Orban OPTIMOD-FM 8600, Operating Manual

Page: 229 / 397

OPTIMOD-FM DIGITAL OPERATION
3-49
Advanced 8500-Style Peak Limiter Controls
The following Peak limiter control is found only in the Advanced Modify screen.
OSComp Dr (Overshoot Compensation Drive) sets the drive into the overshoot
compensator with reference to the final clip threshold, in units of dB. The normal
setting is “0 dB.”
The overshoot compensator can produce audible distortion on material
with strong high frequency content (like bell trees) and this control lets
you trade off this distortion against loudness. (Such material can cause
strong overshoots, forcing the overshoot compensator to work hard to
eliminate them.) We do not recommend operating this control above “0”
because this would reduce the effectiveness of the distortion cancellation
used in earlier processing. However, you can reduce it below “0” if you
value the last bit of high frequency cleanliness over loudness.
The overshoot compensator works at 256 kHz sample rate and is fully an-
ti-aliased.
Hard Clip Shape (Hard Clip Shape) allows you to change the knee of the in-
put/output gain curve of the bass clipper when
B
ASS
C
LIP
M
ODE
is set to
HARD
. It al-
lows you to control the shape of the “knee”—the transition between no clipping
and flat-topping. “0” provides the hardest knee, where the transition between line-
ar operation and flat-topping occurs abruptly as the clipper’s input level is changed.
“10” is the softest knee, where the transition starts 6 dB below
B
ASS
C
LIP
T
HRESH
set-
ting and occurs gradually. The factory default setting is “7.6.” See Figure 3-3.
The
M
ED
and
S
OFT
bass clipper characteristics use sophisticated look-
ahead algorithms that produce lower distortion than
H
ARD
mode, regard-
less of where the
H
ARD
C
LIP
S
HAPE
control is set. However, operating in
H
ARD
mode with the
H
ARD
C
LIP
S
HAPE
control set beyond “0” may produce
a tradeoff between punch and bass distortion that is more appropriate
for pop music requiring substantial bass punch to make its musical point.
In any event, the
H
ARD
C
LIP
S
HAPE
control adds a useful color to the 8600’s
sound palette—one that is not duplicated by the existing
M
ED
and
S
OFT
bass clipper characteristics.
This control does nothing if the
B
ASS
C
LIP
M
ODE
is set to
M
ED
or
S
OFT
.
Speech Bass Clip Threshold
(“S
PEECH
BCT
HR
”)
(See Bass Clip Mode on page 3-45.)
8600 MX Technology Peak Limiter Controls
The MX peak limiter is designed to make FM analog broadcasts more competitive
with the cleanliness, punch, and open high frequencies of the digital media against
which FM analog transmissions now battle. To achieve this, it offers decreased audi-
ble distortion, more transient punch and a crisper, more open high frequency tex-
ture. Compared to the 8500-style peak limiter, the MX peak limiter typically provides
2.5 to 3 dB more power at high frequencies, which minimizes audible HF loss caused
by preemphasis limiting. Drums and percussion cut through the mix. Highs are airy.
See
Measuring the Improvements in Optimod-FM 8600’s FM Peak Limiting Technolo-
gy starting on page 3-97 for a more detailed discussion.