McIntosh MC252 User Manual

Power Amplifier

MC252

Owner’s Manual

McIntosh Laboratory, Inc. 2 Chambers Street Binghamton, New York 13903-2699 Phone: [phone] FAX: [phone]

The lightning flash with arrowhead,
within an equilateral triangle, is intended
to alert the user to the presence of
uninsulated “dangerous voltage” within
the product’s enclosure that may be of
sufficient magnitude to constitute a risk
of electric shock to persons.

The exclamation point within an equi­lateral triangle is intended to alert the
user to the presence of important
operating and maintenance (servic­ing) instructions in the literature ac­companying the appliance.

WARNING - TO REDUCE RISK OF

FIRE OR ELECTRICAL SHOCK, DO

NOT EXPOSE THIS EQUIPMENT TO

RAIN OR MOISTURE.

IMPORTANT SAFETY

INSTRUCTIONS!

PLEASE READ THEM BEFORE

OPERATING THIS EQUIPMENT.

1. Read these instructions.

2. Keep these instructions.

3. Heed all warnings.

4. Follow all instructions.

5. Do not use this apparatus near water.

6. Clean only with a dry cloth.

7. Do not block any ventilation openings. Install in
accordance with the manufacturer’s instructions.

8. Do not install near any heat sources such as
radiators, heat registers, stoves, or other
apparatus (including amplifiers) that produce
heat.

9. Do not defeat the safety purpose of the polarized
or grounding-type plug. A polarized plug has two
blades with one wider than the other. A grounding
type plug has two blades and a third grounding
prong. The wide blade or the third prong are
provided for your safety. If the provided plug
does not fit into your outlet, consult an electrician
for replacement of the obsolete outlet.

10. Protect the power cord from being walked on or
pinched particularly at plugs, convenience
receptacles, and the point where they exit from
the apparatus.

NO USER-SERVICEABLE PARTS

INSIDE. REFER SERVICING TO

QUALIFIED PERSONNEL.

To prevent the risk of electric shock, do not remove cover or

back. No user serviceable parts inside.

11. Only use attachments/accessories specified by the
manufacturer.

12. Use only with the cart, stand, tripod, bracket, or
table specified by the manufacturer,
or sold with the apparatus. When a
cart is used, use caution when moving
the cart/apparatus combination to
avoid injury from tip-over.

13. Unplug this apparatus during lightning storms or
when unused for long periods of time.

14. Refer all servicing to qualified service personnel.
Servicing is required when the apparatus has
been damaged in any way, such as power-supply
cord or plug is damaged, liquid has been spilled
or objects have fallen into the apparatus, the
apparatus has been exposed to rain or moisture,
does not operate normally, or has been dropped.

15. Do not expose this equipment to dripping or
splashing and ensure that no objects filled with
liquids, such as vases, are placed on the
equipment.

16. To completely disconnect this equipment from
the a.c. mains, disconnect the power supply cord
plug from the a.c. receptacle.

17. The mains plug of the power supply cord shall
remain readily operable.

2

Thank You

Your decision to own this McIntosh MC252 Power Ampli­fier ranks you at the very top among discriminating music
listeners. You now have “The Best.” The McIntosh dedica­tion to “Quality,” is assurance that you will receive many
years of musical enjoyment from this unit.

Please take a short time to read the information in this
manual. We want you to be as familiar as possible with all
the features and functions of your new McIntosh.

Please Take A Moment

The serial number, purchase date and McIntosh Dealer
name are important to you for possible insurance claim or
future service. The spaces below have been provided for
you to record that information:

Serial Number:

Purchase Date:

Dealer Name:

Table of Contents

Safety Instructions ............................................................ 2

Thank You and Please Take a Moment............................. 3

Technical Assistance and Customer Service .................... 3

Table of Contents and Important Information .................. 3

Connector Information ..................................................... 4

Introduction ...................................................................... 4

Performance Features ....................................................... 4

Dimensions ....................................................................... 5

Installation ........................................................................ 6

Top Panel Connections and Switch .................................. 7

How to Connect in Stereo................................................. 8

How to Connect in Mono Bridged Mode ....................... 10

How to Connect in Mono Bi-Amp (Parallel) ................. 12

Front Panel Displays and Controls ................................. 14

How to Operate ............................................................... 15

Technical Description ..................................................... 16

Notes ............................................................................... 20

Specifications ................................................................. 22

Packing Instruction ......................................................... 23

Technical Assistance

If at any time you have questions about your McIntosh
product, contact your McIntosh Dealer who is familiar with
your McIntosh equipment and any other brands that may
be part of your system. If you or your Dealer wish addi­tional help concerning a suspected problem, you can re­ceive technical assistance for all McIntosh products at:

McIntosh Laboratory, Inc.
2 Chambers Street
Binghamton, New York 13903
Phone: [phone]
Fax: [phone]

Customer Service

If it is determined that your McIntosh product is in need of
repair, you can return it to your Dealer. You can also return
it to the McIntosh Laboratory Service Department. For as­sistance on factory repair return procedure, contact the
McIntosh Service Department at:

McIntosh Laboratory, Inc.
2 Chambers Street
Binghamton, New York 13903
Phone: [phone]
Fax: [phone]

Important Information

Caution: The MC252 Amplifier weight is 94.5 pounds

(42.87 kilograms). It requires two or more persons
to safely handle when moving the amplifier.

1. The following Connecting Cable is available from the
McIntosh Parts Department:

Power Control Cable Part No. 170-202

Six foot, 2 conductor shielded, with two 1/8 inch stereo
mini phone plugs.

2. For additional connection information, refer to the owner’s
manual(s) for any component(s) connected to the MC252.

3. The MC252 mutes the speaker outputs for approximately two
seconds when first turned on.

4. It is very important that loudspeaker cables of adequate size
be used, so that there will be no power loss. The size is
specified in Gauge Numbers or AWG, (American Wire Gauge).
The smaller the Gauge number, the larger the wire size:

If your loudspeaker cables are 50 feet (38.1m) or less,
use at least 14 Gauge.
If your loudspeaker cables are 100 feet (76.2m) or less,
use at least 12 Gauge.

5. In the event the MC252 over heats, due to improper
ventilation and/or high ambient temperature, the protection
circuits will activate. The Power Guard LED will stay ON and
the audio will be muted. When the MC252 has returned to a
safe operating temperature, normal operation will resume.

Copyright 2003  by McIntosh Laboratory, Inc.

3

Connector Information

XLR Connectors

Below is the Pin configuration for the XLR Balanced Input
Connectors on the MC252. Refer to the diagram for con­nection:

PIN 1: Shield/Ground
PIN 2: + Input
PIN 3: - Input

Power Control and Trigger Connectors

The MC252’s Power Control Outputs provide a 5 volt sig­nal. Use a 1/8 inch stereo mini
phone plug to connect to the
Power Control Input on other
McIntosh Components.

Pin 2

Positive

Pin 1

Pin 3

N/C

Ground

Introduction

Now you can take advantage of traditional McIntosh stan­dards of excellence in the MC252 Power Amplifier. The
250 watt high current outputs will drive any high quality
Loudspeaker System to its ultimate performance. The
MC252 reproduction is sonically transparent and abso­lutely accurate. The McIntosh Sound is “The Sound of the
Music Itself.”

Performance Features

• Power Output

The MC252 consists of two separate power amplifier chan­nels, each capable of 250 watts into 2, 4 or 8 ohm speakers
with less than 0.005% distortion. The two channels can be
combined into a single channel with 500 watts into 1, 2, 4,
8 or 16 ohm speakers with less than 0.005% distortion.

••

• Balanced and Unbalanced Inputs

••

Balanced connections guard against induced noise and al­low long cable runs without compromising sound quality.

••

Patented Sentry Monitor with Thermal Protection

•

••

McIntosh Sentry Monitor power output stage protection
circuits ensure the MC252 will have a long and trouble free
operating life. Built-in Thermal Protection Circuits guard
against overheating.

••

•

Power Control

••

The McIntosh Power Control Circuit allows for remote
turn-on of the MC252 Power Amplifier from a McIntosh
Audio/Video Control Center or Preamplifier. If any addi­tional McIntosh Power Amplifiers are part of the system, a
delayed Power Control Output Trigger is available. This
delayed Trigger reduces the strain on the house’s electrical
wiring and protection devices.

••

• Illuminated Power Meters

••

The Illuminated Power Output Watt Meters on the MC252
are peak responding, and indicate the power output of the
amplifier. The Peak Watt Hold Mode allows the meter to
temporarily stay at the highest power output and then
slowly decay. The Front Panel Meter Illumination may be
switched Off at any time.

••

• Fiber Optic Solid State Front Panel Illumination

••

The Illumination of the Front Panel is accomplished by the
combination of custom designed Fiber Optic Light Diffus­ers and Light Emitting Diodes (LEDs). This provides even
Front Panel Illumination, together with the extra long life
LEDs.

••

• Patented Autoformers

••

The McIntosh designed and manufactured Output
Autoformers provide an ideal match between the amplifier
output stage and speaker loads of 2, 4 and 8 ohms. The
Autoformers also provide perfect DC protection for your
valuable Loudspeakers.

••

• Patented Power Guard

••

The patented McIntosh Power Guard Circuit prevents the
amplifier from being over driven into clipping, with its
harsh distorted sound that can also damage your valuable
Loudspeakers.

4

••

• Glass Front Panel and Super Mirror Chassis Finish

••

The famous McIntosh Illuminated Glass Front Panel with a
three dimensional look and the Stainless Steel Chassis with
Super Mirror Finish ensures the pristine beauty of the
MC252 will be retained for many years.

Connector Information, Introduction, Performance Features and Dimensions

The following dimensions can assist in determining the
best location for your MC252. There is additional informa­tion on the next page pertaining to installing the MC252
into cabinets.

Front View of the MC252

17-

1/2

44.45cm

16-

13/16

42.70cm

"

8-

13/16

"

7/16

22.38cm

9-

23.97cm

"

"

Rear View of the MC252

Side View of the MC252

13-

1/4

33.66cm

14-

36.83cm

"

1/2

"

13-

5/8

34.61cm

"

8-

1/8

"

20.64cm

8-

3/16

21.11cm

"

7/8"

2.22cm

9-

1/2

"

24.13cm

1-

1/16

2.70cm

"

5

Installation

Caution: The MC252 Amplifier weight is 94.5 pounds

(42.87 kilograms). It requires two or more persons
to safely handle when moving the amplifier.

The MC252 can be placed upright on a table or shelf,
standing on its four feet. The
four feet may be removed
from the bottom of the
MC252 when it is custom
installed as outlined below.
The four feet together with
the mounting screws should
be retained for possible fu­ture use if the MC252 is re­moved from the custom in­stallation and used free
standing. It also can be cus­tom installed in a piece of
furniture or cabinet of your
choice. The required panel
cutout, ventilation cutout
and unit dimensions are
shown.

Always provide adequate
ventilation for your MC252.
Cool operation ensures the
longest possible operating
life for any electronic instru­ment. Do not install the
MC252 directly above a heat
generating component such
as a high powered amplifier.
If all the components are in­stalled in a single cabinet, a
quiet running ventilation fan
can be a definite asset in
maintaining all the system
components at the coolest
possible operating tempera­ture.

A custom cabinet instal­lation should provide the fol­lowing minimum spacing
dimensions for cool opera­tion. Allow at least 6 inches
(15.24 cm) above the top, 2
inches (3.81cm) below the
bottom and 1 inch (2.54 cm)
on each side of the amplifier,
so that airflow is not ob­structed. Allow 16 inches

MC252 Front Panel
Custom Cabinet Cutout

Opening
for Ventilation

MC252 Side View
in Custom Cabinet

MC252 Bottom View
in Custom Cabinet

Cabinet
Front
Panel

Support
Shelf

Installation

(40.64 cm) depth behind the front panel. Allow 1-3/16
inches (3.02 cm) in front of the mounting panel for knob
clearance. Be sure to cut out a ventilation hole in the
mounting shelf according to the dimensions in the drawing.

17-

1/16

"

43.34cm

8-

5

/16

"

21.11cm

Cutout Opening
for Custom Mounting

6"

15.24cm

Cutout Opening for Ventilation

1

-1/4

"

3.18cm

11-

1/2

"

29.21cm

Cutout Opening
for Ventilation

Alternate Rear Foot Location

14-

3/8

"

36.51cm

6

Top Panel Connections and Switch

Main Fuse holder,
refer to information
on the top back
panel of the MC252
to determine the cor­rect fuse size and
rating

POWER CONTROL IN receives
a turn On/Off Trigger from a
McIntosh component. POWER
CONTROL OUT sends a turn On/
Off Trigger to the next McIntosh
component

UNBALANCED IN­PUTS for an audio cable
from a preamplifier or
control center audio out­puts

RIGHT Channel OUTPUTs
connections for 2 ohm, 4 ohm
and 8 ohm Loudspeakers

Connect the MC252
power cord to a live
AC outlet. Refer to
information on the
back panel to deter­mine the correct
voltage

MODE switch selects
between three modes of
operation; STEREO,
MONO (BRIDGED) or
MONO (BI-AMP)
Parallel

LEFT Channel OUTPUTs
connections for 2 ohm, 4 ohm
and 8 ohm Loudspeakers

BALANCED INPUTS for
an audio cable from a
preamplifier or control
center audio outputs

7

How to Connect in Stereo

Caution: The supplied AC Power Cord should not be

connected to the Rear Panel of the MC252
Amplifier until after the Loudspeaker Connections
have been made and the supplied protective
Terminal Connection Covers have been installed.
Failure to observe this could result in Electric
Shock.

1. For Remote Power Control, connect a power control
cable from the Control Center or Preamplifier Power
Control Out to the MC252 Power Control In.

2. Connect cables from the Unbalanced Output of a McIn­tosh Preamplifier or Control Center to the MC252
Unbalanced Inputs.

Note: An optional hookup is to use balanced cables.

3. Prepare the Loudspeaker Hookup Cables that attach to
the MC252 Power Amplifier by choosing one of the
methods below:

Bare wire cable ends:
Carefully remove sufficient insulation from the cable
ends, refer to figures 1,
2 & 3. If the cable is
stranded, carefully twist
the strands together as
tightly as possible.

Note: If desired, the twisted ends can be tinned with

solder to keep the strands together, or attach spade
lug and/or banana connector.

Spade lug or prepared wire connection:
Insert the spade lug connector or prepared section of
the cable end into the terminal side access hole, and
tighten the terminal cap until the cable is firmly
clamped into the terminal so the wires cannot slip out.
Refer to figures 4, 5 & 6.

Banana plug connection:
Insert the banana plug into the hole at the top of the
terminal. Tighten the top portion of the terminal post
and the set screw to secure the banana plug in place.

Note: The use

of
Banana
Plugs is
for use in
the
United
States
and Canada only.

4. Connect the Loudspeaker hookup cables to the output
terminals that match the impedance of the Loudspeak­er, being careful to observe the correct polarities. Out­put impedance connections of 2S (ohm), 4S (ohm) and
8S (ohm) are provided. If the Loudspeaker’s imped­ance is in-between the available connections, use the
nearest lower impedance connection.

WARNING: Loudspeaker terminals are hazardous live

and present a risk of electric shock. For
additional instruction on making
Loudspeaker Connections contact your
McIntosh Dealer or McIntosh Technical
Support.

5. Attach the supplied Terminal Connection Covers with
the four Mounting Screws (6-32 x 1/4 inch Phillips
Head) to the Rear Panel of the MC252 Amplifier. Refer
to figure 9.

Note: The illustration in figure 9 is for the purpose of

installing the Terminal Connection Covers, showing
the opening on the covers for the Loudspeaker
Cables to exit the MC252. It is not intended to show
which terminal connections to use.

6. Connect the MC252 power cord to an active AC outlet.

Terminal Connection Covers

Cable Openings

Cover Mounting
Screw Locations

Figure 9

8

Cover Mounting
Screw Location