OPTIMOD-FM DIGITAL
OPERATION
3-79
FM
Æ
HD
mode. When the
FM
Æ
HD
mode is
I
NDEPENDENT
, a button on the toolbar
toggles between corresponding FM and HD tabs (for example, between
C
OMPRESSORS
and
HD
C
OMPRESSORS
).
HD EQ Gain
determines the depth of high frequency shelving equalization pro-
duced by the parametric HF shelving equalizer, which will be placed either before or
after the digital-channel look-ahead limiter (depending on the setting of the
HD
HF
S
HELF
EQ
control in the
I
NPUT
/
O
UTPUT
HD
D
IGITAL
R
ADIO
screen).
When placed before the look-ahead limiter, this equalizer is sometimes
useful for reducing the audible disparity between the FM and digital-
channel outputs (although the
HD
B
AND
M
IX
controls are probably more
appropriate for this task). The digital-channel output receives no high
frequency limiting or clipping and may therefore be as much as 6 dB
brighter than the FM output. If you wish to reduce this difference to
smooth out the audible difference between the two channels during a
receiver crossfade, you can apply HF rolloff to the digital-channel channel
by ear. Another reason you might want to do this is if the digital-channel
channel sounds excessively bright after you have optimized the 8600Si’s
tuning for FM. Of course, you can also use the
HD
MB
B
AND
M
IX
controls
for this purpose, or use these controls in conjunction with the HF shelving
equalizer.
Yet another reason to use HF rolloff in the digital-channel channel is to
reduce codec artifacts at the high frequencies—the familiar “watery”
sound.
When placed after the look-ahead limiter, the shelving EQ can reduce
the effects of codec overshoot.
The parametric HF shelving equalizer can only produce HF rolloff. It can-
not boost.
HD EQ Freq
sets the corner frequency of the parametric HF shelving equalizer.
HD Limiter Dr
sets the drive level to the digital-channel look-ahead limiter.
•
When the digital radio BS.1770 Safety Limiter is active, you must use the
HD
L
IMITER
D
R
control to set the amount of gain reduction that the BS.1770 Safety
Limiter produces. See step 12 on page 2-35.
The factory default is
+4
. When the BS.1770 Safety Limiter is active, the
HD
L
IMITER
D
R
control will usually need to be set substantially below 0 dB unless
the preset is quiet (like one of the
C
LASSICAL
presets).
•
When setting up an HD Radio facility, set the
O
UT
L
EVEL
control to 0 dBFS. Then
adjust the
HD
L
IMITER
D
RIVE
in the on-air preset to match the loudness of the HD
channel to the loudness of the FM channel at the receiver.
In an HD Radio receiver, the HD channel has 5 dB higher gain than the ana-
log FM channel. Because the digital channel’s loudness must match the FM
channel during receiver crossfades, there is no need to over-process the HD
channel; you can take advantage of the 5 dB of “bonus loudness” in this
channel to do 5 dB less peak limiting compared to the FM channel.
Do not
Summary of Contents for OPTIMOD-FM 8600Si
Page 1: ...Operating Manual OPTIMOD FM 8600Si Digital Audio Processor Version 2 5 Software...
Page 7: ...Operating Manual OPTIMOD FM 8600Si Digital Audio Processor Version 2 5 Software...
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Page 255: ...OPTIMOD FM DIGITAL OPERATION 3 89...
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Page 330: ...6 28 TECHNICAL DATA ORBAN MODEL 8600Si CONTROL BOARD PARTS LOCATOR...
Page 354: ...6 52 TECHNICAL DATA ORBAN MODEL 8600Si...