10 thousandth fuzz circuit. Superfluous, yet interesting...

[brett]

http://www.aronnelson.com/gallery/main.php/v/BinOfBrett/Fuzz+with+no+name+schematic.jpg.html
Apologies for poor image quality.  C2 = 2.2uF.

[akc1973]

Fuzz? Superfluous? Never!!

[Derringer]

and I was just thinking yesterday ... man, haven't seen anything piggy-back related in a while

looks cool

clips?

[Tonemonger]

 :icon_eek:PIGGY-NESS ....EXCELLENT !

[brett]

Apparently, everyone thought I was serious when I say "superfluous".

Look closely - it has a "super FuzzFace" front end, with variable piggybacked gain and pickup loading.
But that's not all.  There's a differential pair for extra cool fuzziness.  This has a widely variable gain for mild to wild fuzz.
Anyone wanna build and post a clip?

[soggybag]

And it could be built from a 3086 or 3046 for extra mojo mystery.

I might have to give it a try. I was just in the middle of trying to make a BMP from a 3086. The chip contains 5 matched NPN transistors two are tied at the emitter to form a differential pair.

[soggybag]

What's up with Q1, is the collector unconnected? Is this acting as sort of a clipping diode?

[BoxOfSnoo]

What's up with Q1, is the collector unconnected? Is this acting as sort of a clipping diode?

That's what's called piggybacking.  Check this out here: http://www.diystompboxes.com/smfforum/index.php?topic=17513.20

[brett]

Hi
An odd thing about piggybacking is that back in the day we would use a fixed resistor between the emitters, so the gain and input impedance were fixed.  Given the variation between people, guitars, etc that doesn't make too much sense when I think about it now. 
This circuit implements a "Piggyness" control.  Low pig = higher gain, high input impedance, no "bloom", plenty of highs.  Lots of piggyness and you get that germanium fuzz-face sound with bloom and high-end roll-off. 
The tone and pig controls might be worth considering as a circuit on its own (it *might* sound a bit like a Rangemaster?).
cheers

[Brymus]

That does look really cool.
It hasnt been tested yet ?
Do you recomend all 3904s or just two 3904s for the piggy back and higher gains for the rest ?

[brett]

The differential pair is similar to a circuit I built a couple of years ago and liked a lot.
There is also a "standard" schematic for a differential distortion on the web, and many people say it's ok.

Piggybacking was popular and successful, but has been mostly replaced by low gain Si transistors (especially the 2N2369A made popular in the Axis Face).  My feeling is that even lower gain devices (especially power devices) can sound good in some circuits (FuzzFace, Bosstone, FuzzRite).  Variable piggybacking may offer the best of both worlds.   

The whole thing is untested except with SPICE simulations. (Since I designed it I've moved house and I still don't have my shed sorted.)

The 2N3904s are mentioned because they are low noise and very easy to get.  None of the specs are critical and most small signal trannies will be indistinguishable: 2N5088, 2N5089, MPSA18, PN100, 2N2222A, BC549C, ....
cheers

[joegagan]

i have been staring at your schem for the last few days. very intriguing. will try it out when i get the chance. i always liked piggybacks, the piggyness control looks very crafty and good to me.