DEMO [Vero] ZVEX Fuzz Factory w/ OC71, MP20

[owlexifry]

earlier this year i finally took the time to breadboard this fantastic fuzz circuit and just went with a pair of MP20 pnp units (cos they’re large and easy to handle) and i was immediately impressed with just the standard thick fuzz face sound it does with the controls in ‘normal’ positions. i knew i had to build it.

and im super stoked to finally have one, it’s heckin crazy and capable of a lot of cool sounds.

when it came time to build it, i actually spent some time auditioning combinations for Q2 and Q3.

i tried everything i have.
MP20, OC71, GT310B, AC128, AC126, AC125, 2SA49.

oddly, what i found didn’t make much sense to me when i was factoring in gain / leakage values when selecting units.
the OC71 units didn’t have a lot of gain, and ranged around 25-40 hfe (@~16’c, probably)
but somehow they sounded better than any of the other options which had higher hfe and good leakage.
(i was also quite pleased with the MP20s in comparison to the other options)

as it turned out - an OC71 worked out the best for Q2.
for Q3, on the breadboard i noticed MP20 offered more gain/saturation and gets a bit noisier, where OC71 was smoother and probably the better choice, but i liked how the MP20 was a bit more aggressive.

in the end i couldn’t decide whether to go with MP20 or OC71 for Q3, so i put them both on a 3PDT.

there’s a really nifty interaction between the gate + comp controls, and the most interesting thing i noticed is how they can affect the tone / grit of the fuzz within the range of ‘normal’ fuzz sounds (that aren’t gating, oscillating, or doing other cool crazy shit that this pedal can do)
and then just backing off the drive does strange things i didn't expect.
it even does an almost-octave thing that sounds really wild and filthy. gnarly

what a ridiculous and hectic unit. love it.

highly recommend this one to all fuzz nerds.

here’s my demo.
starts off with a disgusting octave-ish fuzz tone (one of my favourite things it can do)

in the end with the final build, despite what i found on the breadboard… vs. OC71, MP20 does have slightly more gain/saturation, but tbh it's a very subtle difference. for this demo, MP20 was selected for Q3.

 

[HamishR]

I think the Fuzz Factory is hilarious! I love it! Hardly ever use it but when I do it's a lot of fun.

I frequently find with Ge transistors that all the rules go out the window. I invariably audition a bunch and the ones I expect to work best are never the ones I end up using. hFE seems to mean very little with Ge.

 

[owlexifry]

I frequently find with Ge transistors that all the rules go out the window. I invariably audition a bunch and the ones I expect to work best are never the ones I end up using. hFE seems to mean very little with Ge.

yep this is pretty much what i’ve seen happen again and again whenever im breadboarding with germanium transistors, even when accounting for idle bias voltages etc.

 

[cendle]

Is your layout kinda like a modded Sabrotone vero layout with the 9mm pots?
Super clean vero work as always!
I’m definitely stealing that Ge-transistor on 3dpt idea, I think it will cure my habit of constantly resocketing transistors for the same fuzz every week…

That octave sag/swell drone tone is
I found that other feedback/oscillating fuzzes (LAL, Devi Ever, etc) arent as versatile as the Fuzz Factory

 

[comradehoser]

Did you see Chuck’s take in the Boneyard?

 

[owlexifry]

Is your layout kinda like a modded Sabrotone vero layout with the 9mm pots?
Super clean vero work as always!

ay thanks

yep, it’s this one:

there’s a couple different versions on that page - this is the larger one at the bottom of his post.
as you’ve probably seen, his build method/intention involves using slightly different 9mm pots to mount the board on the side of a 1590B. i meant to order that type but had an idiot moment and ordered a different type, meaning i’d have to mount the board normally, and fortunately there’s just enough room to do it.
to allow this, i needed to relocate Q1 further ‘left’ to clear the input jack, which turned out to be just an easy swap of components.
only other ‘mod’ was inclusion of a 47uF filter cap and 1N5817 polarity protection.

I’m definitely stealing that Ge-transistor on 3dpt idea, I think it will cure my habit of constantly resocketing transistors for the same fuzz every week…

a toggle would have been better, but i only had footswitch 3PDT.

That octave sag/swell drone tone is
I found that other feedback/oscillating fuzzes (LAL, Devi Ever, etc) arent as versatile as the Fuzz Factory

hell yeah i did not expect this fuzz would do things like this

Did you see Chuck’s take in the Boneyard?

looks cool but 5 knobs is already enough for me