Good results with Si Fuzz Face transistors

[col]

I must have built around a dozen variations of the Fuzz Face but last week I was asked to build one for a friend as he really liked my Ge version. I ended up trying some Si transistors in the siliface 2 circuit from Fuzz Central with very close measured hfe to the normally recommended Ge ones and this particular pedal sounded awesome. I used an NKT10339 (hfe 58) for Tr1 and A BC639 (hfe 140) for Tr2 (BCE pinout!!!!). It sounds much better than the one I use and he's over the moon with it! I can see a rebuild coming on.

[alex frias]

I´ve built the AxisFace with a rotary selector for diferente input caps. It sounded more interesting for me than my other Ge FF´s. Another mod I did, suggested in this forum, was to lower the value of feedback resistor. I´ve used 68k and the volume knob on the guitar cleaned up the fuzz quite well. I used 2N2222 and BC238 for trannies. At the begining I´ve tried BC108, but the hfe was too much. Asit was inside a yellow metal box I called it Yell-O-Face. Duh!

[col]

Not the ALEX face?

[Dragonfly]

Pretty much everyone around here knows how much I love low gain silicons in a FF

BTW....try two REALLY low gainers .... 40-80hfe for both positions....

[alex frias]

Not a yellow face myself..

Great Dragon, could you suggest some trannies?

[Dragonfly]

2369's will often be in that range...other than that you'll have to look into nos trannies, which can be "all over the map" hfe wise...

[alex frias]

PHILLIPS ones?

[Dragonfly]

PHILLIPS ones?

those will be just fine for the 2N2369A's

[mac]

2n2369: killing fuzz but some members complain about RF interference. A small pF cap at the input may solve this problem.

mac

[alex frias]

Nice touch!

[petemoore]

  series resistor [10k?] at the input...[maybe, often kills RF].
 ferrite beads...little known and mysterious devices which were once claimed to squelch RF. IME, Lack of info prevented all experimentation.

[Dragonfly]

2n2369: killing fuzz but some members complain about RF interference. A small pF cap at the input may solve this problem.

mac

10pf - 15pf is usually plenty...47pf if you cant find the smaller values

[Dragonfly]

  series resistor [10k?] at the input...[maybe, often kills RF].

usually a 1k - 4k7 is plenty IME

  ferrite beads...little known and mysterious devices which were once claimed to squelch RF. IME, Lack of info prevented all experimentation.

ah, the mysterious beads....

[Shepherd]

I don't think there is a problem with Si FF's sounding bad.

They just don't perform exactly like the Ge FF's.  Which is what some builders expect.

[Dragonfly]

I don't think there is a problem with Si FF's sounding bad.

Believe me, i've heard plenty of BAD sounding silicon FFs

They just don't perform exactly like the Ge FF's.  Which is what some builders expect.

Definitely true to some extent, but I think the vast majority of people building a pedal probably are aware of the differences....maybe not how "much" difference there is between the germanium and silicon versions though, that much is true.

[joegagan]

 i like the differences.
the  si FFs i have liked have a splatty harshness with big bottom, along with hint of octavey sounding ghosts.

the germs are just swirly fat and damn cool.

[mac]

Is it ok to say that I'm using more the 2n2219A Si than the AC121 Ge? 

I have some ferrite beads, I'm going to experiment some day.

mac

[Pushtone]

I got a bunch of 2N2219A's and they sound great in an Axis Face.
All the data sheets I've see have the spec hfe around 75.

I've tried pairing it up with the BC139 (as in the Fuzz Central Axis Face) in Q2 but prefer a pair of the 2219s.

I'm just getting started in my fuzz phase and need to try more transistors myself.
So far I can hear why Dragonfly likes low gain transistors in a FF.
At least as Q1 like the FuzzCentral.com page suggests.
It lets the fuzz stand up on end with the wool being pulled over the sound.

I should try replacing the 5088s in your El Diablo with one or more 2219s.
Wonder what that would sound like? Hum, give me a minute.



True or False: A transistor number ending with "A" indicates a low gain specification?



From my searches here is a list of transistors alternative for a SI Fuzz Face type circuit,
although I was researching the Axis Face specifically.

2N3906
2N2369
2N2219
2N3903
2N1613
2N1893
2N2102
2N2193
2SC1213
BC140
BC139

[drewl]

2369's will often be in that range...other than that you'll have to look into nos trannies, which can be "all over the map" hfe wise...

Hmm, coincidence.....I always check the transistors on junk boards I come across and was looking up some 2369's that are on an oscillator circuit I found.
Seeing their low HFE I was thinking of trying them or asking y'all about them.....now I don't have to!

I also came across a dozen or so unmarked transistors in an old CB radio that have real low gain for fuzz use.

[nelson]

I have a great silicon fuzz facesque circuit that uses high gainers. It sounds great. I suppose the only fuzz face like quality of it is that it utilises negative feedback to Q1 though.

A tip, try a small PF cap 10-100pF paralleled with the resistor in the connection between Q1B and Q2E.

Currently I have an NPN sili high gain fuzz face style circuit with this configuration on my breadboard. I have the small cap paralleled with a 10K resistor in series with a 100K "sustain" pot controlling the amount of negative feedback. This allows you to control the amount of high end shrill from the Si FF as well as other things - it produces a lovely amount of squash and gets incredibly wooly! I have coupled that with a 2KC Gain pot and a 100KA Gate pot to Q2c and biased Q2 rather hot to allow for over bias as well as under bias style sounds.

It's a work in progress and will be the front end for a nice fuzz/octave I am working on.

It's all based around 2N5089 style transistors in a DIL package.