Univox Super Fuzz - tone mod

For #FuzzFriday here's the Univox Super Fuzz (again) with a modified tone stack. I'm in the middle of building this one and wanted more control over the tone than just the on/off switch of the original. This stays true to the tone of the original, but with a bit more control.

Univox SquareWave

This is a pretty unique fuzz from the mid-70s by Univox. It was designed by Shin-Ei and like a few other Shin-Ei designs it can suffer from volume loss. To get it back up to unity or above, DIYSB forum member LucifersTrip made some mods to the circuit that keep the original sound, but improve the circuit a little bit. (Here's the original schematic, and LT's schematic for reference)

Volume problem:
To increase volume, I slowly increased the vol pot. Even at 1M, it was still below unity. So, I added diodes in parallel. Finally it was above unity, but now the distortion (really a tone control...closer to 0K the more bassy) didn't give me a good sweep.  So, I simply increased the 27K cutoff to 100K and subbed a 1M distortion pot instead of the 250K. Beautiful!  That gave me a nice sweep from just barely too bassy to a nice thin fuzz.

Mild Gating Problem:
Anytime I see an odd small value from an emitter, base or collector to a rail, I always suspect it to be very sensitive, and it was...I slowly increased from 0K and hit a perfect spot around 2.6-2.8K. The mild gating and pick percussion were gone, resulting in a killer smooth fuzz with super long sustain.  It was nearly perfect, but a bit too harsh on the highs. A simple tweaking of the 680 gave me a sweet spot right around 1.8-2.2K. If you raise it much higher, you'll wind up with less power...and around 4-5K will start to gate again. Further, I increased the 2M to 3M, which gave a bit more richness to the higher strings. I tried up to 7M...still good (thicker on the high strings)  but I didn't want to take a chance it would change the tone too much.

Here's a demo of the original:

If you want use this layout to build the SquareWave to original specs, follow the below value changes:

• Change the 1.9k resistor to 680Ω
• Change the 2.8k resistor to 3.9k
• Change the 3M resistor to 2M
• Use a 2N5458 for Q2
• Jumper D3 and D4
• Change the 100k resistor by the diodes to 27k
• Use B250k pot for Distortion control
• Use A50k pot for Balance control

Univox Super Fuzz

This circuit is most known for being manufactures and sold by Univox, but was designed by Shin-Ei as the FY-6 and licensed to several manufacturers including Ibanez, Teisco, Kent, Companion, Apollo, and several others. The Super Fuzz has been used by many guitarist since it was first made in 1968, including Pete Townsend, J Mascis, Poison Ivy, and Josh Homme, just to name a few.

I did a layout of the Super Fuzz almost 8 months ago, and was always disappointed it wasn't really 1590B friendly. Well, I finally got around to redoing it and this version should fit just fine in 1590B. I based it off the original Super Fuzz circuit board, but with non-standing components and added polarity protection, increased the power filter cap, and added a pull down resistor.

Univox SuperFuzz (stock)

Here's a layout for the stock Univox SuperFuzz. I probably should have drawn this one first and then the modded one below, but it was actually easier to take the modded layout and reverse it back to stock.

Univox SuperFuzz (modded)

Here the Univox SuperFuzz with the mods done by FSB member derringer. It replaces the stock tone switch with a pot, as well as a few other useful mods. Socket the 2 ceramic caps going from the base to collector on Q1 and Q6 and try some different values (I'm guessing in the 100pf to 500pf range). This one's a little on the wide side, so you'd be hard pressed to fit it in a 1590B, but it should fit quite nicely in a 1590BB.