The Fat Foot Effects Thallium 81 is a hard clipping distortion pedal, a design intended to add gain to your sound without erasing what your guitar and amp already do. Delicious Audio's Paolo De Gregorio described the design goal as "a hard clipper that would retain the character of the guitar and amp combo but adds a little spice to the chain"1. Pedal of the Day, reviewing it in December 2018, heard much the same thing: "Retaining the character of your guitar and amp, while adding in some spice to your sound, the Thallium 81 is versatile"2.
What it does to your sound
The Thallium 81 is built around an amplifier-style gain stage. The Gain control adjusts the gain of that amplifier circuit in the pedal, sweeping from a broken up boost to hard pushed amp sounds21. At the low end of its travel it works as a dirty boost; pushed harder it becomes a full distortion. Pedal of the Day summed it up as "a dirty boost, overdrive and genuine distortion all wrapped in one"2, and found that it "brings the thunder, but not in an overpowering kind of way"2.
Because it is a hard clipping circuit, the pedal shapes the signal by flattening its peaks, which is the classic approach behind many distortion pedals. The difference here is the stated aim of keeping your amp's voice intact rather than replacing it, which puts it closer in spirit to some overdrive pedals even though it is sold as a distortion21.
The controls
There are only three knobs, which was deliberate. De Gregorio wrote that versatility mattered, but that the aim was not to overload the player with options1.
| Control | What it does |
|---|---|
| Gain | Adjusts the gain of the amplifier circuit in the pedal, from broken up boost to hard pushed amp sounds21 |
| Tone | Blends a high pass and a low pass filter; pretty flat at noon with a slight bump at about 400 Hz, clockwise cuts the high end, counter clockwise cuts the low end1 |
| Volume | Sets your output2 |
The Tone control is the most unusual of the three. It does not add any frequencies, it simply cuts highs or lows depending on its position1. Pedal of the Day called it "a subtle but useful tonal EQ adjustment, blending a high and low pass filter together"2. In practice that means noon is close to neutral, and either side of noon thins the top or the bottom rather than boosting anything, a different approach from the tone stacks on many distortions.
The name and the build
The pedal takes its name from the element thallium, whose atomic number is 81. Pedal of the Day leaned into that in its review: "Just like the element it is named after, the Thallium 81 is both teratogenic and carcinogenic at heart, seeking to disrupt your central nervous system and turn your tone toxic"2.
On build quality, Pedal of the Day noted that "this guy is handmade and the quality comes shining through"2. The same review was published as a video on the Pedal of the Day YouTube channel3.
Videos
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Eric Merrow
kylealltogether
Questions
What kind of clipping does the Fat Foot Thallium 81 use?
The Thallium 81 is a hard clipping distortion. Both Pedal of the Day and Delicious Audio describe it that way: the design goal was a hard clipper that would retain the character of the guitar and amp combination while adding a little spice to the chain. Hard clipping flattens the tops of the signal's waveform, which is what gives the pedal its distortion character.
How does the Tone control work on the Thallium 81?
The Tone control blends a high pass and a low pass filter. Paolo De Gregorio of Delicious Audio says it was designed to be pretty flat at noon, with just a slight bump at about 400 Hz. Turned clockwise it cuts the high end, and counter clockwise it cuts the low end. It does not add any frequencies, it only cuts.
Is the Fat Foot Thallium 81 an overdrive or a distortion?
It is a distortion pedal, but reviewers describe it as covering more ground. Pedal of the Day called it a dirty boost, overdrive and genuine distortion all wrapped in one. The Gain control sweeps from a broken up boost to hard pushed amp sounds, so at low settings it can behave more like an overdrive or boost.
Is the Fat Foot Thallium 81 handmade?
Yes. Pedal of the Day's review describes the pedal as handmade, adding that the quality comes shining through. Delicious Audio also describes it as a versatile but straightforward distortion pedal with simple controls.
Why is it called Thallium 81?
The pedal is named after the element thallium, whose atomic number is 81. Pedal of the Day played on that naming in its review, writing that just like the element it is named after, the Thallium 81 is both teratogenic and carcinogenic at heart, seeking to disrupt your central nervous system and turn your tone toxic.
Sources (3)
- Fat Foot Effects Thallium 81 Distortion, Delicious Audio, 2018-06-14
- Fat Foot Effects Thallium 81 Distortion, Pedal of the Day, 2018-12-20
- Fat Foot Effects Thallium 81 Distortion, Pedal of the Day, 2018-12-19