User Manual

3.4. Understanding the Comp VCA-65 Signal Flow
To better understand what happens in Comp VCA-65 let's take a look at a signal as it flows
through the product. The paths are a little more complex than what could be expected, due
to the Advanced Mode features, especially those related to the Advanced Side-Chain Control.
This allows for several special detection modes, many of them taking advantage of Mid/
Side signal encoding.
As the signal enters the plug-in, it is immediately split in two paths:
1. The "main" signal path. The signal on this path is compressed and processed.
2. The "bypass" path. The signal on this path is sent without any processing to a
mixer just before the VCA-65's output. The "Mix" knob on the front panel allows to
blend this unprocessed signal with the compressed signal.
If you are using Comp VCA-65 on a stereo track, the first stop on the main signal path is
the optional M/S encoder. M/S stands for "Mid/Side" and is a way of processing audio where
only the "Mid" channel (the center of the stereo image) or "Side" channel (the edges of the
stereo field) is processed. This is described in detail later [p.26] in the manual. Note that the
Detection Mode control knob is only available on stereo signals and is bypassed when using
a mono version of the plug-in.

♪: M/S requires a stereo signal to work. If VCA-65 is instantiated on a mono track, M/S encoding and
decoding stages are bypassed and the Detection Mode control knob is hidden in the advanced panel.
After this stage, the "main" signal is split again into two other parallel paths:
1. The first (main) path goes to the emulated VCA Gain Reduction circuitry. This
is the heart of the circuit and where the actual compression takes place. This
system is controlled by the Gain Reduction Control circuit, activated by the
Threshold control.
2. The second path (known as the "detection" path) is sent through a source selector
switch to the Gain Reduction Control circuitry. The source selector module
receives the detection signal and also signals from External Source (traditional
Side-Chain) and Manual Source, and routes them to the Gain Reduction Control
circuit, which will be processed by the Advanced Side-Chain Parameters in order
to determine how that circuit will work on the signal.
After compression, the next stage is the M/S decoding block. This is where the signal is
converted from M/S back into a regular stereo signal.
Arturia - User Manual Comp VCA-65 - COMP VCA-65 OVERVIEW 9