TL Audio 5021 - Manual (Page 16)

This switch enables or disables the compressor stage, thus allowing an A/B
comparison to be made between the original untreated signal and the
compressed signal. Any gain make up applied to the signal only becomes
active when the “Compressor On” is enabled. An associated status LED
indicates when the compressor is active. The Gain Reduction on the VU meter
will monitor the level of compression regardless of the compressor stage being
active or non-active.
4.12 Stereo Link.
In dual mono mode, the 5021 can process two separate signals (such as a
vocal on channel A and a bass guitar on channel B) and provide completely
independent control of each. Alternatively the ‘Stereo Link’ mode links the
control voltages of both channels and is typically selected when the 5021 is
used for processing signals such as an overall mix, or a stereo feed from a
sound module.
Stereo linked compression is essential to avoid imbalances in the stereo
image (known as “dips”) to appear on one side of a stereo signal, if the signal
exceeds the threshold on that side only. If a compressor has not been stereo
linked, the “dipping” of one channel can sound very obvious and unnatural. In
linked mode, if either signal crosses the threshold setting, both channels will
react together and will be compressed by the same amount. For best results,
both channel settings should be made the same to maintain a consistency
over the stereo image.
4.13 Meter.
The 5021 is equipped with two illuminated VU meters: one for each channel.
Normally the VU meter reads the audio output level, and is calibrated to read
0VU for a +4dBu output level. Increasing the output level control on the 5021
towards the +20dB setting will cause the 5021’s meters to move further
towards the red area and possibly to the end of the scale if sufficient gain is
applied. When switched to ‘Gain Reduction’, the meter indicates the amount of
compression occurring. If the signal is below the threshold, the meter will
indicate 0dB: i.e. no gain reduction. As the signal passes through the
threshold, the meter will start to indicate the gain reduction at the compressor
stage (this will be a negative value, so the meter will move to the left, away
from 0VU). Note that this reading won’t include any extra gain make-up
applied.
4.14 Frequency Conscious Compression.
The provision of sidechain insert points on the 5021 allows the unit to perform
frequency conscious compression, such as ‘de-essing’. This is achieved by
patching an equaliser (normally a parametric or graphic type) into the
sidechain (the insert point works on a send-and-return principle whereby the
insert ‘send’ connects to the equaliser input, and the equaliser output connects
to the insert ‘return’, thus completing the circuit). Once connected, any