MC312
McIntosh Laboratory, Inc. 2 Chambers Street Binghamton, New York 13903-2699 Phone: 607-723-3512 www.mcintoshlabs.com
MC312
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 MC312 Stereo
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: 607-723-3512
Fax: 607-724-0549
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: 607-723-3515
Fax: 607-723-1917
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 .................................................................5
Installation ..................................................................6
Rear Panel Connections and Switch ........................... 7
Output Terminals and How to Connect .................. 8-9
Output Terminals and How to Connect
for Bi-Amp ......................................................... 10 -11
Front Panel Displays and Controls ............................ 12
How to Operate ......................................................... 13
Technical Description .......................................... 14 -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 MC312.
2. The MC312 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 thru 10.
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 MC312.
4. In the event the MC312 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 MC312 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 MC312 and
other McIntosh Products please visit the McIntosh
Website at www.mcintoshlabs.com.
Copyright 2018 © 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 MC312. Refer
to the diagram for connection:
IN
OUT
PIN 1: Shield/Ground
PIN 2: + Input/Output
PIN 1
PIN 3: - Input/Output
PIN 2 PIN 1
PIN 3
PIN 3
PIN 2
Power Control Connector
The MC312 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 MC312
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 MC312 Power Amplifier. The 300 watts power per channel with high current
output will drive any pair of high quality Loudspeakers. The MC312 reproduction is sonically transparent
and absolutely accurate. The McIntosh Sound is “The
Sound of the Music Itself.”
Performance Features
• Power Output
The MC312 is a Power Amplifier with a capability
of 300 watts per channel into 2, 4 or 8 ohm speakers
with less than 0.005% distortion. The Power Amplifier
Circuitry uses ThermalTrak
lower distortion and cool operation.
• Patented Autoformer
McIntosh designed and manufactured Output Autoformers provide an ideal match between the amplifier
output stages and speaker loads of 2, 4 and 8 ohms.
The Autoformers also provide perfect DC protection
for your valuable loudspeakers.
• Balanced and Unbalanced Inputs
Balanced connections guard against induced noise and
allow long cable runs without compromising sound
qual ity.
• 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.
• Sentry Monitor and Thermal Protection
McIntosh Sentry Monitor power output stage protection circuits ensure the MC312 will have a long and
trouble free operating life. Built-in Thermal Protection
Circuits guard against overheating.
• Special Power Supply
A very large Power Transformer and Large Capacitors ensure stable noise free operation even though the
power line varies.
1
ThermalTrak™ and ON Semiconductor are trademarks of Semi-
conductor Components Industries, LLC
1
Output Transistors for
• Illuminated Power Meters
The Illuminated Power Output Watt Meters on the
MC312 are peak responding, and indicate the true
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.
• 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 MC312 will be
retained for many years.
3
Dimensions
The following dimensions can assist in determining
the best location for your MC312.
Front View of the MC312
17-1/2"
44.5cm
Dimensions
Rear View of the MC312
16-13/16"
43.0cm
DISABLED
8-7/8"
22.5cm
9-7/16"
24.0cm
5/8"
1.6cm
13/16
2.1cm
2-5/8"
6.7cm
Side View of the MC312
20"
50.8cm
16-5/8"
42.2cm
8-1/8"
3/16"
0.5cm
20.6cm
"
13"
33.1cm
2-5/8"
6.7cm
11-3/4"
29.9cm
4
Installation
The MC312 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 MC312 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
MC312 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 MC312.
Cool operation ensures the longest possible operating
life for any electronic instrument. Do not install the
MC312 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 MC312 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
MC312 Front Panel
Custom Cabinet Cutout
Cabinet
Front
Panel
Opening
for Ventilation
MC312 Side View
in Custom Cabinet
MC312 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
12-3/4"
32.38cm
16"
Cutout Opening
for Ventilation
40.64cm
Installation
14-11/16"
37.30cm
Chassis
Spacers
5
Rear Panel Connections and Switch
Balanced OUTputs (LEFT and
RIGHT Channels) for an audio
cable to the next Power Amplifier Input
INPUT MODE switch selects between BALANCED
or UNBALANCED Inputs
Unbalanced INput (RIGHT Channel) for an
audio cable from a Preamplifier or A/V Control Center audio output.
Unbalanced OUTput (RIGHT Channel) for an
audio cable to the next Power Amplifier Input
Balanced INputs (LEFT
and RIGHT Channels) for
audio cables from a Preamplifier or A/V Control
Center audio output
DISABLED
Unbalanced INput (LEFT Channel) for an audio cable from a Preamplifier or A/V Control
Center audio output.
Unbalanced OUTput (LEFT Channel) for an
audio cable to the next Power Amplifier Input
POWER CONTROL IN
receives turn On/Off
signals from a McIntosh
component.
POWER CONTROL OUT
1 and 2 send turn On/Off
signals to the next McIntosh Component
RIGHT OUTPUT Connections
for a 2 ohm, 4 ohm or 8 ohm
Loudspeaker
6
Connect the MC312 power
cord to a live AC outlet. Refer
to the rear panel to determine
the correct voltage
Fuse holder, refer to information
on the rear panel of your MC312
to determine the correct fuse
size and rating
LEFT OUTPUT Connections
for a 2 ohm, 4 ohm or 8 ohm
Loudspeaker
AUTO OFF Mode
Switch selects between ENABLED
or DISABLED
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