The Thermion Stone Age is a multi-engine fuzz pedal: instead of one fixed fuzz circuit, it carries four selectable engines, each a different take on the effect. You choose between Single Transistor, Maestro, Face, and a fourth engine called Thermion, which Thermion describes as a modern Muff modified with improved dynamics and definition1. The idea is one box that covers classic and renowned fuzz sounds as well as modern and experimental ones1.
Thermion is a Spanish effects maker, and Guitar World noted that the company "has put nearly everything you could possibly want into this hugely versatile pedal"2. The pedal is transistor based, with relay switching and true bypass1.
Four fuzz engines in one pedal
The core of the Stone Age is its engine selector. Each engine is a distinct fuzz circuit with its own character, and the Volume and Gain controls serve as a shared base that each engine shapes differently4. The four engines are:
- Single Transistor: a bright, crunchy circuit. Guitar World's reviewer found it "has a bright crunchy vibe to it and, although it's a fuzz circuit, it can offer an array" of broken-up, overdrive-like tones3.
- Maestro: an engine named for the early Maestro fuzz tradition1.
- Face: an engine in the Fuzz Face lineage1.
- Thermion: a modern Muff circuit modified with improved dynamics and definition1.
For a player, this means one pedal can cover the range from vintage-style fuzz to a tighter, more modern Muff voicing, without rebuilding a pedalboard around several boxes. Pedal of the Day described it as "an options-laden fuzz topped with 2 other signal blends and a slew of controls to fit any rig"4.
The controls
The Stone Age front panel is dense but organized. Thermion lists the controls as Volume, Gain, High Cut, Low Cut, an EQ Bypass option, and two footswitch-controlled blends: Clean Mix and Octave Mix1. Guitar World's review adds an Add Octave footswitch and a Fuzz selector switch to that list3.
| Control | What it does |
|---|---|
| Fuzz selector | Chooses between the four engines: Single Transistor, Maestro, Face, Thermion13 |
| Volume | Sets the overall output level1 |
| Gain | Sets the fuzz amount, shared across the engines4 |
| High Cut | Rolls off top end1 |
| Low Cut | Rolls off bottom end1 |
| EQ Bypass | Takes the High Cut and Low Cut controls out of the signal path1 |
| Clean Mix (footswitch) | Blends your clean signal in with the fuzz14 |
| Octave Mix / Add Octave (footswitch) | Adds an octave signal to the fuzz13 |
The two blend footswitches are where the pedal gets flexible. Pedal of the Day called them "the real fun for us": the Clean option lets you "inject as much of your clean signal into the mix as you'd like," which keeps low end and note definition under the fuzz, while the Octave option can "conjure up classic octave fuzz tones, some that get wildly experimental and psychedelic"4. The EQ Bypass means the cut controls can be taken out entirely when an engine sounds right as-is1.
Power, connections and build
The Stone Age runs on standard pedal power: a 9V center negative 2.1mm DC jack1. Guitar World lists the draw at 140mA, with the adapter not supplied3.
At 140mA3, the Stone Age draws considerably more current than a simple two-transistor fuzz. If you power a board from a compact supply, check that the output can deliver it; this is not a low-draw vintage-style circuit.
Input impedance is greater than 1MΩ and output impedance is less than 1kΩ1, figures that suit it to being driven by guitar directly and to feeding long cable runs or later pedals. The enclosure uses anodized metal printing for durability1, and the pedal measures 15.5 x 12 x 5.7 cm and weighs 600g1.
What reviewers said
Pedal of the Day reviewed the pedal in April 2022 and came away impressed by its flexibility: "Powerful, bold and experimental, we love pedals like this"4. The review highlighted the four engines, the true bypass relay switching, and the two blend footswitches as the pedal's strengths4.
Guitar World's review was also positive, with a verdict aimed at players weighing the cost: "If you don't mind splashing the cash, we'd definitely recommend taking a look at Thermion's Stone Age, it may just take" care of all your fuzz needs3. The review lists the price as £2493.
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Questions
Is the Thermion Stone Age true bypass?
Yes. Thermion states the Stone Age is transistor based with relay switching and true bypass, and Pedal of the Day's review confirms the true bypass relay switching. When the pedal is off, your signal passes through untouched.
What power supply does the Stone Age need?
It runs on standard pedal power: a 9V center negative 2.1mm DC jack, the same supply as most modern pedals. Guitar World lists it at 140mA, so it draws more current than a simple analog fuzz and is best on an isolated supply.
Where is the Thermion Stone Age made?
In Spain. Thermion is a Spanish effects maker, and Guitar World's review lists the Stone Age's origin as Spain. The company behind it, Triode Electronic Engineering S.L., is based in the Toledo area.
How much current does the Stone Age draw?
Guitar World lists the power requirement as a 9V DC adapter at 140mA, not supplied. That is a fairly high draw for a fuzz pedal, worth noting if you run a compact power brick.
What does the Octave Mix footswitch do?
It adds an octave signal into the fuzz. Pedal of the Day found it can conjure classic octave fuzz tones and some that get wildly experimental and psychedelic, depending on the engine and gain settings you pair it with.
Is the Thermion Stone Age analog?
Yes. Thermion describes it as transistor based with relay switching, and the four engines are analog fuzz circuits: Single Transistor, Maestro, Face, and a modified Muff-style circuit called Thermion.
Sources (4)
- Stone Age, Thermion (thermion.eu)
- Guitar World's 30 favorite guitar pedals from the past 5 years, Guitar World, 2025-06-02
- Thermion Stone Age review, Guitar World, 2022-07-13
- Thermion Stone Age Fuzz Tone Engine, Pedal of the Day, 2022-04-11