Advertisement
Factor ( 2)
is
taken
into
account
by
summing
the
outputs
of
the
bands
after
rectification, thus eliminating phase cancellation effects and causing the output
current
to
increase
as
the
signal
is " spread
out"
into
more
and
more
bands.
Factor ( 3) is taken
into
account
by
integrating the Loudness Controller
output
current
inside
the " Master"
timing
module
with
the
correct
time
constant.
The Loudness Controller can be operated either from the system output (Cards
#8 and # 9), or from the output of the Dual- Band Compressor (Cards # 3 and # 4).
Operation from the Card # 8/#9 output achieves maximum accuracy because the
effects
of
HF
limiting
and
peak
limiting
are
accounted
for.
In
this
mode,
deemphasis must be applied to the Loudness Controller's input because the Card
#8/#9 output is preemphasized.
Operation from the Card # 3///4 output is required when the system
is operated
in the split- chassis configuration since, in this case, the main system outputs are
not
available to the Loudness Controller card ( which is located in the Accessory
Chassis
at
the studio). However,
if the system
makes
any errors
in
the split-
chassis mode, it will be in the direction of slightly excessive loudness reduction,
which should not cause any problems. ( Because the output of Card # 3/#4 are not
preemphasized, no deemphasis of the Loudness Controller input is required in this
case.)
All
filters
within
the
Loudness
Controller
are
bandpass,
each
consisting
of
a
third- order
lowpass
filter
cascaded
with
a third- order
highpass
filter. ( The
top
band uses a second- order lowpass filter instead of a third- order).
Rectification
and
further
processing
occur
in " current
mode".
This
makes
troubleshooting somewhat
challenging,
because
the
usual
signal
voltages
do
not
exist:
the
control
signal
is
in
the
form
of
a current ( which
is
much
more
difficult
to
observe
with common bench instruments).
Appendix D (Field Audit
Of
Performance
Procedure)
describes
tests
to
determine
if
the
Loudness
Controller is working properly.
If
servicing
of
the Loudness
Controller
is
necessary,
the
OPTIMOD-TV
system
will
function
without
degradation ( except
for
loss
of
the
Loudness
Controller
function)
if
Card # 2 is
simply
removed from
its
slot --
no
jumpers
need
be
moved or other adjustments made.
This concludes APPENDIX A (SYSTEM DESCRIPTION).
A-12
Advertisement
