Operating instructions

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OPERATION ORBAN MODEL 9400
AGC DRIVE
control adjusts signal level going into the slow dual-band AGC, deter-
mining the amount of gain reduction in the AGC. This also adjusts the “idle gain” —
the amount of gain reduction in the AGC section when the structure is gated. (It
gates whenever the input level to the structure is below the threshold of gating.)
The total amount of gain reduction in a given 9400 processing chain is the sum of
the gain reduction in the AGC and the gain reduction in the multiband compressor
in that chain (AM analog or HD). The total system gain reduction determines how
much the loudness of quiet passages will be increased (and, therefore, how consis-
tent overall loudness will be). It is determined by the setting of the AGC
DRIVE con-
trol, by the level at which the console VU meter or PPM is peaked, and by the setting
of the M
ULTIBAND DRIVE (compressor) control for each chain.
AGC REL
(“AGC Master Release”) control provides an adjustable range from 0.5
dB/second (slow) to 20 dB/second (fast). The increase in density caused by setting the
AGC
RELEASE control to fast settings sounds different from the increase in density
caused by setting the a given chain’s M
ULTIBAND RELEASE control to FAST, and you can
trade the two off to produce different effects.
Unless it is purposely speeded-up (with the AGC
RELEASE control), the automatic
gain control (AGC) that occurs in the AGC prior to the multiband compressor makes
audio levels more consistent without significantly altering texture. Then the multi-
band compression audibly changes the density of the sound and dynamically re-
equalizes it as necessary (booming bass is tightened; weak, thin bass is brought up;
highs are always present and consistent in level).
The various combinations of AGC and compression offer great flexibility:
 Light AGC + light compression yields a wide sense of dynamics, with a small
amount of automatic re-equalization.
 Moderate AGC + light compression produces an open, natural quality with
automatic re-equalization and increased consistency of frequency balance.
 Moderate AGC + moderate compression gives a more dense sound, particularly
as the release time of the multiband compressor is sped up.
 Moderate AGC + heavy compression (particularly with a FAST multiband release
time) results in a “wall of sound” effect, which may cause listener fatigue.
 Adjust the AGC (with the AGC
DRIVE control) to produce the desired amount of
AGC action, and then fine-tune the compression and clipping with the 9400
processing’s controls.
AGC GATE
(“AGC Gate Threshold”) control determines the lowest input level that
will be recognized as program by the AGC; lower levels are considered to be noise or
background sounds and cause the AGC to gate, effectively freezing gain to prevent
noise breathing.