Orban OPTIMOD 6300 Operating Manual page 153

OPTIMOD 6300 DIGITAL
Unlike some familiar compressors and limiters (whose gain reduction is adjusted
via threshold controls), the 6300 limiter's threshold is fixed with respect to the
input of the 6300's digital output level control so the limiter's drive level solely
determines the gain reduction. Two cascaded gain controls set this drive level.
One is MB L
IMIT
6300's active D
6300's D
IALNORM
the control is set to 0 dB so it does not affect the look-ahead limiter drive.
In the transmitted Dolby Digital bitstream, setting D
value automatically turns down the home receiver's volume control, so the
6300's output level must be turned up by the same amount to maintain a con-
stant loudness at the receiver. Because it is placed before the 6300's look-ahead
limiter, the 6300's hidden D
6300's look-ahead limiter to prevent digital clipping in the downstream transmis-
sion chain regardless of the 6300's D
user to set the correct loudness at the 6300's output solely by adjusting the
6300's active D
within a preset, so all TV presets automatically adapt to the 6300's current
D
IALNORM value.
Only the "TV" presets are set up to produce correct loudness at the con-
sumer's receiver automatically. However, you can readily adjust other
presets to produce correct loudness in Dolby Digital transmissions by ad-
justing a preset's MB D
meter peak at 0 dB on speech. Then save the result as a User Preset. The
reason that this works is that the 6300's D
automatically scales the sensitivity of the 6300's L
when the D
When the R
sensitivity of the loudness level meter via the L
control. This is useful for keeping the loudness level meter on-scale when
using radio-style presets, which are generally louder than the "TV" pre-
sets. This allows you to compare the loudness of radio-style presets.
Loudness Control: Useful in sound-for-picture applications, the 6300's third-
generation CBS Loudness Controller follows the multiband compressor in the 6300's
signal flow diagram. However, it takes into account the effect of the following look-
ahead limiter so that it effectively monitors the loudness at the limiter's output, not
the loudness at the multiband compressor's output. It does so by scaling its sidechain
drive by two gain factors: (1) the MB L
D
IALNORM value, which is determined either globally or by the active preset depend-
ing on the active preset's D
The Loudness Controller constrains the loudness of most commercials well enough
to eliminate viewer annoyance. It works by constantly monitoring the subjective
loudness of the 6300's output. The subjective loudness is a single value that repre-
sents the listener's impression of the loudness in the listening room. It takes into ac-
count the contribution of both stereo channels.
When subjective loudness would otherwise exceed the threshold set by the
T
L
OUDNESS HRESHOLD
above 200 Hz, preventing loudness from exceeding the threshold. To prevent the
D
; the second is a "hidden" control whose gain is set by the
RIVE
value. This second gain control is only active when the
IALNORM
R O
EFERENCE UTPUT
IALNORM gain control achieves this while allowing the
IALNORM
value—it is unnecessary to adjust any other controls
IALNORM
control to make the 6300's L
RIVE
R S
IALNORM EFERENCE
S selector is O
EFERENCE OURCE
setting. (See step 12.B)a) on page 2-30.)
IALNORM
control, the Loudness Controller reduces the gain of material
(R O ) control is not set O
EF UT
IALNORM
setting. This arrangement allows the
R
IALNORM
OUDNESS
selector is not O
OURCE
FF , you can manually scale the
OUDNESS
D
control and (2) the 6300's active
IMIT RIVE
OPERATION
FF ; otherwise
to a less negative
L
OUDNESS EVEL
control
EFERENCE
L
meter
EVEL
.
FF
M S
ETER ENSITIVITY
3-11