Behringer MDX1400 - Manual (Page 12)

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AUTOCOM PRO MDX1400
Clipping
In contrast to the two previously mentioned limiters, the clipping mode features infinitely fast control times, an
infinite compression ratio and creates an unsurpassable barrier (“brickwall”) for all signals above a certain level.
To be able to control the signal peaks, the clipping function radically cuts signals above the threshold, without
affecting the amplitude of the original signal. If used in normal applications, this function remains inaudible and
under certain circumstances it can even lead to an improved sound, because cutting the transients creates
artificial harmonics. If misused, clipping can cause very obvious and distasteful distortion, which in an extreme
manner, will convert the signal’s waveform into a square wave signal. This effect is often produced in guitar
distortion devices (“fuzz boxes”).
3.2 Expander/Gate Section
The main task of the Expander/Gate is to “inaudibly” eliminate undesirable background noise from the usable
signal. As additionally described in chapter 6.4, a downward expander automatically reduces the overall level
for all signals below an adjustable threshold. The expander therefore operates in opposite way to that of a
compressor/limiter. Expanders generally function with a flat ratio curve, so that the signal continually fades.
Noise gates however, can be seen as “high ratio” expanders. If the signal falls below the threshold, it is
radically attenuated.
The BEHRINGER AUTOCOM PRO is equipped with a newly developed IRC (Interactive Ratio Control)
Expander, the ratio of which is automatically adjusted dependent on the program material. The response
characteristics of conventional expanders tend to cut into the signal abruptly and the result of this is
unacceptable most of the time. Gain changes become audible.
The IRC Expander is therefore equipped with a soft, interactive non-linear ratio curve, which is best suited to
human hearing. Critical signals in the vicinity of the threshold level are processed with a minute expansion
ratio, whereas signals that reduce in level will be subjected to an increasingly higher ratio, which will result in
greater attenuation.
Threshold
Gain 0 dB
Input
Output
1:oo Noise Gate,
Expander, 1:8
IRC-Curve
Fig. 3.1: IRC curve characteristic of the Expander
The result is expansion, which is less critical to adjust and which is more tolerant of useable signals, whose
level is slightly above that of the noise floor. Expansion therefore occurs extremely “soft” with low ratio settings,
while the known negative effects of expansion are inaudible. The Attack time of the IRC expander is set
automatically and program-dependent, i.e. extremely short for quickly changing signals and slower for a more
balanced program material. Since the expander/gate adapts itself automatically to the program material,
you will note that the new IRC (Interactive Ratio Control) circuit produces considerably better results than
conventional expanders.
3.2.1 Controlling Leakage In The Studio
Expander/gates are most commonly used to suppress undesirable leakage of sound from one track to another
during recording or playback. They are usually used when recording drum kits, where the mics are very close
to each other. High volume levels of individual instruments often cause considerable leakage onto all the
3. APPLICATIONS