DarkMBuss

DarkMbuss — G Bus VCA Compressor

A schematic-accurate emulation of the modern G Bus 1.0 DIY VCA compressor (JG & PG, 2022) — a contemporary take on the classic G-style bus compressor topology with Carnhill output transformer, parallel saturation path, and the iconic stepped time-constant network.

Topology:

• NE5532 balanced input/output op-amp stages
• THAT2181 VCA (main + parallel saturation VCA1B sharing the same CV)
• Parallel saturation through 1N4148 diode-clamped path blended at mix node
• Selectable Drive (4.99k / 820R / 510R) — less resistance = harder transformer drive
• Carnhill X1.1 output transformer with 300Ω source impedance, LF saturation, HF rolloff, program-dependent core compression
• Feedforward sidechain with dominant-channel detection (max |L|, |R|)
• SC HPF: Off / 60 / 80 / 120 Hz

Controls (schematic-accurate stepped values):

• Attack: 0.1 / 0.3 / 1 / 3 / 10 / 30 ms
• Release: 0.1 / 0.3 / 0.6 / 1.25 s / Auto (dual-time-constant)
• Ratio: 2:1 / 4:1 / 10:1
• Threshold, Makeup, Mix (parallel compression), Auto-Makeup