Erica Synths Acidbox III Stereo Polivoks VCF

Few filters carry the raw attitude and unmistakable character of the Polivoks and the Erica Synths Acidbox III brings that legendary voice into a compact tabletop stereo analog filter processor. Built around the original Polivoks lowpass and bandpass filter core using programmable op-amps, Acidbox III delivers aggressive resonance, thick saturation and unmistakable Soviet-era bite, now paired with modern modulation and performance control. More than a filter box, it is an analog sound-shaping instrument built for live performance, studio processing and hybrid setups. With true stereo signal paths, built-in overdrive, LFO, envelope follower and flexible external control, Acidbox III can turn guitars, synths, drum machines and full mixes into bold, animated textures.

Stereo Polivoks Filter Core With Signature Overdrive

At the core of Acidbox III is a true stereo Polivoks lowpass and bandpass voltage-controlled filter built with the same programmable op-amps that defined the original circuit’s unruly personality. Cutoff and resonance shape both channels together, supporting wide stereo sweeps and extreme self-oscillation that made the Polivoks famous. An integrated audio overdrive circuit adds harmonic density and grit, moving from subtle saturation to aggressive distortion based on input level and gain. The result is a filter response that is bold, immediate and instantly recognizable for industrial, techno, experimental and rock sound design.

Built-In Modulation With LFO, Envelope Follower and Master Control

Acidbox III expands beyond traditional analog filtering with an internal modulation engine tuned for movement and expression. A syncable LFO offers eight waveforms including sample and hold, with speed, depth and divider and multiplier controls plus tap tempo for rhythmic sync. The envelope follower tracks incoming audio and applies dynamic cutoff modulation, with adjustable rate and an attenuverter for normal or inverted response. A dedicated master modulation control scales all modulation sources at once, making complex filter motion fast to shape during live sets and studio sessions.

Hands-On Performance Control for Tactile Sound Design

Designed for live use, Acidbox III invites physical interaction through its clear front-panel layout and responsive controls. Manual cutoff and resonance knobs deliver immediate access to sweeping filter gestures, while the input level control doubles as a performance overdrive that pushes signals into saturation past the 12 o’clock position. The unit supports hands-on techniques such as wah-style filtering, rhythmic beat-following effects and self-oscillating sound generation with no external input. Whether used as a dramatic performance effect or a subtle tone-shaping tool, Acidbox III fits tactile workflows that reward real-time control.

Flexible CTRL IN for Footswitches, Expression Pedals, CV and Sync

A key strength of Acidbox III is its configurable CTRL IN which expands how the stereo analog filter can be controlled. The input can be assigned to a bypass footswitch, dual footswitch with tap tempo, cutoff CV input, LFO sync trigger or expression pedal, supporting both Roland-style and Korg-style wiring. CV levels up to 20V peak to peak are supported, making Acidbox III compatible with modular synth systems, pedalboards and external controllers. This flexibility helps it integrate cleanly into guitar rigs, synth studios and hybrid performance setups.

Studio and Stage Integration With Distinct Polivoks Character

With adjustable input gain, balanced stereo outputs, analog immediacy and a universal power supply, Acidbox III is built to integrate into modern production and performance environments. It pairs naturally with guitars, synthesizers, drum machines, grooveboxes and modular systems, adding movement, saturation and character wherever it is placed in the signal chain. Compact, rugged and unapologetically bold, the Erica Synths Acidbox III is a go-to tabletop stereo filter for producers and performers who want authentic Polivoks bite with modern control and reliability for today’s studio and stage.