McIntosh MC303 User Manual

Power Amplifier

MC303

Owner’s Manual

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

The lightning ash 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 sufcient
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 im-

portant operating and maintenance

(servicing) instructions in the litera-

ture 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 ampliers) 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 t 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 specied by the

manufacturer.

12. Use only with the cart, stand, tripod, bracket, or

table specied 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 qualied 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 lled 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.

18. Do not expose batteries to excessive heat such as

sunshine, re or the like.

2

Thank You

Table of Contents

Your decision to own this McIntosh MC303 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]

Copyright 2008 © by McIntosh Laboratory, Inc.

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

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

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

Table of Contents ............................................................... 3

General Information .......................................................3-4

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

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

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

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

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

Rear Panel Connections and Switch .................................. 7

How to Connect ..............................................................8-9

Connection Diagrams (Separate Sheet) MC1A and MC1B

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

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

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

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

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

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

General Information

Caution: The MC303 Amplifier weight is 150 pounds (70.3

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

1. The following Connecting Cable is available from the McIn-

tosh 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 MC303.

3. The MC303 mutes the speaker output for approximately two

seconds when first turned on.

4. In the event the MC303 overheats, 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
MC303 has returned to a safe operating temperature, normal
operation will resume.

5. For the best performance it is important to minimize an im-

pedance mismatch. An impedance mismatch can occur when a
Loudspeaker of a given impedance rating is connected to the
MC303 Output Terminals with a different impedance rating.
For example, a Loudspeaker with an impedance rating of 2
Ohms is connected to the MC303 8 Ohm Output Terminals.

The impedance of a Loudspeaker actually varies 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.

3

Connector Information, Introduction and Performance Features

PIN 2

PIN 1

PIN 3

Power
Control

Meter
Illumination
Control

Ground

General Information, con’t

6. 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.

7. For additional information on the MC303 and other
McIntosh Products please vist the McIntosh Web
Site at www.mcintoshlabs.com.

8. When the MC303 is operated in the USA or Canada and the
main fuse, located on the rear panel, is in need of replace­ment use only the following part:

Bussman ABC-15-R or Littlefuse 314-015P

plifier circuitry uses Thermal Trak1 Output Transistors for
lower distortion and cool operation.

• Balanced and Unbalanced Inputs

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

• 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.

Connector and Cable Information

XLR Connectors

Below is the Pin configuration for the XLR Balanced Input
Connectors on the MC303. Refer to the diagram for con­nection:
PIN 1: Shield/Ground
PIN 2: + Output
PIN 3: - Output

Power Control Connector

The MC303’s Power Control Inputs receive On/Off signals
of +5 volts. An additional connection
is for controlling the illumination of
the MC303 Power Output Meters.
The 1/8 inch stereo mini phone plug
connects to a McIntosh A/V Control
Center Power Control Output.

Note: The Power Control Connecting Cable is available from

the McIntosh Parts Department:

Data and Power Control Cable Part No. 170-202

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

Introduction

Now you can take advantage of traditional McIntosh
standards of excellence in the MC303 Power Amplifier.
The 300 watt high current output per channel will drive
any high quality loudspeaker system to its ultimate per­formance. The MC303 reproduction is sonically transpar­ent and absolutely accurate. The McIntosh Sound is “The
Sound of the Music Itself.”

Performance Features

• Power Output

The MC303 is a Power Amplifier with a capability of 300

watts per channel (all channels driven) into 2, 4 or 8 ohm

speakers with less than 0.005% distortion. The Power Am-

4

• Sentry Monitor and Thermal Protection

McIntosh Sentry Monitor power output stage protection
circuits ensure the MC303 will have a long and trouble free
operating life. Built-in Thermal Protection Circuits guard
against overheating.

• 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.

• Special Power Supply

A regulated Power Supply, a very large Power Transformer
and Capacitors ensure stable noise free operation even
though the power line varies.

• Illuminated Power Meter

The Illuminated Power Output Watt Meter on the MC303
is peak responding, and indicates the power output of the
amplifier. The Front Panel Meter Illumination may be
switched Off at any time.

• Fiber Optic Solid State Front Panel Illumination

The even illumination of the Front Panel is accomplished
by the combination of custom designed Fiber Optic Light
Diffusers and extra long life Light Emitting Diodes

(LEDs).

• Glass Front Panel and Super Mirror Chassis Finish

The famous McIntosh Illuminated Glass Front Panel and
the Stainless Steel Chassis with Super Mirror Finish en­sures the pristine beauty of the MC303 will be retained for
many years.

1

ThermalTrak™ and ON Semiconductor are trademarks of Semicon-

ductor Components Industries, LLC

Dimensions

F15AH 125V

17-3/4"

45.09cm

10-7/8"

27.62cm

12-3/8"

31.43cm

18"

45.72cm

19-1/2"

49.50cm

3/16"

0.48cm

10-1/2"

26.70cm

14"

35.60cm

1-9/16"

3.96cm

1-1/2"

3.81cm

12-1/4"

31.11cm

17-3/8"

44.15cm

1-5/8"

4.12cm

Front View of the MC303

Rear View of the MC303

Side View of the MC303

The following dimensions can assist in determining the
best location for your MC303. There is additional informa­tion on the next page pertaining to installing the MC303
into cabinets.

Dimensions

5

Installation

10 -13/16"

27.46cm

17-9/16"

44.62cm

6"

15.24cm

14-1/2"

36.83cm

14"

35.56cm

15-5/16"

38.91cm

21/32"

1.67cm

Cutout Opening
for Ventilation

Cutout Opening for Ventilation

Support
Shelf

Cabinet
Front
Panel

Chassis
Spacers

Cutout Opening for Custom Mounting

Opening
for Ventilation

MC303 Front Panel
Custom Cabinet Cutout

MC303 Side View
in Custom Cabinet

MC303 Bottom View
in Custom Cabinet

1"

2.54cm

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

The MC303 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 MC303 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 MC303 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
MC303. Cool operation
ensures the longest pos­sible operating life for any
electronic instrument. Do
not install the MC303 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 and 1 inch

(2.54cm) on each side of

the Power Amplifier, so
that airf low is not ob­structed. Allow 19-1/2

inches (49.53cm) depth

behind the front panel.

Allow 1-5/8 inch (4.12cm)

in front of the mounting
panel1 for clearance. Be

Installation

sure to cut out a ventilation hole in the mounting shelf ac­cording to the dimensions in the drawing.

1

When the MC303 is installed together with other McIntosh

Components, check clearances on all components before
proceeding.

6