Dunning ∿‌‌ Kruger FX

Effect Pedals and Guitars, etc.

Potentially Broken Fuzz

Is it broken?

Potentially. I was messing around with making cheesy guitar amps based on an LM386 chip, which is basically an “amp on a chip”—it can be used to directly drive a speaker with only a few other components required. I had some leftover LM386s and decided to see if I could make a pedal with one.

This could all be slightly wrong, but one of the primary ways that distortion is produced is to push an amplifier beyond its ability to properly reproduce a signal. It tries to make “taller” waves, but it runs out of juice and the tops get flattened, which makes the waves more square, and we perceive that as distortion. There are other ways to introduce distortion, but for this general type, there are two main ways to go about it: increase the gain factor or decrease the available power and lower the headroom. While there is a built-in gain function on the LM386, I couldn’t figure out how to push it beyond that, so instead I decided to starve it of power and see what would happen. This worked, and it gets filthy.

But there was also this pin on the IC that is referred to as “bypass” in the documentation that isn’t used in any of the example circuits. I thought that it might allow me to put clean signal back into the output, but it doesn’t do that. It makes it go insane and self-oscillate, which is potentially a feature?

Details

I think most production pedals are “safe.” The designers will find the rational limits, then dial it back a bit so that there are no knob settings that will allow the pedal to go completely bonkers. They probably test it with lots of guitars so that a little lipstick pickup or some beefy humbucker named after a demon will both work. This pedal has no such safeguards. There are settings where it basically doesn’t work, but that also allows a user to take it right up to that line at their discretion. This thing has a lot of knobs:

  • Gain: controls the on-board amount of gain in the LM386, which goes from 20 to 200x gain. This produces a sort of distortion that’s more like an overdriven amp. Possibly an overdriven cheap solid state amp, but definitely more overdrive than fuzz.
  • Starve: reduces the power to the IC, which lowers its headroom and sends it into glitchy, messy fuzz. I couldn’t find a potentiometer value that would give me the full range of sounds in a usable way, so this knob is used in conjunction with the “Really Starve” switch, which adds in a fixed resistor to lower the power even more for a lo-fi, gated, bitcrushed kind of sound.
  • Tone: I have no idea how to make a tone control except for the way it’s done on the tone knob of a guitar, so this is that. It rolls off highs.
  • Volume: like a “master volume” on the end of the circuit.
  • Freq: The entire “Freak” section has to do with adding in the “bypass” pin on the IC, which basically makes it self-oscillate. On either end of the range of the Freq knob, the pedal becomes a one-note synth of arbitrary pitch, but depending on how everything else is set up, there are some unique sounds available in the middle of the range. The “Freak” footswitch engages or disengages this section.

The gain, starve, and freq are all highly interactive, and it will go to some weird places.

Vital Stats

Zaniness
Synth Tones
Transparency
On John Mayer’s Pedal Board
Deterministic