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OPERATION ORBAN MODEL 8685
compression and associated multiband clipper audibly change the density of the
sound and dynamically re-equalize 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 look-ahead limiting, and loudness
control.
AGC Gate Threshold
control determines the lowest input level that will be recog-
nized as program by the 8685; lower levels are considered to be noise or back-
ground sounds and cause the AGC or multiband compressor to gate, effectively
freezing gain to prevent noise breathing.
In sound for picture, the settings of the gate threshold controls are quite critical if
you want the processing to be undetectable to the audience. If these controls are
set too low, then the 8685 will pump up quiet sounds like ambience and underscor-
AGC Controls
Intermediate Names Advanced Name Range
AGC On/Off AGC Off/On Off/On
Bass Coupling AGC Bass Coupling Off, 12…0 dB
Drive AGC Drive –10 ... 25 dB
Gate Thresh AGC Gate Threshold Off, –44 ... –5 dB
AGC Release AGC Master Release 0.5, 1.0, 1.5, 2 … 20 dB/S
--- AGC Crossover Allpass, LinearNoDelay, Linear
--- AGC Master Attack 0.2 … 6
--- AGC Bass Attack 1 … 10, Off
--- AGC Bass Release 1 … 10 dB/sec
--- AGC Bass Threshold –12.0 … 12.0 dB
--- AGC Idle Gain –10 … +10 dB
--- AGC Ratio
∞:1, 4:1, 3:1, 2:1
--- AGC Window Release 0.5 … 20 dB
--- AGC Window Size –25 … 0 dB
--- AGC Matrix (2.0 only) L/R, sum/diff
--- Master Delta Threshold (2.0 only) –6.0 … +6.0 dB
--- Bass Delta Threshold (2.0 only) –6/0 … +6.0 dB
--- Maximum Delta GR (2.0 only) 0.0 … 24.0, Off dB
Table 3-5: AGC Controls
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