Univox Super Fuzz, black, grey, orange? whats the difference?

[carboncomp]

I been looking to build a Univox Super Fuzz, but I see there are two board variants, the early grey and black, and then the later orange and grey one with the huge super fuzz rubber pad.

The later ones have a trim pot, and the early one don't, is this the only difference and if so what value is the trim pot? 

But I have only come across this layout (without trim pot):

[digi2t]

Remember... Google is your friend.

[carboncomp]

So the only difference is the 10K pot between the two 22k resistors and ground?

[digi2t]

So the only difference is the 10K pot between the two 22k resistors and ground?

The Q2 base cap value might vary a bit from one box to another, but on the whole, yup... the trimmer is the only difference. It allows for adjusting the balance point of the octave section (more octave / less octave). Probably a production time saver, avoiding having to sift through transistors and matching pairs for the octave section.

[PRR]

"Octave-up" is a fool-the-ear trick. If any of the original fundamental gets through, the output is "richer", not "octave up". You need milliVolt matching across the transistor pair to cancel the fundamental. With 10% resistors this will be very hit/miss. When the idea was new they could sell most of the "misses"; nobody really knew what to expect. For your own DIY and playing pleasure, put in the trim! Set it smack in the middle, smoke-test, play-test, verify that it basically works. Then when you are very calm (not hepped-up from build excitement), strum a single string very steady and *carefully* trim the trimmer. Off-center, the fundamental comes back, "octave up" illusion is lessened. In the middle the fundamental is nearly cancelled, best octave-up effect.

That's a mechanical "optimum". You as a musician may prefer a sound with some fundamental behind the overtones. Another good reason to have the trimmer.