Coldcraft Effects Harmonic Tremolo v2

The Coldcraft Effects Harmonic Tremolo v2 is a tremolo stompbox built around the two-band harmonic tremolo circuit that Fender used briefly in its early-60s "brownface" amplifiers. Instead of turning the whole signal up and down like a standard tremolo, the circuit splits your sound into high and low bands, modulating one with an LFO and the other with an inverted version of it, so the two frequency ranges trade off against each other¹. The result is a swirly, immersive pulse that Premier Guitar's reviewer found "every bit as pretty, immersive, and swirly as it should be," and clearly distinct from a standard single-band tremolo².

The pedal traces back to Coldcraft's original Harmonic Tremolo Dual Band Modulator, announced in March 2014 alongside the EchoVerberator, described then as an adaptation of the classic "harmonic vibrato" circuit of the early 60s, splitting the signal into bass and treble bands modulated out of phase for a sweet, churning effect¹.

What a harmonic tremolo is

A harmonic tremolo is not an ordinary volume tremolo. Strymon's technical white paper on amplifier tremolo describes it as "a dual-band filtering effect that alternately emphasizes low and high frequencies," using a two-phase differential LFO controlling the gain of two frequency bands³. MusicRadar's Trevor Curwen notes that Fender built three basic tremolo circuit designs into its amps, and the harmonic tremolo, found briefly in early-60s brownface amps, is "the most aurally intriguing"⁴. Delicious Audio adds that the effect first appeared in Fender brownface amps made between 1959 and 1963, alternately modulating bass and treble levels with characteristics reminiscent of a phaser⁵.

On That Pedal Show, the presenters put it plainly when discussing the Walrus Audio Monument V2: "your low frequencies are sort of going down as your high frequencies are going up and then they kind of just trade off"⁶.

The controls: speed, intensity, balance, tone and volume

The v2 carries the expected speed and intensity knobs, plus three controls that do the interesting work²:

The balance control was part of the design from the start: the 2014 announcement described it as skewing the modulation from bass-only to treble-only, added to the familiar intensity and speed controls¹. The original also featured an analog output preamp with volume and tone-cut controls for additional boost and tone shaping¹.

Momentary mode

The pedal includes a momentary mode in which the effect is enabled only while the footswitch is held down. You enter it with a tap-tap-hold footswitch sequence, and exit by repowering the pedal².

Uni-Vibe territory

Harmonic tremolo and the Uni-Vibe are close cousins. Anasounds markets its Ages pedal by noting that "harmonic tremolo lives under many names: vibrato, harmonic vibrato, harmonic tremolo, vibe, univibe, and so on"⁷, and Guitar World's review of the Ages likewise frames it as a Univibe-style harmonic vibrato⁸. JHS's Harmonic Tremolo includes a mode emulating the vintage Uni-Vibe-style effect alongside its own take on a conventional harmonic tremolo⁹, and Delicious Audio described the JHS 3 Series version as producing "a dreamy tremolo effect reminiscent of the Uni-Vibe"¹⁰.

On the Coldcraft, the route in is the balance knob: turned fully counterclockwise, it puts the low-frequency effect front and center, which Premier Guitar found "provides a darn good Uni-Vibe sound"².

How close it gets to a brownface Fender tremolo

Premier Guitar's verdict on authenticity was measured: "The stompbox offers a convincing version of the original brownface effect," though without the subtle random variation of the original analog circuit, and not an exact copy from a stompbox placed before the amp's input². With the balance knob centered, the pedal lands close to the original Fender sound².

For comparison, Walrus Audio's Monument V2 describes its Harmonic mode as inspired by Fender brownface amps, with a low-pass and high-pass version of the signal modulated 180 degrees out of phase¹¹, a design Walrus has carried into the Monumental Harmonic Stereo Tremolo¹¹¹²¹³. RockBoard lists the Monument V2 as an analog circuit delivering both harmonic tremolo and traditional amplitude modulation¹⁴.

What reviewers said

Premier Guitar's August 2021 review is the main published assessment of the v2. On build quality, the reviewer found construction solid, aside from soldering-iron scars on a couple of the box capacitors, with high-quality metal knobs lending a classy touch². The overall verdict:

The listed cons were the lack of a battery option and the slight disruption when engaging the effect in momentary mode².

Other harmonic tremolo pedals

If you are comparing two-band tremolos, several other pedals cover the same ground:

• Walrus Audio Monument V2 Harmonic Tap Tremolo: analog, with harmonic and standard tremolo modes and a momentary bypass function¹⁴¹³
• Zeppelin Design Labs Quaverato Harmonic Tremolo: available ready-to-play at $189 or as an $89 DIY kit¹⁵¹⁶
• JHS 3 Series Harmonic Tremolo: $99, with a Uni-Vibe-style mode⁹¹⁷
• Anasounds Ages Harmonic Tremolo: a Univibe-style harmonic vibrato take⁷⁸
• Red Witch Lyria Harmonic Tremolo: controls for speed, depth and volume¹⁸
• Supro 1310 Harmonic Tremolo: a UK retail price of £209¹⁹

For builders, PedalPCB sells a Pendulous Harmonic Tremolo PCB for $12²⁰.

Videos

Click to load

Questions