Analogue OTA-style 4-pole cascaded lowpass VCF with 8 simultaneous outputs at different phase relationships (LP1–LP4, HP1, BB+N, phase shifter, BP4). At high resonance, self-oscillates as an 8-phase sine wave VCO/VCLFO. Includes simultaneous exponential and linear FM, voltage-controlled resonance, hold feature, and dedicated ping input.351
Visualization filter_response
Capabilities 7
LFOlfo
In low frequency range mode, operates as 8-phase LFO down to 2.8 mHz (6 minute period).351
Multiband Filtermultiband-filter
Eight simultaneous filter responses (multiple LP slopes, BP, HP, notch, allpass) on separate jacks.351
Multimode Filtermultimode-filter
OTA-style 4-pole cascaded lowpass with pole-mixing outputs: LP1–LP4 (-6 to -24 dB/oct), 1-pole HP, band boost+notch, phase shifter, and 4-pole BP — all available simultaneously.351
Self-Oscillationself-oscillation
8-pole OTA cascade; self-oscillates with V/Oct tracking, configurable for VCO use.351
Slew Modifierslew-modifier
In low frequency range mode, operates as an 8-output voltage controlled slew modifier.351
At maximum resonance, self-oscillates as 8-phase sine wave VCO with temperature compensation, gain compensation switch, and accurate V/oct tracking over at least 5 octaves. Outputs separated by 45° phase.351
Jacks 16 — 8 in / 8 out
Name
Signal
Voltage
Description
Inputs (8)
EFM
cv
—
Second exponential FM input with polariser knob. In audio mode: ±1 V/oct range. In low mode: sensitivity ~0.66 V/oct.351
Hold
gate
—
Gate input to control the hold feature, freezing the filter core output voltages. When patched, the hold toggle switch enables or disables this input.351
In 1
mixed
—
Signal input for audio or CV to be filtered. Mixed together with In 2. Can be left unpatched when using Filter 8 as an oscillator.351
In 2
mixed
—
Second signal input, identical to In 1. Mixed together with In 1 at the filter input.351
LFM
cv
—
Linear FM input with polariser depth knob and AC-coupling switch. Sensitivity approximately ±7% frequency deviation per volt. AC switch rejects DC offset during audio-rate modulation.351
Ping
trigger
≥3V
Trigger/gate input to strike the filter core and create percussive ping sounds. Requires rising edge above +3V. Amplitude and decay set by frequency and resonance. Each output produces a different timbre.351
1 V/oct exponential FM input for precise pitch tracking. In low range mode, sensitivity is increased to approximately 0.66 V/oct.351
Outputs (8)
BB+N
mixed
—
Band boost and notch pole-mixing output. Boosts frequencies just below the filter frequency and cuts those just above. At high resonance, produces wavefolder-type sounds. Phase shift: 270°.351
BP4
mixed
—
4-pole bandpass pole-mixing output. Selects a band of frequencies around the filter frequency. Phase shift: 360° (= 0°, no shift). Purest ping timbre — suitable for bongo-type sounds.351
1-pole lowpass output at −6 dB/octave. Phase shift: 45°. Has a pronounced transient on ping, useful for kick drums.351
LP2
mixed
—
2-pole lowpass output at −12 dB/octave. Phase shift: 90°.351
LP3
mixed
—
3-pole lowpass output at −18 dB/octave. Phase shift: 135°.351
LP4
mixed
—
4-pole lowpass output at −24 dB/octave. Phase shift: 180°.351
Ø
mixed
—
Phase shifter pole-mixing output. 3-pole allpass response mixed with input signal, creating a combined highpass and notch response (one-stage phaser). Phase shift: 315°.351
Parameters 12
Name
Type
Range
Behavior
Coarse Frequency
knob
22Hz – 22000Hz
Sets the filter/oscillator frequency. In audio mode with fine knob centred: 22 Hz to 22 kHz. In low frequency mode, combined with fine knob: 2.8 mHz to 180 Hz, with 1 Hz at both knobs centred.351
EFM Depth
knob
-1V/oct – 1V/oct
Polariser knob for the exponential FM input. Centre (0) means no modulation; maximum is +1 V/oct and minimum is −1 V/oct in audio mode. In low mode, sensitivity is approximately 0.66 V/oct.351
Selects between low frequency mode (slew modifier/VCLFO) and audio frequency mode (VCF/VCO). In audio mode, range is 22 Hz–22 kHz. In low frequency mode, range is 2.8 mHz to 180 Hz.351
Gain Compensation Switch
switch
—
Enables gain compensation stages on all outputs. By default (off), each output is unity gain relative to the inputs. When on, all outputs have the same amplitude — useful in oscillator mode where outputs otherwise resonate at different levels. Target self-oscillation amplitude is 10 Vpp.351
Hold Switch
switch
—
Manually toggles the hold feature, freezing the filter core output voltages. When the hold gate input is patched, the switch instead enables or disables the gate input.351
LFM AC Switch
switch
—
When enabled, AC-couples the linear FM input, rejecting DC offset and very low frequency content in the modulation signal to prevent fundamental pitch shift during audio-rate modulation.351
LFM Depth
knob
-7% frequency deviation per volt – 7% frequency deviation per volt
Polariser knob for the linear FM input. Sensitivity is approximately ±7% frequency deviation per volt, substantially less than the exponential FM inputs. More 'tonal' in VCO mode as it limits perceived shift in fundamental pitch.351
Resonance
knob
—
Controls the feedback path from filter output to input. All outputs resonate at the filter frequency without LF response loss. At higher levels, self-oscillation is achieved, turning the module into an 8-phase sine wave VCO/LFO. Self-oscillation typically begins just past 3 o'clock.351
Front-panel accessible trim potentiometer that sets the self-oscillation amplitude at maximum resonance. Target is 10 Vpp on the BP4 output. Note: amplitude is not temperature-compensated and will vary slightly with temperature.351
V/Oct Trimmer
knob
—
Front-panel accessible trim potentiometer for calibrating V/oct pitch tracking. Each module is individually calibrated during production. Adjust to achieve exactly 4 octaves interval between 0V and +4V at the V/oct input.351
Firmware history 2 versions
Version
Released
Notes
Rev D
—
Resolved linear FM 'freeze' issue which occurred when voltages of around +10 V were applied to the LFM CV input.351