Electro-Harmonix Blurst Modulated Analog Filter Pedal

Electro-Harmonix Blurst: LFO-Swept Analog Filter With Tap Tempo

The Electro-Harmonix Blurst is a modulated analog low-pass filter pedal that sweeps its cutoff with an internal low-frequency oscillator rather than your playing dynamics. That single design choice turns the familiar auto-wah into a rhythmic, self-driving filter that pulses, pumps and breathes entirely on its own. With resonance, three waveforms, a wet/dry Blend and tap tempo on board, it brings genuine synth-style filter movement to guitar and bass. Plug in and you are suddenly making sounds that feel more like a modular rack than a stompbox.

Modulated Filter Versus Envelope Filter

A traditional envelope filter, or auto-wah, opens its cutoff in response to how hard you pick, so the sweep follows your dynamics. The Blurst instead drives its filter with an internal LFO, meaning the cutoff moves continuously and predictably whether or not you play a note. This distinction is what gives it a synthesizer character: the movement is rhythmic and repeating rather than reactive. Because the sweep is tied to a rate you set, it locks to a groove in a way an envelope filter never can.

The Analog Low-Pass Filter and Range Control

At its core the Blurst uses an analog low-pass filter, a circuit that allows frequencies below its cutoff point to pass while attenuating everything above. The Range control sets the window that the LFO sweeps through, positioning the effect anywhere from a deep, dark wub to a bright, vocal sweep. Because the filtering is analog, the sweep has a smooth, musical slope rather than a stepped digital quality. Setting the Range well is the difference between a subtle tonal shimmer and a dramatic, full-spectrum sweep.

Resonance and the Three Waveforms

The Resonance control emphasizes the frequencies right at the filter's cutoff point, and raising it makes each sweep more pronounced, peaky and vocal. Paired with the waveform selector, it defines the entire personality of the effect. A triangle wave sweeps up and down symmetrically for a smooth, wah-like motion, a rising sawtooth ramps up then snaps back for a rhythmic pulse, and a falling sawtooth does the reverse for a reverse-swell feel. Combining a sharp resonance with a sawtooth wave produces the punchy, synth-sequencer textures the Blurst is known for.

Tap Tempo, Tap Divide and Blend

The footswitchable tap tempo lets you set the sweep rate by tapping in time with the music, and the Tap Divide toggle then multiplies that tempo into quarter-note, dotted-eighth or triplet subdivisions for instant rhythmic variety. This is what turns the Blurst from a novelty into a performance tool that stays locked to the band. The Blend control mixes the filtered signal back against your clean tone, so you can keep the attack and definition of each note even when the modulation is extreme. Together these features let the effect sit musically in a mix instead of swallowing it.

Expression Control and Connectivity

The Blurst offers three expression modes, letting an external expression pedal or a control-voltage source sweep the Range, the Rate or the Filter in real time. Assigning an expression pedal to Range, for instance, turns the Blurst into a foot-swept filter you can ride like a wah, while CV control opens up interaction with modular and synth rigs. This flexibility is unusual on a filter pedal and pushes it toward sound-design territory. The pedal measures roughly 2.75 inches wide by 4.5 inches long and ships with its own power supply rather than using a battery.

Who the Blurst Is For

The Blurst is built for guitarists and bassists who want to step outside standard modulation into synth and electronic textures. It suits funk and groove players chasing tempo-locked auto-wah pulses, ambient artists building evolving pads, and experimentalists who treat the guitar as a sound source. The tap tempo and Tap Divide make it especially valuable for anyone playing to a click or a rhythmic loop. If you have ever wanted the sweeping filter of a modular synth under your feet, the Blurst delivers it in a pedalboard-ready box.