Orban OPTIMOD 6300 Operating Manual page 169

OPTIMOD 6300 DIGITAL
Unlike the presets in Orban's FM processors, no 6300 preset uses phase
rotation. Therefore, if you use the 6300 to process the main digital chan-
nel in HD Radio, some care must be applied in cross fading to avoid mo-
mentary 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 the 6300 is used to process a secondary channel in HD Radio,
there is no need to worry about smoothness of crossfades. This is an ex-
cellent application for this product.
CLASSICAL: As their names imply, the CLASSICAL 5-BAND and CLASSICAL 2-BAND
presets are optimized for classical music, gracefully handling recordings with very
wide dynamic range and sudden shifts in dynamics. The 5-band version uses heavy
inter-band coupling to prevent large amounts of automatic re-equalization, which
could otherwise cause unnatural stridency and brightness in strings and horns and
which could pump up very low frequency rumble in live recording venues.
The 5-band preset defeats the AGC, using only the 5-band compressor for gain re-
duction. It also defeats phase rotation to ensure the most transparent 5-band sound
available.
CLASSICAL-5B+AGC uses the AGC set for 2:1 compression ratio. Because of the
AGC, it affects more of the total dynamic range of the recording than does the
CLASSICAL-5 BAND preset. However, the AGC provides extremely smooth and un-
obtrusive compression because of the gentle ratio and window gating. This preset
uses the 5-band compressor very lightly with a fast release time as a peak limiter.
The AGC does almost all of the compression.
There is also a corresponding 2-band preset called CLASSICAL-2B+AGC. Even more
transparent, "purist" classical processing is available from this preset, which is phase-
linear and which preserves the spectral balance of the original material as much as
possible. However, if you need a bit more automatic re-equalization than the
CLASSICAL 2-BAND preset provides, use the CLASSICAL 5-BAND preset.
CLASSICAL-2B SFTKN (Classical using 2-Band Soft-Knee Compression) defeats the
AGC and exploits the 6300's soft-knee 2-band compression. Quiet material is gently
compressed with a very low compression ratio. The compression ratio increases as
the source material gets louder (see Figure 3-2 on page 3-53). Very quiet material is
typically amplified by 10 dB. This level-dependent compression ratio provides very
smooth, subtle compression.
Because the CLASSICAL presets preserve a significant amount of the dynamic range
present in the source material (including speech), it is wise to use a separate micro-
phone processor to ensure appropriate voice/music balance.
COUNTRY: The COUNTRY-MEDIUM preset uses the ROCK-SMOOTH source preset. It
has a gentle bass lift and a mellow, easy-to-listen-to high end, along with enough
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OPERATION