MC-250
THE McINTOSH MC 250 STEREO SOLID STATE POWER AMPLIFIER
Reading Time: 20 Minutes
Price $1.25
Your MC 250 Stereo Amplifier
will give you many years of pleasant
and satisfactory performance. If you
have any questions, please contact:
CUSTOMER SERVICE
Mclntosh Laboratory Inc.
2 Chambers Street
Binghamton New York 13903
Phone: 607-723-3512
WARNING: TO PREVENT FIRE OR SHOCK
HAZARD, DO NOT EXPOSE THIS UNIT TO RAIN
OR MOISTURE.
CONTENTS
SERVICE CONTRACT 1
INSTALLATION 2
HOW TO CONNECT 2, 3
CONTROL PANEL INFORMATION 4
LISTENING TO YOUR STEREO SYSTEM 4
PERFORMANCE LIMITS AND RATINGS 5
Take Advantage of 3 years
of FREE Service ...
PEFORMANCE CHARTS 6
TECHNICAL DESCRIPTION 7
Fill in the Application NOW.
THREE YEAR SERVICE CONTRACT
An application for a FREE THREE YEAR SERVICE CONTRACT is included with this manual.
The terms of the contract are:
1. Mclntosh will provide all parts, materials and
labor needed to return the measured performance of the instrument to the original performance limits free of any charge. The
SERVICE CONTRACT does not cover any ship-
ping costs to and from the authorized service
agency or the factory.
2. Any Mclntosh authorized service agency will
repair all Mclntosh instruments at normal
service rates. To receive the free service under
the terms of the SERVICE CONTRACT, the
SERVICE CONTRACT CERTIFICATE must accompany the instrument when taken to the
service agency.
3. Always have service done by a Mclntosh
authorized service agency. If the instrument
is modified or damaged, as a result of unauthorized repair the SERVICE CONTRACT
will be cancelled. Damage by improper use
or mishandling is not covered by the SERVICE CONTRACT.
4. The SERVICE CONTRACT is issued to you as
the original purchaser. To protect you from
misrepresentation this contract cannot be
transferred to a second owner.
5. For your protection Mclntosh selects only
dealers who have technical competence to
guide purchasers fairly, and provide service
when necessary. To receive the SERVICE
CONTRACT your purchase must be made
from a Mclntosh franchised dealer.
6. Your completely filled in application for a
SERVICE CONTRACT must be postmarked
within 30 days of the date of purchase of
the instrument.
7. To receive the SERVICE CONTRACT all information on the application must be filled
in. The SERVICE CONTRACT will be issued
when the completely filled in application
is received at Mclntosh Laboratory Incorporated in Binghamton, New York.
BLOCK DIAGRAM 8
Copyright © 1970 by Mclntosh Laboratory, Inc.
1
SPEAKERS
Installation
Adequate ventilation extends the troublefree life of electrical instruments. It is gen-
erally found that each 10° centigrade (18° F)
rise in temperature reduces the life of electrical insulation by one half. Adequate ventilation is an inexpensive and effective means
of preventing insulation breakdown that re-
sults from unnecessarily high operating tem-
peratures. The direct benefit of adequate
ventilation is longer, trouble-free life.
The suggested minimum space for mounting the MC 250 is 18 inches long X 8 inches
wide X 11½ inches high. Always allow for air
flow by either ventilation holes or space next
to the bottom of the amplifier and a means
for the warm air to escape at the top.
It is recommended that the MC 250 be
mounted in a normal or horizontal position.
However with adequate ventilation, the ampli-
fier can be mounted in any position except
upside down. If the amplifier is to be installed
on a vertical surface it is recommended that
the autoformers be on the down side. This
position permit greater air flow around the
transistors and component parts thereby extending the trouble-free life of the amplifier.
HOW to Connect
INPUT—STEREO
The shielded cable from the left output of the Mclntosh preamplifier is plugged into the left jack. The
shielded cable from the right output of the Mclntosh
preamplifier is plugged into the right jack. The INPUT
switch must be in the STEREO position and the OUT-
PUT properly connected to the stereo loudspeakers
or distortion and loss of power may result.
INPUT—MONO
The shielded cable from the program source is
plugged into the right jack. The INPUT switch must
be in the MONO position and the OUTPUT properly
connected for mono loudspeaker operation or dis-
tortion and loss of power may result.
INPUT—STEREO OR TWIN AMPLIFIERS
Speakers are connected at the barrier strips
marked OUTPUT on the sloped panel of the amplifier.
Use lamp cord, bell wire, or wire with similar type
of insulation to connect the speakers to the amplifier.
For the normally short distances of under 50 feet between the amplifier and speaker, #18 wire or larger
can be used. For distances over 50 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 OUTPUT barrier strip. Connect the other
lead from the left loudspeaker to the screw marked
with the number corresponding to the speaker impedance on the LEFT OUTPUT barrier strip. Connect one
of the leads from the right loudspeaker to the screw
marked COM on the RIGHT OUTPUT barrier strip.
Connect the other lead from the right loudspeaker
to the screw marked with the number corresponding
to the speaker impedance on the RIGHT OUTPUT
barrier strip.
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 loudspeaker. Close impedance
matching is desirable for maximum distortion-free
power.
SPEAKER CONNECTIONS
Use this table to determine proper speaker connection:
If the speaker impedance
is between:
3.2 to 6.5 ohms
6.5 to 13 ohms
13 to 26 ohms
STEREO OUTPUT—CONNECTING TO
BARRIER STRIPS
Use this table for stereo connections using the
barrier strips:
Connect one left
speaker to
screw
If the speaker
impedance is:
4 ohms
8 ohms
16 ohms
LEFT-COM and
other to:
LEFT-4
LEFT-8
LEFT-16
Connect the
speaker leads
between COM and:
4 ohms
8 ohms
16 ohms
Connect one
right speaker
lead to the
screw marked
RIGHT-COM and
the other to:
RIGHT-4
RIGHT-8
RIGHT-16
For stereo or twin channel operation it is not necessary to use the same impedance loudspeaker on
each output. Simply connect each channel for the
impedance desired.
For 25 volt line operation connect one of the left
leads to the screw marked COM on the LEFT OUTPUT barrier strip. The other left lead is connected
to the screw marked 16 on the LEFT OUTPUT barrier
2
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