Mental model
VXN1 is a classical subtractive synth with a few intentional deviations from the textbook layout. This page explains the signal path and modulation model in one pass.
Signal path
- Per-voice path: oscillators → mixer → HPF → VCF → VCA. Runs at synthesis sample rate (optionally oversampled 1× / 2× / 4× / 8×).
- Instrument-level path (post voice-mix): phaser → BBD chorus → stereo delay → FDN reverb → master volume → limiter (optional).
- Voice rendering is per-sample (recurrences stay bit-faithful). Modulation runs at control rate — one update per 32-sample
CONTROL_BLOCK.
Two layers, always
VXN1 always carries two complete patches in memory — the Upper and Lower layers. Each layer has 8 channels. What MIDI does to those layers is governed by the Key Mode:
- Whole: 16-voice mono-timbral. Both layers play the same patch.
- Dual: 8 + 8 stereo layering. Both layers play different patches simultaneously on every note.
- Split: 8 + 8 split at a MIDI note. Below split → Lower; at-or-above split → Upper.
This is why some parameters are per-layer (everything in the oscillator / filter / envelope / LFO 1 / mod-route region) and some are global (master, LFO 2, all effects, oversampling).
Modulation: fixed routes, not a matrix
VXN1 does not have a modulation matrix. Instead, every musically common destination is a dedicated panel with explicit source selectors and depths. The full set:
| Destination | Sources | Notes |
|---|---|---|
| Pitch (both osc, vibrato) | LFO 1 / LFO 2 / Env 1 / Env 2 / Pitch Wheel | ±12 st on each route |
| PWM (Osc 1 + Osc 2 pulse width) | LFO 1 / LFO 2 / Env 1 / Env 2 / Mod Wheel | Fixed routes share both osc |
| Filter Cutoff | LFO 1 + LFO 2 + Env 1 + Velocity (four fixed depths) + Mod Wheel + Key Track | No source selector — all four depth knobs are live simultaneously |
| Resonance | Mod Wheel | Single fixed route |
| Cross-Mod Sweep (wide pitch) | Env 1 / Env 2 / Mod Wheel | ±48 st; only active when Cross-Mod Type ≠ Off |
| VCA | Env 2 (hardwired) + Amp LFO source selector + Tremolo depth | Env 2 always drives the VCA; Amp Gate bypasses to gate-only |
If a modulation idea isn’t on a panel, VXN1 doesn’t do it. This was a deliberate trade (ADR 0004): give up the matrix to gain a faceplate where every patch element is visible without diving into menus.
Two envelopes, fixed roles
- Env 1 is the modulation envelope. Default destinations: filter cutoff, pitch envelope, PWM envelope, cross-mod sweep. It is never wired to the VCA.
- Env 2 is the amplitude envelope. Hardwired to the VCA. Can also drive pitch / PWM / cross-mod-sweep destinations, but its role at the VCA is non-negotiable (set Amp Gate to bypass Env 2 and have a gate-only amplitude).
Each envelope has a Shape parameter selecting linear or exponential segments. Env 1 defaults to linear; Env 2 defaults to exponential (smoother amplitude).
Two LFOs, different scopes
- LFO 1 is per-voice. Each voice has its own phase. By default it retriggers at note-on (set Free-Run on to have one continuous phase across all notes). Has delay/fade controls so vibrato or tremolo can ease in.
- LFO 2 is global. One phase, shared by every voice in both layers. Useful for whole-instrument cycles where you want everything moving in lockstep.
Both LFOs can host-sync to tempo via the Sync toggle.
Oversampling
The whole per-voice synthesis chain — oscillators, sub, noise, cross-mod, filter, drive saturation — runs at the oversampled rate. Effects (phaser, chorus, delay, reverb) run at the host sample rate. Higher oversampling reduces aliasing on sync, ring-mod, and resonant filter sweeps at CPU cost. Default is 2× — adequate for most material; bump to 4× or 8× for aggressive sync leads or audible aliasing on bright patches.
Voice allocation modes
Per layer (the Voice & assign panel):
| Mode | Behaviour |
|---|---|
| Poly | First-free voice, oldest-steal when full. Standard polyphonic behaviour. |
| Unison | All 8 channels stack on every note. Per-channel detune (UnisonDetune) and phase decorrelation. Mono — one note at a time. |
| Solo | One channel, last-note priority. Legato controls whether the envelope retriggers on a new note. |
| Twin | Two channels per note, ±UnisonDetune apart. Halves effective polyphony but doubles each note. |
Glide (PortamentoTime) is per-voice and applies in all modes.
With this in hand, the faceplate reference is mostly a walk through which knob does what within each box.