change
of
attenuation
in each channel as
the
CAUTION: THE LOUDSPEAKER TERMINALS
control
is
turned
away from
center
has been designed
to
maintain total
apparent
loudness
from
both
channels. This
feature
makes it a
true
stereo
balance
control.
VOLUME
CONTROL
The
volume
control
attenuates
both
channels
simultaneously
and
maintains tracking
to
within
3dB
at
any
point
of
attenuation
to
-SOdB from
maximum.
Since
the
control
is situated at
the
input
of
the
tone
amplifier,
there
is no possibility
of overlooking
the
amplifier stages
under
maximum
rated
output
conditions
.
Thus
,
distortion
is
kept
to
a minimum.
After
attenuation
by
the
balance
and volume
controls,
the
signal is applied
to
the
tone
amplifier.
TONE
AMPLIFIER
The
TONE AMPLI FI
ER's
circuitry
uses a
continu-
ously variable R-C
feedback-type
configuration.
Figure 10 shows
the
frequency response curves
for
maximum
boost
and
cut
for each
control.
The
signal from
the
TONE AMPLIFIER feeds
the
hi/low
filter
circuit
when
the
Hi FIL
TER
or
the
LOW FIL
TER
pushswitch is depressed.
Hi-LOW
FILTERS
Figure 11 shows
the
frequency
response curves
resulting from use
of
the
two
filters.
OUTPUT
STAGE AND PROTECTIVE
CIRCUITS
The
pre-driver
circuit
amplifies
the
signal from
the
Hi-LOW FI L
TERS
to
sufficient levels
to
drive
the
output
stages. Beyond
the
input
of
the
pre-
driver circuit,
the
amplifier stages are
direct
-
coupled
through
to
the
loudspeakers (and head-
phones) providing
instantaneous
recovery from
overdrive
or
short
circuit
conditions.
The
output
stage consists of a pair of push-pull,
complementary-
symmetry
transistors (PI\IP, NPN).
The
electronic
protective
circuit senses
the
peak
output
current
and limits
the
current
to
the
driver transistors at
a safe,
predetermined
value. This
current
limiting
protects
the
driver and
output
trans
istors
under
overdrive and
short
circuit
conditions
and
effective-
ly prevents
the
driver and
output
transistor
from
exceeding safe
operating
conditions.
This
instan-
taneous
acting safety
circuit
gives
constant
and
unobtrusive
protection
without
causing
annoying
program
interruptions.
OF ONE CHANNEL SHOULD NE-
VER BE CONNECTED DIRECTLY
IN
PARALLEL
WITH ANY OTHER.
ANY RESULTING DAMAGE IS NOT
COVERED
UNDER THE WARRAN-
TY.
13
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