Orban OPTIMOD-FM 8700, Operating Manual

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INSTALLATION ORBAN MODEL 8700i
AES3 Digital Input and Output
In a standard 8700i, there are two digital inputs and two digital outputs. One input
accepts program audio; the other accepts AES11 house sync, although sync is not re-
quired. Either output can be programmed to emit the signal intended for the ana-
log FM channel and/or the signal intended for the digital channel.
If you intend to use the BS.1770 Safety Limiter to drive a digital radio chain, we sug-
gest that you use Digital Output 1 to drive the digital radio transmitter. The BS.1770
safety limiter in the analog processing chain is calibrated with reference to 100%
modulation (see page 1-25) and is usable with the analog, digital, and composite
outputs.
The program input and output are both equipped with sample rate converters and
can operate at 32 kHz, 44.1 kHz, 48 kHz, 88.2 kHz, and 96 kHz.
Per the AES3 standard, each digital input or output line carries both the
left and right stereo channels. The connection is 110

balanced. The
AES3 standard specifies a maximum cable length of 100 meters. While
almost any balanced, shielded cable will work for relatively short runs (5
meters or less), longer runs require used of 110

balanced cable like
Belden 1800B, 1801B (plenum rated), multi-pair 180xF, 185xF, or 78xxA.
Single-pair category 5, 5e, and 6 Ethernet cable will also work well if you
do not require shielding. (In most cases, the tight balance of Category
5/5e/6 cable makes shielding unnecessary.)
The AES3id standard is best for very long cable runs (up to 1000 meters).
This specifies 75

unbalanced coaxial cable, terminated in BNC connect-
ors. A 110

/75

balun transformer is required to interface an AES3id
connection to your Optimod’s digital input or output.
The digital input clip level is fixed at 0 dB relative to the maximum digital word. The
maximum digital input will make the 8700i input meters display 0 dB. The reference
level is adjustable using the Digital
R
EFERENCE
L
EVEL
control.
The 8700i is a “multirate” system whose internal sample rate is 64 kHz and multiples
thereof (up to 512 kHz). The outputs processed for analog FM are band-limited to
16.5 kHz, with a stopband that begins at 18 kHz. Therefore, the output can be
passed through a 44.1 kHz (or higher) uncompressed link without adding significant
overshoot. Because sample rate conversion is ordinarily a phase-linear process that
does not add bandwidth, the 8700i’s output signal will continue to be compatible
with 44.1 kHz links even if it undergoes intermediate sample rate conversions (for
example, 44.1 kHz to 96 kHz to 44.1 kHz) at various points in the program chain.
The audio bandwidth of the AES output dedicated to the HD-processed signal is ad-
justable from 15 kHz to 20 kHz in 1 kHz steps.
Connecting a Ratings Encoder
This allows a ratings encoder having AES3 inputs and outputs to be driven from your
Optimod’s DIGITAL OUTPUT #2, while the rating encoder’s output drives your Opti-
mod’s SYNC INPUT. The ratings encoder can be embedded in one of two places: