theallelectricsmartgrid

Mixdown and Mastering

The final stages of the Smart Grid One DSP engine (private/src/QuadMixer.hpp and private/src/QuadMasterChain.hpp) handle the routing of effects, the mixdown to different channel formats, and the final mastering saturation.

Mixdown

The QuadMixerInternal takes the 9 voices (which have already been panned quadraphonically) and routes them:

1. Direct Out: The quadraphonic signals are summed.
2. Effects Sends: The signals are sent to the Quad Delay and Quad Reverb based on per-voice send levels.
3. Effects Returns: The quadraphonic outputs of the Delay and Reverb are mixed back into the main quad bus.

The system simultaneously generates three parallel mixdowns:

• Quadraphonic: The primary 4-channel output.
• Stereo: A folded-down stereo mix (QuadToStereoMixdown). It uses a specific matrix to fold the rear channels into the front channels while preserving spatial width.
• Sub: A dedicated mono sub-woofer channel, fed by the per-voice sub oscillators and the mono low-band sum in the mastering chain. See Sub Oscillator.

Multiband Saturator

Before leaving the synthesizer, both the Quad and Stereo mixdowns pass through a DualMasteringChain, which contains a MultibandSaturator (private/src/MultibandSaturator.hpp).

The Multiband Saturator splits the signal into 4 frequency bands using 4th-order Linkwitz-Riley crossovers (LinkwitzRileyCrossover).

• Each band can have its gain adjusted independently.
• Each band is then passed through an arctan saturator (ProcessAndSaturate in Metering), providing soft clipping and harmonic saturation.
• Because the saturation is applied per-band, it prevents intermodulation distortion (e.g., heavy bass notes won’t cause the high frequencies to duck or distort).
• The bands are then summed back together, providing a loud, glued, and polished final output.

Related

• DSP Overview
• Quad Delay
• Quad Reverb

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