Vast array of cool envelope filter effects. Expression control. Effects loop. Quality build.

The response pot’s taper feels lopsided. A bit pricy.


3 Leaf Chromatron


Ease of Use:



Reviewing a full-featured envelope filter like 3 Leaf’s Chromatron can feel like evaluating two different products. One of them is quite cool, and the other is ridiculously cool.

Used on its own, the Chromatron is a fine-sounding filter box in the Mu-Tron III or Electro-Harmonix Q-Tron vein, with excellent renditions of the familiar ’70s-style wah and quack effects. But when you insert other stompboxes into the Chromatron’s effects loop, control the filter cut off with an expression pedal, or overdrive the pedal with upstream distortion, the Chromatron becomes a freaky, ferocious noise bomb.

Inside the Box
Yes, the Chromatron is most potent when you populate all five of its rear-panel jacks. But let’s start with what the pedal does with only input and output cables connected.

Five knobs and four toggle switches provide a wealth of filter options. The response (sensitivity) and resonance (feedback) controls are similar to those on most envelope filters. One toggle selects between upward and downward sweeps. Another chooses low-pass or band-pass filtering. (The former is your classic funky filter effect, which retains low frequencies, while the latter filters out frequencies above and below the cut-off frequency for wah-type sounds.) A third toggle provides two filter bandwidth settings.

Offbeat Options
The remaining controls are more unusual. The envelope’s response is determined solely by a sensitivity knob, or maybe an attack time control, on many envelope filters. But the Chromatron has independent attack and decay knobs, which permit slow-rise effects, bubbly percolation, and slow, synth-like sweeps.

Meanwhile, an independent tone control determines the upper limit of filter sweeps. It’s handy for fine-tuning tones after you’ve dialed in the ideal resonance, attack, and decay settings. There’s a wet-dry blend, which can soften the intensity of extreme filtering effects, or add low-end mass to strangled band-passed tones. Finally, there’s a post-filter boost stage. Depending on the Chromatron’s resonance and bandwidth settings, the output level can vary greatly. This added control levels the playing field while specifying how hard the Chromatron drives your amp and any downstream effects.

Expressionist Art
The first demo clip (Clip 1) showcases the Chromatron with only a guitar and amp connected. Clip 2 shows what happens when you connect an expression pedal (not included) to control the cut-off frequency.

The Chromatron is most potent when you populate all five of its rear-panel jacks.

An expression pedal transforms the Chromatron into a superpowered wah. Bandpass mode with a 100 percent wet mix setting delivers classic Hendrix/Clapton flavors. In low-pass mode, you can get everything from near-subliminal sweeps to shrieking feedback, depending on your resonance and mix settings. (The Chromatron has no high-pass setting.) The range and mix controls provide further variation.

The Fuzzier, the Merrier
For the third audio clip (Clip 3), I added a couple of homemade stompboxes: a germanium booster in front of the Chromatron and a gnarly fuzz in the pedal’s effect loop. Some passages feature just Chromatron and fuzz. Others add the upstream distortion, and a few include expression control. Clip 3 is twice as long as the other two because I was having twice as much fun recording it.

Survey the wreckage! Adding fuzz unleashes a menagerie of wild sounds. Tones can howl, cry, grunt, gargle, or hock loogies. Modest adjustments to filter and fuzz settings can yield huge tonal changes. You can fiddle for hours, concocting one vicious tone after another. Sounds can get seriously extreme, though you can always soften their impact via the mix control. This configuration is especially useful for overdubs and doubles—you can choose just the right emphasis to suit a mix. It’s so much fun that it’s probably illegal in a dozen states.

The Chromatron is hand built in the U.S. using top-shelf parts. The circuit board features a mix of surface-mount and through-hole parts. The hardware’s nice. The custom machined aluminum enclosure has cool beveled edges. The soft-touch relay footswitches feel great. The knobs are metal, although the jacks are plastic. All hardware is board-mounted. The Chromatron runs on standard 9-volt power supplies and has no battery compartment.

The Verdict
The Chromatron’s mix of standard and unconventional controls provides an extraordinary assortment of envelope filter sounds. The pedal sounds excellent on its own, and amazing when you exploit its effects loop and expression control. At $349, the Chromatron is pricy, but most lower-priced options can’t match its range. One possible exception is EHX’s Riddle, which also includes expression control and an effects loop and sells for about $200. But that’s a mass-produced pedal, not a handbuilt boutique model. Price notwithstanding, the Chromatron is one of today’s most versatile, expressive, and outrageously fun filter effects.