in trouble.

 

[Chuck D. Bones]

You also want to match Vbe. That's as important as HFE in the Propolis.