Sauce is a polyphonic state-variable filter as described in the following paper by Andrew Simper (Cytomic). See page 6 of that paper for the equations used in Sauce.
Sauce is very similar to the stereo filter Gravy, but is optimized for general polyphonic use.
Sauce provides control over the following parameters:
- FREQ: the filter's corner frequency. The default setting is 0, which corresponds to the note C5 = 523.251 Hz. Each unit on the FREQ dial represents an octave. The dial spans ±5 octaves around the note C5. To use the FREQ CV input as a V/OCT control, set the attenuverter all the way clockwise to +100%.
- RES: the filter's resonance, on a scale from 0 (the default) to 1. Higher resonance causes the filter to concentrate the passband closer in to the corner frequency. Toward the upper end of the resonance scale, you can even get sustained oscillations, also known as "ringing".
- MIX: A value from 0 to 1 that controls how much of the original, unfiltered stereo signal is included in the output. The default MIX value is 1, which means that the output represents 100% filtered audio. As the value is decreased toward 0, more of the original audio is included in the output. At zero, the output is identical to the input (except for a one-sample delay inherent to all VCV Rack modules).
- GAIN: Allows you to make the output louder or quieter, as a convenience. Consider it a built-in VCA.
Each of the controls include a CV input port, a smaller attenuverter knob, and a larger manual control knob. The CV input ports all support full polyphony. Missing channels are normalled forward. For example, this means you can use a 1-channel cable connected to the FREQ CV input to control all 3 signals in a 3-channel audio input. Or you could use 3-channel CV input to control the frequencies independently.
When you right-click on the Sauce panel, you will see the following context menu:
Sauce supports low-sensitivity attenuverters. This option toggles the sensitivity mode on all the attenuverter knobs.
Sometimes an output voltage from Sauce can be excessively large, especially if you use high resonance settings. It can be helpful to keep the output under control. To meet this need, Sauce includes a built-in output limiter option.
In the context menu, the output limiter appears as a horizontal slider. By default, the limiter is turned OFF. If you start to pull this horizontal slider to the left using your mouse, the limiter turns on. You can adjust the output limiter to any value from 5 V to 50 V. You can turn the limiter back off by sliding the level all the way to the right.
When the output limiter is enabled, and the output goes beyond the limit, the limiter causes the GAIN knob to glow red as an indicator that the output level is being attenuated.
Also in the context menu is the toggle option "Limiter warning light". By default, the warning light is enabled, causing the GAIN knob to glow red when the limiter is actively reducing the output level. You can uncheck this option to turn the red glow off.