Stereo VCFQ (SVCFQ)

Stereo version of the iconic Serge Variable Q Filter (VCFQ).

As the 1983 catalog stated, the VARIABLE Q VCF (VCFQ) is an excellent general-purpose VCF offering simultaneous low-pass, high-pass, band-pass outputs. The resonance (Q) of this filter is dynamically variable by manual or voltage-control. The inputs have level control so that the percussive effects of overloading the filter can be exploited.

When a pulse is applied to the Trigger input, the filter will ring, producing a damped waveform similar to that produced by striking a resonant object. The nature of this ringing is controlled by the Q and the filter frequency. Percussive effects ranging from clicks to the sound of wood blocks and bell tones can be produced and controlled. This ringing effect can be used to achieve highly controlled complex, tonal qualities.

AUX IN is mixed into into both input channels (unattenuated). Ideal to add mono signals.

The inputs are attenuated per side, which is useful for managing levels and for driving the filter into percussive overload territory. An unattenuated AUX IN feeds both channels at once; this input can be handy for injecting a mono signal into the stereo field. Send a pulse into the TRIG IN with the resonance cranked, and the filter rings like a struck object, producing everything from woody clicks to bell-like tones, synthesized water drops, etc… If you patch a high-pass output back into the input and push Q further still, the filter will self-oscillate into a nice sine wave, which is trackable via the 1V/Oct input and lets you play it chromatically at that point.

Nearly five decades on, the VCFQ remains an incredibly appealing and musical filter. If you know the VCFQ, you know what this is — having it in stereo feels like a long-overdue gift!

Features:

• Stereo variable state filter based on the original 1976 Serge VCFQ design
• Two 2-pole (12dB/oct) filter channels with shared controls
• Simultaneous High-pass, Band-pass, and Low-pass outputs per channel
• Individual audio inputs (L/R) with attenuators
• AUX IN routed to both channels (unattenuated)
• Trigger input for filter ringing / percussive effects
• Voltage-controllable Frequency and Resonance (Q)
• 1V/Oct input for pitch tracking
• Skiff-friendly depth (<26mm)
• Self-oscillation capable

SERGE Stereo VCFQ for eurorack:

• Based on the original VCFQ design by Serge Tcherepnin from 1976
• Uses High-end VCAs for superior audio performance
• Eurorack format (3U), 18 hp
• Power consumption: ~ 50mA @ +12V, 50mA @ -12V
• (NEW) Skiff-friendly: < 25mm (1″)