McIntosh MC-250 User Manual

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: [phone]

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