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Navigate to:
Setup / Audio Input
:
Turn
the jog wheel to position the brackets around either the
Digital
or the
Analog
audio input, and then
press
the jog
wheel to confirm and save the selection.
SETTING INPUT GAIN
Importance of
AGC Action
The DAVID IV has an intelligent dual-slope ‘windowed’ AGC
(Automatic Gain Control) to gain-ride the program input signal.
AGC has a capture range of ±18dB, meaning that the input sig-
nal can wander aimlessly over this 36dB range and be automat-
ically corrected to the proper level. AGC gain is shown by a
front-panel LED bargraph.
AGC has been designed for symmetrical correction around a
resting-point of
0dB
or unity gain. It will bring up lower levels
and pull down higher ones at the selected correction rate. AGC
action is ‘gated’ to freeze the gain when the program pauses,
returning it to the
0dB
resting point during extended periods of
silence. The front-panel
GATE
indicator glows when the gate is
‘open’; that is, when the AGC is active.
AGC is considered a processing parameter of the DAVID IV, but
one that, by design, does not make an audible contribution to
the station’s “signature sound.” The sole purpose of the AGC is
to normalize levels ahead of the other processing stages with-
out adding coloration. This is possible only with a wideband
AGC, which should always be the first stage in any comprehen-
sive audio processing system. “Multiband AGC” is a misnomer.
Long-term
leveling
in individual frequency ranges may have
utility in some instances, but this amounts to spectrum-
shaping. Using multiband AGC to normalize levels from di-
verse sources or to correct for sloppy operators is analogous to
turning the listening volume in your living room up and down
using the individual sliders of a graphic equalizer.
The DAVID IV AGC delivers a uniform program signal to subse-
quent processing stages. AGC gain is based on both the peak
and average energy values of the program content. Regardless
of changes you might want to make in AGC operation for a spe-
cific need (this will be addressed later), check that the AGC is
set to factory defaults during setup of input levels. Navigate to:
Processing / AGC
to confirm that the AGC is
Active
with a
Cor-
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