Make Noise QPAS
Stereo quad-peak animated filter with radiant resonance
18 HP Eurorack module
The QPAS (Quad Peak Animation System) is a stereo multimode analog filter using four filter cores to animate resonant peaks across Low Pass, High Pass, Band Pass, and the unique Smile Pass filter types simultaneously. Its Radiate controls spread peaks apart from the central cutoff frequency, creating dynamic stereo animation and spectral movement. With a pre-filter exponential VCA, pingable resonance, and extensive CV control, it is a deeply musical filter for evolving, living sounds.
Features
- Four analog filter cores with simultaneous LP, HP, BP, and Smile Pass outputs
- Stereo operation with independent left and right filter core pairs
- Radiate-L and Radiate-R controls spread peak cutoff frequencies apart from central FREQ setting
- Single FREQ control with two CV inputs: FREQ1 (attenuated) and FREQ2 (unattenuated)
- Pre-filter exponential VCA with combo pot and Level CV input
- Q control with CV input and attenuverter, feeds BP output back into filter inputs
- Negative resonance available at counterclockwise Q settings (zero resonance around 9 o'clock)
- !!¡¡ dual inputs for clock, gate, or audio rate modulation of nearly all circuit elements
- Pingable filter: trigger input with high Q produces pitched resonant decays
- Radiate-R CV input normalled to Radiate-L CV input for easy chained modulation
- R Input normalled to L(Mono) Input for mono-to-stereo operation
- Right LP, HP, and BP outputs normalled to Left outputs for mono output from all four peaks
Controls & Jacks (27)
- L(Mono) Input — Signal to be filtered by Left cores of QPAS. Modular level audio. Normalled to feed all four cores when R Input is unpatched.
- R Input — Signal to be filtered by Right cores of QPAS. Modular level audio. Normalled to L(Mono) Input.
- Ping L Out — Left channel Low Pass filter output. When LP Right is unpatched, all four peaks sum into this output for mono use. Patching LP Right splits
- BP Outputs — Band Pass filter outputs. Passes frequencies near the cutoff and attenuates those above and below at 12dB/octave. Right is normalled to Left
- LP L Out — Left Low Pass filter output. Passes frequencies below the cutoff at 12dB/octave. When used alone, all four peaks appear in this output.
- HP Outputs — High Pass filter outputs. Passes frequencies above the cutoff at 12dB/octave. Right is normalled to Left for mono operation.
- Freq CV In — Attenuated CV input for cutoff frequency, scaled by the Frequency CV Attenuverter. Use for modulated frequency sweeps with depth and polarit
- Freq CV Atten — Sets the depth and polarity of CV at the Freq CV input. Center is zero modulation; CW is positive; CCW inverts. Does not affect the unattenu
- Ping R Out — Right channel Low Pass filter output. Normalled to LP Left; patching here splits the four peaks into stereo pairs with two peaks per side.
- SP Outputs — Smile Pass filter outputs. A unique topology that changes filter character with cutoff while maintaining consistent volume. Stereo only; not
- Level — Controls the input signal level entering the filter via a pre-filter exponential VCA. When Level CV is patched, the knob becomes an attenuat
- Ping L In — Trigger or gate input that excites the left filter cores for percussive resonant pings. Higher Q settings produce longer, more pitched decay
- Ping R In — Trigger or gate input that excites the right filter cores for percussive resonant pings. Independent from Ping L for stereo ping patterns.
- Radiate L — Spreads the two left-side filter peaks away from the base cutoff frequency. Fully CCW keeps peaks together for a focused sound; CW spreads t
- Freq 1 CV Atten — Sets the depth and polarity of the FREQ1 CV input signal. Center is no modulation; CW adds positive frequency modulation; CCW inverts it.
- Q — Controls resonance across all four filter cores. Zero resonance is around 9 o'clock; below that produces negative resonance. Higher settings
- Radiate R — Spreads the two right-side filter peaks away from the base cutoff frequency. Operates independently of Radiate L for asymmetric stereo anima
- Radiate L CV Atten — Sets the depth and polarity of CV at the Radiate L CV input. Setting this opposite to the Radiate R attenuverter with a shared CV source cre
- Q CV Atten — Sets the depth and polarity of CV at the Q CV input for dynamic resonance control from envelopes or modulation sources.
- Radiate R CV Atten — Sets the depth and polarity of CV at the Radiate R CV input, which is normalled from Radiate L CV. Inverting relative to Radiate L creates o
- Freq 2 CV In — Unattenuated CV input for cutoff frequency. Bypasses the attenuverter entirely; use for 1V/octave keyboard tracking or full-strength modulat
- Radiate L CV In — CV input for Radiate L peak spread. Also normalled to Radiate R CV, so a single source here drives both Radiate controls simultaneously.
- Level CV In — CV input for the pre-filter exponential VCA. When patched, the Level knob becomes an attenuator for this CV rather than a direct level contr
- Ping CV In — CV input that modulates the ping circuit. Accepts gates, triggers, or audio-rate signals to excite the filter resonance for percussive sound
- Q CV In — CV input for resonance, scaled by the Q CV Attenuverter. Use with envelopes for dynamic resonance or with audio-rate signals for harmonic ef
- Ping In — Trigger input that excites the filter for resonant percussive pings. With high Q, produces pitched decaying tones tuned by the Frequency con
- Radiate R CV In — CV input for Radiate R peak spread. Normalled from Radiate L CV; patching here breaks that normalling for independent stereo modulation of e
How-To Guides
- Basic Mono Filtering
- Mono to Stereo Widening
- Resonant Pings and Plucks
- Feedback Distortion
- Spectral Crossfader
- Transient Resonator
- Animated Stereo Filter Sweep
- VCA and Filter in One
- Audio Rate !!¡¡ Animation
- Smile Pass Subtle Coloration
Explore the interactive QPAS panel on BleepDex — tap any control to learn what it does.
