DarkVar

DarkVar — Variable-Mu Limiter / Compressor

A schematic-accurate emulation of the legendary Manley Variable-Mu — the king of tube bus compressors. Built around the 12BH7 remote-cutoff vari-mu tube model with 12AL5 full-wave rectifier feedback detection and Manley nickel input/output transformers, calibrated against the original hardware manual specifications.

Authentic Manley topology:

• 12BH7 remote-cutoff vari-mu tubes — the compression element (gain reduction by tube bias, not VCA/opto/FET)
• 12AL5 full-wave rectifier sidechain detector (feedback topology)
• Manley nickel input/output transformers with authentic LF saturation and HF behavior
• Program-dependent ratio:
  • COMP mode: 1.5:1 soft knee ramping to 5:1 at 10 dB GR
  • LIMIT mode: 4:1 sharp knee ramping to 20:1 at 12 dB+ GR
• HP Sidechain Filter: 6 dB/oct, -3 dB @ 70 Hz
• x2 / x4 / x8 Kaiser FIR oversampling

Manley front-panel controls:

• Input Level (-8 to +8 dB)
• Threshold (PEAK) — continuous -80 to 0 dB
• Attack — continuous 25–70 ms (Manley manual spec)
• Recovery — 5 stepped positions: Very Slow (8s) / Slow (4s) / Medium (0.6s) / Fast (0.4s) / Very Fast (0.2s)
• LIMIT / COMP mode switch
• HP Sidechain IN/OUT toggle
• Output Trim (-40 to +40 dB, unity at 12 o’clock)
• Per-channel Bypass (L / R), authentic Manley IN/BYPASS toggle

Per-channel mode:

• LINK — stereo-linked operation (both channels share L controls)
• SEP / MONO — fully independent L and R channels, each a standalone vari-mu compressor (authentic Manley MONO operation)

Pro extras:

• 6-band Sidechain EQ — full parametric (Bell / LShelf / HShelf / LCut / HCut)
• 6-band Output EQ — full parametric, post-compression
• Three optional transformers: Carnhill / Sowter / Cinemag
• Saturation drive
• Mix for parallel compression
• GR / Output metering modes