@audio/dynamics-varimu

Vari-Mu compressor model (Fairchild class) — feedback detection, drive-dependent ratio, soft wide knee

import varimu from '@audio/dynamics-varimu'

Models a Fairchild 670-style vari-mu tube compressor: feedback topology — the RMS detector reads the already-compressed output, not the input, which is what gives vari-mu units their characteristic self-limiting smoothness. Ratio ("mu") is not fixed: it grows from 1.8 with drive above threshold (mu = 1.8 + max(0, overDb) / 5), through a 15 dB soft knee.

varimu(data, { threshold: -22 })                 // batch
varimu(data)                                        // defaults

let write = varimu({ threshold: -22 })            // streaming
let out1 = write(block1)
let tail = write()                                  // flush

Ratio is derived, not settable — pass threshold/knee to shape where and how gradually it grows.

Use when: bus glue, mastering — slow, smooth, self-limiting gain reduction with tube-like character.
Not for: fast peak control — use fet or limiter.

Part of @audio/dynamics — the dynamics family umbrella.

MIT © audiojs