Orban OPTIMOD-FM 8600Si, Operating Manual

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OPERATION ORBAN MODEL 8600Si
nel, you can then set the
FM Æ HD C
ONTROL
C
OUPLING
control to
I
NDEPENDENT
and
tweak the HD processing as you wish. This control is located in the
HD L
IMITING
page
of
A
DVANCED
C
ONTROL
. You can also toggle this control via two buttons on the but-
ton bar in 8600Si PC Remote. When
FM Æ HD C
ONTROL
C
OUPLING
is
I
NDEPENDENT
,
a
third button toggles PC Remote focus between corresponding FM and HD tabs. This
allows you to compare your FM and HD settings easily.
Setting the
FM Æ HD C
ONTROL
C
OUPLING
control to
I
NDEPENDENT
defeats the
L
ESS
-
M
ORE
control, so if you want to use
L
ESS
-M
ORE
, adjust it before you start to make
independent adjustments to the FM and HD chains.
If a given preset has certain HD and FM controls set differently, setting the
FM>HD
C
ONTROL
C
OUPLING
to
C
OUPLED
will immediately cause the HD controls to take the
same settings as their FM analog counterparts. If you again set FM>HD CONTROL
C
OUPLING
to
I
NDEPENDENT
, this will restore any edits you made to the HD controls be-
fore you set the
FM>HD C
ONTROL
C
OUPLING
back to
C
OUPLED
.
To control excessive brightness in the HD processing when operating the HD and FM
processing independently:
•
Use little or no high frequency boost in the HD equalization section.
•
Set Band 4>5 coupling to 100%.
•
Set the band 5 compression threshold to match the codec that the 8600Si’s HD
output is driving. Adjust the threshold until you find a good compromise be-
tween presence and high frequency codec artifacts. We find the range from
–6.0 to +6.0 dB to be useful.
•
Use a moderate Band 5 attack time. 25 ms works well.
•
If necessary, lower the Band 4 compression threshold.
An advanced-design look-ahead limiter controls the peak level of the HD output.
The look-ahead limiter (which receives the output of the HD multiband compres-
sor/limiter) is optimized to make the most of the limited bit-rate codec used in the
HD Radio system’s digital channel. By eschewing any clipping, the HD output pre-
vents the codec from wasting precious bits encoding clipping distortion products,
instead allowing the codec to use its entire bit budget to encode the desired pro-
gram material.
The 8600Si’s look-ahead limiter implements “true peak” control by oversampling the
HD peak limiter’s sidechain at 256 kHz. This allows the 8600Si to prevent clipping in
a playback device’s analog signal path by predicting and controlling the analog peak
level following the playback device’s reconstruction filter to an accuracy of better
than 0.4 dB. For typical program material, accuracy is 0.2 dB
Thanks to true peak control, sample rate conversion, unless it removes high fre-
quency program energy or introduces group delay distortion, cannot cause sample
peaks to increase more than 0.4 dB. For example, sample rate con-version from 48
kHz to 44.1 kHz is highly unlikely to cause sample peak clipping of the 44.1 kHz au-
dio data.