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The AGC stage of the DAVID IV has been carefully engineered
for intelligent response to program material, taking into ac-
count both the peak and average values of the audio signal.
The only justification for turning AGC off is for test purposes,
or if the user is 100% confident that the board operator is dili-
gent in riding the gain manually (fat chance!). Even in the latter
instance, trust the AGC to know best what downstream pro-
cessing stages want to see.
AGC
Correction Rate
A ‘normal’ correction rate of the AGC is
5
on the scale, a very
unobtrusive 0.5dB/second. This is a figure that’s been typical
of AGC sections in Inovonics broadcast processors for 30 years
or more. In fact, adjustable AGC rate has seldom been availa-
ble in previous Inovonics broadcast processors.
The DAVID IV allows the user to change the correction rate be-
tween a setting of
1
, an exceedingly slow 0.1dB/second, and
9
, a
really speedy 2.5dB/second.
Slower AGC action would be a proper choice for a classical mu-
sic format where extended
pianissimo
passages want to remain
below
mezzo-piano
ones,
forte
passages then calling for a mod-
icum of compression.
Alternatively, AGC could be turned completely off in such a
case:
Bypass
, assuming that the classical Boss-Jock knows the
music intimately and can make judicious manual corrections on
the fly, watching the meters with nary a blink.
Really fast AGC might be justified in an aggressive pop-music
format. Even at its fastest, AGC in the DAVID IV shouldn’t alter
the perceived dynamics of the program, although it will defi-
nitely erase level variations in a hurry. The faster settings
might cause AGC action to be audible in speech (a talk show for
instance), but probably not in a high-energy rock-n-roll format.
Experiment with various AGC rates using program material rep-
resentative of your format. A setting of
5
is our recommenda-
tion and has proven to work well in nearly all situations.
AGC
Maximum Gain
Classical music and jazz are two genres that often have wide
level variations that beg to be preserved.
Pianissimo
classical
passages and a standup-bass solo are two examples. In these
instances, a normal configuration of the AGC stage would slow-
ly bring up these passages to the 100%-modulation point. This
would not sound authentic.
The
Max Gain
slider is generally kept at
+18.0dB
in normal oper-
ation. If you want to limit the amount of
positive
gain that the
AGC can impart to the program input, this slider can be adjust-
ed anywhere between
+18.0dB
and
0.0dB
. This does not change
the static, ‘resting’ gain of the AGC section, nor does it limit the
amount of negative gain that the AGC can introduce for inputs
that are too loud.
Max Gain
only limits how far the AGC can
bring up low-level material. Experiment with
Max Gain
settings
for formats that call for a wider dynamic range.
Summary of Contents for David IV
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