Electro-Harmonix Blurst

The Electro-Harmonix Blurst is a modulated filter pedal released in 2017. Where an envelope filter such as the EHX Q-Tron sweeps its filter in response to how hard you play, the Blurst drives its filter from an internal low frequency oscillator (LFO), which acts similar to a phaser or tremolo¹. The result is a repeating, rhythmic filter sweep you can sync to your tempo rather than one triggered by every note.

The pedal is built around an analog low pass filter with adjustable resonance², and Electro-Harmonix describes it as "an expressive modulated filter bridging the worlds of guitar effects and modular synthesis"³. MusicRadar's reviewers noted the family resemblance to a wah, with one distinction worth knowing: a wah is a bandpass filter, while the Blurst is a low pass⁴. It was announced at NAMM 2017 in a pink and green enclosure with a lurid graphic on the front, which gearnews.com called "unique-looking"⁵.

What the Blurst does to your sound

The Blurst modulates an instrument's sound like an envelope filter, but instead of the filter's response being controlled by your playing, it is driven by the internal oscillator²⁶. That makes it closer in spirit to a slow phaser or tremolo: the sweep repeats continuously at whatever rate you set, and you shape its character with the knobs and switches rather than with your attack.

Because the sweep is periodic, it suits rhythmic parts where you want the filter to pulse in time. Performer Magazine's Chris Devine found that with an expression pedal added, "it becomes a cross of a hyper tunable wah wah and a Univibe"⁸.

The controls

The front panel keeps it simple: three knobs, three switches and a tap footswitch³.

Rate, Range and Volume are the core sound-shapers: Rate sets how fast the filter sweeps, Range sets where in the frequency spectrum it sweeps, and Volume compensates for level changes when the effect is on³. The modulation itself works off LFOs, and the Shape switch sets the waveform from triangle to rising and falling sawtooth forms⁸. A triangle wave gives a smooth, even sweep; the sawtooth settings produce a sharper rise or fall, which reads as a more vocal, wah-like motion.

Tap tempo, note divisions and LFO shapes

The Tap footswitch lets you set the speed or rate hands-free, tapping quarter notes to lock the sweep to your tempo¹. The Tap Divide switch then sets the note type based on those tapped quarter notes³, with repeats settable to quarter notes, dotted eighths or triplets⁸. Premier Guitar's launch coverage described it as "a combination of the tap footswitch and tap divide toggle switch offering quarter, dotted eighth and triplet rhythms"².

That combination is what separates the Blurst from a plain auto-wah: you can place the sweep on the beat, on an off-beat dotted-eighth pulse, or in a triplet shuffle, and it stays there as long as the tempo holds³²⁸.

Expression pedal and CV control

The quarter-inch EXP jack takes a TRS expression pedal or another control voltage device, such as the EHX 8-Step Program sequencer³. The EXP mode switch selects which of three parameters the pedal controls: range, rate or filter³².

MusicRadar's reviewers found this is where the pedal opens up: "It really comes into its own though when used with an expression pedal, and range, rate or filter can be controlled externally"⁴. With a sequencer like the 8-Step Program driving it, the Blurst produces what Premier Guitar's press coverage called "syncopated shuddering"², stepping the filter through patterns rather than sweeping it smoothly. Delicious Audio also listed the Blurst among its recommended pedals for synths with CV in and out⁷.

Power and connections

The Blurst comes equipped with a standard EHX 9.6VDC-200mA power adapter, included in the box³²⁹. RockBoard lists its current draw as 56mA⁶. Audio in and out are on quarter-inch jacks, with the Output jack carrying the pedal's audio signal³.

What reviewers said

MusicRadar's overall verdict was short and positive: "A great pedal blessed with a vast array of options"⁴. Performer Magazine's Chris Devine highlighted the expression pedal pairing as the pedal's strongest suit, turning it into that tunable wah and Univibe hybrid⁸. Pedal of the Day emphasized the tap tempo workflow, noting the Tap switch sets the speed hands-free while Rate, Range and Filter can all be controlled from the Expression jack¹.

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