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Compressor and Heritage Mix Processing

Stereo mix-bus compressor​

The compressor sits in the main stereo path after the Mix Insert and before the Master Fader.

ASP4816-HE stereo mix-bus compressor controls ASP4816-HE analogue gain-reduction meter

The compressor provides:

  • Threshold: -20 dBu to +20 dBu.
  • Attack: six steps from 0.1 ms to 30 ms.
  • Ratio: 2:1, 4:1 or 10:1.
  • Makeup gain: up to 40 dB.
  • Release: five steps from 0.1 s to 2.4 s, plus Auto.
  • IN: switches the compressor into circuit.
  • BASS EXPAND: inserts a 350 Hz high-pass filter in the sidechain, reducing the extent to which low-frequency energy triggers compression.

The analogue gain-reduction meter shows the amount of gain reduction being applied.

For general mix-bus use, small amounts of gain reduction may be sufficient. A higher threshold with a higher ratio can also be used to control peak signals so the compressor acts primarily when the threshold is exceeded.

Heritage mix-bus processing​

ASP4816-HE XFRMR Drive, Low Bump and High Lift controls

XFRMR Drive​

XFRMR DRIVE introduces two Carnhill output transformers into the signal path. A useful workflow is to engage XFRMR Drive during a mix and then balance the mix with the transformer stage active.

Low Bump​

LOW BUMP applies a broad low-frequency lift centred around 60 Hz.

High Lift​

HIGH LIFT applies a broad high-frequency lift around 20 kHz.

note

Low Bump and High Lift are part of the transformer processing circuit and only affect the Mix while XFRMR Drive is engaged.

John Hardy 990C+ mix-bus op-amps​

The mix-bus summing circuit uses a pair of discrete John Hardy 990C+ op-amps. The manual describes the discrete summing stage as providing a very low noise floor and fast transient response.

Main Mix signal order​

The console block diagram confirms the main Mix signal flow as:

Mix buses → SIP relay → Heritage bus processing → Mix inserts → compressor → Master Fader → Mix outputs.

Continue to Stereo Inputs, Subgroups and Masters.