Analogue OTA-style 4-pole cascaded lowpass multimode VCF with 8 simultaneous outputs (LP1–LP4, highpass, band boost+notch, phase shifter, 4-pole bandpass). At high resonance, self-oscillates as an 8-phase sine wave VCO tracking over at least 5 octaves. Also functions as an 8-output slew modifier or LFO in low-frequency mode. Includes exponential and linear FM, resonance modulation, voltage hold, and ping trigger inputs.224
Visualization filter_response
Capabilities 4
LFOlfo
In low frequency range mode, operates as an 8-phase LFO down to 2.8 mHz (period of 6 minutes).224
Slew Modifierslew-modifier
In low frequency range mode, the 8 outputs can be used as voltage controlled slew modifier outputs.224
Vcfvcf
OTA-style 4-pole cascaded lowpass core with 8 simultaneous outputs at different filter responses and phase relationships.224
Voltage-Controlled Oscillatorvco
At maximum resonance, self-oscillates as an 8-phase sine wave VCO with temperature compensation and accurate 1V/oct tracking over at least 5 octaves.224
Trigger input that strikes the filter core to generate percussive ping sounds. A rising edge above +3V activates it. Works with any trigger or gate signal.224
1V/oct exponential FM input for accurate pitch tracking in filter or oscillator mode. In low range, sensitivity is approximately 0.66 V/oct.224
Outputs (8)
BB+N
mixed
—
Band boost and notch pole-mixing output. Boosts frequencies just below cutoff, cuts just above. At high resonance, produces wavefolder-type sounds. Resonates at 270°.224
BP4
mixed
—
4-pole bandpass pole-mixing output. Selects a band around the filter frequency. Resonates at 360° (0° phase shift).224
HP1
mixed
—
1-pole highpass pole-mixing output. Resonates at 225° phase shift.224
Phase shifter pole-mixing output: 3-pole allpass mixed with input, creating a combined highpass and notch (one-stage phaser) response. Resonates at 315°.224
Parameters 12
Name
Type
Range
Behavior
COARSE
knob
22Hz – 22000Hz
Sets the filter/oscillator frequency. In audio mode (fine centred): 22 Hz to 22 kHz. In low frequency mode, total range is 2.8 mHz to 180 Hz.224
EFM KNOB
knob
-1V/octave – 1V/octave
Polariser for the exponential FM input. Centre is zero modulation depth; maximum is +1 V/oct, minimum is −1 V/oct in audio mode. In low mode, sensitivity is increased to approximately 0.66 V/oct.224
Selects between low frequency mode (slew modifier / VCLFO) and audio frequency mode (VCF / VCO).224
GAIN COMPENSATION SWITCH
switch
—
Enables gain compensation stages on all outputs so that all self-oscillating sine waves have equal amplitude. Default (off) is unity gain relative to signal inputs; when enabled in oscillator mode, all outputs are equalized in amplitude.224
HOLD SWITCH
switch
—
Manually toggles the hold (freeze) feature. When a gate signal is patched to the hold input, the switch enables or disables the gate control.224
LFM AC SWITCH
switch
—
AC-couples the linear FM input when enabled, rejecting DC offset and very low frequency content to prevent fundamental pitch shift during audio-rate modulation.224
LFM KNOB
knob
-7%/V – 7%/V
Polariser for the linear FM input. Sensitivity is approximately ±7% frequency deviation per volt. An AC coupling switch rejects DC offset in the modulation signal.224
RESONANCE
knob
—
Controls feedback from filter output to input, emphasising the filter frequency. All outputs resonate without low-frequency loss. At higher levels, self-oscillation is achieved, turning the module into an 8-phase sine wave VCO.224
Sets the self-oscillation amplitude at maximum resonance. Target is exactly 10 Vpp at BP4 output. Note: amplitude is not temperature-compensated.224
V/OCT TRIMMER
knob
—
Front-panel trim pot for calibrating 1V/oct pitch tracking. Factory calibrated; adjust only when needed. Target: 4 octave interval between 0V and +4V.224
Firmware history 2 versions
Version
Released
Notes
Revision D
—
Resolved linear FM 'freeze' issue which occurred when voltages of around +10 V were applied to the LFM CV.224