Orban OPTIMOD 8685, Руководство по эксплуатации

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OPTIMOD SURROUND PROCESSOR INSTALLATION
2-33
Turning down the 2.0
O
UTPUT
100%
control reduces the peak modula-
tion without significantly affecting the average modulation. Hence, using
this technique keeps the 8685’s
L
OUDNESS
L
EVEL
meter correctly calibrated
and provides correct on-air loudness.
G) Check loudness with respect to other stations in your market and correct your
average modulation if necessary.
Because there is no standard value for the average modulation in analog
TV transmission, the loudness of your analog transmission might be dif-
ferent from other stations in your market. If this is so, match the 8685’s
loudness to the other stations by adjusting the 2.0
D
IALNORM
control in
the on-air preset. In PC Remote, this control is located in the 2.0 L
ESS
-
M
ORE TAB
; on the 8685’s front panel, the control is located in A
DVANCED
M
ODIFY
> D
ISTORTION
. For example, changing
D
IALNORM
from –17 dB to
–15 dB makes the transmission 2 dB louder. Adjusting D
IALNORM
is the
only correct way to adjust on-air loudness after the system has been cali-
brated according to steps (E) and (F) above; this technique will retain cor-
rect calibration of the 8685’s loudness level meter and loudness control-
ler.
Note that increasing the loudness in this way will increase the likelihood
that the 8685’s look-ahead limiter will create audible “pumping” or
“gulping” artifacts on program material that is rich in high frequencies
because the look-ahead limiter is operating on a preemphasized signal
and because turning up
D
IALNORM
drives the look-ahead limiter harder. If
you hear such artifacts, we recommend that you use a 5-Band TVA preset
if you are not doing so already. This allows you to use the Band 5 com-
pressor/limiter as a high-frequency limiter. If you hear audible pumping
on material rich in high frequencies, turn down the
B5 T
HRESHOLD
control
until you find the most subjectively pleasing trade-off between high fre-
quency loss and look-ahead limiter pumping. You can also try speeding
up the
B5 A
TTACK
control by setting it to a lower number, or adjusting
the both controls to taste.
When you use a 2-Band “TVA” preset, some material rich in high fre-
quencies may cause subtle pumping even with
D
IALNORM
set to its nomi-
nal –17 dB value. This is because the 2-band compressor cannot produce
high frequency limiting, so preemphasis control must be performed by
the loudness controller and look-ahead limiter. We have tuned the 5-
Band factory “TVA” presets to produce appropriate amounts of high-
frequency limiting. We therefore recommend that if you need to use a
“TVA” preset, use a 5-Band preset unless you have a very good reason
not to do so.
12. Set the surround output configuration and level.
A)
L
OCATE
to
I
NPUT
/
OUTPUT
> S
URROUND
O
UTPUT
.
B) Follow the procedure in step 9 on page 2-27, replacing “2.0” by “surround.”
Note that the
S
URROUND
O
UTPUT
S
YNC
and 2.0 O
UTPUT
S
YNC
controls track each
other automatically; you cannot have separate sources for surround and 2.0
output sync.
C) Follow the procedure in step 10 on page 2-30, replacing “2.0” by “surround.”