@audio/filter-korg35

Korg MS-20 style filter (Korg35)

npm install @audio/filter-korg35

import korg35 from '@audio/filter-korg35'

Korg MS-10/MS-20, 1978 — 2-pole filter with lowpass and highpass outputs from nonlinear feedback.

Topology: 2 cascaded one-pole sections with nonlinear feedback; HP = input − LP Response: $-12,\text{dB/oct}$; resonance 0–1 adds damping/saturation character — no resonant peak, no self-oscillation at any setting (2 real poles in the loop can't reach the −180° phase Barkhausen's criterion needs at any finite, audible frequency, unlike Moog/Diode's 4-pole loops) Complementarity: LP+HP=input holds exactly only at resonance=0 (verified to 1e-16); at resonance>0 the HP tap's extra feedback term makes LP+HP diverge from the input (measured −7.5 dB to +1.4 dB error at resonance=0.8 across 200 Hz–5 kHz)

korg35(buffer, { fc: 1000, resonance: 0.5, type: 'lowpass',  fs: 44100 })
korg35(buffer, { fc: 1000, resonance: 0.5, type: 'highpass', fs: 44100 })

Circuit: Korg MS-10/MS-20 (1978) Analysis: Stilson & Smith, "Analyzing the Korg MS-20 Filter" (1996); Zavalishin, The Art of VA Filter Design (2012), Ch. 5 vs Moog ladder: 2-pole ($-12,\text{dB/oct}$) vs 4-pole ($-24,\text{dB/oct}$); Korg35 has both LP and HP taps from one circuit, but no self-oscillation

| Param | Default | | |---|---|---| | fc | 1000 | cutoff frequency, Hz | | resonance | 0 | 0–1; feedback k = 2·resonance; never self-oscillates | | fs | 44100 | sample rate, Hz | | drive | 1 | input gain into the feedback-path tanh saturation | | type | 'lowpass' | 'lowpass' or 'highpass' |

Pass the same params object on every call to persist the 2 stage states across blocks.

Use when: MS-20-style aggressive filter character with a highpass tap available; use moogLadder for 4-pole warmth and true self-oscillation instead.

Part of @audio/filter — the filter family umbrella. This README is generated from the umbrella docs.

MIT © audiojs