Stereo and Mono Sidechain Compressors for Tracktion
Examples
Expansion
The red diagonal line added to the graph below, represents unity gain (i.e., the output signal is the same level as the input signal). Contours which are steeper than this, like the segment between T and node 1, represent expansion, those not as steep, compression.
Leveling
Having expansion for low input signals, and compression for higher signals is a good way to level out a signal's dynamics. Quiet signals become louder, and louder signals become quieter. We see an example of this below. For input signals below node 2 in amplitude (approximately
Expansion occurs when the output level change is more than the input level change. For exam- ple, a 3 dB change in input level, might give a 4 dB change in output level.
Compression occurs when the output level change is less than the input level change. For example, a 3 dB change in input level, might give a 2 dB change in output level.
Deft use of the nodes allows expansion or compression above the threshold. Expansion can be used to increase the volume of quiet passages, and bring a little bit more "life" into a perfor- mance. Note that each individual segment can be set as either a compressor, or an expander. Just look at the slope between each node. If it is steeper than the diagonal, this is expansion, and if not so steep, compression.
Note that in the above example, the reduction meter and the output level meters are showing an increase (expansion) in level.
Limiting
When you just want to limit the signal to not go beyond a certain level, set the end point to be the same level as the threshold (Ratio = infinity:1), and keep the Attack time low.
User’s Guide
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