Mcintosh MC255 User Manual

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

MC255

Power Amplifier

Owner’s Manual

Important Safety Information is supplied in a separate document “Important Additional Operation Information Guide”

Thank You

Your decision to own this McIntosh MC255 Five
Channel 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: ________________________________

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]

Table of Contents

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

(Separate Sheet) ................... Important Additional

Operation Information Guide

Thank You and Please Take a Moment ....................... 2

Technical Assistance and Customer Service .............. 2

Table of Contents ........................................................ 2

General Information ................................................... 2

Connector and Cable Information ..............................3

Introduction ................................................................. 3

Performance Features .................................................3

Dimensions .................................................................4

Installation ..................................................................5

Rear Panel Connections and Switch ........................... 6

Output Terminals and How to Connect ................... 7-8

Connection Diagram (Separate Sheets) ........Mc1A-2A

Front Panel Displays and Controls ............................ 10

How to Operate ......................................................... 11

Technical Description .......................................... 12-15

Photos ................................................................... 16 -17

Specifications ............................................................ 18

Packing Instruction ................................................... 19

General Information

1. For additional connection information, refer to the
owner’s manual(s) for any component(s) connected
to the MC255.

2. The MC255 mutes the speaker output for approxi­mately two seconds when first turned on.

3. For the best performance and safety it is important
to always match the impedance of the Loudspeaker
to the Power Amplifier connections. Refer to “How
to Connect” pages 7 and 8.

Note: The impedance of a Loudspeaker actually var-

ies as the Loudspeaker reproduces different
frequencies. As a result, the nominal impedance
rating of the Loudspeaker (usually measured at
a midrange frequency) might not always agree
with the impedance of the Loudspeaker at low
frequencies where the greatest amount of power
is required. Contact the Loudspeaker Manufac­turer for additional information about the actual
impedance of the Loudspeaker before connecting

it to the McIntosh MC255.

4. In the event the MC255 over heats, due to improper
ventilation and/or high ambient temperature, the
protection circuits will activate. The Front Panel
Power Guard LED will continuously indicate ON
and the audio will be muted. When the MC255 has
returned to a safe operating temperature, normal
operation will resume.

5. When discarding the unit, comply with local rules
or regulations. Batteries should never be
thrown away or incinerated but disposed
of in accordance with the local regulations
concerning battery disposal.

6. For additional information on the MC255 and
other McIntosh Products please visit the McIntosh
Website at www.mcintoshlabs.com.

Copyright 2019 © by McIntosh Laboratory, Inc.

2

Cable Information, Introduction and Performance Features

Connector and Cable Information

XLR Connectors

Below is the Pin configuration for the XLR Balanced
Input, Input/Output Connectors on the MC255. Refer
to the diagram for connection:

IN

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

PIN 2 PIN 1

PIN 3

Power Control Connector

The MC255 Power Control Input receives an On/Off
signal from +5 to +12 volts. The Power Control Output
will in turn provide a +12 volt
Output Signal with a total cur­rent up to 50mA. An additional
connection is for controlling
the illumination of the MC255

Trigger
Control

Meter
Illumination
Control

Ground

Power Output Meters. The 1/8
inch stereo mini phone plug connects to a McIntosh
Preamplifier or A/V Control Center Power Control
Output.

Output Terminal Connector

When cables with spade lugs are used
for Loudspeaker Connection, the spade
lugs need an opening of at least 3/10 inch
(7. 6m m).

3/10 of an inch
(7.6millimeters)

Introduction

Now you can take advantage of traditional McIntosh
standards of excellence in the MC255 Power Ampli­fier. This Five Channel Power Amplifier with high
current output will drive any pair of high quality
Loudspeakers. The MC255 reproduction is sonically
transparent and absolutely accurate. The McIntosh
Sound is “The Sound of the Music Itself.”

Performance Features

• Power Output

The MC255 is a Five Channel Home Theater Power
Amplifier with a capability of 250 watts from the
Front Three Channels (Left, Center and Right) and
200 watts from the Surround Channels (Left and
Right) into 4 or 8 ohm speakers with less than 0.005%
distortion. The Power Amplifier Circuitry uses Ther­malTrak
cool operation.

• Balanced and Unbalanced Inputs

Balanced connections guard against induced noise and
allow long cable runs without compromising sound
qual it y.

• 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.

• Zone B Operation

The Zone B on the MC255 provides Two Channel
Music Playback in a second room with 200 watts
per channel, while at the same time Zone A provides
Three Channel Home Theater Playback.

• Sentry Monitor and Thermal Protection

McIntosh Sentry Monitor power output stage protec­tion circuits ensure the MC255 will have a long and
trouble free operating life. Built-in Thermal Protection
Circuits guard against overheating.

1

ThermalTrak™ and ON Semiconductor are trademarks of Semi-

1

Output Transistors for lower distortion and

conductor Components Industries, LLC

• Special Power Supply

A very large Power Transformer and Large Capaci­tors ensure stable noise free operation even though the
power line varies.

• Illuminated Power Meters

The Illuminated Power Output Watt Meters on the
MC255 are peak responding, and indicate the true
power output of the amplifier. The Front Panel Meter
Illumination may be switched Off at any time.

• McIntosh Custom Binding Posts

McIntosh patent pending gold plated output terminals
deliver high current output. They accept large diam­eter wire and spade lugs. Banana plugs may also be
used only in the United States and Canada.

• Glass Front Panel and Super Mirror Chassis
Finish

The famous McIntosh Illuminated Glass Front Panel
uses long life Light Emitting Diodes (LEDs) and
the Stainless Steel Chassis with Super Mirror Fin­ish ensures the pristine beauty of the MC255 will be
retained for many years.

3

Dimensions

Front View of the MC255

Rear View of the MC255

Side View of the MC255

17-

1/2

"

44.5cm

8-

7/8

"

22.5cm

9-

7/16

"

24.0cm

11-

3/4

"

29.9cm

16

-13/16

"

43.0cm

18-

1/4"

46.4cm

3/16

"

0.5cm

16-

5/8

"

42.2cm

13/16

"

2.1cm

12"

30.5cm

8-

5/16

"

21.1cm

2"

5.1cm

3"

7.62cm

5/8

"

1.6cm

The following dimensions can assist in determining
the best location for your MC255.

Dimensions

4

Installation

Installation

The MC255 can be placed upright on a table or
shelf, standing on its four feet. It also can be custom
installed in a piece of furniture or cabinet of your
choice. The four feet may be removed from the bottom
of the MC255 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
MC255 is removed from the custom installation and
used free standing. The required panel cutout, ventila­tion cutout and unit dimensions are shown.
Always provide adequate ventilation for your MC255.
Cool operation ensures the longest possible operating
life for any electronic instrument. Do not install the
MC255 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 (15.24cm) above the top, 2
inches (5.08cm) below the bottom, 3 inches (7.62cm)
behind the rear panel and 2 inches (5.08cm) on each
side of the Power Amplifier, so that airflow is not
obstructed. Allow 7/8 inch (2.22cm) in front of the
mounting

ventilation hole in the mounting shelf according to
the dimensions in the drawing.

1

When the MC255 is installed together with other McIn-

tosh Components, check clearances on all components
before proceeding.

1

panel for clearance. Be sure to cut out a

MC255 Front Panel
Custom Cabinet Cutout

Cabinet
Front
Panel

Opening
for Ventilation

MC255 Side View
in Custom Cabinet

MC255 Bottom View
in Custom Cabinet

Note: Center the cutout Horizontally
on the unit. For purposes of
clarity, the above illustration
is not drawn to scale.

Cabinet Front Panel

Support
Shelf

17"

43.18cm

Opening for Ventilation

Cutout Opening for Custom Mounting

6"

15.24cm

Cutout Opening for Ventilation

3"

7.62cm

10-1/2"

26.7cm

16"

40.64cm

Cutout Opening
for Ventilation

14-11/16"

37.30cm

Chassis
Spacers

5

Rear Panel Connections and Switch

OUPUTS 2 Connec­tions (ZONE B) for Left
Surround Channel and
for an 8 ohm or 4 ohm
Loudspeaker

OUPUTS 4 Connec­tions (ZON E B) for
Right Channel Sur­round for an 8 ohm or
4 ohm Loudspeaker

Fuse holder, refer to
the nomenclature next
to the fuse holder to
determine the correct
fuse size and rating

Connect the MC255
power cord to a live
AC outlet. Refer to
information on the
back panel of your
MC255 to determine
the correct voltage
for your unit

OUPUTS 5 Connec­tions for Right Front
Channel and for an 8
ohm or 4 ohm Loud­speaker

POWER CONTROL IN ZA (Zone
A) receives a turn On/Off signal
from a McIntosh component for all
five channels

POWER CONTROL OUT
ZA (Zone A) sends a turn
On/Off signal to the next
McIntosh Component

OUPUTS 1 Connec­tions for Left Front
Channel and for an 8
ohm or 4 ohm Loud­speaker

OUPUTS 3 Con­nections for Center
Channel and for
an 8 ohm or 4 ohm
Loudspeaker

Sets the impedance
of the Connected
Loudspeakers

6

The Power
Auto Off
Feature is
either ENable
or DISable

POWER CONTROL IN ZB (Zone B) re­ceives a turn On/Off signal from a McIntosh
component for the LS and RS two channels

POWER CONTROL
OUT ZB (Zone B)
sends a turn On/Off
signal to the next Mc­Intosh Component

INPUT 5 Balanced
Connection for the
Right Front Chan­nel

INPUT 5 Unbalanced
Connection for the
Right Front Channel

INPUTS 2 & 4
Unbalanced Con­nection for the Left
and Right Surround
Channels

INPUT 4 Balanced Con­nection for the Right Sur­round Channel

INPUT 3
Balanced
Connection
for the Cen­ter Channel

INPUT 2 Balanced
Connection for the Left
Surround Channel

INPUT 1 Balanced
Connection for the
Left Front Channel

INPUTS 1 & 3 Unbalanced
Connection for the Left Front
and Center Channels