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3-61
OPTIMOD-PC
OPERATION
Band 5 is particularly critical for noise reduction because much of the Downward
Expander's utility lies in hiss reduction. Hiss has most of its energy in band 5, while
program material typically has less energy in this band, so the B5 D
E
OWN
XPANDER
control's setting is critical to removing hiss while minimizing removal of desired pro-
gram energy.
Band 5 is uncoupled from the lower bands so the band 5 downward expander can
produce less gain reduction than other bands. This can help prevent loss of desired
high frequency material in the program.
B3>B4 CPL ("Band 3>4 Coupling") control determines the extent to which the gains
of band 4 (centered at 3.7 kHz) and 5 (above 6.2 kHz) are determined by and follow
the gain of band 3 (centered at 1 kHz). Set towards 100% (fully coupled) this control
reduces the amount of dynamic upper midrange boost, preventing unnatural upper
midrange boost. The gain of band 5 is further affected by the B4>B5 CPL control.
Excessive HF energy is one cause of audibly objectionable artifacts in low bitrate co-
decs. The B3>B4 C
B4>B5 C
controls can be very useful in reducing such arti-
PL AND
PL
facts: Setting them for large amounts of coupling will minimize OPTIMOD-PC's abil-
ity to increase high frequency energy dynamically.
B4>B5 CPL ("Band 4>5 Coupling") controls the extent to which the gain of band 5
(6.2 kHz and above) is determined by and follows the gain of band 4.
The sum of the high frequency limiter control signal and the output of the B4>B5
CPL control determines the gain reduction in band 5. The B4>B5 CPL control re-
ceives the independent left and right band 4 gain control signal. Range is 0 to 100%
coupling.
B3>B2 CPL and B2>B3 CPL controls determine the extent to which the gains of
bands 2 and 3 track each other.
When combined with the other coupling controls, these controls can adjust the five-
band processing to be anything from fully independent operation to quasi-
wideband processing.
B2>B1 CPL control determines the extent to which the gain of band 1 (below 100Hz
or 200Hz, depending on crossover setting) is determined by and follows the gain of
band 2 (centered at 400Hz). Set towards 100% (fully coupled), it reduces the amount
of dynamic bass boost, preventing unnatural bass boost. Set towards 0% (independ-
ent), it permits frequencies below 100Hz (the "slam" region) to have maximum im-
pact in modern rock, urban, dance, rap, and other music where bass punch is crucial.
Accordingly, it can be useful in music video oriented formats.
Bx Out ("Band x Output Mix") controls determine the relative balance of the bands
in the five-band compressor. Because these controls mix after the band compressors,
they do not affect the compressors' gain reductions and can be used as a graphic
equalizer to fine-tune the spectral balance of the program material over a ±6 dB
range.
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