The JHS 3 Series Harmonic Trem is a compact tremolo pedal that puts two tremolo types in one box. Flip the toggle up and you get what JHS calls "a great sounding amp trem," a conventional volume-based tremolo like the built-in effect on a vintage amplifier. Flip it down and the pedal switches to JHS's take on harmonic tremolo, a circuit that splits the signal into high and low frequency channels and modulates them against each other, which JHS describes as "a dreamy effect similar to the Uni-Vibe"1.
It belongs to JHS Pedals' 3 Series, a line of affordable three-knob pedals that the company says is "designed to give you affordability and simplicity without compromising" quality1. The Harmonic Trem joined the range in September 2022 alongside the Octave Reverb, bringing the total number of 3 Series units to 132.
The controls: three knobs and a mode toggle
Every 3 Series pedal follows the same formula: three knobs, one toggle, and one footswitch4. On the Harmonic Trem the three knobs are Volume, Rate and Depth, and the toggle switch selects between the two tremolo types: amp trem and harmonic trem3.
| Control | What it does |
|---|---|
| Volume | Sets the overall output level of the pedal |
| Rate | Sets the speed of the tremolo sweep |
| Depth | Sets how deep the modulation goes |
| Toggle up | Amp tremolo, a conventional volume-based trem1 |
| Toggle down | Harmonic trem, JHS's take on the 1960 Fender circuit1 |
JHS says the three controls and one toggle "offer a wide range of sounds, perfect for beginners and professionals"567, and Vintage Guitar's review of the series noted the same layout: "Each pedal has three knobs, a footswitch, a mini-toggle, and an on/off light"567.
Power and size
The pedal runs on 9V DC negative center power and consumes 65mA1. That draw is high enough that a used battery is not part of the design; it expects a power supply, and the center-negative polarity matches the standard used by most modern pedal power bricks.
The enclosure measures 4.42 inches long, 2.38 inches wide and 1.22 inches high1, the same footprint shared by every pedal in the 3 Series, from the Compressor to the Screamer. For a player building a board, that consistency means the pedals sit in tidy rows without wasted space.
Harmonic tremolo versus amp tremolo
The two modes on this pedal represent the two main branches of tremolo. Amp tremolo, the kind built into classic Fender, Gibson, Magnatone and Premier amps, raises and lowers the volume of the whole signal. Through most of the Fifties it was the only effect available to guitarists, even predating reverb8.
Harmonic tremolo works differently. It splits the signal into high and low frequency channels and modulates their levels alternately, which gives it characteristics reminiscent of a phaser rather than a simple volume wobble9. That is also why the effect gets compared to the Uni-Vibe: both shift the frequency balance of the signal over time, producing a smoother, more swirling motion than straight amplitude tremolo.
Where the circuit came from
The harmonic tremolo traces back to Leo Fender. In 1960 he introduced the circuit in his Bandmaster and Vibrasonic amps, calling it the "Harmonic Tremolo"1. The effect first appeared in Fender "brownface" amps made between 1959 and 19639, and those original amps remain the reference point for every modern pedal version of the effect, including this one.
The 3 Series itself launched in October 2020 as a line of made-in-the-USA pedals priced at $99 each10, with JHS's Josh Scott framing the concept simply: "Every pedal is $99, no matter what the effect is"4. The Harmonic Trem and Octave Reverb arrived two years later with all-new circuits2.
What reviewers said
Pedal of the Day reviewed the Harmonic Trem in May 2025 and praised both its look and its sound, calling it "this clean white beauty" that "looks and sounds amazing," and describing the 3 Series as "a fantastic and affordable way to get into this crazy effects world we all live in"7.
"At just $99, it's hard to beat the value and range of effects you get from the JHS 3 Series pedals"
Delicious Audio's coverage described the pedal as "producing a dreamy tremolo effect reminiscent of the Uni-Vibe"3, echoing JHS's own description. Vintage Guitar's earlier review of the 3 Series line as a whole found that "the JHS 3 Series offers a great tone at a great price"11, and Gearnews wrote at the line's launch that "All the pedals sound good to me"10. Coverage of the series has not been uniformly glowing: a commenter quoted by Gearnews in 2022 said of the 3 Series pedals, "I don't think the JHS 3 series pedals sound very good, they're just fair, even at that price"12.
Videos
Ryan Lutton
Musicmaker
Pedal of the Day
Questions
What is the difference between harmonic tremolo and amp tremolo?
Amp tremolo raises and lowers the volume of the whole signal evenly. Harmonic tremolo splits the signal into high and low frequency channels and modulates them alternately, which gives it a character reminiscent of a phaser. The 3 Series Harmonic Trem has both: toggle up is amp trem, toggle down is JHS's take on the harmonic effect.
Does the JHS 3 Series Harmonic Trem sound like a Uni-Vibe?
JHS describes the harmonic mode as a dreamy effect similar to the Uni-Vibe, and reviewers at Pedal of the Day and Delicious Audio used similar language, calling it dreamy and reminiscent of the Uni-Vibe. It is a tremolo circuit rather than a vibe photocell stage, but the two effects overlap in character because both shift the frequency balance over time.
How much does the JHS 3 Series Harmonic Trem cost?
The list price is $99.00 USD on JHS Pedals' product page. Every pedal in the 3 Series carries the same $99 price tag, which was also the launch price when the line was introduced in 2020.
Where is the JHS 3 Series Harmonic Trem made?
JHS Pedals builds each 3 Series pedal in house in Kansas City, Missouri, using what the company describes as high-quality parts, quality control, and attention to every detail. Press coverage of the line has also described it as made in the USA.
How big is the JHS 3 Series Harmonic Trem?
The enclosure measures 4.42 inches long by 2.38 inches wide by 1.22 inches high. That is the same compact footprint shared across the 3 Series line, so several of them line up neatly on a small pedalboard.
Sources (12)
- 3 SERIES HARMONIC TREM, JHS Pedals
- JHS Pedals adds $99 Harmonic Tremolo and Octave Reverb to its 3 Series range, Guitar World, 2022-09-26
- JHS 3 Series Harmonic Tremolo, Delicious Audio, 2022-12-13
- OUR SUCKIEST PEDALS YET, JHS Pedals
- 3 SERIES FLANGER, JHS Pedals
- 3 SERIES RING MODULATOR, JHS Pedals
- JHS Pedals 3 Series Harmonic Trem, Pedal of the Day (www.pedal-of-the-day.com), 2025-05-25
- Guitar World (September 1996), Guitar World, 1996-09
- Source Audio True Spring Reverb, Delicious Audio, 2022-12-05
- The new JHS Series 3 pedals are priced at $99 each, gearnews.com, 2020-10-02
- JHS 3 Series, Vintage Guitar magazine, 2021-12-07
- A $99 USA made TubeScreamer? JHS Pedals 3 Series Screamer, www.gearnews.com, 2022-04-12
