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For all applications using 600 ohms use
Class I wiring if the installation must meet
the requirements of the National Electrical
Code.
LINE OUTPUT-MONOPHONIC
The octal socket marked LINE OUTPUT
has connections for operating the MC225
monophonically at 70.7 volts, 100 ohms or
300 ohms. For operating at 25 volts connec-
tions are made at the barrier strips.
To feed a 25 volt line, connect one side to
the screw marked COM on the LEFT barrier
strip. Connect the other side to the screw
marked 16 on the LEFT barrier strip. Then
connect with a wire the screw marked COM
on the LEFT barrier strip to the screw marked
COM on the RIGHT barrier strip. Connect,
with another wire, the screw marked 16 on
the LEFT barrier strip to the screw marked 16
on the RIGHT barrier strip.
Before turning the MC225 on check all
connections and plugs to see that they are
firmly and correctly connected. Check to
make sure that the tubes are firmly seated
INPUT SWITCH-STEREO
With the input switch in the left position
marked STEREO the input of the MC225 is
connected to the two jacks marked "L" and
"R" INPUT located below the GAIN con-
trols. The amplifier has an input sensitivity
in this position of 0.5 to 30 volts.
The two center control knobs marked
GAIN should be adjusted to match the input
sensitivity of the MC225 to the output voltage
of the program source equipment.
To balance a stereo system using the
STEREO input position use a monophonic
signal from the program source. A mono-
phonic signal supplies the same voltage to
both channels. Turn the volume control on
the source equipment to the 12 o'clock posi-
tion (half rotation). Turn up the GAIN con-
trol on the LEFT input until the loudness in
the room is not quite as loud as you like to
The 100 ohm and the 70.7 volt connec-
tions are the same. To connect for 100 ohms
or 70.7 volts solder one of the leads to pin
#1 in the octal socket. The other lead is
soldered to pin #7. A wire is connected be-
tween pin #7 and pin #8.
To connect for 300 ohms one lead is
soldered to pin #2. The other lead is sol-
dered to pin #3. Connect pin #2 to pin #4
with a wire. With another wire connect pin
#3 to pin #5. Pin #1 is the center tap of the
300 ohm winding. The 300 ohm winding is
balanced to ground.
AC POWER
The MC225 operates on 105 volt to 130
volt, 50 to 60 cycles power. The amplifier will
be turned on and off if its power cord is
plugged in one of the auxiliary AC outlets on
the program source.
OPERATING THE MC225
in the proper sockets. After the following
adjustments have been completed the MC-
225 will operate without any further attention.
ADJUSTMENTS
listen. Then turn the GAIN control on the
RIGHT input until it is equally as loud as the
left channel. The system is now balanced for
loudness and provides the most convenient
amount of loudness change when using the
volume control on the source equipment.
INPUT SWITCH-MONO
With the switch in the right position
marked MONO the inputs of the MC225 are
internally connected in parallel and to the
jack marked "R" INPUT. This jack is located
below the right control knob marked "RIGHT
MONO GAIN." The input sensitivity in this
position is 0.5 volt. The GAIN control should
be adjusted to match the input voltage sen-
sitivity of the MC225 to the output voltage of
the program source.
For maximum flexibility set the GAIN
control as follows: Turn the volume control
7
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