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3-2
OPERATION
The OPTIMOD-PC Control Application
•
AGC meter shows the gain reduction of the slow AGC processing that precedes
the multiband compressor. Full-scale is 24dB gain reduction.
Because the AGC is a two-band unit with Orban's patented bass coupling
system, this meter actually reads the gain reduction of the AGC Master
band.
•
Gate indicators show gate activity. They light when the input audio falls below
the threshold set by the gate threshold controls. (There are two gating circuits—
one for the AGC and one for the multiband compressor/limiter—each with its
own gate threshold control.) When gating occurs, the AGC and compressor's re-
covery times slow drastically to prevent noise rush-up during low-level passages.
•
Multiband gain reduction meters show the gain reduction in the multiband
compressor. Full-scale is 25 dB gain reduction. Because of the 1101's dual-mono
architecture, each meter is split vertically to show the gain reduction in the left
and right channels.
•
Input Meters show the input level applied to the audio processing following
the Processor mixer. Normal levels are around –20dB. This is because the Proces-
sor Mixer has sufficient headroom to drive the AGC into full 25 dB of gain reduc-
tion without clipping.
•
Output Meters show the output levels of the processed signal before it is ap-
plied to the output routing switcher in the I/O Mixer.
•
Limiter meters show the amount of low-IM look-ahead peak limiting in the left
and right channels, which we chose not to couple because the fast release time
of this circuit would otherwise cause elements in one channel to modulate the
opposite channel objectionably. Full-scale is 12 dB gain reduction.
•
Loudness Level meter shows the subjective loudness of the output, measured
using the 1981 Jones & Torick CBS Technology Center algorithm. (See page 1-8
for a discussion of this algorithm.)
There is only one meter regardless of the number of channels and loud-
speakers in the listening room because a given listener has only one per-
ception of loudness. When the processing is operated in dual-mono
mode, there is one L
The meter is calibrated with reference to the Dolby Digital® Dialnorm
value that you specify in the 1101's active Setup for that processing chain.
(See step 6 on page 2-26.) If you adjust the processing so that the Loud-
ness Level meter peaks at 0 dB on dialog and you set up your Dolby Digi-
tal encoder so that that you are transmitting this same Dialnorm value to
consumer receivers, your transmission will have the correct loudness
compared to other correctly set up transmission channels.
L
meter for each mono channel.
OUDNESS
EVEL
ORBAN MODEL 1101
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