Dreadbox Antidote
Analog Karplus-Strong plucked string voice with BBD chip
10 HP Eurorack module
Antidote by Dreadbox is a complete Karplus-Strong synthesis voice from the Chromatic series, built around an analog circuit with a 512-stage BBD (bucket brigade device) chip. Karplus-Strong synthesis loops a short burst of noise through a filtered delay line to simulate the sound of plucked and hammered strings or percussive tones — a technique more commonly found in digital physical modeling synthesizers, here realized in a fully analog design. The signal path starts with a noise generator whose decay is set by the Pluck slider, then passes through two analog lowpass filters: a pre-filter (Colour) and a post-filter (Filter) that doubles as a lowpass gate. The module tracks accurately over 5 octaves (C0 to B4) via the Pitch input. It can also process external audio through the Ext In jack, enabling resonator-style effects or, with an external LFO, flanger and chorus textures. Four vertical sliders provide hands-on control of Pluck decay, Tune, Feedback, and Filter cutoff, while three CV inputs with attenuator knobs allow voltage control of Tune, Feed, and Filter parameters. Output level varies from 2Vpp to 5Vpp depending on settings.
Features
- Complete Karplus-Strong synthesis voice in 10HP
- Analog circuit built around a 512-stage BBD (bucket brigade device) chip
- Internal noise generator with variable decay exciter (Pluck)
- Dual analog lowpass filters: pre-filter (Colour) and post-filter (Filter/LPG)
- Post-filter doubles as a lowpass gate for combined timbre and amplitude shaping
- Accurate pitch tracking over 5 full octaves (C0 to B4) via 1V/oct Pitch input
- External audio input for resonator, flanger, and chorus effects
- Three CV inputs with dedicated attenuator knobs (Tune, Feed, Filter)
- Separate Trigger and Gate inputs for flexible excitation control
- Four vertical slider controls for hands-on performance (Pluck, Tune, Feed, Filter)
- Part of the Dreadbox Chromatic series — affordable, colorful, feature-rich
- Output level ranges from 2Vpp to 5Vpp depending on parameter settings
Controls & Jacks (16)
- Pluck — Controls the pluck intensity/excitation strength.
- Colour — Controls the tonal color/timbre of the string excitation.
- Out — Main audio output.
- Tune — Coarse tuning of the string pitch.
- Feed — Feedback amount controlling string sustain/decay length.
- Filter — Lowpass filter cutoff for the string tone.
- Gate — Gate input for sustained string excitation.
- Pitch — 1V/Oct pitch input for melodic control.
- Trigger — Trigger input to excite the string.
- Filter Slider — Filter cutoff fine control via slider.
- Tune CV — CV input for pitch/tune modulation.
- Feed CV — CV input for feedback amount modulation.
- Feed Slider — Feedback amount fine control via slider.
- Ext In — External audio input for processing through the Karplus-Strong algorithm.
- Tune Slider — Fine tune control via slider.
- Filter CV — CV input for filter cutoff modulation.
How-To Guides
- Classic Plucked String
- Infinite Sustain Drone
- Metallic Percussion
- External Audio Resonator
- Evolving Pluck Sequence
Explore the interactive Antidote panel on BleepDex — tap any control to learn what it does.
