INPUT-MONO
The shielded cable from the program
source is plugged into the jack marked
MONO INPUT.
OUTPUT-STEREO OR TWIN AMPLIFIERS
For stereo or twin channel operation it is
not necessary to use the same impedance
load on each output. Simply connect each
output for the impedance desired.
Speakers are connected at the barrier
strips marked OUTPUT on the left end of
the panel.
In compliance with the National Electrical
Code, Class II wiring can be used between
the speaker and the amplifier at the 4 ohm,
8 ohm, or 16 ohm connection. Class II wiring
is lamp cord, bell wire, or other wire with
this type of insulation. For the normally short
distances of under 100 feet between the
amplifier and speaker, #18 wire or larger
can be used. For distances over 100 feet
between the amplifier and speaker use
larger wire.
The loudspeaker impedance is usually
identified on the loudspeaker itself. Connect
one of the leads from the left loudspeaker to
the screw marked COM on the left barrier
strip. Connect the other lead from the left
loudspeaker to the screw marked with the
number corresponding to the speaker im-
pedance on the LEFT barrier strip.
If the speaker
impedance is:
4 ohms
8 ohms
16 ohms
Connect one left speaker
lead to screw LEFT-COM
and the other to:
LEFT-4
LEFT-8
LEFT-16
Connect one right speaker
lead to the screw marked
RIGHT-COM and the other to:
RIGHT-4
RIGHT-8
RIGHT-16
OUTPUT-MONOPHONIC
When the MC240 is to operate as an 80
watt monophonic amplifier, the outputs of
the two channels combine to produce a
-single 80 watt output. This chart lists the
proper connections and interconnections for
monophonic operation.
Warning: Do not parallel the amplifier out-
puts when using the amplifier as a stereo
amplifier or twin channel amplifier. Damage
to the output tubes may result if parallel
operation is attempted when the output volt-
ages are not the same phase and amplitude.
If the
speaker
impedance
is:
2 ohms
4 ohms
8 ohms
16 ohms
32 ohms
Connect one speaker
lead to the screw
marked LEFT-COM
and the other to:
LEFT- 4
LEFT- 8
LEFT-16
RIGHT-8
RIGHT-16
Connect a
wire between:
LEFT-COM and
RIGHT-COM
LEFT-COM and
RIGHT-COM
LEFT-COM and
RIGHT-COM
RIGHT-COM and
LEFT-8
RIGHT-COM and
LEFT-16
Connect another
wire between:
LEFT-4 and
RIGHT-4
LEFT-8 and
RIGHT-8
LEFT-16 and
RIGHT-16
—
—
When connected as outlined the MC240
operates as an 80 watt monophonic amplifier.
LINE OUTPUT-STEREO or TWIN AMPLIFIERS
The octal socket marked LINE OUTPUT
has connections for 70.7 volts, 125 ohms and
140 volts or 600 ohms. The 25 volt line is fed
from the barrier strips.
For 25 volt line operation connect one of
the left leads to the screw marked COM on
the LEFT barrier strip. The other left lead is
connected to the screw marked 16 on the
LEFT barrier strip. Connect the right leads
in the same manner on the RIGHT barrier
strip.
The 125 ohm and 70.7.volt connections are
the same. To connect for 125 ohm or 70.7
volt operation the octal plug supplied in the
hardware bag is used. Solder one of the left
leads to pin #2 and the other to pin #1.
Solder one of the right leads to pin #4 and
the other to pin #1. Pin #1 is the ground
side.
The 600 ohm connections for the left side
are made between pin #2 and pin #3. The
600 ohm connections for the right side are
made between pin #4 and pin #5. The 600
ohm winding is balanced to ground. Pin #1
on the octal socket is the center tap of the
600 winding. Pin #1 is grounded.
If the speaker impedance
is between:
3.2 to 6.5 ohms
6.5 to 13 ohms
13 to 26 ohms
Connect the
speaker leads
between COM and:
4 ohms
8 ohms
16 ohms
6
The only adverse effect on the operation
of a Mclntosh amplifier when it is improperly
matched is a reduction in the amount of
distortion-free power available to the loud-
speaker. Close impedance matching is de-
sirable for maximum distortion-free power.
Use this table to determine proper speaker
connections:
