Instruction manual
"pop"
noise for
smooth
tune
in and
tune
out.
AM
TUNER
The
AM
tuner
portion
of
the
Model
2270
has been
provided with a
tuned
RF amplifier incorporating
a three-section variable
capacitor
for improved
selectivity and spurious response.
The
ceramic filters utilized in
the
AM IF
amp
lifier
have very high selectivity and
adequate
bandwidth
for interference-free AM
reception
.
Following
the
AM IF amplifier,
the
AM
detector
re-
covers
the
audio
modulation
and provides
this
sig-
nal
to
the
selector switch.
The AM
tuner
and
IF
amplif
ier are sub
jected
to
the
action
of
an effective
automatic
volume
control
cir-
cuit which maintains
constant
the
level of all sta-
tions
in
the
AM band.
SELECTOR SWITCH
Your Model
2270
has
the
capability
to
operate
from a variety
of
program sources, e.g., AM
or
FM broadcasts,
turntable
(PHONO),
tape
recorders
or
any
other
source capable of providing
100
millivolts
output
level (AUX).
The
selector switch
connects
the
inputs
of
the
TONE amplifiers
selectively
to
the
desired source.
TAPE SIGNALS
With
the
exception
of
tape
input,
all high-leve l
inputs are fed directly
to
the
selector switch.
Tape
input
is
routed
through
the
MONITOR (1, 2)push-
switch and
front
panel
dubbing
IN jack
to
a
section
of
the
MONITOR (TAPE/SOURCE) switch.
The
dubbing
IN jack is a
three-conductor
stereo
jack which has
two
built-in switches,
one
for
each
channel. Normally, these switches are closed,
allowing
the
tape
input
signals from
the
PLAY
(1 and 2) jacks on
the
rear panel
to
be fed
to
the
MONITOR (TAPE/SOURCE) switch. When a plug
is inserted in
the
dubbing
IN jack,
the
switches
are opened, disconnecting
the
PLAY (1 and 2)
jacks and allowing
the
signal from
the
dubbing
IN jack
to
reach
the
MONITOR (TAPE/SOURCE)
switch.
Thus
only
one
tape
recorder
at
a
time
can
feed playback signals
into
the
Model
2270
.
MONITOR (TAPE/SOURCE) SWITCH
When
the
MONITOR (TAPE/SOURCE) pushswitch
is in
the
"out"
position
tape
input
signals from
the
PLAY (1 and 2) jacks on
the
rear panel or
dubbing IN jack on
the
front
panel are fed
to
the
selector switch. When
the
MONITOR
(TAPE/
SOURCE) is depressed,
the
output
of
the
selector
switch is disconnected from
the
balance
control
and
the
tape
input
signals from
the
TAPE IN
or
dubbing
IN jacks feed
the
balance
control
directly.
MONITOR (1
and
2) SWITCH
This switch selects
between
the
tape
PLAY 1
or
2
jacks on
the
rear panel. Depressing
the
switch se-
lects
input
signal
connected
to
the
PLAY 1 jacks
and releasing
the
switch
(out
position) PLAY 2 ja-
cks.
PHONO SIGNALS
Phono
signals
of
up to
100
millivolts can be handled
without
overloading.
The
RfAA equalization
network
provides precise equalization and sets
the
voltage gain
of
the
phono
preamplifier to
40dB
(at
1,OOOHzl. This RIAA reproducing charac-
teristic,
together
with
the
recording characteristic,
is
shown
in Figure 9. Notice
that
the
net
result
after
playback is a
flat
response.
Hi BLEND AND MONO (L
and
R) FUNCTIONS
When
the
Hi BLEND switch is depressed
the
left
and right channel
outputs
of
the
selector switch
are
connected
together
through
mixing resistors and
a capacitor.
The
value
of
the
capacitor
has been
selected
to
effect
moderate
suppression of
out-of
-
phase noise
and
d
istortion
components
while main -
taining
moderate
stereo
separation. When
both
MO-
NO (L and R) switches
are
in
the
"in
"
pos
ition,
the
two
channels are
connected
directly
together
th-
rough mixing resistors. In
addition,
the
left and
right
channe
l
tape
input
signals are
connected
to
-
gether
through
a similar resistor
network.
This faci-
lity allows all
inputs
to
be
converted
to
the
mono-
phonic mode.
CONTROL CIRCUITS
The
control
circuits
portion
of
the
Model
2270
consists of
the
balance, volume, bass, mid, treble,
Hi
FILTER,
and
LOW FILTER controls. All con -
trois
affect
the
left
and
right channels simultane-
ously.
The
bass, mid and
treble
controls
have
clutched
sections which allow individual adjust-
ment
of tonal balance
for
each channel. With
the
controls
set
for
flat response and volume con-
trol
at
maximum,
the
over-all voltage gain from
any
high-level
input
to
the
loudspeaker
termi
-
nals is
approximately
43dB.
BALANCE
CONTROL
The
balance
control
is a wide-range
control
which
permits
attenuat
ion of each channel
to
cutoff.
The
12