Owner’s Manual
MC402 Power Amplifier
MC402
McIntosh Laboratory, Inc. 2 Chambers Street Binghamton, New York 13903-2699 Phone: 607-723-3512 FAX: 607-724-0549
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Thank You
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.
Your decision to own this McIntosh MC402 Power Ampli-
fier ranks you at the very top among discriminating music
listeners. You now have “The Best.” The McIntosh dedica-
tion 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.
18. Do not overload wall outlets, extension cords or inte-
gral convenience receptacles as this can result in a risk
of fire or electric shock.
Please Take A Moment
19. To completely disconnect this equipment from the AC
Mains, disconnect the power supply cord plug from the
AC receptacle.
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:
Care of Equipment:
20. Clean only with a dry cloth.
21. Do not permit objects or liquids of any kind to be
pushed, spilled and/or fall into the equipment through
enclosure openings.
Serial Number:
Purchase Date:
Dealer Name:
22. Unplug the power cord from the AC power outlet
when left unused for a long period of time.
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 addi-
tional help concerning a suspected problem, you can re-
ceive technical assistance for all McIntosh products at:
Repair of Equipment:
23. Refer all servicing to qualified service personnel. Ser-
vicing is required when the equipment has been dam-
aged in any way, such as power-supply cord or plug is
damaged, liquid has been spilled or objects have fallen
into the equipment, the equipment has been exposed to
rain or moisture, does not operate normally, or has
been dropped.
24. Do not attempt to service beyond that described in the
operating instructions. All other service should be re-
ferred to qualified service personnel.
McIntosh Laboratory, Inc.
2 Chambers Street
Binghamton, New York 13903
Phone: 607-723-1545
Fax: 607-723-3636
25. When replacement parts are required, be sure the ser-
vice technician has used replacement parts specified by
McIntosh or have the same characteristics as the origi-
nal part. Unauthorized substitutions may result in fire,
electric shock, or other hazards.
26. Upon completion of any service or repairs to this prod-
uct, ask the service technician to perform safety checks
to determine that the product is in proper operating
condition.
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 as-
sistance 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
Copyright 2002 by McIntosh Laboratory, Inc.
3
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Introduction and Performance Features
Table of Contents
Connector Information
Safety Instructions ............................................................ 2
Thank You and Please Take a Moment............................. 3
Technical Assistance and Customer Service .................... 3
Table of Contents, Important Information and
XLR Connectors
Below is the Pin configuration for the XLR Balanced Input
and Output Connectors on the MC402. Refer to the dia-
gram for connection:
Connector Information ..................................................... 4
Introduction ...................................................................... 4
Performance Features ....................................................... 4
Dimensions ....................................................................... 5
Installation ........................................................................ 6
Top View........................................................................... 8
Rear Panel Connections and Switches ............................. 9
How to Connect for Stereo ............................................. 10
How to Connect for Mono .............................................. 12
Front Panel Displays and Controls ................................. 14
How to Operate............................................................... 15
Technical Description ..................................................... 17
Specifications ................................................................. 18
Packing Instructions ....................................................... 19
PIN 1: Shield/Ground
PIN 2: + Input
PIN 3: - Input
Pin 1
Pin 3
Pin 2
Power Control and Trigger Connectors
The MC402’s Power Control Outputs provide a 5 volt sig-
nal. Use a 1/8 inch stereo mini
phone plug to connect to the
Power Control Input on other
McIntosh Components.
Positive
N/C
Ground
Important Information
Caution: The MC402 Amplifier weight is 110.5 pounds
(50.1 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 MC402.
3. The MC402 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 that the MC402 over heats, due to improper
ventilation and/or high ambient temperature, the protection
circuits will activate. The Front Panel Power Guard LEDs
will continuously indicate ON and the audio will be muted.
When the MC402 has returned to a safe operating
temperature, normal operation will resume.
6. The MC402 incorporates the very latest in Fully Double
Balanced Circuitry. As a result, the Loudspeaker - Negative
Connections are above chassis ground and are not common
between channels. Do not combine any connections together
or ground them, except as illustrated in this manual.
4
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Introduction
Now you can take advantage of traditional McIntosh stan-
dards of excellence in the MC402 Power Amplifier. Two
400 watt high current output channels will drive any high
quality Loudspeaker system to its ultimate performance.
The MC402 reproduction is sonically transparent and abso-
lutely accurate. The McIntosh Sound is “The Sound of the
Music Itself.”
• Balanced and Unbalanced Inputs
Balanced connections guard against induced noise and al-
low long cable runs without compromising sound quality.
• Illuminated Power Meters
The Illuminated Power Output Watt Meters on the MC402
are peak responding, and indicate the true power output of
the amplifier. The Peak Watt Hold Mode allows the meters
to temporarily stay at the highest power output and then
slowly decay. The Front Panel Meter Illumination may be
Performance Features
• Power Output
The MC402 consists of two separate power amplifier chan- switched Off at any time.
nels, each capable of 400 watts into 2, 4 or 8 ohm speakers
with less than 0.005% distortion.
• Fiber Optic Solid State Front Panel Illumination
The Illumination of the Front Panel is accomplished by the
combination of custom designed Fiber Optic Light Diffus-
ers and Light Emitting Diodes (LEDs). This provides even
Front Panel Illumination, together with the extremely long
life LEDs.
• Exclusive Double Balanced Circuity
Each channel of the MC402 consists of two balanced
power amplifiers operating in push-pull with their outputs
combined in a McIntosh Autoformer. This double balanced
configuration from input to output cancels virtually all dis-
tortion.
• 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
MC402 will be retained for many years.
• Patented Autoformers
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 Loud-
speakers.
• Patented Power Guard
Both channels include the patented McIntosh Power Guard
circuit that prevents the amplifier from being over driven
into clipping, with its harsh distorted sound that can also
damage your valuable Loudspeakers.
• Patented Sentry Monitor with Thermal Protection
McIntosh Sentry Monitor power output stage protection
circuits ensure the MC402 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 MC402 Power Amplifier from a McIntosh
Audio/Video Control Center or Preamplifier. If any addi-
tional 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.
5
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Dimensions
Dimensions
The following dimensions can assist in determining the
best location for your MC402. There is additional informa-
tion on the opposite page pertaining to installing the
MC402 into cabinets.
17-1/2"
44.45cm
Front View of the MC402
8-13/16"
22.38cm
9-7/16"
23.97cm
16-13/16"
42.70cm
Rear View of the MC402
12-1/4"
31.12cm
18-3/4"
47.63cm
16-5/16"
41.43cm
8-1/4"
20.96cm
Side View of the MC402
3/16"
0.48cm
7/8"
2.22cm
15/16"
2.38cm
13"
33.02cm
6
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Installation
Installation
bottom and 3 inch (7.62cm) on each side of the amplifier,
so that airflow is not obstructed. Allow 22 inches
(55.88cm) depth behind the front panel. Allow 1 inch
(2.54cm) 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.
The MC402 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 MC402 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
MC402 is removed
from the custom
17-1/16"
43.34cm
installation and
used free standing.
The required panel
cutout, ventilation
cutout and unit di-
mensions are
shown.
Always provide
adequate ventila-
tion for your
MC402 Front Panel
Custom Cabinet Cutout
8-5/16"
21.11cm
MC402. Cool op-
eration ensures the
longest possible
operating life for
any electronic in-
strument. Do not
install the MC402
directly above a
heat generating
6"
15.24cm
Cutout Opening
Cabinet
Front
Panel
for
Custom Mounting
Opening
for Ventilation
component such as
a high powered am-
plifier. If the
MC402 Side View
in Custom Cabinet
MC402 is installed
in a cabinet, a quiet
running ventilation
fan can be a defi-
nite asset in main-
taining the coolest
possible operating
temperature.
Cutout Opening for Ventilation
Chassis
Spacers
Support
Shelf
3-1/4"
8.26cm
A custom cabi-
net installation
12-1/16"
30.64cm
should provide the
following mini-
mum spacing di-
mensions for cool
operation. Allow at
least 6 inches
MC402 Bottom View
in Custom Cabinet
16"
40.64cm
10-3/8"
26.35cm
Cutout
Opening
for
Center the
opening horizontally
with the
Ventilation
MC402 Chassis
(15.24cm) above
the top, 2 inches
(3.81cm) below the
13"
33.02cm
7
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Top View
8
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Rear Panel Connections and Switches
OUTPUT MODE
Switch selects STE-
REO, or MONO
PARALLEL Modes
of operation
POWER CONTROL IN
receives a turn On/Off
Trigger from a McIntosh
component
UNBALANCED INPUTS
for audio cables from a
preamplifier or control
center audio outputs
Main Fuse holder,
BALANCED INPUTS
POWER CONTROL
INPUT MODE
Switch selects be-
tween the BAL-
ANCED or UNBAL-
ANCED INPUTS
refer to information
on the back panel
of the MC402 to
determine the cor-
rect fuse size and
rating
for audio cables from a
preamplifier or control
center audio outputs
OUT sends a turn On/Off
Trigger to the next McIn-
tosh component
RIGHT OUTPUTs
LEFT OUTPUTs
Connections for 2,
4, and 8 ohm
Loudspeakers
Connections for 2,
4, and 8 ohm
Loudspeakers
Connect the MC402
power cord to a live
AC outlet. Refer to
information on the
back panel to deter-
mine the correct volt-
age
9
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How to Connect for Stereo
Caution: The supplied AC Power Cord should not be
connected to the Rear Panel of the MC402
Amplifier until after the Loudspeaker Connections
have been made and the supplied protective
Terminal Connections Cover has been installed.
Failure to observe this could result in Electric
Shock.
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 Banana Plugs are for use in the United States
and Canada only.
1. For Remote Power Control, connect a power control
cable from the Audio Control Center or Preamplifier
Power Control Out to the MC402 Power Control In.
2. Connect cables from the Balanced Outputs of a McIn-
tosh Preamplifier or Control Center to the MC402 Bal-
anced Inputs.
Note: An optional hookup is to use unbalanced cables.
3. Prepare the Loudspeaker Hookup Cables that attach to
the MC402 Power Amplifier by choosing one of the
methods below:
4. Remove the five screws from the MC402 Chassis Rear
Panel and Left Side. Retain these screws for later use.
Refer to figure 7.
5. Insert the Loudspeaker Hookup Cable Ends through
the openings of the supplied Terminal Connections
Cover and connect to the output terminals that match
the Loudspeakers’ Impedance, being careful to observe
the correct polarities. Output impedance connections of
2 ohms, 4 ohms and 8 ohms are provided. If the Loud-
speakers’ Impedance is in-between the available con-
nections, use the nearest lower impedance connection.
WARNING: Loudspeaker terminals are hazardous live
and present a risk of electric shock. For
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.
additional instruction on making
Loudspeaker Connections contact your
McIntosh Dealer or McIntosh Technical
Support.
Spade lug or prepared wire connection:
Insert the spade lug
connector or pre-
6. Attach the Terminal Connections Cover, with the five
previously removed screws, to the Rear Panel of the
MC402 Amplifier. Refer to figure 7.
pared section of the
cable end into the
terminal side access
7. Connect the MC402 power cord to an active AC outlet.
Cover
Terminal
Connections
Cover
Mounting
Screw
Location
Cover
Cover
Mounting
Screw
Locations
Mounting
Screw
Locations
Cable Openings
Figure 7
10
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How to Connect for Stereo
McIntosh Audio Control Center
To AC
Outlet
Right
Loudspeaker
4 ohm
Left
Loudspeaker
4 ohm
11
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How to Connect for Mono Parallel
Caution: The supplied AC Power Cord should not be
connected to the Rear Panel of the MC402
Amplifier until after the Loudspeaker Connections
have been made and the supplied protective
Terminal Connections Cover has been installed.
Failure to observe this could result in Electric
Shock.
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 se-
cure the banana plug in place.
1. For Remote Power Control, connect a power control
cable from the Audio Control Center or Preamplifier
Power Control Out to the MC402 Power Control In.
2. Connect a cable from the Balanced Output of a McIn-
tosh Preamplifier or Control Center to the MC402
R/MONO Balanced Input.
Note: The Banana Plugs are for use in the United States
and Canada only.
4. Remove the five screws from the MC402 Chassis Rear
Panel and Left Side. Retain these screws for later use.
Refer to figure 14.
Note: An optional hookup is to use an unbalanced cable.
3. Prepare three Loudspeaker Hookup Cables, one twelve
inch (30.48 cm) and one thirteen inch (33.02 cm) Jumper
Cables, along with the desired length in a Loudspeaker
Hookup Cable that attaches to the MC402 Power Am-
plifier Output Terminals by choosing one of the meth-
ods below:
5. Connect the prepared twelve inch (30.48 cm) Jumper
Cable between the two - Output terminals and the
thirteen inch (33.02 cm) Jumper Cable between the two
appropriate Impedance + Output Terminal as outlined
in the chart located on the next page.
6. Insert the Loudspeaker Hookup Cable Ends through
the openings of the supplied Terminal Connections
Cover and connect to the output terminals that match
the Loudspeakers’ Impedance, being careful to observe
the correct polarities. Output impedance connections of
1 ohms, 2 ohms and 4 ohms are provided. If the Loud-
speakers’ Impedance is in-between the available con-
nections, use the nearest lower impedance connection.
WARNING: Loudspeaker terminals are hazardous live
and present a risk of electric shock. For
additional instruction on making
Bare wire cable ends:
Carefully remove sufficient insulation from the cable
ends, refer to figures 8, 9
& 10. 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.
Loudspeaker Connections contact your
McIntosh Dealer or McIntosh Technical
Support.
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 fig-
7. Attach the Terminal Connections Cover, with the five
previously removed screws, to the Rear Panel of the
MC402 Amplifier. Refer to figure 7.
8. Connect the MC402
ures 11, 12 &
13.
power cord to an ac-
tive AC outlet.
Cover
Terminal
Connections
Cover
Mounting
Screw
Location
Cover
Cover
Mounting
Screw
Locations
Mounting
Screw
Locations
Cable Openings
Figure 14
12
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How to Connect for Mono Parallel
McIntosh Audio Control Center
Jumper
Cables
To AC
Outlet
Mono Parallel Hookup Connections
Loudspeaker Loudspeaker Negative
Loudspeaker Positive
Connection
Impedance
Connection
Left and Right Output 2
(Negative) Connection
Left and Right Output 2
+ (Positive) Connection
S
S
Loudspeaker
System
4 ohm
1
2
4
(Ohm)
(Ohm)
(Ohm)
S
S
S
-
Left and Right Output 4
(Negative) Connection
Left and Right Output 4
+ (Positive) Connection
S
S
-
Left and Right Output 8
-
Left and Right Output 8
+ (Positive) Connection
S
S
(Negative) Connection
13
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Front Panel Displays and Controls
POWER GUARD LED lights when
the Amplifier Left Channel POWER
GUARD Circuit activates
POWER GUARD LED lights when
the Amplifier Right Channel
POWER GUARD Circuit activates
METER indicates the Left Channel
Power Output of the amplifier
METER indicates the Right Channel
Power Output of the amplifier
Remote On Indicator
lights when the amplifier
is in the Remote Turn-On
Mode
METER Switch selects
the display modes of the
Power Output Meters
POWER Switch Turns
AC Power Off, Remote
or On
14
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How to Operate the MC402
How to Operate the MC402
Mode Switches
Power On
The MONO PARALLEL/STEREO Mode Switch, which is
located above the Right Channel Outputs
on the Rear Panel of the MC402, allows
To have the MC402 automatically turn On or Off when a
McIntosh Control Center turns On or
Off, rotate the power switch to the RE-
MOTE Position. For manual opera-
tion, rotate the power switch to the ON
or OFF Position as desired. Refer to
figure 15.
selection of either MONO PARALLEL or
STEREO Modes of Operation. Refer to
figures 18.
Figure 18
Note: There is additional
information for
Note: There must be a power control
connection between the MC402
connecting the MC402
and pertaining to both
modes of operation:
“How to Connect
Figure 15
and the McIntosh Control Center,
in order for the remote power turn-on to function.
for Stereo” on
pages 10 and 11.
“How to Connect
for Mono
Parallel” on
pages 12 and 13.
Meter Selection
Rotate the meter mode switch to select the meter operation
mode you desire. Refer to figures 16 and 17.
Lights Off - Meter lights are turned off and the meters will
continue to indicate the power output.
Watts- The meters respond to
all the musical infor-
The Input Mode Switch,
which is located below the
UNBALANCED INPUTS
on the Rear Panel of the
MC402, allows selection of either the UNBALANCED or
BALANCED Input Connectors. Refer to figure 19.
mation being pro-
duced by the ampli-
fier. They indicate to
an accuracy of at
least 95% of the
Figure 19
power output with
Figure 16
only a single cycle of
a 2000Hz tone burst.
Hold - The meter pointer is locked to the highest
power peak in a sequence of peaks. It is elec-
tronically held to this power level until a
higher power peak passes through the ampli-
fier. The meter pointer will then rise to the
Figure 17
newer higher indication. If no further power
peaks are reached, the meter pointer will very
slowly return to its rest position or lower
power level.
Note: The MC402 Power Output Meters
indicate the wattage delivered to the
Loudspeakers. When in Mono Parallel,
the actual power output is the sum of both
the Right and Left Meter Indications.
15
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Technical Description
McIntosh Laboratory, the company who introduced the
world’s first amplifier that could be called “High Fidelity”,
has done it again. The McIntosh engineering staff has cre-
ated a power amplifier without compromise, using the most
advanced McIntosh circuit design concepts.
A continuous average power output rating of 400 watts
and with an output current of greater than 100 amperes per
channel, makes this not only the most advanced, but also
one of the most powerful amplifiers McIntosh has ever
manufactured. The distortion limits for the MC402 are no
more than 0.005% at rated power output for all frequencies
from 20Hz to 20,000Hz. Typical performance at mid fre-
quencies is less than 0.002%. The true distortion readings
on the MC402 are so low, it takes special measuring tech-
niques to make accurate readings. The MC402 can deliver
the best possible performance from any type of high qual-
ity Loudspeaker system.
tive feedback. McIntosh engineers know how to properly
design negative feedback circuits so they contribute to the
extremely low distortion performance expected from a
McIntosh amplifier. The typical McIntosh owner would
never accept the approximately 100 times higher distortion
of many non-feedback designs.
Double Balanced Push-Pull design is used from input to
output. Each half of the amplifier contains complimentary
balanced circuitry. The resulting double balanced configu-
ration cancels even order distortion. Refer to figure 20.
All transistors are selected to have nearly constant cur-
rent gain over the entire current range they must cover.
Output transistors in particular, have matched uniform cur-
rent gain, high current bandwidth product and large active
region safe operating area. An automatic tracking bias sys-
tem completely eliminates any trace of crossover distor-
tion. Precision metal film resistors and low dielectric ab-
sorption film capacitors are used in all critical circuit loca-
tions.
The output signals of the balanced circuit are coupled in
the unique McIntosh MC402 Output Autoformer. It pro-
vides low distortion power transfer at frequencies from be-
low 20Hz to well beyond 20,000Hz with optimum imped-
ance points of two ohms, four ohms and eight ohms. The
unequaled expertise of McIntosh in the design and manu-
facturing of autoformers is legendary in the high fidelity
industry.
Creating an amplifier with this level of performance did
not come easily. Many months of design, testing and mea-
suring were required. Extensive controlled listening tests,
the ultimate form of measuring, were made before the final
design was accepted.
Design Philosophy
The design philosophy incorporated in the MC402 in-
volved several different techniques, all based on sound sci-
entific logic. Every stage of voltage or current amplifica-
tion must be as linear as possible prior to the use of nega-
The high efficiency circuit design of the MC402 con-
Block Diagram
of the
Amplifier and Meter Circuitry
Figure 20
16
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Technical Description
tributes to low operating temperatures. More than 2,000
square inches of heat sink area keep the MC402 operating
safely with convection cooling. No fans are needed.
tion. Refer to Figure 22.
The MC402 also includes the unique patented McIntosh
Power Guard circuit. Power Guard eliminates the possibil-
ity of ever overdriving the amplifier into clipping. Figures
23, 24 and 25 are actual Spectrum Analyzer measurements
Autoformers
All solid state power amplifier output circuits work best
into an optimum load. This optimum load may vary consid-
erably from what a Loudspeaker requires. In the case of
more than one Loudspeaker connected in parallel, the load
to the power amplifier may drop to two ohms or even less.
A power amplifier connected to a load that is lower than
optimum, causes more output current to flow, which results
in extra heat being generated in the power output stage.
This increase in temperature will result in a reduced life
expectancy for the amplifier.
of a McIntosh Power Amplifier,
with a test signal consisting of
14kHz and 15kHz sine waves. An
overdriven amplifier can produce
both audible and inaudible distor-
tion levels exceeding 40%. The
audible distortion is unpleasant to
hear, but the inaudible ultrasonic
distortion is also undesirable,
since it can damage valuable
Input Test Signal
Figure 23
The Autoformer creates an ideal match between the
power amplifier output stage and the Loudspeaker. A
McIntosh amplifier with an Autoformer can be used to
safely drive multiple speakers
Loudspeaker system tweeters. You
will never experience the harsh
and damaging distortion due to
clipping.
Without Power Guard
without reducing the life ex-
pectancy of the power ampli-
fier. Refer to Figure 21.
There is absolutely no per-
formance limitation with an
Autoformer. Its frequency re-
sponse exceeds that of the out-
put circuit itself, and extends
well beyond the audible range.
Its distortion level is so low it
is virtually impossible to mea-
sure.
In the rare event of a power amplifier output circuit fail-
ure, the McIntosh Autoformer provides absolute protection
from possible damage to your valuable Loudspeakers. The
unequaled expertise of McIntosh in the design and manu-
facturing of Autoformers is legendary in the high fidelity
industry. McIntosh engineers know how to do it right.
The Power Guard circuit is a
waveform comparator, monitoring
both the input and output wave-
forms. Under normal operating
conditions, there are no differ-
ences between the shape of these
waveforms. If an amplifier chan-
nel is overdriven, there will be a
difference between the two signal
waveforms. When the difference
exceeds 0.3% (equivalent to 0.3%
harmonic distortion), the Power
Guard activates the PG light and a
dynamic electronic attenuator at
the amplifier input reduces the in-
put volume just enough to prevent
any further increase in distortion.
The Power Guard circuit acts so fast that there are abso-
lutely no audible side effects and the sonic purity of the
music reproduction is perfectly preserved. The MC402
Power Amplifier with Power Guard is not limited to just
the rated power output, but will actually produce distortion
free output well above its rated power due to the McIntosh
philosophy of conservative design.
Figure 24
With Power Guard
Figure 21
Figure 25
Protection Circuits
The different types of protection circuits incorporated in
the MC402 insure a long and safe operating life. This is
just one of the many character-
istics of McIntosh Power Am-
plifiers that make them world
famous. The MC402 incorpo-
rates the McIntosh Sentry
Monitor Output Transistor Pro-
tection Circuit, which protects
the amplifier in the event of a
Power Supply Circuits
To compliment the fully balanced design of the MC402,
there are huge main filter capacitors that guarantee an ex-
cellent signal to noise ratio and the energy storage neces-
sary for the wide dynamic range that “Digital Audio” de-
mands.
shorted Loudspeaker Connec-
Figure 22
17
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Specifications
Specifications
Power Output Stereo
Wide Band Damping Factor
Greater than 40
Minimum sine wave continuous average power output per
channel, all channels operating is:
400 watts into 2 ohm load
Power Requirements
400 watts into 4 ohm load
400 watts into 8 ohm load
100 Volts, 50/60Hz at 12 amps
110 Volts, 50/60Hz at 11 amps
120 Volts, 50/60Hz at 10 amps
220 Volts, 50/60Hz at 5 amps
230 Volts, 50/60Hz at 5 amps
240 Volts, 50/60Hz at 5 amps
Power Output Mono Parallel
Minimum sine wave continuous average power output is:
800 watts into 1 ohm load
800 watts into 2 ohm load
800 watts into 4 ohm load
Note: Refer to the rear panel of the MC402 for the correct
voltage.
Output Load Inpedance
2, 4 or 8 ohms (Stereo Mode)
1, 2 or 4 ohms (Mono Mode)
Overall Dimensions
17-1/2 inches (44.45cm) W, 9-7/16 inches (23.97cm) H, 20
inches (50.8cm) D, including clearance for connectors
Rated Power Band
20Hz to 20,000Hz
Weight
110.5 pounds (50.1kg) net, 143.5 pounds (65.1kg) in ship-
ping carton
Total Harmonic Distortion
Maximum Total Harmonic Distortion at any power
level from 250 milliwatts to rated power output is
0.005%
Intermodulation Distortion
Maximum Intermodulation Distortion if instanta-
neous peak output per channel does not exceed
twice the rated output, for any combination of fre-
quencies from 20Hz to 20,000Hz, with all channels
operating is 0.005%
Dynamic Headroom
2.1dB
Frequency Response
+0, -0.25dB from 20Hz to 20,000Hz
+0, -3dB from 10Hz to 100,000Hz
Sensitivity
2.0 Volts Unbalanced Input
4.0 Volts Balanced Input
A-Weighted Signal To Noise Ratio
94dB Unbalanced (120dB below rated output)
98dB Balanced (124dB below rated output)
Input Impedance
10,000 ohms Unbalanced Inputs
20,000 ohms Balanced Inputs
18
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Packing Instructions
Packing Instructions
In the event it is necessary to repack the equipment for
shipment, the equipment must be packed exactly as shown
below. It is very important that the four plastic feet are at-
tached to the bottom of the equipment. Four 1/4 - 20 x 2-1/
2 inch screws and washers must be used to fasten the unit
securely to the bottom pad and shipping skid. This will en-
sure the proper equipment location on the bottom pad. Fail-
ure to do this will result in shipping damage.
Use the original shipping carton and interior parts only
if they are all in good serviceable condition. If a shipping
carton or any of the interior part(s) are needed, please call
or write Customer Service Department of McIntosh Labo-
ratory. Please see the Part List for the correct part numbers.
Quantity Part Number
Description
Shipping carton top
Shipping carton bottom
Foam Pad (top and bottom)
Foam Pad (front and rear)
Foam Pad (sides)
1
1
2
2
2
034052
034051
034054
034186
034187
1
1
1
1
1
4
4
034136
034137
034188
034008
034226
101212
104058
Inner carton top
Inner carton bottom
Foam Pad (inner carton)
Bottom pad
Shipping skid
1/4 - 20x2-1/4 cap screw
Flat washer
19
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McIntosh Laboratory, Inc.
2 Chambers Street
Binghamton, NY 13903
McIntosh Part No. 040838
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