# Bias Trimmer and Tone Knobs for Uberfuzz



## debrad (Nov 17, 2020)

Hello again PedalPCB Forum members!

A friend has asked me to build him something SIMILAR to the Danelectro "Eisenhower Fuzz" which, based on my internet browsing, appears to be a Univox "Super Fuzz" (or PedalPCB "Uberfuzz") with additional controls for "Bass" and "Treble".

I've looked into a few options for the tone controls and I'm thinking of using "The New AMZ Tone Control" based on the Big Muff Tone Stack.  I don't think it's a 1:1 replacement for the Eisenhower's "Bass+Treble" but it should give my friend a little more tone control than just using the stock 2 position "Tone" switch (which I will also leave on the build).  At this point my only real concern is whether I can sandwich the 2 additional potentiometers (Tone+Body) between the board and the enclosure along with the additional tone circuit which I should be able to build directly on the 2 pots.

Obviously my preference is to go with the PedalPCB board but I've noticed that the "Uberfuzz" doesn't include the bias trimmer attached to the R19 and R20 resistors around Q4 and Q5 that all the other "Super Fuzz" circuit offering seem to have.  Does anyone know if there is a reason for this?  If it's useful, would it be very difficult to squeeze the trimmer into the "Uberfuzz" circuit and the enclosure?

Any other thoughts on my plans for this build?

Thanks!

- brad -


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## Jovi Bon Kenobi (Nov 17, 2020)

Just throwing this out there, but the Hyped Fuzz is also based off the Super Fuzz but with an active treble and bass as well as a tone switch that chooses between scooped and full range, which in turn seems more similar to that Eisenhower fuzz. It might be worth looking into.


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## debrad (Nov 17, 2020)

Thanks @Jovi Bon Kenobi, I did start to look at the Boss/Behringer forms of the Super Fuzz but thought I read there were some notable differences and I got the sense it would take a number of mods to convert the Boss Hyper Fuzz into a Univox Super Fuzz (I just dug back through my browser history to find this comment on freestomboxes.org:

_"to mod an FZ-2 into a convincing Superfuzz all you need to do is change one resistor and one capacitor, jumper another resistor, cut another capacitor, and move the level pot and output to the 1k resistor after IC1a. Then change the diode clippers, and you should be good to go"_

That, combined with the fact that this individual also said:

_"the business end of the FZ-2 - the octave and clipping section - is pretty much identical to the Univox, and the voicing of Fuzz I is similar to the notch switch on Superfuzz, only with a higher notch frequency and a little more treble rolloff. Then BOSS added the Fuzz II channel with a different voicing, the (maybe superfluous) Boost option, and a pretty nice tone section"_

got me thinking that, even after making all those mods to the circuit, I still might not end up with the two main sounds of the Super Fuzz (i.e. the two settings of the stock "Tone" switch.

Maybe I should take a little closer look (and listen)...


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## debrad (Nov 20, 2020)

Looks like I have a pretty good plan of attack for this modified Super Fuzz.  My only remaining question is about that trimmer around Q4 and Q5.  Is there any particular reason why @PedalPCB would have opted to leave it out (from what I understand, the trimmer is just there to fine tune the bias on these two components to help optimize the octave)?


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## Coda (Apr 27, 2021)

debrad said:


> Looks like I have a pretty good plan of attack for this modified Super Fuzz.  My only remaining question is about that trimmer around Q4 and Q5.  Is there any particular reason why @PedalPCB would have opted to leave it out (from what I understand, the trimmer is just there to fine tune the bias on these two components to help optimize the octave)?


I see this is an older thread, but I thought I would chime in, somewhat. I just finished this build, and I noticed that the pcb had no trim pot, while the build doc did, so it looks like the change was made. I will say that I wouldn’t mind lessening the octave effect a tad, but c’est la vie...


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