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7
ADMS 44.22 Installation and Operation Manual
DESCRIPTION
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Fade Up/Fade Down
The ADMS 44.22 can fade one or more channels up or down at a prepro-
grammed Fade Rate ranging from 0.5 to 10.0 seconds. The Fade Rate is
global for all channels. In Interlock and Overlap Modes, fading one channel
up initiates an automatic equal-power cross fade by fading down any con-
nected input(s) at the same rate.
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Dim
Any connected input may be dimmed (gain reduced) by any amount from -
0.1 to -20.0 dB without affecting any other input connection. Sending a con-
nect, fade, or disconnect command to a dimmed channel cancels the dim
state. Dim Levels can set on a channel-by-channel basis, and affect the
input’s Dim Level in both outputs. When a fade is applied to a dimmed
channel, the fade times are adjusted to match the time taken to fade between
the same gain levels on non-dimmed channels.
1.2.2
Automatic Level Control
Each input and output channel contains an automatic level control circuit
(ALC) that is designed to normalize the program signal peaks to a target output level
without dramatically altering the dynamic range of the material. If the average level
of the program signal is below the target output level, the gain is slowly raised until
the program peaks in the vicinity of the target output level. If the average level is
above the target output level, the gain is quickly reduced. A built-in limiter prevents
program peaks from causing clipping. The ALC can be enabled/disabled on a chan-
nel-by-channel basis.
The ADMS 44.22 ALC combines features from several commonly used DSP
processes: compression, limiting, and automatic gain control. However, the ALC
controls described below are unique to the ADMS 44.22, and therefore must be
understood in order to set up the ALC for effective operation.
•
Target Output Level
The target output level sets the upper ALC output’s upper dynamic range
detector. The factory default for this setting is +4 dBm/-20 dBFS (0 VU).
Set the target output level to match or slightly exceed the nominal program
level for your facility. Because the ALC employs a fast-averaging detector,
when on-air program levels are set using VU meters, under some circum-
stances it may be appropriate to set the target output level 3 to 6 dB above
the facility’s nominal VU level. Ideal operation occurs when the average
level of the program source does not substantially differ from the target out-
put level.
•
Threshold
To prevent the gain from increasing during silence gaps in the program, once
the program level drops below a programmable threshold setting the ALC
gain is ‘held’ until the level exceeds the threshold once again. This allows
the ALC to adjust its nominal gain to the average level of the program mate-
rial without the silence gaps affecting the average gain calculations. The net
effect is that when program level returns, there are no sudden gain changes