Mcintosh MC611 User Manual

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

MC611

Quad Balanced

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 MC611 Quad
Balanced 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 .................................................................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 MC611.

2. The MC611 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 MC611.

4. In the event the MC611 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 MC611 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 MC611 and
other McIntosh Products please visit the McIntosh
Website at www.mcintoshlabs.com.

Copyright 2017 © 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 MC611. 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 MC611 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 MC611

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. 6 m m).

3/10 of an inch
(7.6millimeters)

Introduction

Now you can take advantage of traditional McIntosh
standards of excellence in the MC611 Quad Balanced
Power Amplifier. The 600 watts high current output
will drive any high quality Loudspeaker. The MC611
reproduction is sonically transparent and absolutely
accurate. The McIntosh Sound is “The Sound of the
Mu sic Itself ”.

Performance Features

• Power Output

The MC611 is a Power Amplifier with a capability of
600 watts into 2, 4 or 8 ohm speakers with less than

0.005% distortion. The Power Amplifier Circuitry
uses Thermal Trak
tortion and cool operation.

• Quad Balanced Circuitry

The MC611 is fully balanced from input to output. It
consists of two matched power amplifiers operating
in push-pull with their outputs combined in a McIn­tosh Autoformer. The Quad Balanced configuration
cancels virtually all distortion.

• 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
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 loudspeaker.

• Sentry Monitor and Thermal Protection

McIntosh Sentry Monitor power output stage protec­tion circuits ensure the MC611 will have a long and

1

ThermalTrak™ and ON Semiconductor are trademarks of Semi-

conductor Components Industries, LLC

1

Output Transistors for lower dis-

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.

• Illuminated Power Meter

The Illuminated Power Output Watt Meter on the
MC611 is peak responding, and indicates 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.

• Fiber Optic Solid State Front Panel Illumination

The even Illumination of the Front Panel is accom­plished by extra long life Light Emitting Diodes
(LED s).

• 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 MC611 will be
retained for many years.

3

Dimensions

The following dimensions can assist in determining
the best location for your MC611.

Front View of the MC611

17-1/2"

44.45cm

Dimensions

Rear View of the MC611

16-13/16"

42.70cm

8-7/8"

22.54cm

9-7/16"

23.97cm

2-1/4"

5.71cm

Side View of the MC611

20-3/16"

51.27cm

17-15/16"

45.55cm

13"

33.02cm

3/16"

0.48cm

8-3/8"

21.27cm

2-3/16"

5.55cm

11-3/4"

29.85cm

4

Installation

is not drawn to scale.

Installation

The MC611 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 MC611 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
MC611 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 MC611.
Cool operation ensures the longest possible operating
life for any electronic instrument. Do not install the
MC611 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 2-1/2 inches (6.35 cm) in front of
the mounting

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

1

When the MC611 is installed together with other McIn-

tosh Components, check clearances on all components
before proceeding.

1

panel for clearance. Be sure to cut out

MC611 Front Panel
Custom Cabinet Cutout

Cabinet
Front
Panel

Opening
for Ventilation

MC611 Side View
in Custom Cabinet

MC611 Bottom View
in Custom Cabinet

Note: Center the cutout Horizontally
on the unit. For purposes of
clarity, the above illustration

Cabinet Front Panel

Support
Shelf

17"

43.18cm

Opening for Ventilation

Cutout Opening for Custom Mounting

6"

15.24cm

Cutout Opening for Ventilation

2-1/2"

6.35cm

12-3/4"

32.38cm

16"

Cutout Opening
for Ventilation

40.64cm

14-11/16"

37.30cm

Chassis
Spacers

5

Rear Panel Connections and Switch

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

Fuse holder, refer to infor­mation on the rear panel of
your MC611 to determine
the correct fuse size and
rating

BALanced OUTput for
an audio cable to the next
Power Amplifier Input

UNBALanced INput for an au­dio cable from a Preamplifier or
A/V Processor audio output

INPUT MODE switch selects between
UNBALanced or BALanced Input

BALanced INput for audio
cables from a Preamplifier or
A/V Processor audio output

AUTO OFF Mode
Switch selects
between ENAbled
or DISabled

UNBALanced OUTput
for an audio cable to the
next Power Amplifier
Input

OUTPUT Connections for
a 2 ohm Loudspeaker

Connect the MC611 power
cord to a live AC outlet. Refer
to the rear panel to determine
the correct voltage

Caution: The Loudspeaker Negative Connections are above chassis ground. Do not combine any connections together, ground them or connect with another MC611.

6

OUTPUT Connections for
a 4 ohm Loudspeaker

OUTPUT Connections for
an 8 ohm Loudspeaker

Output Terminals

When connecting the Loudspeaker Hookup Cables to
the MC611 Power Amplifier Output Terminals please
follow the steps below:

1. Rotate the top of the Output Terminal Post coun­terclockwise until an opening

appears. Refer to gures A and

B.

2. Insert the Loudspeaker hookup
cable into the Output Terminal
Post opening or the cable spade
lug around the center post of

Figu re A

Opening

Figu re B

the Output Terminal. Refer to

gure C.

3. Rotate the top of the Output
Terminal Post clockwise until it

is nger tight. Refer to gure D.

4. Place the supplied McIntosh
Wrench over the top of the Out-

Figu re C Figu re D

put Terminal and rotate it one
quarter of a turn (90° ) to secure
the Loudspeaker Cable Connec­tion. Do not over tighten. Refer

to gure E.

Figu re E

How to Connect

1. For Remote Power Control, connect a power control
cable from the Audio Preamplifier or A/V Control
Center Power Control Output 1 to the Amplifier
POWER CONTROL IN.

2. Connect XLR cables from the Balanced Output 1
Right Channel, (refer to note 2 below) of an Audio
Preamplifier or A/V Processor to the Amplifier
BALanced INput. Place the INPUT MODE Switch
in the BALANCED Position.

Notes: 1. An optional hookup is to use an unbal-

anced cable and place the INPUT MODE
Switch in the UNBALanced Position.

2. When multiple MC611s are used in a Ste­reo or Multichannel System, match up the
Preamplifier or A/V Processor Channel
Output designation to each MC611 with
Loudspeaker and the Loudspeaker loca­tion in the room.

3. Using a suitable tool remove the two screws from
the MC611 Rear Panel and temporarily place them
in a safe place. Refer to figure 1.

Remove Screws

When connecting Loudspeakers to the MC611 it
is very important to use cables of adequate size, so
there is little to no power loss in the cables. The size is
specified in Gauge Numbers or AWG (American Wire
Gauge). The smaller the Gauge number, the larger the
wire size:

Loudspeaker Cable Distance vs Wire Gauge Guide

Loudspeaker

Impedance

2 Ohms

4 Ohms

8 Ohms

25 feet

(7.62 meters)

or less

12AWG 10AWG 8AWG

14AWG 12AWG 10AWG

16AWG 14AWG 12AWG

50 feet

(15.24 m eters)

or less

100 fe et

(30. 48 meters)

or less

4. Prepare the Loudspeaker Hookup Cable for attach­ment to the MC611 Power Amplifier:

Bare wire cable ends:
Carefully remove sufficient insulation from the
cable ends, refer to figures 2, 3 & 4. If the cable
is stranded, carefully twist the strands together
as tightly as possible.

Figure 2

Figure 3 Figure 4

Caution: Do not connect the AC Power Cord to the

MC611 Rear Panel until after the Loudspeaker
Connections are made and the protective Termi­nal Connections Cover is installed. Failure to
observe this could result in Electric Shock.

The connection instructions below, together with the
MC611 Connection Diagram located on the separate
folded sheet “Mc1A”, is an example of a typical audio
system. Your system may vary from this, however the
actual components would be connected in a similar
manner. For additional information refer to “Connec­tor and Cable Information” on page 3.

Figu re 1

This McIntosh MC611 Quad Balanced Power Ampli­fier is designed for Loudspeakers with an impedance
of 2 ohms, 4 ohms or 8 ohms. Connect a single Loud­speaker only to the Output Terminals.

Notes: 1. If desired, the twisted ends can be tinned

with solder to keep the strands together.

2. The prepared bare wire cable ends may be
inserted into spade lug connectors.

3. Banana plugs are for use in the United
States and Canada only.

Banana Plugs are for use in the United States and
Canada only:

5. Locate the Terminal Connections Cover from the
inside of the MC611 shipping carton. Insert the
just prepared Loudspeaker hookup cables thru the

7

Output Terminals and How to Connect

Figure H

cover opening on the left side. Refer to figure 5.

Cover

Cover Opening

Cover Screws

Figure 5 (Inside USA and Canada)

6. Attach the previously prepared bare wire cable ends
into the banana plugs and secure the
connections. Refer to figure F.

7. Rotate the top of the Output Terminal

Post clockwise until it is nger tight.

Figure F

Refer to gure G. Then using the Mc­Intosh Wrench, rotate the top of the
Output Terminal one quarter of a turn
(90° ). Do not over tighten. Refer to

gure E.

8. Referring to figure H, connect the

Figu re G

Loudspeaker hookup
cables with banana plugs
into the hole at the top of
the MC611 Negative and
Positive Output Terminals.

Figure H

The terminals are indenti­fied as 2Ω (ohms), 4Ω (ohms) or 8Ω (ohms) connec­tion to match the impedance of the Loudspeaker,
being careful to observe the correct polarities.

Note: The illustration in figure 5 is connections for

8Ω (ohms) Loudspeakers.

If the Loudspeaker’s impedance is in-between the
available connections, use the nearest lower imped-

ance connection. Refer to “General Information” Note
3 on page 2 for additional information.

WARNING: Loudspeaker terminals are hazardous

live and present a risk of electric shock.
For additional instruction on making
Loudspeaker Connections contact your
McIntosh Dealer or McIntosh Techni­cal Support.

9. Attach the Terminal Connections Cover to the
MC611 Rear Panel with the previously removed
Screws. Refer to figure 5.

10. Connect the MC611 power cord to an active AC
outlet.

Spade Lug or Wire Connections:

11. Locate the Terminal Connections Cover from the

inside of the MC611 shipping carton. Insert the
just prepared Loudspeaker hookup cables thru the
cover opening on the right side. Refer to figure 6.

12. Connect the Loudspeaker hookup cables to the

MC611 Negative Output Terminal and Positive

Output Terminal indentified as 2Ω (ohms), 4Ω
(ohms) or 8Ω (ohms) connection to match the

impedance of the Loudspeaker, being careful to
observe the correct polarities. 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 terminals so the lugs or wire cannot slip out.
Refer to figures 7 and 8.

Note: The illustration in figure 6 is connections for

8Ω (ohms) Loudspeakers.

If the Loudspeaker’s impedance is in-between
the available connections, use the nearest lower
impedance connection. Refer to “General Informa­tion” Note 3 on page 2 for additional information.

Cover

Cover Screws

Figure 6 (Outside USA and Canada)

Figure 7

WARNING: Loudspeaker terminals are hazard-

ous live and present a risk of electric
shock. For additional instruction on
making Loudspeaker Connections con­tact your McIntosh Dealer or McIn­tosh Technical Support.

Cover Openings

Figure 8

13. Attach the Terminal Connections Cover to the
MC611 Rear Panel with the previously removed
Screws. Refer to figure 6.

14. Connect the MC611 power cord to an active AC

outlet.

8

Output Terminals

When connecting the Loudspeaker Hookup Cables to
the MC611 Power Amplifier Output Terminals please
follow the steps below:

1. Rotate the top of the Output Terminal Post coun­terclockwise until an opening

appears. Refer to gures A and

B.

2. Insert the Loudspeaker hookup
cable into the Output Terminal
Post opening or the cable spade
lug around the center post of

Figu re A

Opening

Figu re B

the Output Terminal. Refer to

gure C.

3. Rotate the top of the Output
Terminal Post clockwise until it

is nger tight. Refer to gure D.

4. Place the supplied McIntosh
Wrench over the top of the Out-

Figu re C Figu re D

put Terminal and rotate it one
quarter of a turn (90° ) to secure
the Loudspeaker Cable Connec­tion. Do not over tighten. Refer

to gure E.

Figu re E

How to Connect for Bi-Amp

Caution: Do not connect the AC Power Cord to the

MC611 Rear Panel until after the Loudspeaker
Connections are made and the protective Termi­nal Connections Cover is installed. Failure to
observe this could result in Electric Shock.

The connection instructions below, together with the
MC611 Connection Diagram located on the separate
folded sheet “Mc1B”, is an example of a typical audio
system. Your system may vary from this, however the
actual components would be connected in a similar
manner. For additional information refer to “Connec­tor and Cable Information” on page 3.

1. For Remote Power Control, connect a power control
cable from the Audio Preamplifier or A/V Proces­sor Power Control Trig 1 Output to Amplifier One
POWER CONTROL IN.

2. Connect a power control cable from Amplifier One
Power Control OUTput 1 to Amplifier Two POW­ER CONTROL IN.

3. Connect XLR cables from the Balanced Output 1
Right Channel (refer to note 2 below) of an Audio
Preamplifier or A/V Processor to Amplifier BAL­anced INput. Place the INPUT MODE Switch in
the BALanced Position.

Notes: 1. An optional hookup is to use an unbalanced

cable and place the INPUT MODE Switch in
the UNBALanced Position.

2. When multiple MC611s are used in a Stereo
or Multichannel System, match up the
Preamplifier or A/V Processor Channel
Output designation to each MC611 with
Loudspeaker and the Loudspeaker location
in the room.

4. Connect XLR cables from Amplifier One Audio
BALanced OUTput to Amplifier Two BALanced
INput.

5. Using a suitable tool remove the two screws from
the MC611 Rear Panel and temporarily place them
in a safe place. Refer to figure 1.

This McIntosh MC611 Quad Balanced Power Ampli­fier is designed for Loudspeakers with an impedance
of 2 ohms, 4 ohms or 8 ohms. Connect a single Loud­speaker only to the Output Terminals.

When connecting Loudspeakers to the MC611 it

is very important to use cables of adequate size, so
there is little to no power loss in the cables. The size is
specified in Gauge Numbers or AWG (American Wire
Gauge). The smaller the Gauge number, the larger the
wire size:

Remove Screws

Figu re 1

Loudspeaker Cable Distance vs Wire Gauge Guide

Loudspeaker

Impedance

2 Ohms

4 Ohms

8 Ohms

25 feet

(7.62 meters)

or less

12AWG 10AWG 8AWG

14AWG 12AWG 10AWG

16AWG 14AWG 12AWG

50 feet

(15.24 m eters)

or less

100 fe et

(30. 48 meters)

or less

6. Prepare the Loudspeaker Hookup Cable for attach­ment to the MC611 Power Amplifier:

Bare wire cable ends:
Carefully remove sufficient insulation from the
cable ends, refer to figures 2, 3 & 4. If the cable
is stranded, care­fully twist the
strands together
as tightly as pos-

Figure 2

Figure 3 Figure 4

sible.

Notes: 1. If desired, the twisted ends can be tinned

with solder to keep the strands together.

2. The prepared bare wire cable ends may be
inserted into spade lug connectors.

3. Banana plugs are for use in the United
States and Canada only.

9

How to Connect for Bi-Amp

Figure H

Banana Plugs are for use in the United States and
Canada only:

7. Locate the Terminal Connections Cover from the
inside of the MC611 shipping carton. Insert the
just prepared Loudspeaker hookup cables thru the
cover opening on the right side. Refer to figure 5.

Cover

Cover Opening

Cover Screws

Figure 5 (Inside USA and Canada)

8. Attach the previously prepared bare wire cable
ends into the banana plugs and secure
the connections. Refer to figure F.

9. Rotate the top of the Output Terminal

Post clockwise until it is nger tight.

Figure F

Refer to gure G. Then using the Mc­Intosh Wrench, rotate the top of the
Output Terminal one quarter of a turn
(90° ). Do not over tighten. Refer to

gure E.

10. Referring to figure H, connect the

Figu re G

Loudspeaker hookup cables with ba­nana plugs into the hole
at the top of the MC611
Negative and Positive
Output Terminals. The

Figure H

terminals are indentified

as 2Ω (ohms), 4Ω (ohms) or 8Ω (ohms) connection

to match the impedance of the Loudspeaker, being

careful to observe the correct polarities.

Note: The illustration in figure 5 is connections for

8Ω (ohms) Loudspeakers.

If the Loudspeaker’s impedance is in-between the
available connections, use the nearest lower imped­ance connection. Refer to “General Information” Note
3 on page 2 for additional information.

WARNING: Loudspeaker terminals are hazardous

live and present a risk of electric shock.
For additional instruction on making
Loudspeaker Connections contact your
McIntosh Dealer or McIntosh Techni­cal Support.

11. Attach the Terminal Connections Cover to the
MC611 Rear Panel with the previously removed
Screws. Refer to figure 5.

12. Connect the MC611 power cord to an active AC
outlet.

Spade Lug or Wire Connections:

13. Locate the Terminal Connections Cover from the
inside of the MC611 shipping carton. Insert the
just prepared Loudspeaker hookup cables thru the
cover opening on the right side. Refer to figure 6.

14. Connect the Loudspeaker hookup cables to the
MC611 Negative Output Terminal and Positive

Output Terminal indentified as 2Ω (ohms), 4Ω
(ohms) or 8Ω (ohms) connection to match the

impedance of the Loudspeaker, being careful to
observe the correct polarities. 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 terminals so the lugs or wire cannot slip out.
Refer to figures 7 and 8.

Note: The illustration in figure 6 is connections for

8Ω (ohms) Loudspeakers.

Cover

Cover Screws

Figure 6 (Outside USA and Canada)

Figure 7

Cover Openings

Figure 8

If the Loudspeaker’s impedance is in-between
the available connections, use the nearest lower
impedance connection. Refer to “General Informa­tion” Note 4 on page 2 for additional information.

WARNING: Loudspeaker terminals are hazard-

ous live and present a risk of electric
shock. For additional instruction on
making Loudspeaker Connections con­tact your McIntosh Dealer or McIn­tosh Technical Support.

15. Attach the Terminal Connections Cover to the
MC611 Rear Panel with the previously removed
Screws. Refer to figure 6.

16. Connect the MC611 power cord to an active AC

outlet.

10

11

LED indicates when the Amplifier
POWER GUARD circuit activates

Front Panel Displays and Controls

Meter indicates the Output
of the amplifier

Standby Power
On Indicator

12

METER Switch selects
the display modes of the
Power Output Meter and
Meter Illumination

POWER Switch Turns AC Power Off,
Remote, AC Power On

How to Operate

Power On

To have the MC611 automatically turn On or Off
when a control center turns on or off, rotate the power
switch to the Remote position. For manual operation,
rotate the power switch to the On
or Off position as desired. Refer
to figure 8.

Note: There must be a power

control connection between
the MC611 and the Audio
Preamplifier or A/V Control
Center, in order for the
remote power turn-on to
function.

Meter Selection

Rotate the meter mode switch to select the meter
operation mode you desire.
Refer to figures 9 and 10.

Lights Off - Meter

illumination
is switched
Off and the
meter will
continue to
indicate the power output.

Note: When Power Control Input of the

MC611 is connected to an Audio
Preamplifier or A/V Control Cen­ter with Remote Meter Illumination
Control, the Meter Illumination
will automatically be remotely con­trolled (On/Off) with the METER
Switch set to the WATTS or HOLD
position.

Watts- The meter responds to all the musical

information being produced by the am-

Figure 8

Figure 9

plifier. It indicates to an accuracy of at
least 95% of the power output with only
a single cycle of a 2000Hz tone burst.

Fig ure 10

Hold - The meter pointer is locked to the high-

est power peak in a sequence of peaks.
It is electronically held to this power
level until a higher power peak passes
through the amplifier. The meter point­er will then rise to the 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. The decay rate is
approximately 6dB per minute.

Note: The MC611 Power Output Meter

indicates the actual power delivered
to the loudspeakers by responding
to the combination of current and
voltage output.

Input Mode Switch

The Input Mode Switch, which is lo­cated on the Rear Panel of the MC611,
allows selection of either the Bal­anced or Unbalanced I nput. Refer to
f i g u r e 11.

Fi g ure 11

How to Operate

Auto Off Switch

The MC611 incorporates Power Save Circuitry to
automatically place the MC611 into the power saving
Standby Mode approximately 30 minutes after there
has been an absence of an audio input signal.

When there is a Power Control Connection be-

tween the MC611 and a Preamplifier with Power Save
Circuitry, the AUTO OFF Switch is bypassed (located
on the Rear Panel of the MC611). Refer to
figure 12.

In the event there is no Power Control

Connection and the Power Save Circuitry
is activating inappropriately relative to
your specific use of the MC611, place
the AUTO OFF Switch in the DISable
position.

Note: If the Power Save Circuitry has switched Power

to the MC611 OFF, place the POWER in the OFF
Position and then in the ON position to reset the
circuitry.

Figure 12

13

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 created a Power Amplifier without compro­mise, using the most advanced McIntosh circuit design
concepts.

Figure 13

The MC611 has a continuous average power output
rating of 600 watts and with a peak output current of
90 amperes; making this one of the most advanced
amplifiers available today. The distortion limits for the
MC611 are no more than 0.005% at rated power output
for all frequencies from 20Hz to 20,000Hz. Typical

performance at mid frequencies is
less than 0.002%. The true distor­tion readings on the MC611 are
so low, it takes special measur­ing techniques to make accurate
readings. The MC611 can deliver
the best possible performance
from any type of high quality
loudspeaker system. Refer to
figure 13.

Creating an amplifier with
this level of performance did not
come easily. Many months of de­sign, testing and measuring 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 MC611 involved
several different techniques, all
based on sound scientific logic.
Every stage of voltage or cur­rent amplification must be as
linear as possible prior to the use
of negative 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 Quad
Balanced configuration cancels even order distortion.
Refer to figure 16.

All transistors are selected to have nearly constant
current gain over the entire current range they must
cover. Output transistors in particular,
have matched uniform current gain, high
current bandwidth product and large
active region safe operating area. These
Power Transistors are the very latest in
semiconductor technology and incorpo­rate a new design known as Thermal­Trak™. Refer to figure 14. This allows for
the instantaneous and accurate monitor-

Figu re 14

ing of the Power Transistor Temperature.
The MC611 Power Output Circuitry has a specially
designed bias circuit to take full advantage of the
ThermalTrak™ Power Transistors and thus precisely
controls the power amplifier operation over a wide
range of music conditions with the benefits of lower
distortion and cooler operation. Precision metal film
resistors and low dielectric absorption film capacitors
are used in all critical circuit locations.

The output signals of the two balanced circuits
are coupled together in the unique McIntosh MC611
Output Autoformer. It provides low distortion power
transfer at frequencies from below 20Hz to well
beyond 20,000Hz with optimum impedance points of
two ohms, four ohms and eight ohms. The unequaled

14

Technical Description

UNBALANCED

INPUT

UNBALANCED

OUTPUT

BALANCED

INPUT

BALANCED

OUTPUT

+

AMP

INPUT MODE

-

AMP

+

-

+

-

Block Diagram

of the

Power Amplifier

SWITCH

POWER GUARD

ATTENUATOR

BALANCED

AMP

Fig ure 15

THERMAL
SENSORS

MUTE

ThermalTrak
DC BIAS

ThermalTrak
DC BIAS

Figu re 16

expertise of McIntosh in the
design and manufacturing of
autoformers is legendary in
the high fidelity industry.

The high efficiency circuit
design of the MC611 contrib­utes to low operating tem­peratures. More than 1400
square inches of heat sink
area keep the MC611 operat­ing safely with convection
cooling. No fans are needed.
Refer to figure 15.

Autoformers

All solid state power ampli­fier output circuits work best

into what is called
an optimum load.
This optimum load
may vary consider­ably 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

OUTPUT

expectancy for the amplifier.

The special Balanced Winding Autoformer
creates an ideal match between the power am­plifier output stage and the loudspeaker. Refer
to figure 17.

There is absolutely no performance limita­tion with an Autoformer. Its frequency re­sponse exceeds that of the output circuit itself,
and extends well beyond the audible range. Its
distortion level is so low it is virtually impos­sible to measure.

Fig u re 17

15

Technical Description, con’t

In the rare event of a power amplifier output circuit
failure, the McIntosh Autoformer provides absolute
protection from possible damage to your valuable
loudspeakers. The unequaled expertise of McIntosh in
the design
and manu­facturing
of Auto­formers is
legendary
in the high
fidelity
indust r y.
McIntosh
engineers
know how
to do it

Figure 18

right.

Power Output Meter

The McIntosh MC611 has a large Output Watt
Meter that responds 95% full scale to a single cycle
tone burst at 2kHz. Refer to figure 18. Voltage and
current outputs are electronically measured, multiplied
and fed to a special circuit that accelerates the pointer
movement in the upward direction. Refer to figure
26 on the next page. When the pointer reaches its
peak it pauses only long enough for the human eye to
perceive its position, then drops. It is almost 10 times
faster than a professional VU meter.

A front panel switch is provided to change the
meter to the Watts Hold Mode of operation. This al­lows fast upward movement of the pointer but greatly
increases Hold Time at the peak of its travel. The
highest power output of the source material is thus
recorded.

Protection Circuits

The MC611 incorporates the McIntosh Sentry Monitor
Output Transistor
Protection Circuit.
Refer to Figure 19.
There is absolutely
no compromise in
sonic performance

Normal Operating Area

with this circuit,
and it ensures safe
operation of the
amplifier under
even the most

Sentry Monitor
Safety Area

Fig ure 19

Output
Transistor
Failure

extreme operating
conditions. The different types of protection circuits
incorporated in the MC611 insure a long and safe
operating life. This is
just one of the many

Input Test Signal

(14kHz & 15kHz)

characteristics of McIn­tosh Power Amplifiers
that make them world
famous.

The MC611 also
includes the unique
patented McIntosh
Power Guard circuit.
Power Guard eliminates
the possibility of ever
overdriving the ampli-

Figure 20

fier into clipping. Refer
to figures 20, 21 and 22. An overdriven amplifier can
produce both audible and inaudible distortion levels
exceeding 40%. The audible distortion is unpleasant
to hear, but the inaudible ultrasonic distortion is also
undesirable, since it can damage valuable loudspeaker
system tweeters. You will never experience the harsh

and damaging distortion

Without Power Guard

due to clipping.

The Power Guard
circuit is a waveform
comparator, monitoring
both the input and output
waveforms. Under normal
operating conditions,
there are no differences
between the shape of
these waveforms. If the
amplifier is overdriven,
there will be a difference
between the two signal
waveforms. When the

Figure 21

With Power Guard

difference exceeds 0.3%,
the Power Guard acti­vates the PG light and
a dynamic electronic
attenuator at the ampli­fier input reduces the
input volume just enough
to prevent any further in­crease in distortion. The
Power Guard circuit acts
so fast that there are ab-

Figure 22

solutely no audible side
effects and the sonic purity of the music reproduction
is perfectly preserved. The MC611 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.

16

Technical Description, con’t

Block Diagram

of the

POWER

CONTROL

Power Supply

AC Power

BACKUP

POWER SUPPLY

FUSE

Figure 24

LIGHTING
CONTROL

CURRENT

INRUSH

LIMITER

CONTROL

LOGIC

Power Supply Circuits

To compliment the design of the MC611 Power Am­plifier Circuitry, there is a high current high voltage
power supply. Refer to figures 23 and 26. The very
large Power Transfomer can supply over 13 amps of
current. Refer to figure 24 (golf ball is for size com­parsion).
It is enclosed in the legendary McIntosh Potted En­closures and weighs 28 lbs. The four super size main
filter capacitors can store over 140 Joules of energy

AUTO

OFF

POWER
SWITCH

MAIN RELAYS

Figu re 23

LOW VOLTAGE

SUPPLY

POWER

TRANSFORMER

MAIN

SUPPLY

Figure 25

which is necessary for the wide dynamic range that
“Digital Audio” demands. Refer to figure 25.

Figure 26

The power amplifier draws high current from the AC
power line. Therefore, it is important that they plug
directly into the wall outlet.
Also, most owners desire one power switch for the
whole audio system. The MC611 is equipped with a
circuit that provides remote Power Control from a Mc­Intosh A/V Control Center. Refer to figure 26. When
the A/V Control Center is switched On, a (+5V) signal
operates the power relay in the MC611. The MC611
also has two remote Power Control Out Jacks. The
Power Control signal from these jacks are delayed by
a fraction of a second so that the turn on power surge
of the next power amplifier occurs at a later time.
This helps prevent power circuit overload that could
trip circuit breakers or blow fuses, a very important
feature in a high power Home Systems employing
multiple MC611 Power Amplifiers.

17

Specications

Specications

Power Output

Minimum sine wave continuous average power
output is:
600 watts into 2 ohm load
600 watts into 4 ohm load
600 watts into 8 ohm load

Output Load Impedance

2, 4 or 8 ohms

Rated Power Band

20Hz to 20,000Hz

Total Harmonic Distortion

0.005% maximum harmonic distortion at any power
level from 250 milliwatts to rated power, 20Hz to
20,000Hz

Dynamic Headroom

2.8dB

Frequency Response

+0, -0.25dB from 20Hz to 20,000Hz
+0, -3.0dB from 10Hz to 100,000Hz

Intermodulation Distortion

0.005% maximum, if the instantaneous peak power
output does not exceed twice the rated power output
for any combination of frequencies from 20Hz to
20,000Hz.

Wide Band Damping Factor

Greater than 40

Input Impedance

22,000 ohms Balanced
22,000 ohms Unbalanced

Volt a ge Ga i n

29dB, 8 Ohms
26dB, 4 Ohms
23dB, 2 Ohms

Power Guard

Less than 2% Total Harmonic Distortion with up to a

14dB overdrive signal

Power Control Input

5-15VDC, less than 1mA

Power Requirements

Field AC Voltage conversion of the MC611 is not
possible. The MC611 is factory configured for one of
the following AC Voltages:

100V ~ 50/60Hz at 8 Amps
110V ~ 50/60Hz at 6.6 Amps
120V ~ 50/60Hz at 6.6 Amps
127V ~ 50/60Hz at 6.6 Amps
220V ~ 50/60Hz at 3.6 Amps
230V ~ 50/60Hz at 3.3 Amps
240V ~ 50/60Hz at 3.3 Amps
Standby: less than 0.5 watt

Note: Refer to the rear panel of the MC611 for the cor-

rect voltage.

Overall Dimensions

Width is 17-1/2 inches (44.45cm)
Height is 9-7/16 inches (23.97cm) including feet
Depth is 22 inches (55.88cm) including the Front
Panel, Handles and Cables

Weight

97.5 pounds (44.32 kg) net, 130.5 pounds (59.32 kg) in
shipping carton

Input Sensitivity (for rated output)

4.8 Volts Balanced

2.4 Volts Unbalanced

Signal To Noise Ratio (A-Weighted)

124dB below rated output, Balanced
120dB below rated output, Unbalanced

18

Power Control Output 1 and 2

12VDC, 50mA maximum total
Output is delayed 0.2 seconds from turn On

Shipping Carton Dimensions

Width is 29-1/2 inches (74.93cm)
Height is 17 inches (43.18cm)
Depth is 29 inches (73.66cm)

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 attached to the bottom of the equipment. Four
1/4 - 20x2-1/4 inch screws and washers must be used
to fasten the unit securely to the bottom pad and wood
skid. This will ensure the proper equipment location
on the bottom pad. Failure 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 Laboratory. Refer to page 2. Please
see the Part List for the correct part numbers.

Quantity Part Number Description
1 034052 Shipping carton top
1 034051 Shipping carton bottom
2 034054 Foam Pad (top and
bottom)
2 034186 Foam Pad (front and rear)
2 034187 Foam Pad (sides)

Packing Instructions

1 034136 Inner carton top
1 034137 Inner carton bottom
1 034188 Foam Pad (inner carton)
1 034479 Shipping skid
4 401212 1/4 - 20x2-1/4 cap screw
4 104058 Flat washer

19

McIntosh Laboratory, Inc.

2 Chambers Street
Binghamton, NY 13903
www.mcintoshlabs.com

The continuous improvement of its products is the
policy of McIntosh Laboratory Incorporated who
reserve the right to improve design without notice.
Printed in the U.S.A.

McIntosh Part No. 04184201