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FM broadcasts, turntable (PHONO), tape player,
or any other source capable of providing 200 mV
output level (AUX). The SELECTOR switch con-
nects the inputs of the TONE control amplifier
to the desired source.
TAPE 1 MONITOR SWITCH
The TAPE 1 MONITOR switch selects between
source and TAPE 1 INPUT jacks. When the TAPE
1 MONITOR switch is in its normal "out"
posi-
tion, the preamplifier receives its input from the
SELECTOR switch. When the TAPE 1 MONI-
TOR switch is depressed, the preamplifier receives
its input from the TAPE 1 I N jacks.
PHONE EO AMPLIFIER
Phono signals of up to 100 mV can be hand led
without
overloading. The equalization network
provides precise equalization to the RIAA stand-
ard and sets the voltage gain of the phono pre-
amplifier to 40 dB (at 1 kHz).
MONO FUNCTIONS.
When the MONO pushswitch is in the "in" posi-
tion, the two channels are connected together
through mixing resistors. In addition, the left and
right channel tape input signals are connected
together through the same resistor network. This
facility allows all inputs to be converted to the
monophonic mode.
CONTROL CIRCUITS
The control circuits portion of the Model 2252
consists of the BALANCE,
VOLUME,
BASS,
MID, TREBLE,
and HI FI LTER, controls. All
controls affect the left and right channels simulta-
neously. However, the BASS, MID and TREBLE
controls have clutched sections which allow indi- .
vidual
adjustment
of tonal
balance for each
channel. With the controls set for flat response
and volume control at maximum, the overall volt-
age gain from any high-level input to the loud-
speaker terminals is approximately 41 dB.
BALANCE CONTROL
The BALANCE
control is a full range control
which permits attenuation
of each channel to
cutoff. The change of attenuation in each channel
as the control
is moved from center has been
designed to maintain
total
apparent loudness
from both channels. This feature makes it a true
stereo balance control.
9
VOLUME CONTROL
The VOLUME control attenuates both channels
simultaneously and maintains tracking to within
3 dB at any point of attenuation to
-60
dB from
maximum. Since the control is situated at the in-
put of the tone amplifier, there is no possibility
of overloading the amplifier stages under maxi-
mum 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 control amplifier.
TONE CONTROL AMPLIFIER
The TONE CONTROL AMPLIFIER's
circuitry
uses a continuously
variable negative feedback
type configuration
for
lowest distortion.
The
signal from the TONE CONTROL AMPLIFIER
feeds the HI filter circuit when the HI FILTER
is activated.
AMPLIFIER
The amplifier
section of the Model 2252 is a
direct
coupled, full
complimentary
circuit.
It
utilizes current limiting
and thermal compensa-
tion circuits to provide safe, highly stable operat-
ing conditions. The silicone output devices used
in the power amplifier section provide a large
collector dissipation margin.
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