resofilter

resofilter · processors · schema v1

Multi-mode filter — clean-room TypeScript port of gabrielsoule/resonarium's MultiFilter (Source/dsp/MultiFilter.{h,cpp}). 5 modes drawn straight from upstream's MultiFilter::Type enum and filterTextFunction: LP / HP / BP / Notch / Allpass. All five characters share a single Cytomic / Zavalishin TPT state-variable filter per channel, so the MODE knob is a pure output picker — switching modes mid-render is pop-free. Cutoff 20 Hz – 20 kHz (log), resonance 0..1 (k = 2 − 2·res, edge-of-self-oscillation at the top), per-param CV inputs (cutoff_cv, reso_cv) sum into the AudioParams with a 50 Hz internal one-pole smoother on cutoff to prevent the steep transfer function from clicking on rapid CV jumps. Stereo input (independent L/R SVF state). The card displays the long-form mode name (e.g. "Low-pass") in a label next to the MODE knob — the headline UX feature: the dial updates the text reactively as you turn it. Drive is intentionally omitted (upstream MultiFilter has no drive stage; saturation lives in WrappedSVF / Distortion which is out of scope for this port).

A clean multi-mode resonant filter (ported from Resonarium's MultiFilter) built on a zero-delay-feedback state-variable topology, so all of its modes share one filter state and switching between them mid-sound is pop-free. One MODE knob picks the response — Low-pass (attenuate above cutoff), High-pass (attenuate below), Band-pass (peak at cutoff), Notch (dip at cutoff), or Allpass (flat magnitude, phase-rotating) — and the card prints the long-form name of the current mode next to the knob. The input is stereo-aware (independent L/R filter state preserves the image), CUTOFF and RESONANCE are CV-modulatable, and a MIX knob crossfades dry to wet (turn it to 0 for bypass). A general-purpose tone-shaper for both subtractive synth voices and full mixes.

the faceplate

3 inputs · 2 outputs · 4 params

about this module

Hover a control, or open the patch panel and hover a jack.

inputs

id	cable	what it does
`audio`	audio	The signal to filter (mono or stereo). A stereo source keeps its left/right separation through independent per-channel filter state; a mono source feeds both channels. audio signal
`cutoff_cv`	cv	CV control of the CUTOFF frequency — patch an envelope or LFO here for filter sweeps (it adds to the knob position). control voltage (CV); modulates cutoff (additive offset — ±1 CV sweeps the full range, centered on the knob)
`reso_cv`	cv	CV control of the RESONANCE — modulate the emphasis at the cutoff for talking/wah-style motion (adds to the knob position). control voltage (CV); modulates resonance (additive offset — ±1 CV sweeps the full range, centered on the knob)

outputs

id	cable	what it does
`out_l`	audio	Left filtered output (with the dry/wet MIX applied). audio signal; L/R stereo pair with out_r
`out_r`	audio	Right filtered output. With a mono input it carries the same filtered signal as OUT L. audio signal; L/R stereo pair with out_l

params

id	label	range	default	curve
`cutoff`	Cutoff	20..20000Hz	1000	log
`resonance`	Reso	0..1	0.3	linear
`mode`	Mode	0..?	0	discrete
`mix`	Mix	0..1	1	linear

controls

control	what it does
Cutoff	The corner frequency the filter pivots around (20 Hz to 20 kHz, log, default 1 kHz) — what 'above'/'below'/'at cutoff' refers to for the selected mode. The CUTOFF CV input adds to this.
Mix	Dry/wet balance (0 to 1, default fully wet): 1 is the pure filtered signal, 0 is full bypass (the unfiltered input), and in between blends the two.
Mode	Picks the filter response among Low-pass, High-pass, Band-pass, Notch, and Allpass (the chosen name is shown on the card). All five share one filter state so changing mode while audio plays is pop-free.
Reso	Emphasis at the cutoff frequency (0 to 1, default 0.3): higher values sharpen the peak and ring more — subtle by default, pronounced toward 1. The RESO CV input adds to this.

source

resofilter.ts on GitHub.