Adjusting Multiband Agc's - Omnia 6EX Installation And Operation Manual

The drive level to each AGC band can be set by the controls at the top of the window. There is +/-6 dB of gain
adjustment available for each band. Just as in properly setting a program equalizer, the best sound, consistent with
preserving signal headroom is usually obtained by reducing the gain of the louder band(s) rather than increasing the
gain of the lower level band(s).
For example: if the program source material has widely varying high frequency levels, a common action is to just
turn up the output mixer controls. However, consistency can be improved much more effectively by adding a bit
more drive level to the upper AGC bands, and then reducing their output levels slightly in the post AGC Mixer. This
type of adjustment strategy will result in better long-term high frequency consistency, and a more pleasing air sound.
Multiband AGC Windows
Each of the multiband AGC's has its own set of controls similar to those in the Wideband AGC section. The four
controls in these windows, Attack, Release, Make-Up Gain and Gate Threshold, and the two parameter selections,
RTP Speed and RTP Level, function like those in the Wideband AGC window. Adjustment strategies are similar,
however in the mutiband AGC sections adjustments are on a "per-frequency band" basis.
Low Band AGC shown as example – other bands are identical
As with any multiband processor, improper adjustment can exaggerate noise at high frequencies, particularly with
older recordings that possess a good deal of tape hiss. This can especially occur if the higher AGC bands are driven
so that significant gain reduction occurs, and the band's gating control is set to the lower end of the scale. During
audio segments that have little or no HF content, the AGC will try to increase its gain in an effort to restore treble
balance. Even during periods when the gate function is in the default Freeze mode, the problem might still exist
with some programming. In those situations, even an increase of the gate threshold control to higher numbers may
not help the situation.
Therefore, each band of the multiband AGC incorporates a Return To Platform (RTP) feature similar to that
available within the Wideband AGC process block. When the RTP function is set to a value other than Freeze, the
band gain will be forced to recover its gain to a static value lower (less gain = more gain reduction) than might be
achieved if the control was set to Freeze. This will reduce hiss and other high frequency noise. The RTP levels can
be tailored for each individual AGC band as desired.
Omnia-6ex Use and Operation Manual – V: 1.10
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