Fusion VCO2

Erica Synths 14HP
VCO OSCILLATOR DISTORTION WAVESHAPER

Verified sheet

The facts on this sheet have been cross-checked against the sources below.

Sources
Suggest a correction

Analog AS3340 VCO through a vacuum tube overdrive. -1 oct transistor sub with Colour low-pass, BBD Detune emulates a second drifting VCO, and a main OUT sums VCO + sub + external audio through the tube.

Patch Ideas · 10

★ Fat tube bass
Pitch CV → 1V/OCT · -1 OCT down · SUB LEVEL high with a darker COLOUR · TUBE CRUNCH past noon · OUT through a VCA shaped by the gate.
Walkthrough
  1. Patch your sequencer's pitch CV → Fusion VCO2 1V/OCT.
  2. Set the +1/-1 OCT switch to -1 OCT for a bass register.
  3. Turn TUNE so the lowest note lands where you want the kick to sit.
  4. Set SUB LEVEL to 3 o'clock and choose the rounder COLOUR position for fat low-end (or the brighter one if you want bite).
  5. Set DETUNE fully CCW (off) to keep the bass tight.
  6. Set PULSE WIDTH around 11 o'clock for a slightly asymmetric square.
  7. Turn TUBE CRUNCH to about 3 o'clock for warm harmonic distortion.
  8. Patch your sequencer's gate → VCA gate input.
  9. Patch Fusion VCO2 OUT → VCA input → mixer.
Signal out OUT — the post-tube main mix, ~10 Vptp, gated by the VCA.
Listen for A thick, growling tube bass with a solid sub fundamental and gritty harmonics from the tube stage. Pulling TUBE CRUNCH back gives a rounder, jazzier tone; pushing SUB LEVEL CCW thins it out into more of a mid-bass.
▸ Show diagram
Patch diagramPatch diagram with 4 modules and 4 connections. Modules: FUSION VCO2, Seq, VCA, Mixer. Signals: 2 audio, 1 pitch, 1 gate.FUSION VCO2SeqVCAMixer+1/-1 OCT: -1 OCTSUB LEVEL: 3 o'clockCOLOUR: rounder posTUBE CRUNCH: 3 o'clockDETUNE: off1V/OCT1v/octOUTaudioCV1v/octGategateGategateInaudioOutaudioInaudioaudiopitchgate
★ Detuned unison lead
Sequencer → 1V/OCT · DETUNE around noon for a 'second VCO' shimmer · PULSE WIDTH animated by a slow LFO · OUT into a filter for screaming leads.
Walkthrough
  1. Patch your sequencer's pitch CV → Fusion VCO2 1V/OCT.
  2. Centre the +1/-1 OCT switch (no transpose) and tune TUNE to your lead register.
  3. Set DETUNE to noon — you should hear two oscillators beating against each other.
  4. Patch a slow LFO → Fusion VCO2 PWM IN, set PULSE WIDTH knob to noon for symmetric starting point.
  5. Set TUBE CRUNCH around noon for a warm but musical drive.
  6. Set SUB LEVEL low (8 o'clock) so the sub adds body without dominating.
  7. Patch Fusion VCO2 OUT → filter input.
  8. Patch an envelope → filter cutoff CV for per-note brightness.
  9. Patch filter output → VCA → mixer.
Signal out OUT — fat detuned lead, ~10 Vptp, filter-shaped per note.
Listen for A wide, chorused lead voice that sounds like two VCOs running into a tube preamp. The PWM LFO adds slow timbral motion; raising DETUNE further pushes the second 'VCO' into more dramatic frequency-shifter territory.
▸ Show diagram
Patch diagramPatch diagram with 6 modules and 5 connections. Modules: FUSION VCO2, Seq, LFO, VCF, Env, VCA. Signals: 2 audio, 2 cv, 1 pitch.FUSION VCO2SeqLFOVCFEnvVCADETUNE: noonPULSE WIDTH: noonTUBE CRUNCH: noonSUB LEVEL: 8 o'clock1V/OCT1v/octPWM INcvOUTaudioCV1v/octOutcvInaudioCutoffcvOutaudioOutcvInaudioaudiocvpitch
Slow PWM pad
Hold a chord on TRI OUT for a clean sine-ish layer, animate the dirty OUT with PWM CV, blend in a touch of DETUNE for shimmer, and send the whole thing to reverb.
Walkthrough
  1. Patch your sequencer/keyboard pitch CV → Fusion VCO2 1V/OCT.
  2. Set TUNE for a mid-pad register and centre the +1/-1 OCT switch.
  3. Set PULSE WIDTH to 1 o'clock and patch a very slow LFO (~0.1 Hz) → PWM IN.
  4. Set DETUNE to about 9 o'clock — gentle chorus.
  5. Set SUB LEVEL low and TUBE CRUNCH around 11 o'clock for warmth without crunch.
  6. Patch Fusion VCO2 TRI OUT → Mixer Input 1 (clean fundamental).
  7. Patch Fusion VCO2 OUT → Reverb → Mixer Input 2 (animated body).
  8. Sum and listen — the mix gives a clean carrier with a breathing tube layer behind it.
Signal out Mixer output — clean TRI fundamental + reverbed, PWM-animated tube OUT.
Listen for A soft, evolving pad: the TRI provides a clean pitch reference while the PWM-modulated OUT slowly breathes underneath. Raise TUBE CRUNCH for a darker, more saturated pad; raise DETUNE for more chorus motion.
▸ Show diagram
Patch diagramPatch diagram with 5 modules and 5 connections. Modules: FUSION VCO2, Seq, LFO, Mixer, Reverb. Signals: 3 audio, 1 cv, 1 pitch.FUSION VCO2SeqLFOMixerReverbPULSE WIDTH: 1 o'clockDETUNE: 9 o'clockTUBE CRUNCH: 11 o'clockSUB LEVEL: low1V/OCT1v/octPWM INcvTRI OUTaudioOUTaudioCV1v/octslowcvCh 1audioCh 2audioInaudioOutaudioaudiocvpitch
★ Sync lead scream
Master VCO → SYNC IN · envelope → FM IN for per-note FM kick · TUBE CRUNCH cranked · OUT to the amp for searing sync leads.
Walkthrough
  1. Patch a master VCO's square or saw → Fusion VCO2 SYNC IN.
  2. Patch your sequencer's pitch CV → both the master VCO 1V/oct and Fusion VCO2 1V/OCT.
  3. Tune Fusion VCO2 TUNE noticeably above the master so you hear sync sidebands.
  4. Patch a fast envelope → Fusion VCO2 FM IN, FM LEVEL to 1 o'clock.
  5. Set TUBE CRUNCH fully CW for screaming harmonics.
  6. Set SUB LEVEL low (3 o'clock or less) so the sub doesn't muddy the sync.
  7. Patch Fusion VCO2 OUT → VCA → amp.
  8. Mult the same envelope → VCA CV for per-note dynamics.
Signal out OUT — searing sync lead through the tube, ~10 Vptp.
Listen for Classic hard-sync formants — sweeping TUNE while the master holds steady creates that 'ow!' sync-sweep voice, here amplified and coloured by the tube. Rolling FM LEVEL back tames the FM kick into a softer sync attack.
▸ Show diagram
Patch diagramPatch diagram with 5 modules and 6 connections. Modules: FUSION VCO2, Master VCO, Seq, Env, VCA. Signals: 2 audio, 2 cv, 2 pitch.FUSION VCO2Master VCOSeqEnvVCATUBE CRUNCH: full CWFM LEVEL: 1 o'clockSUB LEVEL: lowSYNC INaudio1V/OCT1v/octFM INcvOUTaudio1V/oct1v/octSqraudioCV1v/octOutcvCVcvInaudioaudiocvpitch
External audio tube colour
Drum bus → AUDIO IN · SUB LEVEL down · VCO inaudible (low PWM contribution / TUNE out of register) · TUBE CRUNCH to taste · OUT into the mixer for parallel grit.
Walkthrough
  1. Patch a drum bus or any submix → Fusion VCO2 AUDIO IN.
  2. Set SUB LEVEL fully CCW (sub off).
  3. Pull TUNE to an extreme so the VCO is out of the way (or unpatch 1V/OCT and ignore it).
  4. Set the AUDIO LEVEL knob to noon for unity.
  5. Set TUBE CRUNCH to 2 o'clock for a warm, edge-of-breakup tone.
  6. Patch Fusion VCO2 OUT → an aux channel on your mixer.
  7. Blend the parallel tube channel under the dry drums for thickness.
  8. Push TUBE CRUNCH further CW for grungier saturation.
Signal out OUT — your external audio re-coloured by the vacuum tube stage, ~10 Vptp.
Listen for Anything you feed in (drums, vocals, a synth submix) takes on the warm, slightly gritty character of the Fusion's tube. Useful for parallel saturation, a 'tape' colour, or full-on overdriven destruction at higher TUBE CRUNCH settings.
▸ Show diagram
Patch diagramPatch diagram with 3 modules and 2 connections. Modules: FUSION VCO2, Drum Bus, Mixer. Signals: 2 audio.FUSION VCO2Drum BusMixerSUB LEVEL: 0TUBE CRUNCH: 2 o'clockAUDIO LEVEL: noonAUDIO INaudioOUTaudioOutaudioAux Inaudioaudio
FM bells from TRI
Modulator VCO → FM IN · FM LEVEL moderate · take TRI OUT (clean, pre-tube) → VCA for bell-like FM tones without saturation.
Walkthrough
  1. Patch a modulator VCO's sine or triangle → Fusion VCO2 FM IN.
  2. Set FM LEVEL to noon for a moderate index.
  3. Patch your sequencer's pitch CV → Fusion VCO2 1V/OCT.
  4. Tune the modulator to a non-integer ratio of the carrier (e.g. 1.41×) for inharmonic bells.
  5. Set TUBE CRUNCH fully CCW (clean) — we're using TRI OUT, but keep the rest of the module quiet.
  6. Patch Fusion VCO2 TRI OUT → VCA input (TRI OUT bypasses the tube stage).
  7. Patch a percussive envelope → VCA CV.
  8. Trigger the envelope per note for clean FM bells.
Signal out VCA out — clean FM bell tone derived from TRI OUT, no tube colour.
Listen for Crystalline FM bells with the inharmonic spectrum of classic 4-op FM. Switching the modulator to integer ratios gives metallic mallets; raising FM LEVEL pushes into chaotic, gong-like territory.
▸ Show diagram
Patch diagramPatch diagram with 5 modules and 4 connections. Modules: FUSION VCO2, Mod VCO, Seq, VCA, Env. Signals: 1 audio, 2 cv, 1 pitch.FUSION VCO2Mod VCOSeqVCAEnvFM LEVEL: noonTUBE CRUNCH: 0 (clean)FM INcv1V/OCT1v/octTRI OUTaudioSinecvCV1v/octInaudioCVcvOutcvaudiocvpitch
BBD chorus stack
Hold one note · DETUNE swept slowly by hand or LFO · TRI OUT and OUT mixed in stereo for a wide chorused drone.
Walkthrough
  1. Patch a fixed pitch CV (or just hold a note) → Fusion VCO2 1V/OCT.
  2. Set TUNE to a comfortable mid register, +1/-1 OCT centred.
  3. Set DETUNE around 1 o'clock for clear beating.
  4. Set SUB LEVEL low, TUBE CRUNCH around 11 o'clock for warmth.
  5. Patch Fusion VCO2 TRI OUT → Mixer Left (clean fundamental).
  6. Patch Fusion VCO2 OUT → Mixer Right (detuned, tubed signal).
  7. Optional: patch a very slow LFO → PWM IN for extra timbral shimmer on the OUT side.
  8. Listen in headphones — the channels should beat against each other slowly across the stereo field.
Signal out Stereo mixer — TRI OUT (L) clean vs. OUT (R) detuned + tubed.
Listen for A wide stereo chorus drone. The clean TRI on one side stays steady while the BBD-detuned OUT on the other side drifts in and out of tune, producing rich beating and a 'breathing' stereo image. Raise DETUNE for stronger frequency-shifter motion.
▸ Show diagram
Patch diagramPatch diagram with 4 modules and 4 connections. Modules: FUSION VCO2, Pitch, Mixer, LFO. Signals: 2 audio, 1 cv, 1 pitch.FUSION VCO2PitchMixerLFODETUNE: 1 o'clockTUBE CRUNCH: 11 o'clock1V/OCT1v/octPWM INcvTRI OUTaudioOUTaudioCV1v/octLaudioRaudioslowcv11. optional shimmeraudiocvpitch
PWM square with parallel tube grit
LFO → PWM IN for classic chorus-y PWM · TUBE CRUNCH high · OUT into a filter for fat PWM lead with tube body.
Walkthrough
  1. Patch your sequencer's pitch CV → Fusion VCO2 1V/OCT.
  2. Patch a moderate LFO (~3 Hz) → Fusion VCO2 PWM IN.
  3. Set the PULSE WIDTH knob to noon as the LFO centre.
  4. Set TUBE CRUNCH to 2 o'clock for grit.
  5. Set DETUNE off and SUB LEVEL low.
  6. Patch Fusion VCO2 OUT → filter input.
  7. Patch an envelope → filter cutoff for per-note movement.
  8. Patch filter → VCA → mixer.
Signal out Filter/VCA output — PWM-modulated tubed lead voice.
Listen for A classic chorused PWM tone that's been pushed through a tube, giving it more midrange weight than a clean PWM. The LFO rate determines the chorus 'wobble'; faster LFO settings move into vibrato-like timbral motion.
▸ Show diagram
Patch diagramPatch diagram with 5 modules and 4 connections. Modules: FUSION VCO2, LFO, Seq, VCF, Env. Signals: 1 audio, 2 cv, 1 pitch.FUSION VCO2LFOSeqVCFEnvPULSE WIDTH: noonTUBE CRUNCH: 2 o'clockDETUNE: offPWM INcv1V/OCT1v/octOUTaudio~3HzcvCV1v/octInaudioCutoffcvOutcvaudiocvpitch
Drone with slow detune sweep
Fixed pitch · slow LFO modulating PWM · DETUNE high so the BBD frequency shifter drifts heavily · SUB LEVEL maxed · OUT into reverb.
Walkthrough
  1. Patch a fixed pitch CV (or use the keyboard) → Fusion VCO2 1V/OCT.
  2. Set DETUNE to 3 o'clock — heavy BBD detune AND fast internal LFO.
  3. Set SUB LEVEL fully CW with the rounder COLOUR position for big low-end.
  4. Set PULSE WIDTH around noon and patch a slow LFO → PWM IN for breathing.
  5. Set TUBE CRUNCH at noon for warmth.
  6. Patch Fusion VCO2 OUT → reverb → mixer.
  7. Optional: also patch SUB OUT → mixer for a clean sub layer underneath.
Signal out OUT through reverb — a thick, drifting tube drone with optional clean sub layer.
Listen for A massive, slowly evolving drone that breathes between in-tune fundamentals and frequency-shifted dissonance as the BBD's internal LFO sweeps. Reverb glues the moving partials into a single immersive bed.
▸ Show diagram
Patch diagramPatch diagram with 5 modules and 4 connections. Modules: FUSION VCO2, Pitch, LFO, Reverb, Mixer. Signals: 2 audio, 1 cv, 1 pitch.FUSION VCO2PitchLFOReverbMixerDETUNE: 3 o'clockSUB LEVEL: max (rounder COLOUR)TUBE CRUNCH: noon1V/OCT1v/octPWM INcvOUTaudioSUB OUTaudioCV1v/octslowcvInaudioInaudio11. optional clean subaudiocvpitch
Kick body with sub reinforcement
Fast decay envelope → FM IN for the pitch click · -1 OCT switch · SUB LEVEL up · short VCA on OUT for a tube-coloured kick with built-in sub layer.
Walkthrough
  1. Set the +1/-1 OCT switch to -1 OCT and TUNE for a low fundamental.
  2. Patch a fast-decay envelope → Fusion VCO2 FM IN, set FM LEVEL to 2 o'clock.
  3. Set SUB LEVEL to about 2 o'clock with the rounder COLOUR position for kick weight.
  4. Set DETUNE off so the kick stays tight.
  5. Set TUBE CRUNCH around 1 o'clock for body and bite.
  6. Patch a trigger → envelope (Trig).
  7. Mult the envelope → VCA CV for the kick amplitude shape.
  8. Patch Fusion VCO2 OUT → VCA → mixer.
Signal out VCA out — analog tube kick, pitched by FM IN, with built-in sub layer.
Listen for A thick, club-ready kick. The envelope on FM IN gives the classic pitch-down click on the attack; the sub adds weight; the tube glues it together with harmonic warmth. Tighten TUBE CRUNCH for cleaner kicks; push it for distorted industrial thumps.
▸ Show diagram
Patch diagramPatch diagram with 4 modules and 4 connections. Modules: FUSION VCO2, Trig, Env, VCA. Signals: 1 audio, 2 cv, 1 trigger.FUSION VCO2TrigEnvVCA+1/-1 OCT: -1 OCTSUB LEVEL: 2 o'clockCOLOUR: rounder posTUBE CRUNCH: 1 o'clockFM LEVEL: 2 o'clockFM INcvOUTaudioOuttrigTrigtrigOutcvCVcvInaudioaudiocvtrigger

Behaviors

Tube warm-up power-on

Vacuum tube needs a brief warm-up after powering the rack. Tone darkens and gain stabilises over the first minute as the heater reaches operating temperature.

BBD detune as fake-unison DETUNE knob > 0

Two BBD delay lines act as a frequency shifter that returns a pitch-drifted copy of the oscillator. Low settings produce chorusing; higher settings emulate a second detuned VCO without using a second core. The same DETUNE knob also speeds up the internal LFO that sweeps the BBD clock, so detune motion gets faster as you turn CW.

External audio through the tube signal → AUDIO IN

Any modular or line-level source patched into AUDIO IN is summed with the oscillator before the tube stage. Pull SUB LEVEL and the VCO's contribution down and the module becomes a stand-alone tube overdrive / colour effect.

PWM CV animation CV → PWM IN

Modulating PWM with an LFO or envelope animates the duty cycle of the internal square that feeds the tube stage, producing classic chorus-like timbral movement on the main OUT.

Hard sync sweeps pitched audio → SYNC IN

SYNC IN hard-resets the VCO phase on each rising edge. Sweeping TUNE over a synced master produces the classic formant-like sync-lead timbres, amplified and coloured by the tube stage on OUT.

Sub Colour voicing COLOUR switch

The COLOUR switch is a fixed low-pass filter on the -1 oct sub. One position keeps the sub bright and edgy; the other rounds it off into a smoother low-end reinforcement. Choose per bassline character.

Octave-switch register jumps +1 / -1 OCT switch

Hard transposes the principal VCO by an octave up or down without touching TUNE — handy live for jumping the same melody or sequence between bass, mid and lead registers.

Clean taps via TRI / SUB OUT patch TRI OUT or SUB OUT

TRI OUT and SUB OUT bypass the tube stage entirely, giving you clean oscillator material for FM duty, filter input, or layering the dirty OUT against a clean fundamental in the mixer.

Controls

VCO core TUNE Manual coarse tuning knob.
~2-octave knob range · 1V/oct CV tracks over 8+ octaves (C0–C8 and beyond)
VCO core +1 / -1 OCT switch Three-position octave switch transposing the principal VCO up an octave, leaving it centered, or down an octave.
useful for jumping registers without retuning
VCO core FM LEVEL Logarithmic attenuator for the external FM CV input before it reaches the exponential frequency control.
exponential FM · CCW: no FM · CW: deep modulation/inharmonic
VCO core PULSE WIDTH Manual pulse-width control for the internal square waveform that feeds the tube stage and main output.
center: ~50% duty · CCW/CW: asymmetric · also CV-modulatable via PWM IN
BBD detune DETUNE Sets the amount of BBD-delayed, pitch-shifted signal mixed back into the principal oscillator to emulate a second detuned VCO. Also raises the internal LFO that sweeps the BBD clock.
two BBD delay lines acting as a frequency shifter · CCW: off · CW: more detune AND faster internal LFO
sub-oscillator SUB LEVEL Mix level of the -1 oct transistor sub-oscillator into the main signal path.
CCW: sub off · CW: max sub presence (added on top of the VCO before the tube)
sub-oscillator COLOUR Switch acting as a fixed low-pass filter on the sub, selecting between two timbre flavours.
two positions · brighter (square-like edge) vs. rounder (filtered, smoother low-end)
tube stage TUBE CRUNCH Drives the vacuum tube overdrive that processes the sum of VCO + sub + external audio. Manual gain into the dual tube stages.
CCW: clean · noon: warm saturation · CW: aggressive harmonic crunch
ext input AUDIO LEVEL Sets how much external audio (from AUDIO IN) is summed into the tube stage alongside the oscillator.
use as a stand-alone tube colour by lowering SUB LEVEL and the VCO's contribution

I/O

IN · 5

  • 1V/OCT ±5 V typical
    Precision 1V/oct pitch input. Tracks great over 8+ octaves.
  • FM IN audio/CV CV
    Exponential FM input attenuated by the FM LEVEL knob. Patch audio-rate sources for classic FM-style tones.
  • PWM IN -5 V to +5 V GATE
    CV input for pulse-width modulation, summed with the PULSE WIDTH knob position.
  • SYNC IN gate / audio GATE
    Hard-sync input. Rising edges reset the VCO core phase for classic sync sweeps.
  • AUDIO IN modular / line audio AUDIO
    External audio input summed into the tube overdrive stage alongside the oscillator core. Line-level friendly.

OUT · 3

  • TRI OUT 10 Vptp CV
    Dedicated triangle output tapped from the AS3340 core, before the sub mix and the tube stage. Use for clean modulation duties or to feed an external filter.
  • SUB OUT 10 Vptp
    Dedicated -1 oct transistor sub output, post-Colour switch, pre-mix.
  • OUT 10 Vptp AUDIO
    Main mix output: principal VCO (square, PWM-shaped) + BBD detune + sub, all driven through the dual tube overdrive. The 'Fusion' voice.