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3-20
OPERATION
Radio-Style Presets
look-ahead limiter always constrains the peak level to 0 dBfs at the digital outputs
and to +24 dBu at the analog output, which prevents any output from clipping. To
produce a lower peak level at a given output, turn down the corresponding output
level control in the I/O Mixer. Another use for the output level controls is to produce
unity below-threshold gain between the active input and output, which is some-
times desired in protection limiting applications.
The analog output can produce +24 dBu into a balanced load without
clipping. If you are driving an unbalanced load (by grounding one side of
the output), the gain does not change. However, the clipping level de-
clines to slightly above +18 dBu, so you must turn down the analog out-
put level control to –6.0 dB or lower to avoid clipping.
PROTECT-0DB: This preset is an alias for C
The presets (Table 3-2 on page 3-21) have been named similarly to their radio coun-
terparts in Orban's OPTIMOD-FM 8400 and 8500. The basic audio texture of corre-
sponding OPTIMOD-PC and 8500 presets (heard through the 8500's digital radio
output) is similar, although the 1101 will tend to have 1-2 dB more bass. In addition,
all 1101 presets have the stereo enhancer turned off to reduce potential codec ste-
reo encoding artifacts.
If you wish to reduce the bass, set the Band 1 and/or Band 2 compression
thresholds lower to taste. Then save your work as a User Preset.
The texture of the corresponding OPTIMOD-PC and 8382 presets is quite similar, al-
though the OPTIMOD-PC presets will usually have a less restricted high frequency
sound because OPTIMOD-PC performs no high frequency limiting other than that
created by gain reduction in Band 5 in the Five-band presets.
Unlike the presets in Orban's FM processors, no OPTIMOD-PC preset uses
phase rotation. Therefore, if you use OPTIMOD-PC to process the main
digital channel in HD Radio, some care must be applied in cross fading to
avoid momentary audible comb filtering because of the different phase
responses of the analog and digital channels. In practice, this means that
the cross-fade should be quite fast—perhaps 50 milliseconds.
Broadcasters using Orban's Optimod-FM 8300, 8400, or 8500 will ordinar-
ily use these processors' HD FM digital outputs to feed the digital channel
in an IBOC transmission. This eliminates any potential comb filtering be-
cause both analog and digital outputs have identical amounts of phase
rotation.
Of course, if OPTIMOD-PC is used to process a secondary channel in HD
Radio, there is no need to worry about smoothness of crossfades. This is
an excellent application for this product.
2
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LASSICAL
BAND
ORBAN MODEL 1101
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