Orban OPTIMOD-FM 8500S Operating Manual page 90

2-34
INSTALLATION
c) Connect the ratings encoder's AES3 output to your Optimod's S
When DO2 O
UT
posed automatically to drive the input of your Optimod's stereo encoder.
d) Set the DO2 output S
e) Set the DO2 output W
• In Ratings Encoder Loop-through mode, you cannot use your Optimod's
S I to receive a sync reference signal. You can still lock your Opti-
YNC NPUT
mod's output sample rate to a signal applied to its AES3 input.
• The Ratings Encoder Loop-through mode has a standard fallback strategy:
To prevent an audio mute, your Optimod will automatically bypass the ste-
reo encoder loop-though and will drive its stereo encoder from the output
of its FM audio processing if there is no valid AES3 signal at your Optimod's
Sync Input. When this occurs, ratings encoding is not occurring, so warn-
ings will flash on both the Optimod's front panel and in PC Remote (if pre-
viously connected to your Optimod). Nevertheless, we recommend moni-
toring the presence of valid ratings encoding via the monitor supplied by
the ratings provider.
L) If you selected FM or FM+D
modulation analyzer to adjust the DO 100% control to make the modulation
monitor read 100% modulation (usually ±75 kHz deviation).
See the notes in step (10.D) on page 2-31.
M) If you selected HD in step (I), set the DO 100% control to the maximum peak
output, in units of dBFS, that the following transmission system can accom-
modate.
Once you have set the DO 100% control, you may use the HD L
the active processing preset to set the final loudness. This is the correct
method for matching the loudness of the analog and HD1 channels in HD Ra-
dio transmission.
If the BS.1770 Safety Limiter is active, the DO 100% control does not affect
loudness, only peak headroom. Refer to the explanation in step (12.A) on
page 2-35.
In a transmission system using a lossy codec, it is usually wise to leave 1 to
2 dB of headroom to accommodate codec overshoots.
If the transmission system uses linear PCM, we recommend setting the DO
100% control to –0.2 dBFS. Because the peak limiter is a "true peak" lim-
iter whose sidechain is oversampled to 256 kHz, setting the DO 100%
control to –0.2 dBFS or lower will prevent overshoots following the
transmission system's final D/A converter if the D/A converter is phase-
linear (i.e. introduces no group delay distortion). This setting will also
prevent overshoots caused by phase-linear sample rate conversion unless
the sample rate converter removes a significant amount of spectral en-
ergy, which is typically true when the output sample rate is 32 kHz. To
control is set to R
S
OURCE
R to 48 kHz.
AMP ATE
to 24-bit.
L
ORD ENGTH
in step (I) above, use a modulation monitor or
ELAY
,
he S input is repur-
T
ATINGS YNC
D
IM
ORBAN MODEL
I .
YNC NPUT
control in
R