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Frequency- Contoured
Sidechain ( FCS)
Overshoot
Compensator
Characteristics
(patent pending)
System Overshoot: The FCS circuit
is best
thought
of
as
a " bandlimited safety
clipper".
It
operates
like
a hard
clipper,
but
does
not
produce
out- of- band
frequency
components
as
a simple
hard
clipper
would.
Because
the
audio
processing will
sometimes limit
steady-state
material
with high
average
energy
(like
sinewaves)
or
with
very
little
high- frequency
energy
to
levels
below
the
threshold of clipping, it is difficult to state a clear and meaningful specification
for the system overshoot performance of the FCS circuit.
The
FCS
circuit
is
followed
by
a safety
clipper.
The
overshoot
specification
could
be
slightly
improved
if
this
safety
clipper
were
set
up
to
clip
more
frequently. However, the system
is aligned at the factory such that the safety
clipper is almost never active, thus fully preserving the bandlimiting provided by
the FCS circuit. With this safety clipper alignment, the peak modulation will be
controlled + 3.5%
on
arbitrary
waveforms
clipped
to
any
degree
by
the
FCS
circuit ( acting as a bandlimited safety clipper); peak modulation will not exceed
this
level
on
other
material.
With
typical
program
material,
peak
modulation
uncertainty is less than 2%.
Sinewave Modulation Ability: 93%
modulation ( i.e.,
0.6dB
below
maximum
overshoot
level) at
all
sinewave
frequencies, assuming sinewaves
are applied to
FCS input.
Dynamic Separation: better than 45dB
Difference-Frequency Intermodulation: FCS
circuit
causes
no
more
audible
IM
(such as sibilance splatter) than would a simple hard clipper clipping to the same
depth.
The
entire
OPTIMOD-TV
processing
system
is
specifically
configured
to
prevent
the
FCS
circuit
from
audibly
degrading
the
difference- frequency
distortion- cancellation properties of the earlier peak limiting system.
System Separation
Greater than 50dB, 50-15,000Hz; 60dR typical
Input
Impedance: greater
than
10K
ohms,
electronically
balanced
by
means
of
true
instrumentation amplifier. Requires balanced source.
Common Mode Rejection: Greater than 60dB f60Hz
Sensitivity: - 10dBm
produces
10dB " Master"
Band
gain
reduction
1kHz.
Removal
of
internal
20dB
pad
permits - 30dBm
to
produce
same
effect.
Connector: Barrier strip (# 6 screw).
Output
Source Impedance: 370 ohms,
independent
of OUTPUT
ATTEN setting,
balanced.
Level: variable - infinity
dBm
to
greater
than + 20dBm
by
means
of
15- turn
OUTPUT ATTEN controls.
Connector: Barrier strip (# 6 screw). RF suppressed.
Test Jacks ( for Test use only)
Provides
L and R lowpass filter output on RCA phono - type connectors on rear
panel. Outputs are unbalanced.
L-3
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