Focusrite Red 1, Manual

Page: 10 / 16

four channel microphone preamplifier
p a g e 9
compressor/limiter
Gain Change
This modifies what the meter displays. When the switch
is out, the meter displays the level of the input signal.
When the switch is in, the meter displays the amount of
compression. Since compression reduces the volume of
the signal, the meter drops as compression is applied.
For example, a 3 dB drop shows as -3 VU on the meter.
+14 dB
This switch affects the input-level meter:
• When it is out, a signal of +4 dB registers as 0 VU
• When it is lit, a signal of +14 dB registers as 0 VU
The switch lets you monitor very loud signals without
overloading the meters (for example, if the incoming
signal is very loud).
Limiter
The limiter sets an absolute threshold for the signal
volume after compression, and does not allow the
volume to go above that threshold.
Note that the threshold for the limiter is independent
of the threshold for the compressor (the dB value of
the limiter’s threshold is an absolute value, not a
relative value above the compressor’s threshold).
Therefore, it is possible to set the threshold for the
limiter below the threshold for the compressor - if you
do this, the limiter will not work.
When the limiter is working, the limit light comes on.
Using the Key Input
Pressing the key input button switches control of the
compressor to a signal entering the unit through the
key input. Note that the key input signal is not output
from the unit, it is the original input that is
compressed, but compression is applied as if the key
input signal were being compressed.
For example, one of the problems in compressing a
mixed programme is that gain reduction tends to be
controlled by one dominant instrument or sound. For
more natural compression, you need to attenuate
(reduce the volume of) the sound of the dominant
instrument, but this is probably not acceptable since it
would affect the mix. Therefore, you can use the key
input: take a second feed of the programme, and feed
it through an equaliser that attenuates the dominant
instrument, then take that signal and feed it into the
key input, as shown in the diagram.
Now, you can use the key input to control the
compression of the original signal. The original signal
is compressed as if the dominant instrument had been
attenuated.
This technique can be very useful when compressing
bass-heavy dance music. By attenuating the bass in the
key input signal, the bass in the original retains more
of its dynamics.
Another application of this technique is in de-essing.
When de-essing, you want sibilants in a voice to be
heavily compressed. To achieve this, accentuate the
sibilants in the key input signal by adding gain to the
correct frequencies, which means they are heavily
compressed in the original signal.
VCA
Line I/P
Key I/P
KEY SWITCH
O/P
Control Voltage
Side Chain
Processing
Can be driven from
either line in or Key
Audio Compression
applied here
EQ
Line In
Key In