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

UNIVOX: Common Super Fuzz Mods

While cleaning up some old posts, I thought I might turn back on one of my old favourites - the Univox Super Fuzz.

Here are some common mods on LTspice.

STOCK SUPER FUZZ SCHEMATIC

TONE POT MOD

It's a nice simple one and the most common mod.  The tone switch is replaced with a pot to sweep between the notch and unfiltered outputs.  I think, in the process, this actually reduces the depth of the notch.

SUPERFUZZ NOTCH POT MOD

Another common mod - this time, the pot dials in the notch.  There is no unfiltered output, just varying degrees of the notch.

SUPER FUZZ DIODE POT MOD

This one can be a bit more subtle tonally, as it doesn't specifically effect the frequency response - the pot dials in a bit of extra resistance before the diodes hit ground.  Given the signal is already heavily clipped before it hits the diodes, this one is often referred to as changing the 'body' of the fuzz and is a little rougher around the edges.

UNIVOX: SQ-150 Square Wave

I started this layout ages ago and never finished it for some reason - anyways, here it it, the Univox SQ-150 Square Wave.  Mark Hammer mods included below.

UNIVOX SQ-150 SQUARE WAVE - VERO LAYOUT

UNIVOX SQ-150 SQUARE WAVE - MARK HAMMER MODS - VERO LAYOUT

ORIGINAL SQUARE WAVE SCHEMATIC

UNIVOX: Super Fuzz, Notch Filter Mod

This is a handy little mod for the Univox Super Fuzz - especially for those who always leave the tone switch on the notch setting.  

Instead of a tone switch, there's a pot from the 100n capacitor to ground in the bridged-t notch filter, so the amount of notch can be dialled in.  If you really want to, you can have almost no notch...  but why???    

I usually like to include an octave pot in my builds, but I decided to keep the knob count down on this one.  Easy enough to add; there's space for this if you want to add it.

UNIVOX SUPER FUZZ - NOTCH FILTER MOD - VERO LAYOUT

UNIVOX SUPER FUZZ - ON THE BENCH

I used a few old transistors for low gain and a Motorola dual transistor for the long-tailed pair.  The diodes are Soviet-era D9B, not that it makes much difference on a Super Fuzz (they don't really do much).

I intentionally made a few resistors standing to leave room around the many 10uf capacitors and the sizeable dual transistor.  2 x 47uf capacitors have been used instead of the usual 100uf on the power filter, as the 100uf was too cramped.  

UNIVOX: UD-50 Unidrive, Point to Point Layout

Univox Unidrive boost with Aion FX mods

The original Univox Unidrive was a straight boost, with a bit of dirt - it was a large rocker pedal with preset gain levels on a rotary switch, and the rocker controlled the output level, not unlike a regular volume pedal, but with the increased level of a booster.  The don't really make guitar effects like this anymore, and perhaps for good reason when consider the practicalities.

The Monad adds a capacitor blend on the input to swing form top boost through to full range, and adds a pot instead of a rotary switch for gain control.  There's also a trimmer added to control feedback between gain stages - might be worth trying a larger value, or even changing this to an external pot.

UNIVOX UNIDRIVE - POINT TO POINT LAYOUT

UNIVOX UNIDRIVE SCHEMATIC

If you would prefer to make the stock model, I'm sure you can make adjustments to suit using the schematic.

UNIVOX: Super Fuzz

The Univox Super Fuzz is indeed super - possibly my most favourite octave fuzz ever...   that was until I discovered the Foxx Tone Machine.  It's now second on the list, although it's kind of special to me, largely due to Poison Ivy from the Cramps.

It's a legendary fuzz sold under many different names, with early beginnings in Japan as the Honey Psychedelic Machine.  

UNIVOX SUPER FUZZ - VERO LAYOUT

Note:  with the exception of the cap from Q4 & Q5 to ground, all 10u caps can be 1u without much effect on the frequency response.

Sixties version (grey box)

Seventies version with trimmer (super fuzz on stomp switch)

ORIGINAL UNIVOX SUPER FUZZ SCHEMATIC

There are two versions around - one is referred to as the sixties version, the other is the seventies.   

The sixties version has a 1n cap across the collector and base of Q2.  

The seventies version has a 2n cap in the same position mentioned above, and the 10k internal trimmer to adjust the octave

SUPER FUZZ LTSPICE ANALYSIS

Note:  all responses below use the first schematic, without the trimmer / 2n cap unless marked as such.

Reference voltages (approx, VCC ≈ 9.5V):

Use as a guide; results will vary.

Q1:   C 5.6V,   B 0.8V,   E 0.2V

Q2:   C 9.5V,   B 5.6V,   E 5.0V

Q3:   C 6.4V,   B 3.7V,   E 3.0V

Q4:   C 2.1V,   B 1.9V,   E 1.3V

Q5:   C 2.1V,   B 1.9V,   E 1.3V

Q6:   C 4.0V,   B 1.2V,   E 0.6V

Octave effect

The octave effect is probably clearer on the actual scope screen grabs at the end of the post, but here it is anyway.

Frequency response - pre-output stage

Output tone 1 and tone 2

Caps

Firstly, with the exception of the 10u cap on the emitter of Q4 & Q5, all 10u caps can be replaced with 1u caps with almost no impact on the frequency response.

As a reference, this is the output of the boost stage with a few different cap values.  At 40hz there's less than half a db difference between using 470n caps and 10u caps.  

1u is a safe bet, and you can easily avoid electrolytic caps with this value - why avoid electros?  Well at least try and avoid them on the input and output caps as electros leak, contributing to any potential switch pop.  The bigger the value, the higher the leakage.

If you do want to play with the frequency response, here are two caps that may not come to mind immediately.  The 10u from the emitter of Q4 and Q5 (C9) has a pretty large effect on the bass / low-end response.  The 1n cap on Q2 (C4) has a direct effect on high frequencies.

Trimmer

I'd never looked at the 10k trimmer properly until recently.  It's a common mod to adjust the amount of octave to account for using unmatched transistors for Q4 and Q5.   I'd built pedals using it, and could hear the differences, just never ran it on spice before.

As you can see, the trimmer affects the frequency response and output in certain positions.  No doubt a result of less octave being produced.

The trimmer does change the total resistance from the base of Q4 and Q5 from 22k to anywhere in the range of 22k - 32k depending on where you like to set it.

Alternatives to the stock trimmer set-up:

Reduce the 22k resistors to 18k - this way when the 10k trimmer is set to the middle position (5k), the total resistance is 23k, which is closer to the original value of 22k.

Another option is to only have the trimmer on the base of a single transistor, to adjust it to match the other.  Same values as above work just fine.   

SUPER FUZZ ON THE SCOPE - BENCH TEST

These are screen grabs from my oscilloscope. The input signal is a 440hz sine wave, approx 130mv RMS

This is the output of the first gain stage - which is just a boosted signal that has some clipping already.

The fuzz was sitting on around 50% for all below.  I didn't include the output of the long-tailed pair, as it just looks almost the same as the output without the notch filter (I may have even gotten these two images mixed up that are so similar).

This is a reasonably hot signal, I have other Super Fuzz builds where it's still a fairly clean sine wave at this stage.

This is the collector of Q3, which is where the signal is split and inverted from both the collector and emitter, which feeds into either side of the long-tailed pair.  

Now here's the emitter of Q3, which always seems a bit different to the collector

This is the output with the notch filter on

and again with the notch filter off - but who does that, right?

This is fuzz on zero, with the notch on - quite the strange looking wave