Omnia Audio Omnia A/XE - Manual (Page 53)

level. There is a 30dB range of adjustment between –20dB and +10dB.
Using normal program audio, a correct gain setting results in peak indications (the
“bouncing balls”) hitting -12 dBFS (where the level meters turn red) or a little higher. This
corresponds to system headroom of 12 dB. You may adjust for more headroom if you wish
(lower indications), but setting the input level for less headroom (higher meter indications)
is strongly discouraged.
WB-AGC (WideBand AGC)
A very flexible wideband leveler section provides smooth, transparent control of the input
program. This is achieved through two significant Omnia innovations, a dual referenced
release gate and a hidden, intelligent “makeup” gain algorithm. The dual gate reference is a
unique process that correlates the dynamics of the audio input signal to a “rolling” reference
level, and from that information makes conditional decisions affecting the character of the
release function.
A hidden, Make-Up Gain, control signal determines when the amplitude of the input
program suddenly falls to a reduced level. It then adjusts the side chain gain in order to “fill
in” the softer program passages so that the average level is increased. This allows the AGC
function to operate with slower time constants, while significantly increasing the average
audio level. These slower overall time constants yield lower intermodulation distortion,
contributing to Omnia’s trademark sound.
Using Classical music for an example, the orchestra often plays forte, and then enters
abruptly into a quiet passage. Conventional AGC algorithms would hold the softer passage
down until it was able to slowly recover at the static release time setting, making such
passages nearly inaudible at normal listening levels. Omnia A/XE’s makeup gain function
allows a hidden, faster time constant to provide quick recovery, but only during the softer
passage. As soon as the orchestra starts to play louder, the “makeup” time constant yields
control back to the primary AGC circuit, returning gain to the previous platform level. This
sophistication preserves the dynamic integrity of the signal while greatly enhancing the
listenability of the program.
This is the first processing section within the Omnia A/XE, so the controls in this section
affect the overall signal, its density, and hence affect every other processing section following
it. The job of the Wideband AGC is to erase long-term audio level fluctuations, while doing
so in a very unobtrusive manner. This sub-menu provides a few parameters that tailor the
action of this section.
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