PANEL FACILITIES
Fig. 3—The end panel of the MC240 showing all input and output facilities.
INPUT
The input of the MC240 has a three posi-
tion lever switch to permit the amplifier to be
used in any one of three ways:
(1} As a monophonic 80 watt amplifier
(2) As twin 40 watt amplifiers used with an
electronic crossover network, or two
completely separate amplifiers, or in
stereo applications requiring 0.5 volt
sensitivity in the power amplifiers
(3) As a stereo amplifier used with a
Mclntosh preamplifier or other high
output stereo program sources.
The input marked STEREO has a sensi-
tivity of 2.0 volts controlled by a BALANCE
control. The input impedance is 250,000
ohms.
The input marked TWIN AMP has a sensi-
tivity of 0.5 volt. Each TWIN AMP input is
controlled by a GAIN control. The GAIN con-
trol allows signal sources with output from
0.5 volt up to 30 volts to be connected with-
out overloading the input to the amplifier.
The input impedance is 250,000 ohms.
The input marked MONO has a sensitivity
of 0.5 volt. The MONO position of the input
switch parallels the inputs to both ampli-
fiers. When the outputs are properly con-
nected the MC240 becomes an 80 watt
monophonic amplifier. The MONO input has
a GAIN control that permits connecting signal
sources up to 30 volts without overloading
the amplifier's input. The input impedance
is 250,000 ohms.
OUTPUT
The two barrier terminal strips marked
OUTPUT provide stereo connections for the
normal speaker impedances of 4 ohms,
8 ohms, and 16 ohms. For monophonic oper-
ation connections for 2 ohms, 4 ohms, 8
ohms, 16 ohms, and 32 ohms are provided.
The terminal strips may also be connected
for a constant voltage output of 25 volts in
either stereo or mono.
The secondary of the Mclntosh output
transformer may be operated either grounded
or not grounded. As supplied, the secondary
of the MC240 is not grounded. If grounding
is desirable a wire may be connected be-
tween chassis and common of either or both
output terminal strips.
The barrier strip output connections are
fed from the secondary of the output trans-
former.
LINE OUTPUT (See also pages 6 and 7)
The octal socket marked LINE OUTPUT
has connections for 70.7 volts, 125 ohms,
140 volts, or 600 ohms for stereo operation.
For monophonic operation the octal socket
provides connections for 70.7 volts, 62
ohms, 140 volts, or 300 ohms.
The 600 ohm winding and the 300 ohm
winding are balanced to ground. Pin 1 of the
octal socket is the center tap for these wind-
ings and is grounded.
The connections at the octal socket are
fed from taps on the cathode winding in the
primary of the output transformer.
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