Flexible Configuration - Orban Optimod-FM 8300 Operating Manual

OPTIMOD-FM DIGITAL

Flexible Configuration


The 8300 includes analog and AES3 digital inputs and outputs. Both digital in-
put and digital output are equipped with sample-rate converters and can oper-
ate at 32 kHz, 44.1 kHz, 48, 88.2, and 96 kHz sample rates. The pre-emphasis
status and output levels are separately adjustable for the analog and digital out-
puts.

The 8300 has an internal, DSP-based stereo encoder (with a patented "half-
cosine interpolation" composite limiter operating at 512 kHz sample rate)
to generate the pilot tone stereo baseband signal and control its peak level. The
composite limiter is a unique, "you can only do this in DSP" process that beats
composite clippers by preserving stereo imaging while fully protecting the
stereo pilot tone, RDS / RBDS, and subcarriers.

The 8300's digital output can be switched to emit processed audio suitable for
HD Radio, digital radio, and netcasts. Meanwhile, the analog output and
composite output continue to emit audio processed for the analog FM channel.
To do this, the output of the multiband compressor (5-band or 2-band) splits into
two paths. The FM path feeds an advanced, distortion-canceling clipper and
overshoot compensator, while the HD path is de-emphasized and then feeds a
look-ahead limiter.
Note that the "UL" [ultra-low-latency] presets do not offer HD process-
ing. If a UL preset is put on-air, the HD output will emit a de-emphasized,
FM-processed signal.

The analog inputs are transformerless, balanced 10k instrumentation-
amplifier circuits, and the analog outputs are transformerless balanced, and
floating (with 50 impedance) to ensure highest transparency and accurate
pulse response.

The 8300 has two independent composite baseband outputs with digitally
programmable output levels. Robust line drivers enable them to drive 100 feet
of RG-59 coaxial cable without audible performance degradation.

The 8300 has two subcarrier inputs that are mixed with the output of
OPTIMOD-FM's stereo encoder before application to the composite output con-
nectors. One input can be re-jumpered to provide a 19 kHz pilot reference out-
put. The other input has an internal level trim to accommodate subcarrier gen-
erators with output levels as low as 220 mV.

The 8300 precisely controls the audio bandwidth to 15 kHz. This prevents
overshoots in uncompressed digital links operating at a 32 kHz-sample rate and
prevents interference to the pilot tone and RDS (or RBDS) subcarrier.

The 8300 has a defeatable multiplex power limiter that controls the multiplex
power to ITU-R BS412 standards. An adjustable threshold allows a station to
achieve maximum legal multiplex power even if the downstream transmission
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INTRODUCTION