OPTIMOD-AM DIGITAL OPERATION
3-41
Previous Orban AM processor AGCs had compression ratios very close to :1, which
produces the most consistent and uniform sound. However, the 9400 compressor can
reduce this ratio to as low as 2:1. This can add a sense of dynamic range and is
mostly useful for subtle fine arts formats like classical and jazz.
This control reduces the available range of AGC gain reduction because it acts by at-
tenuating the gain control signal produced by the AGC sidechain. The range is 25 dB
at :1 and 12 dB at 2:1. However, the range of input levels that the AGC can handle
is unaffected, remaining at 25dB.
AGC Bass Threshold
determines the compression threshold of the bass band in the
AGC. It can be used to set the target spectral balance of the AGC.
As the AGC
B CPL control is moved towards “100%,” the AGC BASS THRESHOLD con-
trol affects the sound less and less.
The interaction between the AGC
BASS THRESHOLD control and the AGC B CPL con-
trol is a bit complex, so we recommend leaving the AGC
BASS THRESHOLD control at
its factory setting unless you have a good reason for readjusting it.
AGC Idle Gain
. The “idle gain” is the target gain of the AGC when the silence gate
is active. Whenever the silence gate turns on, the gain of the AGC slowly moves to-
wards the idle gain.
The idle gain is primarily determined by the AGC
DRIVE setting — a setting of 10 dB
will ordinarily produce an idle gain of –10 dB (i.e., 10 dB of gain reduction). How-
ever, sometimes you may not want the idle gain to be the same as the AGC
DRIVE
setting. The AGC I
DLE GAIN control allows you to add or subtract gain from the idle
gain setting determined by the AGC
DRIVE setting.
You might want to do this if you make a custom preset that otherwise causes the
gain to increase or decrease unnaturally when the AGC is gated.
For example, to make the idle gain track the setting of the AGC
DRIVE control, set
the AGC I
DLE GAIN control to zero. To make the idle gain 2 dB lower than the setting
of the AGC
DRIVE control, set the AGC IDLE GAIN control to –2.
AGC Bass Attack
sets the attack time of the AGC bass compressor (below 200Hz).
AGC Master Attack
sets the attack time of the AGC master compressor (above
200Hz).
AGC Bass Release
sets the release time of the AGC bass compressor.
AGC Master Delta Threshold
allows you to set the difference between the com-
pression thresholds of the sum and difference channels. (This control is only useful
when you set the AGC
MATRI X to SUM/DIFFERENCE.) If you set the threshold of the dif-
ference channel lower than the sum channel, the AGC will automatically produce
more gain reduction in the difference channel. This will reduce the separation of
material with an excessively wide stereo image (like old Beatles records). To make
this work, you must set the AGC M
AXIMUM DELTA GAIN REDUCTION control away from
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