Orban Optimod-PC 1101, Руководство по эксплуатации

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OPTIMOD-PC INSTALLATION
2-53
typical analog microwave STL may only be 70-75dB. In this case, it is wise to use
an Orban Studio Level Controller (like an Orban 6300 or another OPTIMOD-PC)
to perform the AGC function prior to the STL transmitter and to control the STL's
peak modulation. This will optimize the signal-to-noise ratio of the entire trans-
mission system. An uncompressed digital STL will perform much better than any
analog STL. Section 1 of this manual has a more detailed discussion.
Shrill, harsh sound; excessive sibilance
•
Excessively high settings of the HF G
AIN
control can cause this problem. It can also
be caused by excessively high settings of the
B5 T
HRESHOLD
(Band 5 Compression
Threshold) control. In the latter case, you are first likely to notice the problem as
harsh sibilance on voice.
Gain pumping when high frequency energy is present
•
This will occur with most OPTIMOD-PC factory presets when OPTIMOD-PC’s pre-
emphasis is set to 50
µ
s or 75
µ
s. [See step 5 on page 2-25.] The gain pumping
happens because the preemphasis creates a large high frequency boost before
the look-ahead limiter, so the look-ahead limiter must produce large amounts of
gain reduction to control peak levels.
To correct this problem, turn down the
F
INAL
L
IMIT
D
RIVE
control (page 3-48) until
the pumping is no longer audible (see Processing for Audio Codecs on page 3-6).
It may also be helpful to adjust band 5 so that it produces some high frequency
limiting. (The
AGC+75
US
LIMITER factory preset illustrates this technique; see
page 3-24.) Then save your work as a User Preset.
System receiving OPTIMOD-PC’s AES digital output will not lock
•
Be sure that OPTIMOD-PC’s output sample rate is set to match the sample rate
that the driven system expects.
•
Be sure that OPTIMOD-PC’s digital output format control is set to match the
standard expected by the driven system (either
AES3
or
S/PDIF
). (See step 4 on
page 2-23.)
System will not pass line-up tones at full output level/100% modulation
•
This is normal in
O
PERATE
mode. Sine waves have a very low peak-to-average ra-
tio by comparison to program material. The processing thus automatically re-
duces their peak level to bring their average level close to that of program mate-
rial, promoting a more consistent and well-balanced sound quality.
To pass line-up tones transparently, recall OPTIMOD-PC’s
P
ROTECT
preset. If nec-
essary, adjust its gain and save your edited preset as a User Preset.
These tones should be injected into the transmitter after OPTIMOD-PC or
OPTIMOD-PC should be temporarily switched to
P
ROTECT
to pass the tones.