The Ethos 60's Harmonic Bias Trem is a tremolo pedal from Custom Tones Inc, the company led by Rob Hall, and it is the company's first step into modulation effects. It is derived from the tremolo circuit of Fender's Brown Panel amps, and Delicious Audio describes it as "a meticulously designed tremolo pedal that channels the swirling, three-dimensional modulation of 1960s Brownface and Blackface Fender amps"1.
What sets it apart from most tremolo pedals is that it does the job two ways. There are two footswitchable modes: an amplitude-based standard tremolo, the kind that pulses the volume, and a harmonic tremolo, the phase-shifted vintage style used on the Brown Panel amps, where different frequency bands move against each other. Each mode has its own independent speed setting, and there is tap tempo for on-the-fly rhythmic control1.
The controls
The pedal carries six controls on its top panel, set out by Guitar Pedal X at the announcement2:
| Control | What it does |
|---|---|
| Tone | Tone control; Delicious Audio suggests it likely fine-tunes high-end response1 |
| Volume Trim | Level trim; the "VTrim", which Delicious Audio suggests likely fine-tunes bias voltage for added vintage authenticity1 |
| Slow Speed | Speed setting for the slow rate2 |
| Fast Speed | Speed setting for the fast rate2 |
| Intensity | Adjusts modulation depth across both modes1 |
| Mode | Amplitude / Harmonic switch2 |
Three footswitches handle the switching: a Speed footswitch toggling Slow / Fast, a Bypass footswitch, and mode toggling between the amplitude-based and harmonic effects12. The enclosure comes in a brown colourway, replacing the usual black-and-white approach, in keeping with the Brown Panel inspiration2.
History: Custom Tones' first modulation pedal
Custom Tones Inc had built its name on other pedal categories before this release. Guitar Pedal X reported in June 2025 that the company, led by Rob Hall, was branching into modulation with the Ethos 60's Harmonic Bias Trem, derived from Fender Brown Panel amps2. By November 2025, Delicious Audio reported the company was set to release the pedal, with full specifications not yet published1.
"This Fender Brown Panel Amp-derived Harmonic Bias Tremolo will undoubtedly complete the trifecta for me."
Price and availability
The launch price given in June 2025 was $249 plus shipping, which Guitar Pedal X's writer called very reasonable2. In Guitar Pedal X's December 2025 buying guide of the year's new modulation pedals, the price was listed as from $2493.
At the time of the June 2025 announcement there was a pre-order list in effect: you needed to email Rob@Customtonesinc.com to get on that list2. Two demos of the pedal were already available when that was written2.
What reviewers said
In the December 2025 buying guide, Stefan Karlsson summed the pedal up: "A really cool new 2-mode fully analog vintage style Amplitude and Harmonic Bias Tremolo." He noted it was still on his target list, with fluctuating priority overall3.
Videos
Mike Hermans
Tim Lerch
Shawn Tubbs
Questions
What is the difference between harmonic tremolo and amplitude tremolo?
Amplitude tremolo, the standard kind found on most Fender amps, works by raising and lowering the signal's volume. Harmonic tremolo, used on Fender's Brown Panel amps, splits the signal into phase-shifted bands and modulates them against each other, which gives a swirling, three-dimensional movement rather than a simple pulse. The Ethos offers both, as two footswitchable modes with independent speed settings.
How much does the Custom Tones Ethos tremolo cost?
Guitar Pedal X's June 2025 report gave a launch price of $249 plus shipping, which the writer called very reasonable. By the December 2025 buying guide the price was listed as from $249.
How do I order a Custom Tones Ethos 60's Harmonic Bias Trem?
At the time of the June 2025 announcement there was a pre-order list in effect, and you needed to email Rob@Customtonesinc.com to get on that list, according to Guitar Pedal X.
Is the Ethos Harmonic Bias Trem fully analog?
Yes. In Guitar Pedal X's December 2025 buying guide, Stefan Karlsson described it as a really cool new 2-mode fully analog vintage style Amplitude and Harmonic Bias Tremolo.
Can you switch between two speeds on the Ethos tremolo?
Yes. The pedal has a Speed footswitch that toggles between Slow and Fast, and each mode has independent speed settings, so you can set a slow and a fast rate and switch between them on the fly. There is also tap tempo for on-the-fly rhythmic control.
Sources (3)
- Custom Design Ethos 60's Harmonic Bias Trem, Delicious Audio, 2025-11-05
- Guitar Pedal X, Guitar Pedal X, 2025-06-11
- Guitar Pedal X, Guitar Pedal X, 2025-12-09
