fuzzface q2?

[lightningfingers]

im currently building a fuzzface, and im waiting for my transistors to arrive from small bear, but people have said to me to use a regular si 2N3906 for q2 to save on germaniums. would this have a big (or even audible) effect on the vintage sound?

[AL]

Joe Gagan's Easyface uses a 3906 for Q1.  There is a schem at General Guitar Gadgets. My best advice would be test different combinations yourself and go with what your ears tell you.

AL

[petemoore]

3906 in Pos Gnd PNP FF will/should work.
 Ge's sound different.
 I like the Ge/si hybrid sound, and 3906 should be a suitable candidate as far as Hfe for Q2.
 It sure makes It easier to get it to hold bias IME.
 A trimpot for bais, I always say, for FF Q2 collector.

[brett]

3906 should be a suitable candidate as far as Hfe for Q2.

Sorry to disagree, Pete, but I figure that the 2N3906 has too high an hFE.  Ideal values are 70 to 130, whereas the 2N3906 is more like 160 to 200. (My current batch at home are mostly 180 to 190).  

But fortunately, you can reduce the hFE of a 2N3906.  Simply align 2 2N3906s, one in front of the other, and solder the bases and emitters together.  Then cut off one of the collectors.  You now have a "piggybacked" 2N3906 with a working hFE of about 1/3 of the individual transistors.  I like piggybacked PN200s because the hFE reduces from high 300s to low 100s.  The only rules are to use the same type of transistor and leave one collector disconnected (this maximises base current increase and hFE reduction).

Try it out.  For a cost of about 50c you might be pleased with the results.

have fun

[dosmun]

Use the  3906's to get your pedal up and going before you try the GE's.  That way you don't have to worry about ruining the vintage ones.  The Si's actually don't sound that bad.  not as good as the GE's but at least you can get the FF up and working properly.

I may actually build a FF using just 3906's or something similar for the heck of it.

[Torchy]

... you can reduce the hFE of a 2N3906.  Simply align 2 2N3906s, one in front of the other, and solder the bases and emitters together.  Then cut off one of the collectors.  You now have a "piggybacked" 2N3906 with a working hFE of about 1/3 of the individual transistors.  I like piggybacked PN200s because the hFE reduces from high 300s to low 100s.  The only rules are to use the same type of transistor and leave one collector disconnected (this maximises base current increase and hFE reduction).

Try it out.  For a cost of about 50c you might be pleased with the results.

have fun

Now THAT is sumething Ive not heard of before ... live and learn eh ?
Momma, pass me them thar three-legged hamster turds ...

[petemoore]

I just HATE that ammdded ALT key...totally disappears the page I'd been typing on...stupid !!!
 8 Pin IC socket, the three holes at the 'top' of each 'column' [socket oriented so pins go up each side] used for cct transistor and piggybacked one.
 the left side of the socket connected just like the schematic.
 The right side of the socket...top pin open, the next two pins go to Base and Collector [straight across the socket], and the bottom pins of each column will get different resistors or a wire...you can dial in many different Hfe's for that Q position this way. also its real sturdy.
 Try a resistor of between 1k and 10k connected to the pigged Q's emitters...this will reduce the reduction of gain from piggybacking...ie you can dial up/down Hfe within parameters.
 take a look at the Miss Piggy.
 yes 3906 Are probably a little hot for some...some use 5088's too.
 I like the Piggyback FF. Especially handy for dialing Si's Hfe Down for use in Q1.
 Ive also used an 8 pin IC, wired through a small piece of perf, so that it will plug directly into a transistor socket, I dial in what I want then configure the transistors and resistor [pigs] and plug into the boards socket. this is nice for already built FF's. You can try pig configs, then use the sample-pig socket for the some other Pig build.

[petemoore]

Just about any type of Q could work in a FF with biasing.
 It is recommended to do alot of tweeking on 'your' FF, swapping Q's being one of the most important changes to try.
 I believe extensive FF testing should be performed, as it is the best way to get your FF cct to act in a way you like.

[RedHouse]

Hey Bret,

About that piggyback thing, I just tried a piggy back of 2- 2N3906's (both with an hfe of 180) in my transistor tester, it read hfe=6 which isn't near the 1/3 you were speaking of.  Is piggybacking not testable in a DMM (mine's a decent one) transistor test socket? if not, would one I test them to get accurate hfe readings when piggybacked?

[RedHouse]

I'm sorry Brett, a thousand pardon-me's for mis-spelling your name!

(sheesh I hate typing!)

[brett]

Hi.

Hey Redhouse, good on you for trying a piggybacked 2N3906.

About that piggyback thing, I just tried a piggy back of 2- 2N3906's (both with an hfe of 180) in my transistor tester, it read hfe=6 which isn't near the 1/3 you were speaking of. Is piggybacking not testable in a DMM (mine's a decent one) transistor test socket? if not, would one I test them to get accurate hfe readings when piggybacked?

You got it.  DMMs measure the hFE of transistors at a single point on their hFE vs Ic (collector current) curve.  Usually, that doesn't matter too much, coz the curve is kinda flat.  e.g. hFE of a 2N3906 might range from 100 (at low Ic) to 200 (high Ic).  But piggybacking a 2N3906 makes that range really wide, and start at zero.  So the range might be from 0 to 200.  Your DMM, like mine, measures hFE at low Ic (say 10uA), which makes piggybacked transistors look like they have almost no hFE.  But at the operating Ic in Q2 (or Q1) in a fuzzface, which is more like 500uA, the hFE is going to be much more useful, like 50 or 100.

Sorry if that's as clear as mud.  Main thing is that it works.

One of these days I should build a transistor tester (like RG's tester at geofex) and plot hFE vs Ic for a range of regular and piggybacked transistors, which will help explain what's going on.  

have fun with that fuzzface