Let's start by showing you the first pedal I've ever made from a kit on Musikding. Oh, many were the things I didn't know! Anyway, it's a Fuzz Factory clone, and a good starting point both as nostalgic look back and to show the later developments. I've reworked most of the things I've made at some point and this is no exception.
Given that the kit was about 30€ and the original pedal sells for about ten times that, this seemed a good motivation to try building pedals, and that was all I needed at the time.
Since then, I've added another knob and a switch on a second row. The graphics were made with the help of a friend as vector graphics and printed on a white decal. The enclosure was primed and then just clear-coated, because I enjoyed the grey color of the primer at the time.
Let's go straight to the updates. You might know of the existence of other variations of this pedal. The first thing I had done was to add a capacitor switch to emulate the "fat" version with a 2.2µF capacitor, but also a "thin" version with a smaller value than the standard 100n between the first two stages. I've ended up liking this second one so much that the version below shows two thin versions and the stock. The concept is the same. Here's a demo with 100n, 33n and 2.2µ
Much later, I've also added a tone control. It's of the passive shelving type and helps to tame some excessive fizziness, but most critically, as with most of my mods, it can be set so that it doesn't affect the original sound if wanted. Together these two additions make what's usually known as a crazy noisemachine into a tame and usable distortion/fuzz. Don't get me wrong, the craziness is all still there if you want, I'm just adding options.
The volume control is changed: instead of being in series with a 5.1k resistor, a logarithmic potentiometer makes up the whole collector load. As far as the transistor is concerned there's no change, but it means that the pedal can in theory go 6dB louder, which might seem scary given the loud reputation of this pedal. Critically, that depends on the fact that the original uses a linear potentiometer, which means that by a quarter of the rotation you're already past what's at half on a log pot and then it has nowhere to go. In the end you get a much more easily adjustable volume. I normally would frown upon this kind of DC-coupled volume control, but it doesn't scratch and I've decided to keep it for a reason I'll explain later.
The last change is the addition of a power supply filter. This doesn't affect the operation and drops negligible voltage, but allows the circuit to perform properly even with power supplies without unwanted noises.
About the name: a "7" version exists too and no schematics for it are available as far as I know. I came up with the name after finding out that the added controls are a capacitor switch and a tone control, the same I had independently came up with. I want to say they're almost more useful than some of the original controls, like the redundant "gate" and "comp" or "stab".
Final note about the tone control: some might know that as first approximation, the small signal output impedance of a common emitter is equal to the collector load. This is true if the transistor isn't saturating. If one were to use the output impedance as the "R" in an RC filter, it would work as expected only in that case. Here's a little demonstration of two filters with the same cutoff:
As you can see the transistor pulling down hard results in unavoidable sharp peaks on the negative half-wave in the first one. Although the volume control belongs to last century and the 4.7k ruins the output impedance a bit, they both serve to isolate the amplifier from the tone control and give it an almost constant resistance.