Quad VCA

Intellijel 12HP
fw 1.0
VCA MIXER ATTENUVERTER

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Four-channel voltage controlled amplifier with cascaded CV inputs and cascaded mix outputs. Each channel has variable linear-to-exponential response, a level bias knob, and a +6dB boost switch.

Patch Ideas · 3

Envelope-controlled VCA with bias
Use channel 1 as a standard voice VCA with an envelope shaping the amplitude.
Walkthrough
  1. Set LEVEL 1 fully counterclockwise so no signal leaks through when the envelope is at rest.
  2. Set the Linear / Exponential Response knob for channel 1 fully clockwise (Linear) if you're doing clean CV work, or fully CCW (Exponential) for natural-sounding note dynamics.
  3. Set BOOST 1 to the left (off) for unity max gain.
  4. Patch VCO output → Quad VCA IN 1.
  5. Patch envelope generator output → Quad VCA CV 1.
  6. Turn the CV 1 Attenuator fully clockwise so the envelope reaches unity (watch the CV LED go full green at the peak).
  7. Patch Quad VCA OUT 1 → your mixer or output.
Signal out OUT 1 — VCO audio shaped by the envelope, peaking near the input level (or doubled if BOOST is on).
Listen for A clean note that rises and falls with the envelope. Linear response tracks the envelope shape literally; Exponential response gives a more musical, percussive feel. Nudge LEVEL 1 clockwise only if you want some signal bleed under the envelope (useful for drones with accents).
▸ Show diagram
Patch diagramPatch diagram with 4 modules and 3 connections. Modules: Quad VCA, VCO, Envelope, Output. Signals: 2 audio, 1 cv.Quad VCAVCOEnvelopeOutputLevel 1: noonLinear / Exponential Response: Linear (CW)IN 1audioCV 1cvOUT 1audioOutaudioOutcvInaudioaudiocv
Three-voice submix + independent fourth voice
Use channels 1–3 as a submix out of OUT 3, and channel 4 as a fully separate VCA out of OUT 4/MIX.
Walkthrough
  1. Patch three sound sources → IN 1, IN 2, IN 3.
  2. Leave OUT 1 and OUT 2 unpatched so channels 1 and 2 cascade into OUT 3.
  3. Patch OUT 3 → mixer input A — this is your three-voice submix.
  4. Use LEVEL 1, LEVEL 2, LEVEL 3 as manual faders for that submix (CV inputs optional).
  5. Patch a fourth sound source → IN 4.
  6. Patch OUT 4/MIX → mixer input B — because OUT 3 is patched, OUT 4/MIX now only carries channel 4.
  7. Set LEVEL 4 to taste for the independent voice level.
Signal out OUT 3 — summed mix of channels 1–3. OUT 4/MIX — channel 4 alone (the mix chain was broken by patching OUT 3).
Listen for Three voices glued together on one fader-set plus a fourth voice you can send somewhere else (effect send, stereo pan, separate level). Patching any OUT jack breaks the cascade above it, which is exactly how you isolate channel 4 here.
▸ Show diagram
Patch diagramPatch diagram with 6 modules and 6 connections. Modules: Quad VCA, Voice 1, Voice 2, Voice 3, Mixer, Voice 4. Signals: 6 audio.Quad VCAVoice 1Voice 2Voice 3MixerVoice 4IN 1audioIN 2audioIN 3audioIN 4audioOUT 3audioOUT 4 / MIXaudioOutaudioOutaudioOutaudioIn AaudioIn BaudioOutaudio121. 3-voice submix2. independent voiceaudio
Dynamic FM index
Use channel 1 as a variable attenuator on a modulator oscillator so an envelope can sweep FM depth per note.
Walkthrough
  1. Patch modulator VCO (usually a sine) → Quad VCA IN 1.
  2. Set the Linear / Exponential Response knob for channel 1 fully clockwise (Linear) — you want predictable CV scaling of the modulator level.
  3. Set LEVEL 1 around 9 o'clock to set a small baseline FM index (quiet, almost no modulation at rest).
  4. Patch envelope → Quad VCA CV 1.
  5. Set the CV 1 Attenuator around noon to start — this controls how much the envelope opens the FM depth.
  6. Patch Quad VCA OUT 1 → linear FM input of the carrier VCO.
  7. Trigger notes: tweak LEVEL 1 for resting timbre, CV 1 Attenuator for how bright the attack sweep becomes.
  8. Flip BOOST 1 on if you need more modulation range (aggressive FM).
Signal out OUT 1 — the modulator oscillator, scaled by (LEVEL 1 + envelope). Patch into the carrier's FM input.
Listen for A timbre that starts dark and opens brighter on each note attack, then closes back down as the envelope decays — the classic evolving FM bell/brass behavior. Turn the CV 1 Attenuator clockwise for more dramatic sweeps, counterclockwise for subtle motion.
▸ Show diagram
Patch diagramPatch diagram with 4 modules and 3 connections. Modules: Quad VCA, Modulator VCO, Envelope, Carrier VCO. Signals: 1 audio, 2 cv.Quad VCAModulator VCOEnvelopeCarrier VCOLevel 1: base FM indexIN 1audioCV 1cvOUT 1cvOutaudioOutcvFM Incv11. dynamic indexaudiocv

Behaviors

4 Independent VCAs CV → CV 1–4

Each channel operates independently. Connect audio to IN, CV to CV input, take signal from OUT. LEVEL knob biases the gain. Response knob adjusts linear-to-exponential curve.

Cascaded CV single CV source → CV 1

One CV controls multiple channels. Unpatched CV inputs inherit from the previous channel. Each channel's attenuator and response knob independently shape the cascaded CV amount.

4-Channel Mixer audio → IN 1–4

Leave OUT 1–3 unpatched; take mix from OUT 4/MIX. LEVEL knobs act as mix faders. CV inputs can automate individual channel levels.

Controls

CH 1–4 CV Attenuator Controls amount of CV modulation applied to the channel's level. Cascades from previous channel if input unpatched.
0 = no CV · full CW = unity CV
CH 1–4 Linear / Exponential Response Sets VCA response curve. Full CCW = exponential. Full CW = linear. In-between = variable blend.
CCW: exponential (natural loudness) · CW: linear (CV processing)
CH 1 Level 1 Manual bias level for channel 1. Full CW ≈ +5V CV equivalent, unity gain in linear mode.
Summed with CV input · 0–+5V equivalent
CH 2 Level 2 Manual bias level for channel 2. Sets base gain without CV.
Summed with CV input
CH 3 Level 3 Manual bias level for channel 3. Sets base gain without CV.
Summed with CV input
CH 4 Level 4 Manual bias level for channel 4. Sets base gain without CV.
Summed with CV input
CH 1–4 BOOST Switch Increases output level by approximately +6dB (2:1). Useful for boosting low-level signals or mild overdrive.
Left = off (unity max) · Right = +6dB
CH 1–4 CV LED Bicolor LED shows post-attenuator CV signal level. Green = positive, red = negative voltage.
Monitors bipolar CV signals

I/O

IN · 8

  • CV 1 +5V for unity (linear) CV
    CV input for channel 1 level control.
  • CV 2 +5V for unity CV
    CV input for channel 2. Normalled to CV 1 when unpatched.
    NORM → CV 1
  • CV 3 +5V for unity CV
    CV input for channel 3. Normalled to CV 2 when unpatched.
    NORM → CV 2
  • CV 4 +5V for unity CV
    CV input for channel 4. Normalled to CV 3 when unpatched.
    NORM → CV 3
  • IN 1 any CV
    Audio or CV signal input for channel 1.
  • IN 2 any CV
    Audio or CV signal input for channel 2.
  • IN 3 any CV
    Audio or CV signal input for channel 3.
  • IN 4 any CV
    Audio or CV signal input for channel 4.

OUT · 4

  • OUT 1
    Channel 1 output. Normalled to mix input of OUT 2 when unpatched.
    NORM → OUT 2 mix
  • OUT 2
    Channel 2 output. Normalled to mix input of OUT 3 when unpatched.
    NORM → OUT 3 mix
  • OUT 3
    Channel 3 output. Normalled to mix input of OUT 4 when unpatched.
    NORM → OUT 4 mix
  • OUT 4 / MIX
    Channel 4 output. When OUT 1–3 are unpatched, serves as master mix output of all 4 channels.