DarkLumi

DarkLumi

An optical bus compressor with a real photocell (Vactrol VTL5C-style) gain element in a feedback topology — the smooth, natural opto sound with a self-shaping soft knee, voiced for mix-bus and master “glue.” It pairs the opto core with fast class-A op-amp stages and H2-dominant photocell saturation, and lets you switch between vintage feedback and modern feedforward detection. Adds a sidechain EQ, output EQ, parallel mix, and transformer color.

Main panel — compression

THRESHOLD (−100…0 dB) — Sets where compression begins. Lower = more gain reduction.

GAIN (0…50 dB) — Makeup gain at the output.

RATIO (7 detented positions: 2 / 2.5 / 4 / 6 / 8 / 10 / 20) — Detented ratio ladder. Default 4:1. Lower ratios have a softer, mastering-grade knee; higher ratios harden toward aggressive limiting.

ATTACK (0.1…30 ms) — Continuously variable, log-skewed. Default 1 ms.

RELEASE (0.05…1.5 s) — Continuously variable, log-skewed. Default 0.6 s.

FB / FF — Detector topology. FB (feedback) is default — classic opto/LA-2A character, smoother and more vintage. FF (feedforward) is punchier, more transparent, catches transients more tightly.

ON/OFF — Compression in/bypass.

Metering

VU — Gain reduction metering.

ADV panel

MIX (0…100%) — Parallel compression, blends dry with compressed.

INPUT (−18…+18 dB) — Pre-compressor input-gain trim (auto-compensated after, so level stays neutral).

KNEE (−10…+10):

• negative = harder knee — compression kicks in more abruptly at threshold, snappier/more aggressive.
• 0 = stock — the opto cell’s natural soft knee.
• positive = softer knee — compression eases in more gradually, smoother and more musical.

OUTPUT (−12…+12 dB) — Final post-everything output trim.

EQ display + EQ MODE (SC / OUT) — One 6-band parametric EQ display that toggles between two destinations:

• SC — Sidechain EQ: shapes what the detector hears, so the compressor reacts more or less to certain frequencies.
• OUT — Output EQ: post-compression tone shaping on the audio itself.

Drag bands on the display; per band On, Type (Bell/LShelf/HShelf/LCut/HCut), Freq/Gain/Q.

Transformer (combobox) — Output transformer emulation, 17 options (None, Carnhill, Sowter, Cinemag, Marinair, Haufe V72, Triad HS-30, Reichenbach, EA Edcor, Neve 1272, API 2520, UTC A-20, Peerless S-415, St Ives, Lundahl LL1538, Jensen JT-11, Tamura TKS-27). Default None keeps the transformerless sound.

Oversampling

x2 / x4 / x8 (combobox) — Anti-aliasing. Default x4.