Anthony Leo, A Fuzz Box for Electric Guitar, Electronics Australia, August 1967 🇦🇺

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modman
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Post by modman »

This is the original publication of A. Leo's fuzz article in Electronics Australia, later published in Popular Electronics.

PDF:
Leo Fuzzbox EA 1967.pdf
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Post by modman »

Italian version of the above article:
PDF:
Radiorama 1968_08 Fuzz.pdf
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Post by mictester »

There was a follow-up to that article, correcting an error:
Popular-Electronics-1968-03-p0097 Errata for Schematic PopE 1968-02.gif
Popular-Electronics-1968-03-p0097 Errata for Schematic PopE 1968-02.gif (118.04 KiB) Viewed 1236 times
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Post by mictester »

It's actually a very good fuzz box with buffering! The only (minor) problem is that you can get a "pop" when switching off. I updated it a few years later with switching done with a 4066 CMOS switch, which completely eliminated the switching noise. I also used the usual stereo input jack to switch the power, and added a bicolour LED for mode indication. I built quite a few of the updated version for friends, and it has that 60s fuzz sound that many are looking for.
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Post by Axldeziak »

Here's a layout I found a few years back. It originally was posted here.
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Post by rockola »

I did a PCB for this, it's been in the to-be-tested queue for a while now though.

https://github.com/rockola/leo-fuzz-box

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Post by VIgeoff »

Just finished building one of these. Not the greatest or most versatile fuzz in the world but well worth having in the collection for instant classic garage fuzz.
I also get the loud pop that mictester mentioned previously. I'll try a pulldown resistor before the input cap but would welcome any other suggestions for a possible fix.
Both transistors used were Bc209c with hfe in the 500 range. I tried lots of various transistors with hfe ranging from 150 to 550 and there wasn't really much difference.
Tweaks I made were ...
Omitted 15k off q1 collector because it's not needed in a true bypass build and makes a minuscule difference.
Replaced 47k at the input with a 33k because it ate too much input volume and didn't like my low output pickups. Only got a weak fuzz with the stock value.
Swapped q2 collector resistor from the stock 6k8 to 14k. Q2 sounded dull to my ears and dropping the collector voltage just a little was a bit more to my liking.
Replaced the 10k to earth at the output with a 50k pot and parralel 33k resistor to form an output volume control. There is a ton of volume available at the output if you want it, 100k pot and 33k resistor was very loud when I tried that combination.
I repurposed an old power supply housing for my enclosure and it was plenty big enough to fit the Anthony Leo Treble Booster as well. The two circuits work very well together for a slightly wilder fuzz (bonus is I really like the treble booster on its own). I also added a switchable 0.01uf cap to earth at the output of the fuzz to stop it getting to toppy at some settings when running treble booster into fuzz.
Might be a rustic looking unit but it's solid and pretty consistent with a hobby build from the late 60s. Plenty of Australian parts in it too including the transistors which are Aussie made Fairchild from around 1970 :)
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Post by VIgeoff »

Update on switch pops. After some testing I found my popping was happening at the input and output of the treble booster. The fuzz only popped when the treble booster was also engaged. Added 1M pulldown resistors at input and output of the treble booster and no more pops.
I'm assuming that means the fuzz circuit doesn't inherently have to pop. The 10k resistor at the ouput makes for a built-in pulldown resistor at that end. A healthy input cap with no leakage or a 1meg pulldown resistor should do the trick.
Just making sure I don't put anyone off building this cool little fuzz :)

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