Expander/Gate Section - Alto Professional ACOM2 Guide D'utilisation

The range of these devices is actually further reduced when accounting for 10-20 dB of "headroom" to avoid
distortion from the source audio, which has its own dynamic range. The device's operating level must be as
high as possible but not high enough to generate distortion. We recommend using ACOM2's AGC (automatic
gain control), which monitors the signal in real time and adjusts the gain to an optimal SNR without producing
distortion.
COMPRESSORS AND LIMITERS
To prevent an audio signal from "clipping" or distorting at high levels, ACOM2 uses a compressor/limiter.
Both do the same job, but a limiter reduces the audio signal above a set threshold, while a compressor
reduces the signal in a much more complex way and over a wide range of levels. A compressor reduces the
signal based on various parameters you set (attack, release, ratio, knee, etc.).

EXPANDER/GATE SECTION

Microphones, amplifiers, guitar pickups, etc. generate some noise that will reduce your signal quality, either
at low frequencies (hum) or at high frequencies (hiss). The signal itself often "masks" this noise, but it's more
noticeable during quiet parts or silence, when the signal is closer to the noise floor. To prevent this, ACOM2
uses an expander and noise gate.
An expander is the opposite of a compressor: it attenuates (reduces) the signal when the amplitude drops
below a set threshold. The expander automatically reduces the level of the audio signal below a set
threshold, using a flat ratio curve. ACOM2 is equipped with a new kind of expander, the SRC (Smart Ratio
Control). The ratio of the SRC is automatically adjusted according to the audio signal level. While
conventional expanders can often make overly "conspicuous" gain changes, the SRC has a non-linear ratio
curve, which is softer and user-adjustable. Quiet sounds close to the noise floor level will be processed with a
minimum ratio of expansion while higher-level signals will be processed with a higher ratio, resulting in
greater attenuation.
A noise gate is like a simpler version of the expander. While the expander continuously attenuates the signal
below the set threshold, a noise gate simply silences the signal completely below a set threshold.
Threshold Adjustment
The threshold control covers a wide range and is efficient with any working level. To turn off the
Expander/Gate completely, turn the threshold control fully counterclockwise.
Output
SRC
Curve
Compressor Threshold Control
The compressor threshold control sets the point where the input level starts to be reduced. For instance, if
the level is +12 dBu and the threshold control is set to +2 dBu, then up to 10 dB can be compressed. If the
input level is +12 dBu and the control is set to -10 dBu, then the maximum compression will be 22 dB.
The threshold control's operating range is -40 dBu to +20 dBu. Remember that the degree and the type of
compression depend not only on the threshold control but also on other controls, like Ratio, Attack, and
Release.
Threshold
Conventional
Expander Curve
Input
5