McIntosh MI128 Owner's Manual

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

MI128

Eight Channel

Power Amplier

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 MI128 Eight
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]
Fa x: 607-72 3 -1917

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, Switches and Selection .... 6-7

Output Terminals and How to Connect ................. 8-13

Front Panel Displays and Push-button ...................... 14

How to Operate ......................................................... 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 MI128.

2. The MI128 mutes the speaker output for approxi­mately two seconds when first turned on.

3. Included with the MI128 and located in the
Owner’s Manual Packet are two Side Rack Mount
Brackets and screw fasteners. Below are graphic
images of the MI128 with and without the Side
Rack Mounted Brackets attached. Refer to page 5
for installing the Side Rack Mount Brackets.

MI128 4 Channel Power Amplifier

MI128 8 Channel Power Amplifier with
Side Rack Mount Brackets installed

4. For the best performance and safety it is impor­tant to always attach a single Loudspeaker with
an 8 Ohm or 4 Ohm impedance to the Channel
1 - Channel 8 output terminals. Refer to “How to
Connect” pages 8 thru 11.

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 MI128.

Copyright 2018 © by McIntosh Laboratory, Inc.

2

General Information, Connector and Cable Information, Introduction and Performance Features

5

. In the event the MI128 Channels over heat, due to

improper ventilation or Loudspeaker Impedance,
the protection circuits will activate. The Front
Panel Channel LED will change color and the audio
will be muted. Refer to page 13. When the MI128
has returned to a safe operating temperature, the
Channel(s) normal operation will resume.

6. If it becomes necessary to replace the Loudspeaker
Connection Plugs used on the MI128 Rear Panel,
order part number 31065800 from the McIntosh
Parts Department.

7. For additional information on the MI128 and
other McIntosh Products please visit the McIntosh
Website at www.mcintoshlabs.com.

Connector Information

Power Control Connector

The MI128 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 MI128 Meter
Power Output Indicators. The 3.5mm
stereo mini phone plug connects to a
McIntosh Preamplifier or A/V Control Center Power
Control Output.

Power
Control

Meter
Illumination
Control

Ground

Introduction

Now you can take advantage of traditional McIntosh
standards of excellence in the MI128 Power Amplifier.
The Eight Channel Power Amplifier produces high
power output per channel and will drive quality Loud­speakers to a high level of performance. The MI128
reproduction is sonically transparent and absolutely
accurate. The McIntosh Sound is “The Sound of the
Mu sic Itself.”

Performance Features

• Power Output

The MI128 consists of Eight Power Amplifier Chan­nels, each capable of 120 watts into 8 ohm or 150
watts into 4 ohm Loudspeakers with distortion less
than 0.025%.

• Loudspeaker Guard

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

• Versatile Operation

The MI128 provides power amplification for up to
eight channels in a multi Zone Audio System.

• Unbalanced Inputs

There are eight Unbalanced Analog Audio Inputs for
all eight Power Amplifier Channels.

• Sentry Monitor and Thermal Protection

McIntosh Sentry Monitor power output stage protec­tion circuits ensure the MI128 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 MI128 Power Amplifier from a McIn­tosh A/V Control Center or Preamplifier for a single
or dual Zone System.

• Special Power Supply

A regulated Power Supply ensures stable noise free
operation even though the power line varies.

• LED Solid State Front Panel Illumination

The even Illumination of the Front Panel is accom­plished by extra long life Light Emitting Diodes
(LEDs). The Metal and Glass Front Panel ensures the
pristine beauty of the MI128 will be retained for many
years.

Digital Audio Inputs

The Digital Inputs decode PCM Signals from external
sources. The Optical Inputs process Digital Signals
from 32kHz to 192kHz with 24-Bit resolution.

3

Dimensions

The following dimensions can assist in determining
the best location for your MI128.

Front View of the MI128

1/2"

17-

44.5cm

Dimensions

Front View of the MI128 with Side Mount Brackets

19"

48.3cm

Rear View of the MI128

16-1/2"

41.9cm

3-15/32"

8.8cm

4-5/16"

11.0cm

.25"

.64cm

2.0"

5.0cm

Side View of the MI128

18-1/2"

47.0cm

17-1/16"

43.3cm

13-19/32"

34.7cm

3/16

"

.5cm

1-5/16"

3.4cm

3-1/4"

8.2cm

13-1/4"

33.7cm

4

Installation

The MI128 needs to be placed upright on its four feet.
It also can be custom installed. Remove the four feet
when it is custom installed and retain them with the
fastening screws for possible future use. The required
panel cutout, ventilation cutout and unit dimensions
are shown in the drawing on the right side of this
page.

It is necessary to provide adequate ventilation for
cool operation, ensuring long life for the MI128. Do
not install the MI128 above heat generating compo­nents. When the MI128 is installed in a cabinet with
other components, use a ventilation fan to provide cool
operating temperature.

A custom cabinet installation needs to provide the
following minimum spacing for cool operation:

Allow at least 3 inches (7.6cm) 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 MI128, providing
airf low. Allow 2-1/2 inches (6.35 cm) in front of the
mounting1 panel for clearance. Be sure to cut out a
ventilation hole in the mounting shelf according to
the dimensions in the drawing.

1

When the MI128 is installed together with other

McIntosh Components, check clearances on all
components before proceeding.

Installation of Side Rack Mount Brackets

When desired, to install MI128 Side Rack Mounting
Brackets, follow the steps below for one side at a time:

1. Refer to figure A to remove the two side screws and
save them for possible future use.

2. Position the Side Rack Mounting Bracket as illustrated
in figure B. Then attach the Bracket to the Front and
Side Panel of the MI128, using the screws supplied
with the Bracket.

3. Perform steps 1 and 2 to mount the second Bracket to
the other side of the MI128.

MI128 Front Panel
Custom Cabinet Cutout

MI128 Side View
in Custom Cabinet

MI128 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.

Front Panel

Remove two
Screws from
the Chassis
Sidewall
and save
them

Figure A

Cabinet
Front
Panel

Opening
for Ventilation

Support
Shelf

29/32

2.4cm

3"

7.6cm

Side Panel

Installation

16-7/8"

42.8cm

3-1/4"

8.2cm

3"

7.6cm

"

Cutout Opening for Custom Mounting

Cutout Opening for Ventilation

25/32

"

2.0cm

10-

9/16

"

26.9cm

14-

Cutout Opening
for Ventilation

7/16

36.2cm

11- 19/32"

29.7cm

Side Rack
Mounting
Bracket

"

Front Panel

Supplied
Screws

Chassis
Spacers

Figure B

15"

38.1cm

Side Panel

Supplied
Screws

5