Dual voltage controlled filter (inspired by the Korg MS-20 OTA filter) with an innovative modulation matrix. Contains two dedicated filter circuits in series: a 12dB/oct low-pass filter and a 6dB/oct high-pass filter, both OTA-based. Features CV control over input gain and resonance, a link switch for band-pass configurations, and a modulation matrix for internal patching.335
Visualization filter_response
Capabilities 2
Self-Oscillationself-oscillation
Both LPF and HPF can self-oscillate simultaneously; their dominance is determined by relative cutoff frequencies and gain settings, producing complex chaotic tones when cutoffs are equal.335
Dual OTA VCF: 12dB/oct LPF in series with 6dB/oct HPF, both inspired by the Korg MS-20. CV control over cutoff, resonance, and input gain. Link switch creates band-pass configurations.335
Jacks 4 — 3 in / 1 out
Name
Signal
Voltage
Description
Inputs (3)
ACV
cv
—
Auxiliary CV input, normalled to FCV. Routes to the modulation matrix as AUX+ and AUX- signals.335
Frequency CV input, normalled to 0V. Attenuated version routes to LP and HP cutoff control voltages.335
Outputs (1)
Audio output
audio
—
Audio output protected by a 1K output resistor.335
Parameters 10
Name
Type
Range
Behavior
ACV attenuator
knob
—
Attenuates the ACV input to produce the AUX+ internal signal. AUX- is the inverted copy of AUX+. Both are routable via the modulation matrix switches.335
FCV attenuator
knob
—
Attenuates the FCV input signal before it is summed into the LP cutoff control voltage.335
Gain mod switch
switch
—
Routes AUX-, 0V, or AUX+ to the gain control voltage summed with the gain offset potentiometer. Note: only positive (RES) and (GAIN) voltages yield useful results — monitor via green LEDs.335
Gain offset
knob
—
Sets the input gain level driving both the LPF and HPF input VCAs. Higher gain makes the LPF resonance more dominant and adds grit/warmth. Can be further modified by the gain mod switch.335
HPF mod switch
switch
—
Routes AUX-, 0V, or AUX+ to the HPF cutoff control voltage. AUX+ is the attenuated ACV; AUX- is its inverse.335
HPF offset
knob
—
Sets the cutoff frequency offset of the high-pass filter (labeled 'Spread' on panel). Contributes to the (HP) internal control voltage along with the HPF mod switch selection and optionally a proportion of (LP) via the link switch.335
LPF offset
knob
—
Sets the cutoff frequency offset of the low-pass filter. Fully CW is maximum frequency (green LED). Contributes to the (LP) internal control voltage along with attenuated FCV.335
LPF-HPF link switch
switch
0% – 100%
Links the LP cutoff control voltage to the HP cutoff at 0%, 50%, or 100%, creating two flavors of band-pass filter. At 50%, minimum bandwidth occurs when LP LED is fully dimmed (LP offset at noon); bandwidth grows at maximum/minimum LP offset settings. Also used as a performance effect to create instant drops.335
Resonance mod switch
switch
—
Routes AUX-, 0V, or AUX+ to the resonance control voltage summed with the resonance offset potentiometer.335
Resonance offset
knob
—
Sets the resonance level for both LPF and HPF simultaneously. Below 10 o'clock is moderate; around 12 o'clock enables pinging; past 12 o'clock enters self-oscillation with complex LPF/HPF interaction. Can be further modified by the resonance mod switch.335