User Manual

4.2.2. Compression
Together with Threshold, and complemented with Attack and Release, this is where we
mainly act to find the best settings for the compressor.
This is the parameter which defines how much compression (level and dynamic reduction)
is applied to the audio when the detected level exceeds the Threshold. Like it happens with
Threshold, the way this parameter acts is also influenced by the "compressor knee". With a
hard knee of 100%, basically all frequencies above the Threshold will be compressed the
same way. As we saw, that's not the case in the Comp VCA-65, which features a very gentle
knee. Therefore, the compression effect appears gradually, starting still below the defined
Threshold, and the maximum compression effect is only reached way beyond that same
Threshold level.
Compression level is expressed as a ratio. The right value is the compressed level, while the
left value is the original. When we see a compression ratio of 4:1, it means that an original
value of +12 dB will become reduced to just +3 dB, after compression is applied.
A gentle value is desirable (no more than 4:1 and usually even less). This also depends
on the type of music, the instrument and the results that we want to achieve. Some drum
instruments commonly use higher compression ratios, for example.
Usually, it is better to start with a very small compressor ratio, and raise it when you feel
the need to do so. Remember that Attack and Release times are also important to take into
account. As the compression curve in Comp VCA-65 is very gentle, this means it starts below
and reaches the maximum compression way above the Threshold.
Compression range goes from 1 (1:1, meaning no compression) up to Infinite (where the
compressor will act in practice as a limiter, if we define a very fast attack). Values over 10:1
are used only in extreme cases. By default, Compression is positioned at 1, which means no
compression.
The tip we gave for the Threshold is a good way to start trying the Compression parameter,
as it allows to define with reasonable precision the average signal level, and we can start
from there to achieve a good compression ratio.
Comp VCA-65
Compression control set
to a ratio of 2:1
16 Arturia - User Manual Comp VCA-65 - COMP VCA-65 CONTROL PANEL