Serge Stereo VCFQ

Random Source 18HP
FILTER VCF RESONATOR OSCILLATOR

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Stereo version of the classic Serge variable-Q filter. Paired low/band/high outputs, voltage-controlled frequency and resonance, and trigger pings turn it into a resonant filter or twin sine source.

Patch Ideas · 5

★ Stereo formant wash
Pad into IN L and IN R · gentle Q · slowly move FREQ with an LFO · use LOW L and BAND R for a wide, speech-like stereo wash.
▸ Show diagram
Patch diagramPatch diagram with 4 modules and 5 connections. Modules: Serge Stereo VCFQ, Pad, LFO, Output. Signals: 4 audio, 1 cv.Serge Stereo VCFQPadLFOOutputFREQ: noonQ: lowVC F: gentleVC Q: gentleIN LaudioIN RaudioFREQ CVcvLOW LaudioBAND RaudioOut LaudioOut RaudioOutcvLaudioRaudioaudiocv
★ Pinged resonator
Set Q high · send short triggers to TRIG IN · use AUX IN for a quiet source or leave it empty · the filter rings as a struck resonator instead of a static EQ.
▸ Show diagram
Patch diagramPatch diagram with 4 modules and 4 connections. Modules: Serge Stereo VCFQ, Trigger, Noise, Output. Signals: 3 audio, 1 trigger.Serge Stereo VCFQTriggerNoiseOutputQ: highFREQ: 1-2 o'clockVC Q: highTRIG INtrigAUX INaudioBAND LaudioBAND RaudioOuttrigOutaudioLaudioRaudioaudiotrigger
Twin sine source
No input, Q full up, 1V/OCT tracking on the cutoff, and HIGH patched back into the inputs · the stereo filter turns into a dual sine voice.
▸ Show diagram
Patch diagramPatch diagram with 3 modules and 5 connections. Modules: Serge Stereo VCFQ, Sequencer, Output. Signals: 4 audio, 1 pitch.Serge Stereo VCFQSequencerOutputQ: full CWFREQ: tunedVC Q: none1V/OCT1v/octIN LaudioIN RaudioHIGH LaudioHIGH RaudioLOW LaudioLOW RaudioPitch1v/octLaudioRaudioaudiopitch
★ Mono source, stereo band split
Mono audio into AUX IN · use the band outputs as a stereo splitter for one source · FREQ sets the crossover point while the two sides stay phase-coherent.
▸ Show diagram
Patch diagramPatch diagram with 3 modules and 3 connections. Modules: Serge Stereo VCFQ, Mono Source, Output. Signals: 3 audio.Serge Stereo VCFQMono SourceOutputFREQ: noonQ: mediumAUX INaudioBAND LaudioBAND RaudioOutaudioLaudioRaudioaudio
Tuned filter voice
Pitch CV into 1V/OCT · gate to TRIG IN · use the low-pass outputs as a playable stereo voice with resonance as the tone control.
▸ Show diagram
Patch diagramPatch diagram with 4 modules and 4 connections. Modules: Serge Stereo VCFQ, Sequencer, Gate Source, Output. Signals: 2 audio, 1 pitch, 1 trigger.Serge Stereo VCFQSequencerGate SourceOutputQ: highFREQ: tracked1V/OCT1v/octTRIG INtrigLOW LaudioLOW RaudioPitch1v/octOuttrigLaudioRaudioaudiopitchtrigger

Behaviors

Stereo variable-Q filtering patch audio into IN L and IN R

Both channels share the same frequency and Q controls, so one movement reshapes the stereo pair together.

Aux input summing patch AUX IN

AUX IN runs into both channels without attenuation, making it the quickest way to feed a mono source into the stereo filter pair.

Ping mode high Q plus TRIG IN

A trigger excites the resonant peak and rings the filter like a struck object.

Self-oscillation Q high and no damped input

At high resonance the filter behaves like a sine source. The sheet calls out that patching HIGH back to IN pushes it into oscillation.

Pitch tracking patch 1V/OCT

The filter can track pitch closely enough to act as a tuned voice, especially with the low-pass response and resonance pushed high.

Controls

Global FREQ Sets the center frequency of both stereo filter sections.
shared stereo frequency control
Global Q Sets resonance across both channels, from gentle peak to self-oscillation.
low Q to self-oscillation
Left channel IN L level Sets the amount of signal fed into the left filter path.
input attenuator
Right channel IN R level Sets the amount of signal fed into the right filter path.
input attenuator
Global VC F Attenuates frequency CV into the shared filter cutoff.
voltage control over FREQ
Global VC Q Attenuates resonance CV into the shared Q path.
voltage control over resonance

I/O

IN · 7

  • IN L audio AUDIO
    Left audio input with level control.
  • IN R audio AUDIO
    Right audio input with level control.
  • AUX IN audio AUDIO
    Unattenuated auxiliary input that runs into both channels.
  • TRIG IN trigger GATE
    Trigger input used to ping the filter at high resonance.
  • 1V/OCT 1V/oct CV
    Pitch CV for tracking the filter as an oscillator.
  • FREQ CV CV CV
    Voltage control over filter frequency.
  • Q CV CV CV
    Voltage control over resonance.

OUT · 6

  • LOW L audio AUDIO
    Left low-pass output.
  • BAND L audio AUDIO
    Left band-pass output.
  • HIGH L audio AUDIO
    Left high-pass output.
  • LOW R audio AUDIO
    Right low-pass output.
  • BAND R audio AUDIO
    Right band-pass output.
  • HIGH R audio AUDIO
    Right high-pass output.