The Keeley Electronics Bubble Tron is a flanger, phaser and filter pedal in one enclosure, built around a single idea: effects that respond to how hard you pick. In Flanger mode the sweep starts and stops based on your pick attack rather than running constantly, the phaser combines an LFO-driven swirl with an envelope-driven phase, and the Filter mode produces stepped, random, keyboard-like sounds12.
Keeley unveiled the pedal in 2016, and it drew on a specific vintage source: the MicMix DynaFlanger rack unit that Frank Zappa used. Robert Keeley called the concept "Neo Vintage", because these effects never existed in quite this combined form before23.
A dynamic flanger and phaser with a filter mode
The pedal has three modes of operation: Flanger, DynaMoPhase and Filter1. What makes the first two unusual is that they are dynamic, meaning the effect starts and stops based on your playing, or pick attack1. As Delicious Audio's Paolo De Gregorio explained when he revisited the pedal in 2018:
"A dynamic flanger is one that starts and stops based on your pick attack or envelope."1
The Flanger mode draws its inspiration from the MicMix DynaFlanger1. The Phaser mode is actually made up of two phasers: one with an LFO whose speed you set with the Rate control, with its depth dynamically controlled, and a second envelope-driven phaser called DynaPhase12. The phaser also offers a more typical LFO-based swirl for players who want conventional operation3.
The Filter mode is the odd one out: it is the only effect on the pedal that is not dynamic1. Instead it produces a stepped random filter, engaging keyboard-like sounds whose ramps or random character you control directly23.
The controls by mode
The control set is shared across the modes, with each knob doing something different depending on which mode is active. The core controls are Sensitivity, Depth, Shape, Rate, Feedback and Level16.
| Control | Mode | What it does |
|---|---|---|
| Sensitivity | Flanger | Sets how delicately you can play before the flanger goes fully active1 |
| Feedback | Flanger | Dials in the flanger sound, together with Sensitivity7 |
| Depth | Flanger | Adds in as much or as little of the effect as desired7 |
| Rate | Phaser | Sets the LFO phaser speed; turning it off runs DynaPhase only1 |
| Depth and Sensitivity | Phaser | Yield a wide array of phaser sounds7 |
| Shape | Filter | Controls the different ramps or random nature of the effect1 |
| Sensitivity | Filter | Works like a vintage synth-style bandpass filter control for keyboard-type sounds12 |
The Sensitivity control in Flanger mode is the heart of the dynamic behavior. De Gregorio described it as "the very exciting part of this pedal", noting that it behaves like a vintage synth style bandpass filter in Filter mode1. Pedal of the Day found Filter mode itself to be "super experimental, giving you many interesting and exploratory tones to work with"7.
The pedal can also run as a conventional effect: an internal switch shifts the overall production to standard, non-dynamic flanger and phaser sounds7. In the phaser section, turning the Rate control off disables the standard LFO phaser and leaves only the DynaPhase1.
From MicMix Dynaflanger to Zappa tones
The Bubble Tron's Flanger mode focuses on the legendary MicMix DynaFlanger, the rack unit Frank Zappa used7. The pedal attempts to re-create some of Zappa's tones from his late-70s through mid-80s period, when that unit was part of his rig7.
Gearnews framed the pedal as a combination of three envelope-driven concepts squeezed into one box2:
"So Keeley have combined the DynaFlange, DynaMoPhase and a Random Filter then squeezed them into the Bubble Tron pedal."2
The Larry LaLonde artist edition
The main functional change is that the envelope filter mode is accessed on the top of the enclosure via a three-way mini-toggle mode switch, and an internal mini-toggle selects a modern or vintage analog filter mode, the latter rolling off a little high-end6. MusicRadar's Jonathan Horsley called the pedal "a fantastic contemporary tribute to the classic MicMix DynaFlanger, as used by Frank Zappa"6.
What reviewers said
Guitar World included the Bubble Tron in a 2021 roundup of pedals for 80s guitar tones, listing it at $19957.
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Questions
What is the Keeley Bubble Tron based on?
Its Flanger mode is based on the MicMix DynaFlanger, a rack unit from the era that Frank Zappa used for his late-70s through mid-80s tones. Keeley combined that dynamic flanger with a dual phaser and a random filter in one pedal, which Robert Keeley described as Neo Vintage.
Who designed the Keeley Bubble Tron?
The pedal was designed and engineered by Aaron Tackett, Craighton Hale and Robert Keeley of Keeley Electronics. Robert Keeley described the concept as Neo Vintage, since these effects never existed in this combined form before.
Can the Keeley Bubble Tron work as a non-dynamic flanger or phaser?
Yes. An internal switch shifts the pedal to standard, non-dynamic flanger and phaser sounds. In the phaser section, you can also turn the Rate control off, which disables the LFO-based phaser and leaves only the envelope-driven DynaPhase.
What does the Filter mode do on the Bubble Tron?
Filter mode produces stepped, random filter sounds and keyboard-like tones. The Shape control sets the ramps or random character, and the Sensitivity knob works like a vintage synth-style bandpass filter control. It is the only mode on the pedal that is not dynamic.
Is there an artist edition of the Keeley Bubble Tron?
Yes. In April 2022 Keeley Electronics released the Larry 'Ler' LaLonde Artist Series Edition Le Bubble Tron with the Primus guitarist, priced at $229. It moves the envelope filter mode to a three-way mini-toggle on top of the enclosure.
What Frank Zappa sounds is the Bubble Tron meant to recreate?
The pedal aims to recreate Frank Zappa's guitar tones from the late 1970s through the mid 1980s, the period when he used the MicMix DynaFlanger rack unit. The dynamic flanging responds to pick attack, mimicking how that envelope-driven effect behaved.
Sources (7)
- Rediscovering The Keeley Bubble Tron Dynamic Flanger/Phaser, Delicious Audio, 2018-10-17
- Keeley Bubble Tron: The new vintage effect that never was!, gearnews.com, 2016-07-23
- Keeley Electronics' Bubble Tron pedal assembles "the vintage effect classics that never were", MusicRadar, 2016-07-22
- Keeley Electronics Bubble Tron Dynamic Flanger Phaser, Pedal of the Day, 2016-09-09
- 5 pedals that nail '80s guitar tones, Guitar World, 2021-04-12
- Keeley Electronics and Primus guitarist Larry LaLonde join forces for the Artist Series Edition Le Bubble Tron, MusicRadar, 2022-04-29
- Keeley Electronics Bubble Tron Dynamic Flanger Phaser Pedal of the Day, Pedal of the Day, 2016-09-12
