The-One

The-One is a virtual analog emulation of the Sequential Circuits Pro-One (Model 100, 1981), developed from the original schematics and service manual.

Every stage of the Pro-One's signal path is modeled at the circuit level, including the nonlinear behavior and component interactions that give this synthesizer its distinctive sound.

Oscillators Two CEM 3340 oscillators with MinBLEP antialiasing, saw/pulse/triangle waveforms, variable pulse width, and hard sync. A dedicated CEM 3340-based LFO provides saw, triangle, and square modulation with gate sync.

Filter CEM 3320 4-pole 24dB/oct OTA low-pass filter with self-oscillation, keyboard tracking, and per-stage nonlinear modeling. The OTA saturation behavior and resonance response are derived from the original circuit topology.

Envelopes & VCA Two CEM 3310 ADSR envelopes with exponential curves and overshoot targeting, matching the documented timing range (2ms to 10s). CA3280 OTA VCA with a transfer curve derived from the original circuit's resistor values and linearization diodes.

Modulation Full modulation matrix: 3 sources (Filter Envelope, Oscillator B, LFO), 5 destinations (Osc A/B frequency & pulse width, Filter cutoff), with independent Wheel and Direct buses. Bus gains and modulation depths are calibrated from the resistor ratios in the original summing networks.

Sequencer & Arpeggiator 40-step sequencer (2 banks) with real-time transposition. Arpeggiator (UP / UP-DOWN). Both can be clocked by the internal LFO or locked to DAW tempo with 22 subdivision options.

Additional features Koren 12AX7 tube saturation and Revox B77 tape saturation model, mono/stereo algorithmic reverb, sidechain audio input (reproducing the original back-panel Audio In behavior), MIDI Learn on all continuous controls, and 20 factory presets transcribed from the original Owner's Manual.

Formats: VST3 & AU Platforms: macOS & Windows.