Strymon SuperKar+
32-voice Karplus-Strong string synthesizer with independent Solo and Chord engines.
12 HP Eurorack module
SuperKar+ is Strymon's first dedicated Eurorack voice module: a 12 HP polyphonic Karplus-Strong synthesizer running on a 520 MHz ARM Superscalar processor with 32-bit float DSP. The architecture behind every voice is short, finely-tuned delay lines with high feedback, excited by an Attack burst and shaped by Decay (feedback gain), Damp (low-pass in the loop), and Timbre (feedback polarity for string-like vs hollow-tube timbres). The module runs two completely independent voices in parallel — a monophonic-or-polyphonic Solo Voice (up to 16 simultaneously sustaining notes via CV or MIDI, stable over 6 octaves) and a Chord Voice that builds intervals and smart harmonies (15 settings, 8 selectable scales) on the root V/Oct it receives. Every front-panel knob has a secondary function accessed by holding the right TIMBRE (alt) button, and the left TIMBRE has tertiary calibration functions for V/Oct compensation and reference fine tune. An internal mixer sums or splits both voices across OUT L / OUT R with four output modes (wide stereo, narrow stereo, split, mono sum).
Features
- Karplus-Strong delay-feedback voice model with positive/negative feedback (string/tube)
- Two fully independent voices: Solo (mono or up to 16-voice poly) and Chord (interval + smart harmony)
- Solo Voice tracks 6 octaves via CV, 8 octaves via MIDI
- Chord Voice with 15 harmony settings and 8 selectable scales
- Smart-harmony region following the active scale (Major, Minor, Dorian, Lydian, Phrygian, Aeolian, Harmonic Minor, Expanded Voicing Major, All Major Chords)
- Per-voice CV for Attack, Decay, Damp, Trigger, V/Oct, and Audio In
- Solo Voice exclusive Detune CV (per-note random tuning) and Pitch CV (per-note ±1 octave)
- TRS MIDI Type A in for 16-voice polyphonic Solo Voice play with velocity
- Audio Inputs feed each voice's strings for sympathetic resonator effects
- Four output modes: Wide Stereo, Narrow Stereo, Split Outputs, Mono Sum
- Independent per-voice output levels via TIMBRE (alt) + DAMP
- Portamento (glide) per voice via TIMBRE (alt) + DECAY
Controls & Jacks (28)
- Tune — Pitch range over 1 octave; 12 o'clock to max quantizes to half steps. Hold left TIMBRE for fine tune.
- Chord Damp — High-frequency damping for the Chord Voice. Secondary: Chord output level.
- Solo Damp — High-frequency damping for the Solo Voice string vibration. Secondary: Solo output level.
- Solo Decay — Solo Voice string sustain length. Secondary: portamento glide time for solo.
- Harmony — Selects 15 harmony settings (intervals + smart harmonies). Secondary: scale type when holding right TIMBRE.
- Chord Decay — Chord Voice string sustain. Secondary: portamento glide time for chord.
- Solo Attack — Solo Voice attack from sharp pluck to bowed/breath. Secondary: Solo polyphony 1-16.
- Chord Attack — Chord Voice attack character. Secondary: stereo / mono output configuration.
- Solo Timbre — Solo Voice feedback polarity: green LED = positive (string), red LED = negative (tube). Hold for tertiary calibration functions.
- Chord Timbre — Chord Voice feedback polarity: green LED = positive (string), red LED = negative (tube). Hold to access secondary functions on knobs.
- Solo V/Oct In — 1V/Octave pitch input for the Solo Voice. C0 = 0V; six-octave range.
- Chord TRIG In — Rising-edge trigger for the Chord Voice. 0 to +5V.
- Solo TRIG In — Rising-edge trigger for the Solo Voice. 0 to +5V.
- Chord V/Oct In — Chord-root V/Oct input quantized to nearest half step; five-octave range.
- Chord Attack CV In — Continuous attack CV; the Chord ATTACK knob acts as offset. -5V to +5V.
- Solo Attack CV In — Continuous attack CV; the Solo ATTACK knob acts as offset. -5V to +5V.
- Chord Harmony CV In — Continuous harmony CV; sweeps Harmony with extra range across the smart-harmony region.
- Solo Damp CV In — Continuous damping CV; the Solo DAMP knob acts as offset. -5V to +5V.
- Solo Detune CV In — Per-note random detune; 0V = perfect, 5V = max random detune.
- Solo Decay CV In — Continuous decay CV; the Solo DECAY knob acts as offset. -5V to +5V.
- Chord Decay CV In — Continuous decay CV; the Chord DECAY knob acts as offset. -5V to +5V.
- Chord Damp CV In — Continuous damp CV; the Chord DAMP knob acts as offset. -5V to +5V.
- Solo Pitch CV In — Per-note pitch offset, ±1 octave. -5V to +5V. Use for vibrato/trills.
- MIDI In — 3.5mm TRS MIDI Type A input controlling the Solo Voice; 8 octaves, velocity-sensitive, up to 16 voices.
- Chord Audio In — 20Vpp audio input fed in parallel with trigger to excite Chord Voice strings or use as sympathetic resonator.
- Out R — Right audio output. Use ATTACK (out config) to choose stereo/split/mono routing. 17.5Vpp max.
- Solo Audio In — 20Vpp audio input fed in parallel with trigger to excite Solo Voice strings or use as sympathetic resonator.
- Out L — Left audio output. Use ATTACK (out config) to choose stereo/split/mono routing. 17.5Vpp max.
How-To Guides
- Bass Line and Chord Pad
- Lifelike Strings via Damp CV
- 16-Voice Polyphonic MIDI Solo
- Drums Through the Strings
- Split Outputs to Separate Effects Chains
- Harmony-Density Tremolo
Explore the interactive SuperKar+ panel on BleepDex — tap any control to learn what it does.
