Univox Superfuzz

INPUT STAGE

An overly complicated input amplifier for a fuzz effect. Q1 is biased up by the 100k feedback resistor that makes a dc path through the 470k resistor, up to Q2's emitter. ac feedback takes a separate path through the 10µF and 47k path in parallel to the 470k resistor, however some of this just gets bypassed to ground via the 100nF cap. There's another bypass cap across Q2's base-collector junction, presumably to suppress high frequency oscillations.

Gain is approximately x10, and this is a decent little preamp/boost circuit on its own. Q1's collector will bias up to a bit above 1/2 V+, and Q2's emitter will be an diode drop below that. The 3.3k resistor at the output sets the lower limit of output attenuator with the interesting title of "EXPANDER."

In troubleshooting Superfuzz circuits, I often get a weak input amplifier, especially if the trouble is that the effect is working, but "doesn't sound right." The signal at the CW terminal of the EXPANDER should be strong and close to something like x10 of the input signal. Check that the coupling caps aren't shorted or open, and check that the resistors haven't drifted in value (their resistance can drift quite high).

I've worked on quite a few of the older Superfuzz pedals. This was the first "big stomp" versions I worked on. This has a different circuit board than the earlier boards. The push-push amp trim pot has been completely eliminated here. The designator is "UF-1."

To change a footswitch on one of these, you have to knock out the pin that the heel end of the "stomp-pad" is attached to. The rubber covering has to be lifted or removed to access this pin.

The footswitch itself has a beveled head that fits neatly into a metal cut out in the "stomp-pad." I couldn't find a perfect fit for this, so altering either the metal cut out or putting a bevel into the head of the new footswitch are the only options.

This adds up to a very labor intensive footswitch replacement!

The Superfuzz and the Uni Fuzz use the same circuit. Since I already wrote most of the troubleshooting in the Uni Fuzz article, I'll simply direct you there for now.

The octave up section of the pedal is examined on a separate page: Push-Push Amp Frequency Doubler

Following the double is passive diode clipping.

A passive filter follows the clipping stage, with a simple series feedback amplifier stage to provide make-up gain.

The Superfuzz seems to appear on Earth around 1967 in the form of the Fumio Mieda designed Honey Baby Crying. US distributor Unichord sold this design as the Univox Superfuzz, and this variant is the best known version. There are many additional variants, copies, and offshoots of this famous circuit.

Other pedals that contain all or some of the Superfuzz circuit:

Honey Baby Crying

Honey Special Fuzz

Psychedelic Machine

Uni Fuzz

Kay Fuzztone ("economy" version)

Malekko Fuzz