@audio/filter-moog-ladder

import moogLadder from '@audio/filter-moog-ladder'

Robert Moog's 4-pole transistor ladder, 1965 — the most imitated filter in electronic music.

Circuit: 4 cascaded one-pole transistor ladder sections, global feedback from output to input
Implementation: Zero-delay feedback (ZDF) via trapezoidal integration — Zavalishin, The Art of VA Filter Design (2012), Ch. 6
Response: $-24\,\text{dB/oct}$ lowpass; resonance peak at $f_c$; self-oscillation (sine wave) at resonance=1, at $f_c$
Modes: type lowpass, highpass or bandpass, poles 4 or 2 — the ladder's taps mixed by binomial weights, $(1-L)^n$ highpass, $L^n(1-L)^n$ bandpass (Zavalishin §5.5; JUCE's LadderFilter modes, Pedalboard's)
Nonlinearity: $\tanh$ saturation at input (transistor ladder characteristic)

let params = { fc: 800, resonance: 0.7, fs: 44100 }
moogLadder(buffer, params)

// Self-oscillation — runs indefinitely from a single impulse
let silent = new Float64Array(4096); silent[0] = 0.01
moogLadder(silent, { fc: 1000, resonance: 1, fs: 44100 })

// Highpass, -12 dB/oct
moogLadder(buffer, { fc: 300, resonance: 0.4, fs: 44100, type: 'highpass', poles: 2 })

Patent: Moog (1965) US3475623
vs Diode ladder: Moog saturates only at input; diode saturates at each stage — different character at high resonance

Pass the same params object on every call to persist the 4 stage states across blocks.

Use when: synth-filter warmth, resonance, and true self-oscillation at resonance=1 — the reference analog-modeled lowpass.

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

MIT © audiojs