Orban OPTIMOD 6300, Руководство по эксплуатации

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INTRODUCTION ORBAN MODEL 6300
function that can radically change the frequency balance of the program (some-
times by more than 10 dB). This can cause noise that would otherwise have been
masked to become unmasked because the psychoacoustic masking conditions under
which the masking thresholds were originally computed have changed. Accordingly,
if you use lossy data reduction in the studio, you should use the highest data rate
possible. This maximizes the headroom between the added noise and the threshold
where it will be heard. In addition, you should minimize the number of encode and
decode cycles because each cycle moves the added noise closer to the threshold
where the added noise is heard.
Interfacing to the Transmitter
Sync Input
In the Eureka-147 system, several programs are combined into one “ensemble mul-
tiplex.” This requires synchronization of the sample rates applied to the transmitter.
DTV and HD Radio also require synchronization.
The 6300 provides a BNC connector that accepts “house sync” in AES11id (75

un-
balanced) or wordclock (square wave at the sample frequency) format. A setup
menu selection determines whether the 6300’s output will be synchronized to word-
clock, AES11, the 6300’s internal clock, or the signal applied to its AES3 audio input.
Because the 6300’s digital input is equipped with a sample rate converter, an asyn-
chronous digital input can be applied to the 6300 while its output is synchronized to
a master sync generator.
AES User Bits
In Setup , you can configure the 6300 to either block or pass AES User Bits from its
digital input to its digital output.
Sample Rate and Audio Bandwidth
Most DAB audio is at 48 kHz sample rate. However, the iBiquity™ HD-AM™ system
operates at 32 kHz, requiring 15 kHz audio bandwidth. The Eureka-147 system of-
fers a 24 kHz sample rate option, requiring 10 kHz audio bandwidth. The Digital Ra-
dio Mondiale (DRM) system also allows reduced audio bandwidths and sample rate
for speech-grade services.
OPTIMOD 6300’s bandwidth can be adjusted from 10 kHz to 20 kHz to provide cor-
rectly anti-aliased audio for any of these systems. As long as any anti-aliasing filters
following OPTIMOD 6300’s output are phase-linear and have integer sample time
delays, these filters will pass the band-limited OPTIMOD 6300 output without intro-
ducing overshoot because they remove no further spectrum and do not cause their
output samples to become asynchronous with the peak-controlled samples at
OPTIMOD 6300’s output.
The bandwidth-limiting filter is located before the processing, so it affects all out-
puts equally.
OPTIMOD 6300 always operates at 48 kHz sample rate internally. Its output is
equipped with a sample rate converter that can output at 32 kHz, 44.1 kHz, 48, 88.2,