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OPERATION
Orban Model
464A
Pre-emphasis
Up 3dB
at
Application
none
—
Recording tape
at
30ips
(Set
HF
LIMIT to
DEFEAT)
25p.s
6.37kHz
Recording tape
at
15ips
37.5p.s
4.24kHz
Recording tape
at
7.5ips
50|iS
3.18kHz
FM
broadcast (Europe)*
75|J.S
2.12kHz
FM
broadcast*, cassette
duplication**
microwave
STLs
lOOpS
1
.59kHz
Cassette
duplication**
150|jS
1
.06kHz
FM SCA
subcarriers
*
FM
broadcast pre-emphasis standards vary by
country.
**
Depends
on
tape
quality
and
whether Dolby®
HX
Pro processing
is
used.
(To ensure accuracy
in
broadcast
STL
or
SCA
applications, the
pre-emphasis network
in the
STL
or
SCA
generator should
be
defeated,
and
the
Co-Operator's
jumpers
should be
set
for
p re-emphasized output
—
see
"Installation
—
FM
Transmitter,
STL, and
Subcarrier
Generator
Protection"
in
Section
2.)
If
high-frequency
distortion
is
observed,
try
switching
the
HF
limit
PRE-EMPHASIS
switches
to
a higher
setting.
If
excessive high-frequency
loss
is
heard,
try
a
lower
setting.
It
is
difficult
to
suggest
an
appropriate
pre-emphasis curve
for
LF
and
HF
drivers,
since the
choice
depends
on
the
power-handling
capabilities
of
the individual
drivers.
Experience
is
the best
guide
here.
Higher
pre-emphasis curves provide
more
overload
protection,
but
will
produce a
duller
sound from
HF
drivers.
Feed
to
LF
drivers
should
typically
be
clipped
very
slightly
below
the clipping threshold
of
the
power
amp
(unless
you
are
using a
power
amp
that
is
too
powerful
for the
driver, in
which
case
you might want
to clip
the input to the
power
amp
substantially
below
the
amp's
own
clipping point and/or
use
the
Co-Operator's
leveling function
to limit
the
average
power
applied
to
the
driver).
Activate the
compressor
function
in
any
case,
to
avoid excessive
clipping
or high-frequency
limiting.
The
thresholds,
time
constants,
and compression
ratios
of
the
high-frequency
limiter
have been
optimized
for
unobtrusive processing of
dynamic program
material.
Con-
sequently,
if
swept
sine
wave
measurements (which do
not resemble
real
program
material) are
made
on
the
high-frequency
limiter,
the
curves
that are
produced
will
not
be
the exact inverses
of
the
curves
selected
with
the
HF
umtt
pre-emphasis
switch.
(The primary
reason
for
this
is
that
the threshold
of
the
high-frequency
limiter
has
been
set
several
dB
above
the steady-state threshold
of
the leveling
cir-
cuit to
avoid
having
transient
overshoots
from
the leveling
circuit
cause unnecessary
high-frequency gain
reduction.)
Stereo
and
dual
modes.
Setting the
mode
button
to
stereo
ensures
stable stereo
imaging.
In
STEREO
mode,
all
leveler
and compressor
VCAs
will track the
channel
requiring the greater
amount
of gain
reduction.
If
the
gate THRESH
controls for
both channels
are
set identically,
both channels
will
remain ungated
as
long
as
at
least
one
channels
receives
sufficient
input
level to
ungate. In
STEREO
mode,
all
controls are usually
set identically.
The
HF
limiters
remain
independent.
When
the
MODE
button
is
set to
DUAL,
the
left
and
right
channels
function indepen-
dently.
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