More and more FM stations are transporting their audio
digitally, from studio to
Transmitter. However, digital
links typically handle left/right rather than composite.
Orban’s
8218 Digital FM Stereo Encoder can extend your
all-digital performance through to the stereo encoder. It’s
designed to perfectly complement Orban’s OPTIMOD-FM digital
audio processors in an all-digital transmission system.
All encoding is done entirely in the digital domain by a
dedicated DSP chip, producing two analog composite outputs
with outstanding specifications and long-term stability. The
8218 accepts either analog or AES/EBU digital inputs. The
digital input automatically synchronizes to and de-jitters
any standard incoming sampling rate. In addition, it
responds to status bits in the AES/EBU data stream that may
be used to turn de-emphasis on or off. This feature allows
automatic switching of pre-emphasis and/or J.17 (NICAM)
de-emphasis to accommodate different transmission schemes.
An Overshoot Control Limiter can be applied to the incoming
audio, limiting overshoots to less than 0.5dB while
introducing minimal (or no) audible artifacts and without
contaminating the baseband spectrum above 57kHz. The
Overshoot Control Limiter is particularly useful if the
processed audio has been passed to the
8218 through a
digital STL that uses lossy encoding, like MPEG,
Dolby, or
APT-X. The Overshoot Control Limiter uses lookahead
techniques, and, when activated, adds a time delay of 4
milliseconds to the stereo encoding process.
Features
• >70dB separation, 20Hz- 15kHz.
• <-90dB noise and distortion (after de-emphasis, and
referenced to 100% modulation output).
• Digitally-created composite signal, from either analog or
AES/EBU digital input. The
8218 also accepts two analog SCA
inputs, and sums them with analog composite output. The
analog composite appears on two outputs, each with
individual level control.
• Built-in sample rate
Converter that allows
8218 to accept
any digital AES/EBU input sample rate between 32kHz and 48kHz.
• Recessed front panel controls for selecting Input type
(Analog/Digital), Stereo/MonoL/MonoR mode, Pilot On/Off, and
Crosstalk Tests.
• Front panel metering of Left and Right inputs plus
Composite or Pilot outputs.
• Recessed front panel multi-tum screwdriver potentiometers
for Analog Left, Analog Right, and Digital input levels, as
well as for Pilot, Composite #1, and Composite #2 output levels.
• Recessed rear panel DIP switch for selecting pre-emphasis
In/Out, pre-emphasis type (50fxs/75|j.s), J.17 de-emphasis
In/Out, and whether or not the stereo encoder’s pre-emphasis
and J.17 de-emphasis settings respond to status bits of the
AES/EBU digital input, Overshoot Control Limiter in/out, and
AES/EBU input range.
• Remote (contact closure) interface using opto-isolation
has pins to select between analog or digital input, turn
pre-emphasis on or off, and to select among stereo, mono
from left, or mono from right operational modes. Also on the
remote connector is a digital pilot reference output clock
for external subcarrier generators like RDS. This is a TTL
level signal with 0 to +5V transition occurring at the pilot
zero crossing.
• Overshoot Control Limiter limits overshoot to less than
0.5dB with minimum artifacts.
• AES/EBU error alarm function provides an alarm that
indicates if a faulty AES/EBU signal is being received at
the 8218’s digital input.
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