The Thermion PowerTrem is a compact tremolo pedal from Thermion, a Spanish builder whose pedals are handcrafted in Spain as part of the company's PowerBolt series. It is a 100% analog circuit with two switchable modes: Normal, a warm, traditional volume-based tremolo, and Harmonic, which alternately modulates the high and low frequencies for a more complex and organic effect. Thermion describes the pedal as combining "the vintage soul of a classic tremolo with the richness of a harmonic tremolo in a compact, robust" format1.
What it does: normal and harmonic tremolo
Tremolo pedals come in two broad families. A classic or amplitude tremolo swells the whole signal's volume up and down, the effect heard on vintage amplifiers. A harmonic tremolo splits the signal into frequency bands and modulates them against each other, which produces a richer, more layered movement. The PowerTrem offers both in one box. Thermion's product page describes the two modes this way: "With two switchable modes Normal and Harmonic this pedal covers everything from smooth, rhythmic strokes to enveloping" sounds1. A mode selection switch on the pedal chooses between harmonic tremolo and classic tremolo1.
For a player, that means one pedal can cover a straightforward pulsing tremolo and the more involved harmonic movement, without carrying two pedals. The PowerTrem offers two switchable modes, Normal and Harmonic: Normal mode provides a warm, traditional tremolo volume, while Harmonic mode alternately modulates the high and low frequencies. If you are new to the effect type, the Tremolo Pedals page explains the wider field1.
The controls
The PowerTrem keeps its top panel simple, with an internal switch for waveform shape1:
| Control | What it does |
|---|---|
| Speed | Sets the tremolo speed1 |
| Depth | Sets the depth of the effect1 |
| Level | Level control for output1 |
| Intensity | Intensity control1 |
| Mode selection switch | Chooses harmonic tremolo or classic tremolo1 |
| Internal selector | Internal sine or square wave selector1 |
The internal sine or square wave selector is worth knowing about before you buy: the choice of LFO waveform, a smooth sine or a sharper square, is made inside the pedal rather than from the top panel, so it is a set-and-forget decision rather than a performance control1.
Power and specifications
The PowerTrem runs on standard pedal power: 9V center negative through a 2.1mm DC jack, drawing 35mA1. The input impedance is greater than 1MΩ and the output impedance is less than 1kΩ1. The pedal measures 7x11x5cm (WxHxD) and weighs 235gr1.
Thermion lists protection against polarity inversion, AC connection and momentary overvoltage1. Even so, the pedal has no battery option mentioned and needs a 9V DC center negative supply; an AC adapter or a reversed plug is exactly what the protection circuit is there for.
True bypass means the pedal is out of the signal path when switched off1.
Where it came from and what reviewers said
Guitar Pedal X's Stefan Karlsson, writing in April 2026, described the PowerTrem as "in part based on JAM Pedals' Harmonious Monk"3. The PowerTrem sits alongside other PowerBolt series pedals from Thermion, which also include the analog PowerDrive overdrive and PowerMuff fuzz distortion3.
In Guitar Pedal X's December 2025 buying guide to the year's modulation pedals, Karlsson gave this verdict23:
"Great Amplitude and Harmonic Tremolo at a brilliant affordable price - budget / affordable pedals are rarely this good"
The same guide listed the pedal at €125 / $145 as of December 20252.
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Questions
Is the Thermion PowerTrem true bypass?
Yes. Thermion's product page lists the PowerTrem as true bypass, so when the pedal is off your guitar's signal passes through without the circuit loading it. The pedal runs on standard 9V center negative power through a 2.1mm DC jack and draws 35mA.
Is the Thermion PowerTrem based on the JAM Pedals Harmonious Monk?
In part. Guitar Pedal X's Stefan Karlsson described the PowerTrem as in part based on JAM Pedals' Harmonious Monk, and in a later buying guide called it a great amplitude and harmonic tremolo at a brilliant affordable price, noting that budget and affordable pedals are rarely this good.
Can the PowerTrem switch between sine and square wave?
Yes, but not from the top panel. The PowerTrem has an internal selector that chooses between a sine or square wave for the tremolo's LFO, so you set the waveform shape inside the pedal and leave the external controls for speed, depth and level.
How much does the Thermion PowerTrem cost in the US?
Guitar Pedal X's 2025 buying guide listed the PowerTrem at €125 / $145. That figure dates from December 2025, so the current US price may have changed since.
Where is the Thermion PowerTrem made?
Thermion builds the PowerTrem in Spain, Europe, handcrafted as part of the company's PowerBolt series. The maker says this is to ensure the highest quality.
Sources (3)
- PowerTrem, Thermion
- Guitar Pedal X, Guitar Pedal X, 2025-12-09
- Guitar Pedal X, Guitar Pedal X, 2026-04-28
