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Page 1
DESCRIPTION
The
436B
Amplifier
is
a
self-powered
unit
which
occupies
3
W
of
rack
space,
with
input
gain
control,
power
switch,
fuse,
pilot
light
and
compression
meter
mounted
on
a
hinged
front
panel.
It
is
equipped
with
a
bridging
input
transformer.
Output
loads
of
150
or
600
ohms
may
be
accommodated.
The
threshold
and
amount
of
compression,
as
well
as
the
attack
and
recovery
time
of
the
circuit,
are
fixed
quantities
considered
optimum
for
average
program
service.
APPLICATIONS
The
436B
Amplifier
is
intended
for
use
in
automatic
level
control
applications
in
public
address
systems.
It
may
be
used
to
control
level
differences
between
two
or
more
medium-level
program
sources
or
as
a
program
line
compressor,
or
it
may
be
used
for
automatic
fading
for
voice-over-music
announcements.
Level
differences
caused
by
individual
voice
intensities
and
unequal
distances
of
performers
from
the
microphone,
where
single
microphone
pickup
is
employed,
can
be
minimized
by
the
use
of
the
436B
Compressor.
In
industrial
locations
where
sudden
high
level
sounds
might
cause
"blasting"
with
attend¬
ant
danger
to
amplifiers
and
loudspeakers,
the
436B
Amplifier
will
prevent
such
overloading.
The
436B
can
be
used
as
a
line
amplifier
by
simply
removing
the
6AL5
tube
from
its
socket.
INSTALLATION
AND
OPERATION
The
design
of
the
436B
Compressor
Amplifier
is
versatile
enough
that
it
can
be
connected
into
any
high-
or
low-impedance
line
between
preamplifiers
and
power
amplifiers,
without
adapters
or
other
modification.
In
high-impedance
lines,
as
exemplified
by
the
Altec
Lansing
1500
series
P.A.
amplifiers,
the
bridging
input
transformer
of
the
436B
Amplifier
provides
a
suitable
load
for
the
mixer-preamplifiers.
The
output
of
the
436B
Amplifier,
when
ter¬
minated
with
600
ohm
resistance,
is
of
sufficient
level
to
operate
directly
into
the
high
impedance
of
the
power
amplifiers.
Where
it
is
desired
to
insert
the
436B
into
a
transmission
line
of
500/600
ohms,
a
resistive
termination
of
600
ohms
should
be
installed
and
the
input
of
the
436B
Amplifier
connected
across
this
load.
The
600
ohm
output
then
provides
a
suitable
source
for
the
input
of
the
following
power
amplifier.
A
600
ohm
line
level
of
+7
dbm
(1.7
volts)
will
drive
the
436B
Amplifier
to
full
30
db
compression,
with
a
level
of
+19
dbm
at
the
output
of
the
compressor.
Since
this
level
is
great
enough
to
overdrive
most
power
amplifiers,
it
is
necessary
to
install
a
suitable
loss
pad
at
the
input
of
the
power
amplifier,
unless
the
power
amplifier
is
already
equipped
with
a
gain
control.
Level
Adjustments
For
unattended
sound
reinforcement
systems
in
lecture
halls
and
other
places
where
the
microphone
and
loudspeaker
are
in
the
same
room,
precautions
must
be
taken
to
prevent
acous¬
tic
feedback
when
no
performer
is
at
the
microphone.
Level¬
setting
procedure
for
this
case
is
as
follows:
adjust
input
gain
so
that
the
average
voice
speaking
at
a
normal
distance
from
the
microphone
causes
the
meter
on
the
436B
Amplifier
to
indi¬
cate
5
db
of
compression.
Then
,in
the
absence
of
the
per¬
former,
adjust
the
power
amplifier
gain
to
the
maximum
level
available
without
acoustic
feedback.
With
this
level
adjust¬
ment,
the
weaker
voices
are
reinforced
the
maximum
possible.
Louder
voices
will
automatically
be
compressed.
Where
the
microphone
is
not
in
the
same
location
as
the
loud¬
speaker,
input
levels
to
the
436B
Compressor
Amplifier
should
be
adjusted
so
that
average
program
material
will
drive
the
compressor
into
10
to
15
db
of
compression,
as
indicated
on
the
meter.
System
output
should
then
be
set
for
appropriate
volume
by
means
of
the
power
amplifier
gain
control.
With
the
levels
adjusted
as
above,
input
variations
of
±15
db
from
average
program
level
will
result
in
only
±5
db
change
at
the
output
of
the
436B
Amplifier.
When
it
is
desired
to
automatically
fade
"background"
music
for
voice
announcements,
the
gain
control
of
the
music
chan¬
nel
should
be
set
so
that
for
average
music
level,
the
com¬
pression
threshold
is
barely
reached.
Proper
listening
level
is
then
set
by
means
of
the
power
amplifier
gain
control.
The
voice
channel
gain
control
is
adjusted
to
provide
approxi¬
mately
25
db
of
compression,
as
shown
on
the
meter,
during
normal
announcements.
The
above
settings
will
result
in
announcements
at
a
level
approximately
15
db
above
the
original
music
level,
same
time,
the
music
will
drop
to
a
level
ab<
the
announcement
level.
SERVICING
All
circuit
components
are
easily
reached
by
opening
the
hinged
front
panel
of
the
unit.
Normal
servicing
can
be
done
with
a
voltmeter.
All
pertinent
information
is
shown
on
the
schematic.
436B
Amplifier
Average
Compression
Characteristics
50
45
40
35
30
OUTPUT
25
DBM
20
COMPRESSION
METER
It
is
usually
desirable
to
have
the
compression
m
from
the
operating
position.
When
conditions
dictate
a
location
for
the
436B
Amplifier,
an
Altec
#6049
meter
sh
be
ordered
for
installation
at
the
console.
The
additional
meter
is
connected
in
parallel
with
the
436B
Amplifier
meter
by
means
of
a
pair
of
wires
extended
to
the
console
location.
I
4
i
\vOv
R\vl
UPRESSH
k\\"1
I
\p\
p
y\\
10
20
30
^O
50
60
DB
INPUT
ABOVE
THRESHOLD
Page 2
typical
applications
Fig.
1
The
436B
Amplifier
in
typical
high
impedance
line.
A
600
ohm
terminating
resistor
must
be
connected
across
the
output
of
the
436B
as
shown.
Fig.
2
Fig.
3
A
typical
low
impedance
line
installation.
The
remote
fader
serves
as
proper
termination
for
the
436B.
Low
impedance
line
with
remote
submasters.
The
600
ohm
terminating
resistor
must
be
installed
at
the
the
436B
Amplifier.
The
1550A
Apparatus
Unit
feeding
the
436B
should
be
strapped
for
a
secondary
p
17,500
ohms.
FIG.2
Qfnky®
PARTS
LIST
C2,
3,
5,
6
.022
mfd,
400
V.,
Micamold
Tropicap
pi
Altec
Lansing
13021
C4
1
mfd,
200
V.,
Astron
ML-2-IM
T1
Peerless
4651A
C
7
80
mfd,
350
V.,
Mallory
FP-138
T2
Peerless
16402
C8
80-40-10
mfd/200-450-450
V.,
Mallory
FP
370
T3
#
Peerless
6216
R3,
4
47,000
ohms,
±1%,
Vi
watt.
Deposited
Carbon
Ml
Altec
Lansing
6049
R5,
6,
9
1
megohm,
±
10%,
'A
watt
PL1
Mazda
#44
R7
220
ohms,
±
10%,
}
A
watt
FI
V
2
amp
3AG
Fuse
R8
34
ohms,
±1%,
Vi
watt,
Deposited
Carbon
SI
Altec
Lansing
12180
R10,
11
220,000
ohms,
±
10%,
y
A
watt
Rectifier
Sarkes
Tarzian
58-D
R12
33,000
ohms,
±
10%,
V
2
watt
VI
6BC8
Vacuum
Tube
R13
10,000
ohms,
±
10%,
1
watt
V2
6CG7
Vacuum
Tube
R14
6,800
ohms,
±
10%,
1
watt
V3
6AL5
Vacuum
Tube