Introduction
VXN1 (“vixen 1”) is an 80s-style analogue polysynth by Vulpus Labs, built in Rust as a CLAP plugin. A VST3 build via clap-wrapper is on the roadmap (see Distribution).
This manual covers installation, the faceplate panel-by-panel, performance features (key modes, presets, MIDI), and engine internals. Read top-to-bottom for an end-to-end tour, or jump to the Parameter reference and Glossary for lookups.
What VXN1 is
A two-layer subtractive polysynth with 16 voices total (8 channels per layer). Each voice runs:
- Two oscillators (Sine / Triangle / Saw / Pulse), plus a square sub-oscillator below osc 1 and a White/Pink noise source.
- Cross-modulation between the oscillators: band-limited hard Sync, through-zero Phase Modulation (“FM” in UI labels), or diode-bridge Ring modulation.
- OTA-C ladder filter (R3109/IR3109-flavoured) with LP / HP / BP / Notch modes and a 12 / 24 dB/oct slope switch. Separate pre-VCF high-pass filter.
- Two ADSR envelopes (modulation + amplitude) with linear or exponential shapes.
- Per-voice LFO 1 (retriggered or free-running) plus a global LFO 2 shared across both layers.
- Fixed-route modulation panels: pitch, PWM, filter cutoff, cross-mod sweep, mod-wheel. No matrix — every route is labelled.
The instrument-level signal path adds a pre-chorus phaser, a vintage BBD chorus (Juno-60-flavoured), a stereo delay, and an FDN reverb, finished with a master volume, optional brick-wall limiter, and selectable oversampling at 1× / 2× / 4× / 8×.
What VXN1 is not
- Not a matrix-modulation synth — modulation routes are fixed and named (ADR 0004).
- Not a wavetable or sample-based instrument — strictly analogue-modelled subtractive.
- Not a multitimbral workstation — two layers, one patch role each (Upper / Lower), no per-key splits beyond a single split point.
- Not configurable for runtime polyphony — voice counts are static (8 per layer, 16 total).
Layout of this manual
| Section | What it covers |
|---|---|
| Getting started | Install the plugin, run it for the first time, build a mental model. |
| Faceplate reference | One page per panel on the faceplate, in signal-flow order. |
| Performance | Key modes, presets, MIDI, and the full parameter table. |
| Internals | Engine architecture, MVC layering, distribution. For developers and curious users. |
| Appendices | Glossary and changelog. |
Parameter names and ranges in this manual come directly from vxn-engine/src/params.rs and the ADRs in vxn-1/adrs/. Where an ADR carries decision context that didn’t make the manual, cross-references are noted inline.