UNIVOX Super Fuzz vs SHIN-EI FY-6

I'll have to admit that I always thought these two guitar effects were the same circuit - well they’re almost identical; it's amazing what a difference two resistors can make.  That being said - they will sound almost the same on most settings, but there will be subtle differences primarily due to the lower boost level.

The Shin-Ei FY-6 has a 100k resistor instead of the 22k resistor found on the input of the Univox Super Fuzz, which really affects the output of the boost stage.

There's a slightly larger resistor on the emitters of the transistors responsible for the fuzz and the octave effect - 2k instead of 1k8, reducing the potential fuzz a little.

The Shin-Ei has a 1n cap across the collector and emitter of one of the transistors in the boost section, which is also common to earlier Super Fuzzes (grey box).  Later Super fuzzes had 2n caps (the colourful 1970's boxes).

BOOST

SHIN-EI FY-6

This is sweeping the Expander pot (fuzz) - on lower settings, there's much less clipping than the Super Fuzz.  Signal has been taken from the unfiltered output, as it's easier to see the differences.

UNIVOX SUPER FUZZ

Same as above, but more heavily clipped.

BOTH - NOTCH FILTERS