Mcintosh ma6900om04 schematic

Integrated Amplifier

MA6900

Owner’s Manual

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

The lightning flash 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
sufficient 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 important
operating and maintenance (servic­ing) instructions in the literature 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 amplifiers) 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 fit 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

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.

the apparatus.

11. Only use attachments/accessories specified by the
manufacturer.

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

13. Unplug this apparatus during lightning storms or
when unused for long periods of time.

14. Refer all servicing to qualified 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 filled 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.

2

Thank You

Table of Contents

Your decision to own this McIntosh MA6900 Integrated
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:

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

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

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

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

Important Information ...................................................... 4

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

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

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

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

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

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

How to Connect for Loudspeakers ................................... 8

How to Connect for Audio and Data Control ................... 9

How to Connect for Video .............................................. 10

How to Connect for a Second Room .............................. 11

Front Panel Controls, Display, Indicator Push-Button

and Switch ...................................................................... 12

How to Operate............................................................... 13

Remote Control Push-Buttons ........................................ 16

How to Operate by Remote Control ............................... 17

Technical Description ..................................................... 18

Specifications ................................................................. 22

Packing Instruction ......................................................... 23

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 2004 © by McIntosh Laboratory, Inc.

3

Introduction and Performance Features

Important Information

1. The following parts are 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.

Jumper Plugs Part No. 117-781

RCA Phono Jumpers, 14mm center spacing.

2. For additional connection information, refer to the owner’s
manual(s) for any component(s) connected to the MA6900.

3. The MA6900 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 MA6900 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 MA6900 has returned to a safe operating
temperature, normal operation will resume.

Connector Information

XLR Connectors

Below is the Pin configuration for the XLR Balanced Input
Connectors on the MA6900. Refer to the diagram for con­nection:

PIN 1: Shield/Ground
PIN 2: + Input
PIN 3: - Input

Pin 2

Pin 1

Pin 3

Introduction

Now you can take advantage of traditional McIntosh stan­dards of excellence in the MA6900 Integrated Amplifier.
Two 200 watt high current output channels will drive any
high quality loudspeaker system to its ultimate perfor­mance and the flexible Preamplifier Selection provides for
hookup and control of various input sources. The MA6900
reproduction is sonically transparent and absolutely accu­rate. The McIntosh Sound is “The Sound of the Music It­self.”

Performance Features

••

• Power Output

••

The MA6900 consists of two separate power amplifier
channels, each capable of 200 watts into 2, 4 or 8 ohm
speakers with less than 0.005% distortion.

••

• Electronic Input Switching

••

Digital Logic integrated circuits drive Electromagnetic
Switches on all six inputs and operating functions for reli­able, noiseless, distortion free switching.

••

• Power Guard

••

Both channels include the patented McIntosh Power Guard
circuit that prevents the amplifier from being overdriven
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 MA6900 will have a long and trouble
free operating life. Built-in Thermal Protection Circuits
guard against overheating.

Power Control and Trigger Connectors

The MA6900’s Power Control Outputs provide a 5 volt
signal. Use a 1/8 inch stereo mini
phone plug to connect to the
Power Control Input on other
McIntosh Components.

Data Port Connector

The MA6900’s Data Port Output provides Remote Control
Signals. Use a 1/8 inch stereo
mini phone plug to connect to the
Data Port Inputs on McIntosh
Source Units.

4

Positive

N/C

Ground

Data Signal

N/C

Ground

••

• 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 loud­speakers.

••

• Illuminated Power Meters

••

The Illuminated Power Output Meters on the MA6900 are
peak responding, and indicate the power output of the am­plifier.

MA6900 Dimensions

The following dimensions can assist in determining the
best location for your MA6900. There is additional infor­mation on the next page pertaining to installing the
MA6900 into cabinets.

17-

1/2

44.45cm

MA6900 Dimensions

"

Front View of the MA6900

Rear View of the MA6900

16-

1/16

40.8cm

12-

3/16

30.96cm

7 -

5/8

7 -

1/8

"

18.10cm

19.37cm

"

"

6"

15.24cm

"

Side View of the MA6900

13/16

2.06cm

18-

3/4

"

47.63cm

16-

1/2

"

41.91cm

6-

1/4

3/16

"

0.48cm

"

13"

33.02cm

1"

2.54cm

"

15.88cm

5

Installation

Installation

The MA6900 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 MA6900 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 MA6900 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 MA6900.
Cool operation en­sures the longest
possible operating
life for any elec­tronic instrument. Do

MA6900 Front Panel
Custom Cabinet Cutout

not install the
MA6900 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 as-

Cabinet
Front
Panel

Opening
for Ventilation

set in maintaining all
the system compo­nents at the coolest
possible operating
temperature.

MA6900 Side View
in Custom Cabinet

A custom cabinet
installation should
provide the follow­ing minimum spac-

Support
Shelf

ing dimensions for
cool operation. Al­low at least 6 inches
(15.24cm) above the
top, 2 inches
(3.81cm) below the

MA6900 Bottom View
in Custom Cabinet

2"

5.08cm

bottom and 1 inch

(2.54cm) on each side of the amplifier, so that airflow is
not obstructed. Allow 20 inches (50.8cm) 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.

17-

1/16

"

43.34cm

6 -

5/8

"

16.83cm

6"

15.24cm

1"

2.54cm

14-

36.83cm

Cutout

Opening

for

Ventilation

Cutout Opening for Custom Mounting

Cutout Opening for Ventilation

1/2

"

13"

33.02cm

Chassis
Spacers

10-

3/8

26.35cm

"

14-

1/8

35.88cm

"

13"

33.02cm

6

MA6900 Rear Panel Connections and Switch

Main Fuse holder,
refer to information
on the back panel
of your MA6900 to
determine the cor­rect fuse size and
rating

The EXT
(external)
SENSOR(s)
for a Keypad
or IR Sensor

Right OUTPUT
Connections for
2, 4 or 8 ohm
loudspeakers

POWER CONTROL 1 and 2
Outputs send a turn-on signal
to an external McIntosh
Power Amplifier when the
MA6900 Front Panel Output
1 and/or 2 is On

CD1 balanced INPUTS
accept high level program
source signals

OUTPUTS 1
and 2 supply
the Preamplifier
Output to either
the internal or
external power
amplifier

TAPE OUTPUTS
provide the Record
Out Signal

VIDEO inputs
for audio signals
from a LV, VCR,
TV or an A/V
Selector

Left OUTPUT
Connections for
2, 4 or 8 ohm
loudspeakers

GND terminal
accepts a
ground wire
from a turn­table

POWER CONTROL
MAIN Output sends
a turn-on signal to an
external McIntosh
Power Amplifier
when the MA6900 is
turned on

Connect the
MA6900 power
cord to a live AC
outlet. Refer to in­formation on the
back panel to deter­mine the correct
voltage

DATA PORTS send
signals to McIntosh
Compatible Compo­nents to allow control
with the remote con­trol

POWER CONTROL
ACC Output sends a
turn-on signal to a
McIntosh Source
Component or Power
Control unit when the
MA6900 is turned on

JUMPER PLUGS
connect the Pream­plifier OUTPUT 1
Jacks to the POWER
AMP IN Jacks and
are needed for nor­mal operation

POWER AMP IN
inputs accept sig­nals from a sepa­rate external
preamplifier

TUNER and
CD2 inputs ac­cept signals
from the output
of a tuner and
CD player

TAPE input
accepts signals
from the out­put of a tape
deck

AUX accepts high level program
source signals, PH accepts signals
from a Moving Magnet phono car­tridge, and the small slide switch
selects which one of these two in­puts is active when the front panel
PH/AUX Push-button is pressed

7

How to Connect Loudspeakers

Caution: The supplied AC Power Cord should not be

connected to the Rear Panel of the MA6900
Amplifier until after the Loudspeaker Connections
have been made. Failure to observe this could
result in Electric Shock.

1. Prepare the Loudspeaker Hookup Cables that attach to
the Amplifier by choosing one of the methods below:

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.

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 figures 4, 5 & 6.

How to Connect Loudspeakers

Banana plug connection:
Insert the banana plug into the hole at the top of the
terminal.

Note: Banana Plugs are for use in the United States and

Canada only.

2. Connect the loudspeaker hookup cables to the output
terminals that match the impedance of your loudspeak­ers, being careful to observe the correct polarities. Out­put impedance connections of 2 ohms, 4 ohms and 8
ohms are provided. If the impedance of your loud­speakers is in-between the available connections, use
the nearest lower impedance connection.

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.

Right
Loudspeaker
4 ohm

8

Left
Loudspeaker
4 ohm

How to Connect Audio Components

How to Connect Audio Components

1. Connect an Audio Cable from the McIntosh CD Player
Audio Outputs to the MA6900 CD2 INPUTS.

2. Connect an Audio Cable from a McIntosh Tuner 1 Out­puts to the MA6900 TUNER INPUTS.

3. Connect an Audio Cable from a Turntable to the

PH/AUX INPUTS and the Turntable Ground Connec-

tion to the GND grounding post.

4. Connect an Audio Cable from the MA6900 TAPE
OUTPUTS to the Record Inputs of a Tape Recorder
and from the MA6900 TAPE INPUTS to a Tape Re­corder Outputs.

5. Connect a Control Cable from the MA6900 POWER
CONTROL ACC Jack to the Power Control In on the
McIntosh Tuner.

McIntosh Tuner

6. Connect a Control Cable from the McIntosh Tuner
Power Control Out Jack to the Power Control In jack
on the McIntosh CD Player.

7. Connect a Control Cable from the MA6900 TUNER
DATA PORT Jack to the McIntosh Tuner Data In
(Tuner 1).

8. Connect a Control Cable from the MA6900 CD2
DATA PORT Jack to the McIntosh CD Player Data In
Jack.

9. Connect the MA6900 Power Cord to a live AC outlet.

McIntosh CD Player

To AC Outlet

In

Tape Recorder

Out

Turntable

9

How to Connect for Video Switching

How to Connect for Video Switching

1. Connect a Data cable from the MA6900 VIDEO DATA
PORT to the Audio/Video Selector Data In jack.

2. Connect the Audio/Video Selector Control Center Au­dio Outputs to the MA6900 VIDEO INPUTS.

3. Connect the Audio/Video Selector Video Monitor Out­put to a Monitor/TV.

Note: Either or both Audio/Video Selector Monitor

Output(s) may be connected to the Monitor/TV.

4. Connect a McIntosh DVD/CD Player Audio Outputs to
the Audio/Video Selector V-Aux Audio Inputs, the

Audio/Video Selector

Video Output to the Audio/Video Selector Video Input
and the Control Out to the Audio/Video Selector Data
Output jack.

5. Connect a Control Cable from the MA6900 POWER
CONTROL ACC Jack to the Power Control In on the
McIntosh DVD/CD Player.

6. Connect other video source components to the appro­priate audio and video and data jacks on the Audio/
Video Selector.

Monitor/TV

McIntosh DVD Player

10

How to Connect for a Second Room

1. Connect Audio Cables from the MA6900 OUTPUTS 2
to the Second Power Amplifier Inputs.

2. Connect Hookup Cables from the Second Power Am­plifier to the loudspeakers. Refer to page 8 in this
Owner’s Manual for connection details.

3. Connect a Control Cable from the MA6900 POWER
CONTROL 2 Jack to the Power Control In of a McIn­tosh Power Amplifier.

4. Connect an RG6 or RG59U coaxial cable from the
EXTernal SENSOR Jack to a Keypad.

Note: A Wall Mounted IR Sensor may also be used in place

of the keypad.

How to Connect for a Second Room

Keypad

Right
Loudspeaker
4 ohm

McIntosh Power Amplifier

Left
Loudspeaker
4 ohm

11

Front Panel Controls, Push-Buttons and Switch

The BALANCE control
allows adjustment of
the relative volume bal­ance between channels

METER indicates the
Left Channel Power
Output of the amplifier

Equalizer provides
12dB of boost or cut
at the center frequen­cies indicated above
each control

METER indicates the
Right Channel Power
Output of the amplifier

POWER GUARD
LEDs light when the
amplifier’s channel
POWER GUARD
circuit activates

POWER
switch turns
all AC power
completely
ON or OFF

VOLUME control
allows adjustment of
the listening level for
both channels

IR Sensor
receives
commands
from a re­mote con­trol

12

Select any one
of the six Audio
signal sources

HEADPHONES jack
allows connection of
Stereo Headphones for
private listening

MONO push-button
combines the left and
right channel signals for
Mono operation

OUTPUTS 1
and 2 push­buttons turn the
Speakers and
Preamplifier
Outputs On or
Off

MUTE push-button
mutes the listening
audio

LOUDNESS
provides fre­quency re­sponse con­toured to com­pensate for the
behavior of the
human ear at
softer listening
levels

STANDBY/ON
push-button turns
the MA6900 ON,
or OFF (Standby)

How to Operate

How to Operate

Power On

Press the POWER switch to ON. The Red LED above the
STANDBY/ON push-button, lights to
indicate the MA6900 is in Standby
mode. To turn On the MA6900, press
the STANDBY/ON push-button. The
MUTE LED will light for approxi­mately two seconds after turn on. Re-

Figure 1

fer to figures 1 and 2.

Notes: For normal operation,

turn the MA6900 On
and Off with the
Standby/On push­button. If the amplifier
is not going to be used
for an extended time,
turn off all AC Power
with the Power
Switch. You may also
turn On the MA6900
by simply pressing the
desired Source
Selection Push-button
on the Front Panel or
Remote Control. For
an explanation of the
Remote Control Push­button functions, refer
to pages 16 and 17.

PH/AUX Inputs

When using a phono player with a moving magnet cartridge
connected to the PH/AUX inputs, set
the PH AUX switch to the PH position.
When using an auxiliary program source
component connected to the PH/AUX
inputs, set the PH AUX switch to the
AUX position. Refer to figure 4.

Balance Control

Figure 4

Adjust the BALANCE control as needed to achieve ap­proximately equal listening volume levels in each loud­speaker. Turn the BALANCE to the left to emphasize the
Left Channel by reducing the level of the Right Channel.
Turn the BALANCE to the right to emphasize the Right
Channel by reducing the level of the Left Channel.

Equalizer Controls

Each of the five Equalizer Frequency Controls will raise or
lower by approximately12dB, the amplitude of the band of
frequencies centered at the frequency marked above the
controls. Both Left and Right Channels are affected. Refer
to figure 5. At the center detent or flat position of the con­trols, all equalizer circuit components are removed from the
signal path.

Source Selection

Select the desired source
with the appropriate push­button switch on the Front
Panel or Remote Control.
Refer to figures 2 and 3 and
page 16 for additional infor­mation.

Volume Control

Adjust the VOLUME control
for the desired listening level.

Figure 3

Figure 2

Figure 5

Loud Switch

Press the LOUD push-button to add loudness bass com­pensation to the volume control for improved low level lis­tening.

Mono

Press the MONO push-button to combine left and right ste­reo signals to mono at the SPEAKERS 1 and 2 and HEAD­PHONES output.

Mute

Press the MUTE push-button to mute audio in all outputs
except the HEADPHONES and TAPE OUTPUT. The
MUTE LED above the push-button will flash on and off to
indicate that Mute is active. To unmute audio, press
MUTE, press the Remote Control Volume push-button(s)
or press an Input push-button.

13

How to Operate, con’t

Outputs 1 and 2

Press OUTPUTS Push-button 1 to switch the Speakers On
or Off. The
push-buttons
also switch the
Preamplifier
OUTPUTS 1

Figure 6

and 2 On or Off
for connection to external Power Amplifier(s). Press either
push-button individually, or both together. Refer to figure

6.

Headphones Jack

Connect a pair of dynamic headphones to the Headphones
Jack for private listening. Press Mute to mute all other out­puts including the amplifier connected to the loudspeakers.
Refer to figure 6.

Reset of Microprocessors

In the event that the controls of the MA6900 stop function­ing, push the POWER switch OFF and wait about two min­utes. Then push the POWER switch ON followed by push­ing the STANDBY/ON push-button. This will reset the
MA6900 microprocessors and the Integrated Amplifier
should be functioning normally.

Note: The above condition is usually caused by either

interruptions in AC power and/or major changes that
may occur in AC power line voltage.

How To Make A Tape Recording

1. Select the source signal you wish to record with the
appropriate Front Panel input push-button. If you wish
to record from an Audio/Video source connected to the
optional McIntosh Audio/Video Selector Audio/Video
Selector, using the Remote Control, select the desired
source connected to the McIntosh Audio/Video Selec-

Figure 9

tor. Refer to figure 9.

2. Adjust the record level using the tape recorder volume
control and proceed with the recording process.

3. To listen to the tape playback of the program source
just recorded, press the TAPE input push-button.

Note: The MA6900 TAPE OUTPUTS are not affected by the

VOLUME or BALANCE controls.

Power Output Meters

The MA6900 Power Output Meters indicate the power de­livered to the loudspeakers. The meters respond to all the
musical information being produced by the amplifier. They
indicate to an accuracy of at least 95% of the power output
with only a single cycle of a 2000Hz tone burst.

Using a Separate Power Amplifier

There are two different ways to use a separate power am­plifier with a MA6900. The first way
is to use the separate amplifier instead
of the MA6900 built-in Power Ampli­fier. Connect the loudspeakers to the
separate power amplifier and remove
the McIntosh Jumpers that are located

Jumpers

Figure 7

between the OUTPUTS 1 Jacks and
the POWER AMP INput Jacks. Refer to figures 7 and 8.

Note: The McIntosh Jumpers must be connected, between the

above mentioned jacks, when the MA6900 Internal
Power Amplifier is to be used.

The second way is to use both a sepa­rate power amplifier and the MA6900
built-in Power Amplifier. Connect one
pair of loudspeakers to the separate
power amplifier and the second pair to

No Jumpers

Figure 8

the MA6900.

Note: The MA6900 VOLUME Control will affect the sound

level of all the loudspeakers.

14

Notes

15

Remote Control Push-Buttons

LED illuminates during the
time a remote command is
sent to the MA6900

Turns AC Power ON or OFF to cer­tain McIntosh Components when
connected via the Data Port

Selects Functions for McIntosh
Home Controller and as a “shift”
key when used with the AM or FM
push-buttons to select Output
(Spkr) 1 or 2

Switches OFF the entire
MA6900 System

Use to select tuner pre­sets, disc tracks or any
numbered operation

Selects Switched Output 1,
AM Tuner Operating Func­tions and Disc Selection on
certain McIntosh CD Players

Press to REVIEW Tuner Station
Presets and selects certain func­tions on McIntosh CD Players

Press TRIM to turn the
Loudness Control On
or Off

Mutes the audio

Selects Disc Player, Music
Server or Tape Recorder
Functions and also per­forms various functions
on a variety of McIntosh
Components

Press to Power the
MA6900 ON or OFF

Press MODE to switch between
Stereo or Mono Modes

Press to Power ON
the MA6900

Press to Power OFF
the MA6900

Selects Switched Output
2, FM Tuner Operating
Functions and Track Se­lection on certain McIn­tosh CD Players

Adjusts the volume
level up or down

Selects On Screen Func­tions for McIntosh DVD
Players and certain CD
Players

Selects the FF (Fast For­ward) or REWind Mode
on Disc Player, Music
Server or Tape Recorder;
tunes Up or Down the
AM/FM Dial

Selects one of the twelve
High Level Audio/Video
Sources or Phono Input

16

Note: Push-buttons whose function is not

indentified above are for use with
other McIntosh Products.

How to Operate by Remote Control

How to Operate by Remote Control

The supplied remote control is capable of directly control­ling the functions of contemporary McIntosh Source Com­ponents connected to the MA6900. Earlier McIntosh
source components and other brand source components can
be controlled by the MA6900 Remote Control with the ad­dition of a McIntosh Remote Control Translator (RCT).

Note: Your McIntosh Dealer can assist you with the

installation and operation of the Remote Control
Translator (RCT).

Mute

Press the MUTE push-button to mute audio at the Pream­plifier OUTPUTS 1, 2 and Speaker L, R OUTPUTs. The
TAPE OUTPUTS and HEADPHONES output are not af­fected by the MUTE function. The MUTE LED above the
push-button will flash on and off to indicate that Mute is
active. Press MUTE a second time to unmute audio.

Mono

Press the MODE push-button to combine left and right ste­reo signals to mono at the Preamplifier OUTPUTS 1, 2 and
Speaker L, R OUTPUTs.

Trim

Press the TRIM push-button to active the Loudness Com­pensation circuit.

Input Source Selection

Press any of the twelve input push-buttons to select a pro­gram source. When one of the Audio/Video Inputs (SAT,
LV, TV, VCR, VCR2 and DVD) are selected by remote
control, the MA6900 will automatically switch to the
VIDEO Input. If the Front Panel VIDEO Push-button is
pressed, the source device connected to the VIDEO INPUT
Jacks will be heard. When the optional McIntosh MVS Au­dio/Video Selector is added, multiple Audio/Video Inputs
Sources, such as LV, TV, VCR, VCR2 and DVD (V-Aux),
will become available by just pressing the desired program
source push-button on the remote control.

Disc Player, Music Server or Tape Recorder
Functions

Use these push-buttons to operate a CD player, CD
changer or tape recorder.

Disc and Track

Use the DISC and TRACK push-buttons when a Disc
Player, Music Server or Tape Recorder
exis being used.

Tuner Push-buttons

Press the AM or FM push-button to select the desired
broadcast band. Press and release the CHANnel UpS or
DownTpush-button to move from station to station. Press
and hold a CHANnel UpS or DownT push-button to
move continuously from station to station. Press the +10
Push-button to start the automatic brief audition of each of
the presets stored in the tuner memory. Press the +10
Push-button a second time to stop on a station preset and
exit the review process.

Volume

Press the Up or Down VOLUME push-button to raise or
lower the listening volume level.

Note: The TAPE OUPUTS are not affected by volume

changes.

Amplifier Selection

Press the 2nd push-button followed by the OUTPUT 1 or 2
push-buttons to control the rear panel OUTPUTS 1, 2
which can feed signals to a power amplifier or other acces­sory component.

Acc On

Press ACC ON to turn the power ON to a McIntosh Disc
Player.

Acc Off

Press ACC OFF to turn the power OFF to a McIntosh Disc
Player.

Pause

Press to perform various functions on a variety of McIn­tosh Components. It will also pause the playing of a disc or
tape player.

Numbered Push-buttons

Press push-buttons 0 through 9 to access tuner station pre­sets or CD tracks/discs.

17

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.

A continuous average power output rating of 200 watts
and with an output current of greater than 50 amperes per
channel, making this the most advanced Integrated Ampli­fier McIntosh has ever manufactured. The distortion limits
for the MA6900 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 MA6900 are so low, it takes
special measuring techniques to make accurate readings.
The MA6900 can deliver the best possible performance
from any type of high quality loudspeaker system.

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.

Preamplifier Design Philosophy

All signal switching in the MA6900 is done by Electro­Magnetic devices. Electro-Magnetic Switching is a proven
technology that uses the latest in materials and manufactur­ing methods. Each switch consists of a glass tube that is
filled with an inert oxygen­free atmosphere and sealed
with tiny leads protruding
from either end. These leads
extend into the tube and
overlap one another with a
separation of a few thou­sandths of an inch. The leads
are made from a ferrous ma­terial that is influenced by a
magnetic field. They are first
plated with gold as a base
material, then with rhodium
and finally ruthenium. Ru­thenium is the best contact
material known.

The glass assembly is
then placed in the center of a
multilayer coil of copper
wire. The entire assembly is
molded together in a tough
shock absorbing material.

dB

(Decibel)

Figure 10

Bottom Inside View of the MA6900

The switch and coil connectors extend from the bottom in
the form of printed circuit board terminals. When a DC
voltage is applied to the coil, current flows and creates a

Equalizer Control Adjustment Range

Hz (Hertz)

18

Technical Description

magnetic field. The force of the field causes the leads to
bend and contact one another inside the sealed glass tube.
The inert gas eliminates corrosion of the contacts and in­sures a low resistance, distortion free switch.

All inputs, outputs, and data ports are controlled by
logic circuits in the MA6900. The logic is changed by front
panel push-buttons or by a microprocessor IR decoder.
This microprocessor IR decoder is programmed with ex­clusive McIntosh software. It receives data from the front
panel or external sensors and provides the command sig­nals for input switching, data switching, and volume con­trol.

The equalizer section uses several high technology op­erational amplifiers. The amplifier stage has been opti­mized for the best transient performance and minimum dis­tortion. Five other operational amplifiers are arranged in a
circuit configuration that is the equivalent of a series turned
circuit. A control potentiometer inserts this series tuned cir­cuit into either the feedback or input section of the equal­izer amplifier. This provides a 12dB boost or cut at the fre­quency of the tuned circuit. Refer to figure 10. The overall
gain of the stage is 0dB when the potentiometer is at its
center detent position. In this position the tone control ele­ments are completely removed from the signal path.

Power Amplifier Design Philosophy

The design philosophy incorporated in the MA6900 in­volved several different techniques, all based on sound sci­entific logic. Refer to figure 11. 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.

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. An automatic tracking bias sys­tem completely eliminates any trace of crossover distor­tion. Precision metal film resistors and low dielectric ab­sorption film capacitors are used in all critical circuit loca­tions.

The output signal of the circuit is coupled together in
the unique McIntosh MA6900 Output Autoformer. It pro­vides low distortion power transfer at frequencies from be­low 20Hz to well beyond 20,000Hz with optimum imped-

Block Diagram of the Amplifer and Meter Circuitry

Figure 11

19

Top Inside View of the MA6900

ance points of two ohms, four ohms and eight ohms. The
unequaled expertise of McIntosh in the design and manu­facturing of autoformers is legendary in the high fidelity
industry.

The high efficiency circuit design of the MA6900 con­tributes to low operating temperatures. More than 621
square inches of heat sink area keep the MA6900 operating
safely with convection cooling. No fans are needed.

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 expectancy
for the amplifier.

Figure 12

The Autoformer creates an ideal match between the
power amplifier output stage and the loudspeaker. Refer to
figure 12. 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. In the rare event of a power amplifier
output circuit failure, the McIntosh Autoformer provides
absolute protection from possible damage to your valuable
loudspeakers.

Protection Circuits

The MA6900 incorporates it’s version of the McIntosh
Sentry Monitor output transistor
protection circuit. Refer to figure

13. There is absolutely no compro­mise in sonic performance with
this circuit, and it ensures safe op­eration of the amplifier under even
the most extreme operating condi­tions. The different types of pro-

Figure 13

tection circuits incorporated in the
MA6900 insure a long and safe operating life.

The MA6900 also includes the unique patented McIn­tosh Power Guard circuit.

Input Test Signal

Power Guard eliminates the
possibility of ever overdriving
the amplifier into clipping. Re­fer to figures 14, 15 and 16. 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

Figure 14

Without Power Guard

system tweeters. You will never
experience the harsh and dam­aging distortion 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 an am-

Figure 15

plifier channel 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

20

PG light and a dynamic elec-

With Power Guard

tronic 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 absolutely no au­dible side effects and the sonic
purity of the music reproduction
is perfectly preserved. The
MA6900 Amplifier with Power

Figure 16

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.

Power Supply Circuits

To compliment the design of the MA6900, there is a high
voltage power supply for both channels. Refer to figure 17.
The power amplifiers draw high current from the AC
power line. Therefore, it is important that they plug directly
into the wall outlet. Turn on inrush current is cushioned by
thermistors in the power transformer’s primary circuit.
This soft start eliminates component stress during turn-on.

The MA6900 can provide greater than 50 amperes peak
output current to drive uneven speaker loads. Some poor
speaker designs have input impedance that dip to 1 or 2
ohms at various frequencies and the MA6900 has the out­put current reserve to drive them. The MA6900 has main
filter capacitors that guarantee an excellent signal to noise
ratio and the energy storage necessary for the wide dy­namic range that “Digital Audio” demands.

Block Diagram of the Power Supply

Figure 17

21

Specifications

Specifications

Power Output

Minimum sine wave continuous average power output per
channel, all channels operating is:
200 watts into 2 ohm load
200 watts into 4 ohm load
200 watts into 8 ohm load

Rated Power Band

20Hz to 20,000Hz

Total Harmonic Distortion

Maximum Total Harmonic Distortion at any power
level from 250 milliwatts to rated power output is:

0.005% for 2, 4 or 8 ohm loads

Dynamic Headroom

2.4dB

Frequency Response

+0, -0.5dB from 20Hz to 20,000Hz
+0, -3dB from 10Hz to 100,000Hz

Sensitivity

Phono, 2.5mV for 2.5V rated output (0.5mV IHF)
High Level, 250mV for 2.5V rated output (50mV IHF)
Power Amplifier Input, 2.5V for rated output

Signal To Noise Ratio (A Weighted)
90dB (84dB IHF) below 10mV input, Phono Input
100dB (90dB IHF) below rated output, High Level
110dB below rated output, Power Amplifier

Intermodulation Distortion

Maximum Intermodulation Distortion if instanta­neous peak output per channel does not exceed
twice the rated output, for any combination of fre­quencies from 20Hz to 20,000Hz, with all channels
operating is:

0.005% for 2, 4 or 8 ohm loads

Preamplifier Maximum Voltage Output

Phono, 8V at tape output
High Level, 8V at tape output
Main Out, 8V at preamp output

Voltage Gain

High Level to Tape: 0dB
High Level to Main: 20dB

Wide Band Damping Factor

Greater than 40

Power Requirements

100 Volts, 50/60Hz at 5.2 Amps
110 Volts, 50/60Hz at 4.8 Amps
120 Volts, 50/60Hz at 4.4 Amps
220 Volts, 50/60Hz at 2.45 Amps
230 Volts, 50/60Hz at 2.35 Amps
240 Volts, 50/60Hz at 2.25 Amps

Note: Refer to the rear panel of the MA6900 for the correct

voltage.

Overall Dimensions

Front Panel: 17-1/2 inches (44.45cm) wide, 7-1/8 inches
(18.10cm) high. Depth behind front mounting panel is 16­1/2 inches (41.91cm). Clearance required in front of the
Front Panel is 1 inch (2.54cm) for knobs.

Weight

74.5 pounds (33.8 Kg) net, 92.5 pounds (41.7 Kg) in ship­ping carton

Input Impedance

Phono, 47K ohms, 65pF
High Level, 22K ohms

Maximum Input Signal

Phono, 90mV
High Level, 8V

22

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.
tached to the bottom of the equipment. Three #10 x 2-1/4
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.

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. Please see the Part List for the correct part numbers.

It is very important that the four plastic feet are at-

Use the original shipping carton and interior parts only

Quantity Part Number Description

1 033888 Shipping carton only
2 033887 End cap (Foam pad)

1 033697 Inside carton only
1 033725 Top Pad
1 034008 Bottom pad
2 017218 Plastic foot (spacer)
1 033699 Wood skid
2 101204 #10 x 2-1/4 inch Wood screw
2 104033 #10 x 1-3/4 inch Flat washer

4 017218 Plastic foot
4 100159 #10-32 x 3/4 inch Machine

screw

4 104083 #10 x 7/16 inch Flat washer

1 048572 Sipping Carton Complete

23

McIntosh Laboratory, Inc.

2 Chambers Street

Binghamton, NY 13903

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. 04099100