The 3 Leaf Audio Chromatron is an optically controlled analog filter pedal: an envelope filter that also offers a manual mode driven by an external expression pedal. It was designed by Spencer Doren and, after spending nearly ten years in development, began shipping on 11 November 2018, priced at $349 direct from 3leafaudio.com as of April 201912.
The controls
The Chromatron carries the usual envelope filter controls, Response, Tone, Mix, Attack and Decay, plus two more that shape the filter's character. Resonance sets the level of filter feedback, and Boost sculpts the post-filter gain3. The Mix control blends the clean direct signal in with the filtered signal4.
| Control | What it does |
|---|---|
| Response | Input level and filter sensitivity; sets the trigger point of the envelope filter2 |
| Resonance | Sets the level of filter feedback3 |
| Boost | Sculpts post-filter gain3 |
| Mix | Blends the clean direct signal in with the filtered signal4 |
| Tone, Attack, Decay | The usual envelope filter shaping controls3 |
Two footswitches handle switching: one toggles the effect on and off, the other switches between envelope filter mode and expression pedal mode. In expression pedal mode, the filter is controlled manually with an external expression pedal plugged into the dedicated input, which Bass Musician Magazine's reviewer Jake Wolf described as giving it a "wah pedal" type of control. When you are in expression control mode, the Response, Attack and Decay knobs are disabled32.
In expression control mode, the Response, Attack and Decay knobs are disabled, so the external pedal takes over the filter's movement entirely3.
The effects loop
The Chromatron's FX loop lets you run other pedals in its loop, sonically placing those effects before the envelope filter while they are triggered by the clean input signal. That keeps the filter's triggering consistent even when the pedals in the loop change the signal. Bass Musician Magazine notes the arrangement works much like the loop on 3 Leaf Audio's Wonderlove2.
Nearly ten years in development
gearnews.com reported in November 2018 that the Chromatron had been stuck in development for nearly ten years before it was finally ready for release, shipping from 11 November1. Bass Musician Magazine's review put the same story another way: the Chromatron is the result of ten years of tweaking, refining and reimagining the state variable filter circuit2.
On sound, gearnews.com's write-up of the demo said it has "a lovely, organic, chewy sound, with a defined, vintage voice"1.
What reviewers said
Bass Musician Magazine's April 2019 review was positive on the hardware as well as the circuit. The pedal is housed in a brushed metal casing with a row of top-mounted jacks, which the reviewer noted is always nice to see when pedalboard real estate is at a premium. On build, Jake Wolf wrote that "the build quality and feel of the pedal couldn't really be of any higher quality. It is exceptionally robust and well designed"2.
That Pedal Show covered the Chromatron in a video in March 2019, where Dan and Mick demonstrated the pedal's mix control for blending the clean signal with the filtered one, and remarked that 3 Leaf Audio "are making just spectacular filter pedals"4.
Where it sits
The Chromatron is 3 Leaf Audio's envelope filter alongside the Proton Envelope Filter, and its FX loop design follows the same approach as the company's Wonderlove2. For players comparing filters, the combination of an expression pedal mode, an FX loop triggered from the clean signal, and a post-filter boost stage is what sets it apart from more straightforward envelope filters32.
Videos
Zachary Rizer
Mike Hermans
Guitar Interactive Magazine
Questions
Can I control the Chromatron with an expression pedal?
Yes. Alongside its envelope filter mode, the Chromatron has an expression pedal mode for manual control of the filter with an external expression pedal, which Bass Musician Magazine's reviewer described as giving it a wah pedal type of control. The pedal has a dedicated external expression pedal input for this, and in expression control mode the Response, Attack and Decay knobs are disabled.
What does the effects loop on the Chromatron do?
The Chromatron's FX loop lets you run other pedals in its loop. Sonically, those effects are placed before the envelope filter, but they are triggered by the clean input signal, which keeps the filter's triggering consistent. Bass Musician Magazine notes the loop works much like the one on 3 Leaf Audio's Wonderlove pedal.
Who designed the Chromatron?
The Chromatron was designed by Spencer Doren, described by gearnews.com as the brains behind 3 Leaf Audio. The pedal spent nearly ten years in development before its release, the result of a decade of tweaking, refining and reimagining the state variable filter circuit.
What does the Response knob do on the Chromatron?
The Response knob is the input level and filter sensitivity control. It sets the trigger point of the envelope filter, in other words how hard you have to play for the filter to open. In expression control mode, the Response, Attack and Decay knobs are disabled.
Sources (4)
- 3 Leaf Audio Chromatron: Hendrix filter tones in a box?, gearnews.com, 2018-11-06
- 3 Leaf Audio Chromatron Review, Bass Musician Magazine, 2019-04-15
- 3 Leaf Audio introduces the Chromatron, Guitar.com, 2018-11-05
- Mythos Runestone, 3 Leaf Audio Chromatron, Walrus Audio Lillian, SoloDallas Storm, That Pedal Show (YouTube), 2019-03-05
