McIntosh Laboratory, Inc. 2 Chambers Street Binghamton, New York 13903-2699 Phone: 607-723-3512 www.mcintoshlabs.

com

MA252
Integrated Amplifier
Owners Manual
 Important Safety Information is supplied in a separate document Important Additional Operation Information Guide
Thank You Customer Service
Your decision to own this McIntosh MA252 Integrated If it is determined that your McIntosh product is in Setup Mode:
How to Operate the Setup Mode........................................ 19
Amplifier ranks you at the very top among discrimi- need of repair, you can return it to your Dealer. You Setup Functions:
nating music listeners. You now have The Best. The can also return it to the McIntosh Laboratory Service Default Settings..........................................................19
McIntosh dedication to Quality, is assurance that Department. For assistance on factory repair return Firmware Version.......................................................19
you will receive many years of musical enjoyment procedure, contact the McIntosh Service Department Source Input On/Off and Renaming.....................19-21
from this unit. at: Data Port.....................................................................21
Remote Control Codes................................................21
Please take a short time to read the information in McIntosh Laboratory, Inc. IR Sensor.....................................................................22
this manual. We want you to be as familiar as pos- 2 Chambers Street Power Mode................................................................22
sible with all the features and functions of your new Binghamton, New York 13903 Factory Reset..............................................................22
McIntosh. Phone: 607-723-3515 Operation:
How to Operate the MA252..........................................24-27
Please Take A Moment Fax: 607-723-1917
Trim Functions:
Balance........................................................................24
The serial number, purchase date and McIntosh Dealer
Table of Contents Trim Level...................................................................25
name are important to you for possible insurance Tone Control...............................................................25
claim or future service. The spaces below have been Safety Instructions............................................................... 2 Bass Control................................................................25
provided for you to record that information: (Separate Sheet).............................Important Additional Treble Control.............................................................26
Operation Information Guide Information Display....................................................26
Serial Number:________________________________
Thank You and Please Take a Moment................................2 Trim, Mute, Headphone Jack and Power Guard......... 26
Purchase Date:________________________________ Technical Assistance and Customer Service........................2 Protection Circuitry and Microprocessor Reset.......... 27
Table of Contents..................................................................2 Photos.............................................................................28-29
Dealer Name:_________________________________ Specifications..................................................................... 30
Important Information..........................................................3
Unpacking the MA252......................................................4-5 Packing Instructions........................................................... 31
Technical Assistance
General Information.............................................................6
If at any time you have questions about your McIntosh Connector and Cable Information........................................6
product, contact your McIntosh Dealer who is familiar Introduction..........................................................................7
with your McIntosh equipment and any other brands Performance Features...........................................................7
that may be part of your system. If you or your Dealer Dimensions...........................................................................8
wish additional help concerning a suspected problem, Installation............................................................................9
you can receive technical assistance for all McIntosh Connections:
products at: Rear Panel Connections...................................................... 10
Connecting Components............................................... 11-12
McIntosh Laboratory, Inc. Connecting Loudspeakers............................................. 13-14
2 Chambers Street Remote Control and Front Panel:
Remote Control Push-buttons............................................ 16
Binghamton, New York 13903
How to use the Remote Control.......................................... 17
Phone: 607-723-3512
Front Panel Displays, Controls and Jack............................ 18
Fax: 607-724-0549
Copyright 2017 by McIntosh Laboratory, Inc.

2
 IMPORTANT!
INSTRUCTIONS FOR REMOVAL
OF FOAM INSERT OVER THE
VACUUM TUBES PRIOR TO
CONNECTING THE A.C. POWER
SUPPLY CORD, START ON THE
NEXT PAGE.

3
Caution: To prevent damage to the MA252 2. Remove the Warning Sheet and save it with the 3. Carefully lift upright the Foam Insert Vacuum
Tubes during shipping, there is a Shipping Carton for possible future use. Refer to Tube Cover and place it near to the MA252 Inte-
special foam insert surrounding the figures A and B. grated Amplifier. Refer to figure C.
Tubes of the Integrated Amplifier.

The Foam Insert must be

removed from the MA252
before connecting the AC
Remove the
Power Supply Cord to the Foam Insert
integrated amplifier. Vacuum
Tube Cover

Failure to do so has the po- WARNING Figure C

tential of a Fire Hazard,
TO AVOID A FIRE HAZARD, THE FOAM INSERT
OVER THE VACUUM TUBES MUST BE REMOVED
PRIOR TO CONNECTING THE A.C. MAINS POWER
SUPPLY CORD AND OPERATING THIS PRODUCT.

resulting in damage to the

REFER TO PAGE 3 IN THE MA252 OWNERS

4. Remove from the Foam, the four Vacuum Tube

MANUAL FOR INSTRUCTIONS.

Shield Covers and place them along the side of the

MA252 and the surrounding MA252 Integrated Amplifier. Save the Foam In-
Figure A
environment. sert Vacuum Tube Cover with the Shipping Carton
Remove the Warning Sheet for possible future use. Refer to figure D.
Follow these instructions for
removal of the packing foam Remove the four Vacuum Tube Shield Covers
before connecting the AC
Power Supply Cord to the
MA252.
The MA252 has no user serviceable parts,
including the tubes. If repairs are needed they
must be performed by an authorized McIntosh
Service Agency. Follow the steps below to pre-
pare the MA252 for operation:
1. Orient the MA252 so the Front and Top of the Figure D
Integrated Amplifier is facing you. Refer to
figure A. Figure B
Vacuum Tube Shield Covers
4
 Unpacking the MA252

5. The MA252 Integrated Amplifier has four Small

Vacuum Tubes that are inserted into special
Vacuum Tube Sockets on the Stainless Steel Chas-

WARNING: sis. Refer to figure E.

Each of the Tube Sockets have four pin openings
to accept the Vacuum Tube Shield Covers. Refer
to figure F.
The supplied Vacuum Tube Shield Carefully install the Vacuum Tube Shield Covers
Covers must be installed over each into each of the Vacuum Tube Sockets orienting
of the four Small Vacuum Tubes the Shield so the Mc on top of the Shield is fac-
ing forward. Refer to figures G and H.
before the MA252 Integrated Am-
plifier is connected to AC Power
and activated for use!!

Failure to do so has the potential to

cause physical harm to human be-
ings and animals.

This could also result in damage to Figure G

Figure E
the Vacuum Tubes and the MA252 Special Vacuum Tube Sockets
Internal Circuitry.
Pin Openings Vacuum Tube
It also prevents the potential of a Shield Covers
Fire Hazard, resulting in damage BAL 15%

to the MA252 and the surrounding

environment.
Figure F
Figure H

5
 General Information, Connector and Cable Information

General Information
1. For additional connection information, refer to the 7. The MA252 Remote Control is capable of operat- Output Terminal Connector
owners manual(s) for any component(s) connected ing other components. For additional information When cables with spade lugs are used
to the MA252. go to www.mcintoshlabs.com. for Loudspeaker Connection, the spade
2. Apply AC Power to the MA252 and other McIntosh 8. When discarding the unit, comply with local rules lugs need an opening of at least 3/10 inch
Component(s) only after all the system components or regulations. Batteries should never be (7.6mm)
are connected together. Failure to do so may cause thrown away or incinerated but disposed 3/10 of an inch
(7.6millimeters)
a malfunction of system operations as the Micro- of in accordance with the local regula-
processors Circuitry inside the components is tions concerning battery disposal.
active when AC Power is applied. 9. For additional information on the MA252 and
3. The MA252 includes an Auto Off Power Save other McIntosh Products please visit the McIntosh
Feature and the default setting is enabled. For Website at www.mcintoshlabs.com.
additional information including how to disable it,
refer to page 22. Connector and Cable Information
4. When Power Amplifier Protection Circuitry of the
MA252 has activated, the Vacuum Tubes LEDs are XLR Connectors
Below is the Pin configuration for the XLR Balanced
illuminated continuously with the color orange and
the sound will be muted. Input Connectors on the MA252. Refer to the diagram
for connection:
5. When the Power Transformer has overheated due
to improper ventilation and/or high ambient operat- PIN 1: Shield/Ground
PIN 2: + Output
ing temperature, AC Power is removed from the
PIN 3: - Output PIN 1 PIN 2
MA252. Normal operation will resume when the PIN 3

operating temperature is in a safe range again. Power Control Connector

6. For the best performance and safety, it is important The Power Control Output Jack sends Power On/
to always match the impedance of the Loudspeaker Off Signals (+12 volt/0 volt) when
to the Power Amplifier connections. Refer to pages another McIntosh Component is
Power
Control
10 and 11. connected. A 3.5mm stereo mini N/C
Note: The impedance of a Loudspeaker actually var- phone plug is used for connection to Ground
ies as the Loudspeaker reproduces different
the Power Control Output.
frequencies. As a result, the nominal impedance
rating of the Loudspeaker (usually measured at Data Port Connector
a midrange frequency) might not always agree The Data Out Ports send Remote Control Signals to
with the impedance of the Loudspeaker at low
Source Components. A 3.5mm stereo
frequencies where the greatest amount of power
is required. Contact the Loudspeaker Manufac-
mini phone plug is used for connec- Data
Signal
turer for additional information about the actual tion. N/C
Data
impedance of the Loudspeaker before connecting Ground
it to the McIntosh MA252.

6
 Introduction and Performance Features

Introduction
Now you can take advantage of traditional McIntosh Electronic Output Switching McIntosh Custom Binding Posts
standards of excellence in the MA252 Integrated Am- The Preamplifier uses Logic Controlled Electromag- McIntosh Patented gold plated output terminals deliver
plifier. The Power Amplifier Solid State section of the netic Switches on all low level outputs and operating high current output. They accept large diameter wire
MA252, with a power output of 100 watts per channel, functions for reliable, noiseless, distortion free switch- and spade lugs. Banana plugs may also be used only in
will drive a pair of quality Loudspeakers to a high ing. the United States and Canada.
level of performance.
The flexible Tube Preamplifier section provides Moving Magnet Phono Inputs Super Mirror Finish Chassis with Glass Panel
connections for various analog input sources. The MA252 Moving Magnet Input Circuitry uses The famous McIntosh Stainless Steel Chassis with
The MA252 reproduction is sonically transparent the latest design to provide the lowest possible noise, Super Mirror Finish ensures the pristine beauty of the
and absolutely accurate. The McIntosh Sound is The distortion and flat frequency response. MA252 will be retained for many years. The famous
Sound of the Music Itself. McIntosh Illuminated Glass Panel uses long life Light
Tone Controls Emitting Diodes (LEDs).
The Bass and Treble Trim Controls provide up to
Performance Features 10dB of boost or cut. The MA252 remembers the Bass
Power Output and Treble Setting for each input.
The MA252 consists of 100 watts (8 ohm) or 160 watts
(4 ohm) per channel Stereo Power Amplifier with Multifunction Display
less than 0.03% distortion. The McIntosh MA252 is The Front Panel Display indicates source selection,
designed for connection of a single 8 ohm or 4 ohm volume levels and setup functions.
Loudspeaker per channel. The Power Amplifier uses
ThermalTrak1 Output Transistors for lower distortion Power Control Output
and cool operation. A Power Control connection for convenient Turn-On
of a McIntosh Component.
Power Guard
The patented McIntosh Power Guard circuit prevents Remote Control
amplifier clipping and protects your valuable Loud- The Data Port together with the supplied Remote Con-
speakers. trol provide control of McIntosh Source Components
connected to the MA252.
Sentry Monitor and Thermal Protection
McIntosh Sentry Monitor power output stage protec- Special Power Supply
tion circuits ensure the MA252 will have a long and The large Power Transformer, multiple filter capaci-
trouble free operating life. Built-in Thermal Protection tors with 60 Joules of Energy Storage and regulated
Circuits guard against overheating. Power Supply ensure stable noise free operation even
though the power line varies.
1
ThermalTrak and ON Semiconductor are trademarks of Semi-
conductor Components Industries, LLC

7
 Dimensions

Dimensions
The following dimensions can assist in determining
the best location for your MA252. There is additional
information on the next page pertaining to installing
the MA252 into cabinets.
Front View of the MA252 Left Side View of the MA252

16-1/2"
41.9cm

1-1/2"
3.8cm
BAL 15%

7-1/32" 7-5/8"
17.9cm 19.4cm

1-1/2"
3.8cm

Top View of the MA252 Right Side View of the MA252

1-1/2" 14-3/4"
3.8cm 37.5cm
6-13/16"
17.3cm

4-1/16"
10.3cm

12"
30.5cm
3"
7.62cm

8
 Installation

Installation
The MA252 Integrated Amplifier is designed to be
placed upright on a table or shelf, standing on its feet.
The required ventilation requirements are shown.
Always provide adequate ventilation for your MA252.
6"
Cool operation ensures the longest possible operating 2" 15.3cm 2"
life for any electronic instrument. Do not install the 5.1cm 5.1cm
MA252 directly above a heat generating device, such
as a Power Amplifier. Allow at least 6 inches (15.3cm) MA252 Front View
above the top, 5/8 inch (1.6cm) below the bottom and
2 inches (5.1cm) on each side of the Amplifier, so that BAL 15%

airflow is not obstructed. Allow 18 inches (45.7cm) of

depth for airflow and cable connections.

6"
15.3cm
18"
45.7cm

MA252 Side View

9
 MA252 Rear Panel Connections

Right OUTPUT Left OUTPUT

connections for a 4 or connections for a 4 or
8 ohm Loudspeaker POWER CONTROL OUTPUT sends turn 8 ohm Loudspeaker
On/Off signals to a McIntosh Component
when the MA252 is switched On/Off

Main Fuse holder, refer to PHONO accepts signals

information on the back from a Moving Magnet
panel of your MA252 to Phono Cartridge or a
determine the correct fuse high output Moving Coil
size and rating Cartridge

DATA PORT sends signals BALANCED INPUTS GND terminal

to a Source Component accept high level pro- accepts a ground
to allow control with the gram source signals wire from a
MA252 Remote Control turntable

Connect the MA252 power cord to a SUB (MONO) OUTPUT UNBALanced INPUTS
live AC outlet. Refer to information full frequency range Audio 1 and 2 accept high level
on the back panel of your MA252 to Output for connection to program source signals
determine the correct voltage for your an actively powered Sub-
unit Woofer

10
Connecting Components
The MA252 has the ability to automatically switch Audio Connections:
power On/Off to McIntosh Source Components via 6. Connect Balanced Cables from the MA252 BAL-
the Power Control connections. The Data Port Con- anced INPUT Connectors to the CD Player Audio
nections allow for the remote operation of basic func- Output.
tions using the MA252 Remote Control. 7. Connect the Audio Cables coming from the
The connection instructions below, together with Turntable to the MA252 PHONO Input Jacks (for
the MA252 Input and Output Connection Diagram on a Moving Magnet Cartridge or a Moving Coil
the next page is an example of a typical audio system. Cartridge with High Audio Output Level).
Your system may vary from this, however the actual 8. Connect any additional Components in a similar
components would be connected in a similar manner. manner, as outlined in steps 6 and 7.
For additional information refer to Connector and Ground Connections:
Cable Information on page 6. 9. Connect the Ground Cable coming from the Turn-
Power Control Connections: table to the MA252 GND Binding Post.
1. Connect a Control Cable from the MA252
POWER CONTROL OUTPUT Jack to the Power
Control In on the Turntable.
2. Connect a Control Cable from the McIntosh Turn-
table Power Control Out Jack to the CD Player
Power Control In Jack.
3. Connect any additional McIntosh Components in
a similar manner, as outlined in steps 1 thru 2.
Data Control Connections:
4. Connect a Control Cable from the MA252 DATA
PORT Jack to the CD Player Data In Jack.
5. Connect another McIntosh Component in a similar
manner instead of the CD Player Data In Jack, as
outlined in step 7.

11
 Connecting Components

Connect to
AC Outlet

Turntable
CD Player

12
Output Terminals
When connecting the Loudspeaker Hookup Cables to The McIntosh MA252 Power Amplifier Circuitry Banana Plugs are for use in the United States and
the MA252 Power Amplifier Output Terminals please is designed for a Loudspeakers with an impedance Canada only:
follow the steps below: of 8 Ohms or 4 Ohms. Connect a single Loudspeaker 2. Attach the previously prepared bare wire cable ends
1. Rotate the top of the Output Terminal Post coun- only to the Right and Left Output Terminals. into the banana plugs and secure
terclockwise until an opening When connecting Loudspeakers to the MA252 it the connections. Refer to figure I.
appears. Refer to figures A and is very important to use cables of adequate size, so 3. Rotate the Output Terminal Post
B. there is little to no power loss in the cables. The size is clockwise until it is finger tight.
Figure I
2. Insert the Loudspeaker hookup specified in Gauge Numbers or AWG (American Wire Refer to figure J. Then using the
cable into the Output Terminal Opening Gauge). The smaller the Gauge number, the larger the McIntosh Wrench, rotate the top of
Post opening or the cable spade wire size: the Output Terminal one quarter of
Figure A Figure B
lug around the center post of Loudspeaker Cable Distance vs Wire Gauge Guide a turn (90). Do not over tighten.
the Output Terminal. Refer to 25 feet 50 feet 100 feet Refer to figure E.
Loudspeaker
figure C. Impedance
(7.62 meters) (15.24 meters) (30.48 meters) 4. Referring to figure K, connect the
or less or less or less
3. Rotate the top of the Output Loudspeaker hookup cables with Figure J
2 Ohms 12AWG 10AWG 8AWG
Terminal Post clockwise until it banana plugs into the hole at the
4 Ohms 14AWG 12AWG 10AWG
is finger tight. Refer to figure D. top of the terminal to the
8 Ohms 16AWG 14AWG 12AWG
4. Place the supplied McIntosh Figure C Figure D MA252 Negative Output
Wrench over the top of the Out- 1. Prepare the Loudspeaker Hookup Cable for attach- Terminal and Positive
put Terminal and rotate it one ment to the MA252 Power Amplifier: Output Terminal to the
quarter of a turn (90) to secure Bare wire cable ends: Loudspeaker Terminal
the Loudspeaker Cable Connec- Carefully remove sufficient insulation from the Connections being care- Figure K
tion. Do not over tighten. Refer Figure E cable ends, refer to figures F, G & H. If the cable ful to observe the correct
to figure E. is stranded, carefully twist the strands together polarities.
as tightly as possible. Note: The illustration located on the separate folded sheet
How to Connect Loudspeakers Mc2B is for connection to an 8 (ohms) Loudspeak-
Caution: Do not connect the AC Power Cord to the er.
MA252 Rear Panel until after the Loudspeaker If the Loudspeakers impedance is in-between
Connections are made. Failure to observe this the available connections, use the nearest lower
could result in Electric Shock. Figure F Figure G Figure H impedance connection. Refer to General Informa-
The connection instructions below, together with the tion Note 6 on page 6 for additional information.
MA252 Connection Diagram located on the next page Notes: 1. If desired, the twisted ends can be tinned WARNING: Loudspeaker terminals are hazard-
is an example of a typical audio system. Your system with solder to keep the strands together. ous live and present a risk of electric
2. The prepared bare wire cable ends may be shock. For additional instruction on
may vary from this, however the actual components
inserted into spade lug connectors. making Loudspeaker Connections con-
would be connected in a similar manner. For addition- 3. Banana plugs are for use in the United tact your McIntosh Dealer or McIn-
al information refer to Connector and Cable Informa- States and Canada only. tosh Technical Support.
tion on page 6.

13
 Connecting Loudspeakers

5. Connect the MA252 power cord to an active AC

outlet.

Spade Lug or Wire Connections:

6. Connect the Loudspeaker hookup cables to the
MA252 Negative Output Terminal and Positive
Output Terminal to the Loudspeaker Terminal
Connections being careful to observe the cor-
rect 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 L
and M.

Figure L Figure M

Note: The illustration located on the separate folded

sheet Mc2B is for connection to an 8 Right Loudspeaker Left Loudspeaker
(ohms) Loudspeaker.
Refer to General Information Note 6 on page 6
for additional information.
WARNING: Loudspeaker terminals are hazard-
ous live and present a risk of electric
shock. For additional instruction on
making Loudspeaker Connections con-
tact your McIntosh Dealer or McIn-
tosh Technical Support.
7. Connect the MA252 power cord to an active AC
- + - +
outlet.

14
15
 HR091 Remote Control Push-Buttons

Mutes and unmutes the audio

LED illuminates during the time a Powers the MA252 ON or OFF
remote command is sent to the MA252

Decreases the volume level Increases the volume level

Select the desired active TRIM function; also

Directional Push-buttons - Up, Down,
manually tune up the dial with contemporary Mc-
Left and Right
Intosh Tuners

Adjusts the active TRIM Function

Adjusts the active TRIM Function

Select the desired active TRIM function;

also manually tune down the dial with con-
temporary McIntosh Tuners Activates TRIM Mode

Selects the desired INPUT Stop CD Playback

Pause CD Playback Selects Next Track during CD Playback

Selects Previous Track during

CD Playback
Starts CD Playback

Note: Push-buttons whose function is not identified above are for use with other McIntosh Products.

16
 How to use the Remote Control

How to use the Remote Control

The supplied Remote Control performs the various
Operating Functions for the MA252 Integrated Am-
plifier.
Note: Refer to the How to Operate Section of this
manual for additional information.

Input Source Selection

Press the Push-button to select the desired pro-
gram source.

Volume
Press the + or - Push-buttons to increase or de-
crease the listening level.

Mute
Press the (Mute) Push-button to mute the audio and
a second time to resume listening.

Select Push-Button
Press the SELECT/TRIM Push-button to activate the
Trim Mode. Then use the Directional Push-Buttons to
select a Trim Mode Function and make changes.

Directional Push-Buttons
After having pressed the SELECT Push-button,
press the (Up or Down) Push-buttons to scroll
through the various Trim Functions. Then press the
(Left or Right) Push-buttons to make a change to
the current Trim Setting.

17
 Front Panel Displays, Controls and Jack

INPUT Control used to select a Preamplifier Small Signal VOLUME Control allows adjustment
source for listening and recording. Vacuum Tube of the listening level for both chan-
IR Sensor receives
The control is also used to enter the nels. Switches the MA252 ON or OFF
commands from a
TRIM or SETUP Modes and select (Standby). Also used to change the
LED Illumination Color: Remote Control
the various functions various TRIM and SETUP Functions
Orange - Warmup Mode and
and Resets the microprocessors
Power Guard Activates
Green - Normal Operation

BAL 15%

INFORMATION DISPLAY indicates

the Sources, Volume, Trim Operational
Functions and Setup Mode Settings

Connection for low impedance STANDBY/ON LED Indicator

dynamic headphones, for private
listening

18
 Setup

How to Operate the Setup Mode

Your McIntosh MA252 has been factory configured 3. Rotate the INPUT Control to select the Setup Firmware Version
to allow immediate enjoyment of superb audio with- Mode Menu item, SETUP: Inputs, (Hold IN-
The MA252 functionality is controlled by internal
out the need for further adjustments. If you wish to PUT). Refer to figure 3.
software that is know as Firmware. The Firmware for
make changes to the factory default settings, a Setup the MA252 and can be identified at any time by utiliz-
Feature is provided to customize the operating settings SETUP: Inputs
(Hold INPUT) ing the Setup Mode.
using the Front Panel Information Display. Refer to the 1. Press and hold in the INPUT Control to enter
MA252 Front Panel Illustration on the previous page Figure 3
Setup Mode.
while performing the following steps. Continue to rotate the INPUT CONTROL to view
2. Referring to the Front Panel Information Display-
Note: If the MA252 is currently On, the other SETUP Mode Options.
proceed to step 2.
the number after the character V is the Firm-
4. To exit from the SETUP Mode, press and hold in
1. Press the STANDBY/ON Push-button on the Front ware number. Refer to figure 2.
the INPUT Control and the Front Panel Display
Panel or press the (Power ON) Push-button on will indicate its normal display. Refer to figure 1.
the Remote Control to switch On the MA252. The
MA252 will go through a brief startup initializa-
tion with the Front Panel Information Display first
indicating MA252, followed by the last used Default Settings
source and volume setting. This is followed by the The Default Settings Chart below indicates the Func- Input Settings
volume setting indication starting at zero and then tion Name, Default Setting and the Page Number for The MA252 provides the ability to switch unused
increasing to the last used volume setting. Refer to additional information. INPUTS Off (or back On if they have been previously
figure 1. Default Settings switched Off). The default INPUT Names can be
Function Name Setting Page No. changed to match the name of the component con-
UNBAL 1 15% MA252 V_._ _ 19
nected to it or any other custom name desired (within
10 Characters).
INPUTS On / Rename 19-21
Figure 1 INPUT SWITCHED ON/OFF:
DATA PORT All Data 21
2. Press and hold in the INPUT Control until In the following example, the UNBAL 2 Input will be
IR Codes Normal 21
the Front Panel Information Display indicates switched Off.
MA252 V1.00, (or higher Firmware version) IR Sensor Enabled 21 Note: When an INPUT is swiched Off, its name will
- S/N: AGA____ (Serial Number). Refer to Power Mode Enabled 21 no longer appear on the Front Panel Informa-
figure 2. tion Display when using the INPUT Control
(Front Panel or Remote Control).
MA252 V1.00 1. Press and hold in the INPUT Control to enter the
S/N: AGA____ SETUP MODE. Refer to figure 2.
Figure 2

19
Input Settings, cont
2. Rotate the INPUT Control until SETUP: Inputs, UME Control until the display indicates SETUP: play. The character B is flashing to indicate it is
(Hold INPUT) appears on the Information Dis- UNBAL 2, On / Name. ready to be changed. Refer to figure 9.
play. Refer to figure 3 on page 19. 10. Exit the SETUP Mode by several presses of the
3. Press and hold in the INPUT Control until SET- INPUT Control. RENAME: BAL
UP: UNBAL 2, On / Name (Hold IN) appears on RENAME INPUT: >BAL
the Display. If necessary rotate the INPUT Control In the following example, the BAL (BALANCED) In- Figure 9
to select the UNBAL 2 Input. Refer to figure 5. put will be renamed to match up with the component 15. Rotate the VOLUME (ADJUST) Control to change
connected (refer to page 8, step 6). the character B to C. Refer to figure 10.
SETUP: UNBAL 2 The MA252 Default Input Names (UNBAL 1, BAL,
On/Name(Hold IN) PHONO, etc.) as indicated on the Front Panel Dis- RENAME: BAL
Figure 5 play can be customized to a different name up to ten >CAL
4. To switch the UNBAL 2 Input Off, rotate the characters long (TUNER, CD PLAYER, etc.). The Figure 10
VOLUME Control until the display indicates available characters for renaming the input include the 16. Rotate the INPUT Control until the character A
SETUP: UNBAL 2, Off. Refer to figure 6. following: ! < > * , / - _ 0 1 2 3 4 5 6 7 8 9 A B C D E is flashing, then rotate the VOLUME (ADJUST)
FGHIJKLMNOPQRSTUVWXYZ. Control to change the character A to D. Refer
SETUP: UNBAL 2 In the following example, the BAL Input will be re- to figure 11.
Off named to MEDIA SVR.
Figure 6 11. Press and hold in the INPUT Control to enter the RENAME: BAL
5. Exit the SETUP Mode by several presses of the SETUP MODE. Refer to figure 2, on page 19. >CDL
INPUT Control. 12. Rotate the INPUT Control until SETUP: Inputs, Figure 11
In the following example, the UNBAL 2 Input will be (Hold INPUT) appears on the Information Dis- 17. Rotate the INPUT Control until the character L
switched On. play. Refer to figure 7. is flashing, then rotate the VOLUME (ADJUST)
Notes: 1. When an INPUT is swiched ON, its name will Control until the _ empty space to the right of
appear on the Front Panel Information Display SETUP: Inputs character D is flashing. Refer to figure 12.
when using the INPUT Control (Front Panel or (Hold INPUT)
Remote Control). Figure 7 RENAME: BAL
6. Press and hold in the INPUT Control to enter the 13. Press and hold in the INPUT Control until SET- >CD
SETUP MODE. Refer to figure 2, on page 19. UP: UNBAL 1, On/Name(Hold IN) appears on Figure 12
7. Rotate the INPUT Control until SETUP: Inputs, the Display. Rotate the INPUT Control to select 18. Rotate the INPUT Control until the _ empty
(Hold INPUT) appears on the Information Dis- the BAL Input. Refer to figure 8. space to the right of the just entered empty space
play. Refer to figure 3, on page 19. is flashing, then rotate the VOLUME (ADJUST)
8. Press and hold in the INPUT Control until SET- SETUP: BAL Control to change the _ empty space to character
UP: UNBAL 2, Off appears on the Display. If On/Name(Hold IN) to P. Refer to figure 13.
necessary rotate the INPUT Control to select the Figure 8
UNBAL 2 Input. Refer to figure 6. 14. Press and hold in the INPUT Control until RE- RENAME: BAL
9. To switch the UNBAL 2 Input On, rotate the VOL- NAME: BAL, >BAL < appears on the Dis- >CD P
Figure 13

20
 Setup, cont

Remote Control Codes

19. Rotate the INPUT Control until the _ empty 22. Exit the SETUP Mode by several presses of the The HR091 Remote Control included with the MA252
space to the right of character P is flashing, then INPUT Control. utilizes the NORMAL McIntosh Control Codes. The
rotate the VOLUME (ADJUST) Control to change Second Set of Control Codes the MA252 will respond
the _ empty space to character to L. Refer to to is referred to as the ALTERNATE Codes. The Al-
figure 14.
Data Port
ternate Codes are used when the MA252 is used in the
Data Port Connection between the MA252 and a same location as another McIntosh Preamplifier and/or
RENAME: BAL McIntosh Source Component allow for basic function A/V Processor. This will prevent the Remote Control
>CD PL control of the source component using the MA252 from affecting the operation of both units at the same
Figure 14 Remote Control. By default, the Data Port setting of time. To activate the Remote Control ALTERNATE
20. Repeat step 19 until the new name of RENAME: All Data sends the received IR Data to the DATA Codes perform the following steps:
BAL, CD PLAYER is indicated on the Front PORT Output Jack. To dedicate the Data Port for only 1. Press and hold in the INPUT Control to enter the
Panel Display. Refer to figures 15 thru 18. one MA252 source component perform the following SETUP MODE. Refer to figure 2 on page 19.
Steps: 2. Rotate the INPUT Control until SETUP: IR
RENAME: BAL 1. Press and hold in the INPUT Control to enter the Codes, Normal appears on the Information
>CD PLA SETUP MODE. Refer to figure 2 on page 19. Display. Refer to figure 22.
Figure 15 2. Rotate the INPUT Control until SETUP: Data
Ports, All DATA appears on the Information Dis- SETUP: IR Codes
RENAME: BAL play. Refer to figure 20. Normal
>CD PLAY Figure 22
Figure 16 SETUP: Data Port 3. Rotate the VOLUME (ADJUST) Control to the
RENAME: BAL All Data Alternate Codes. Refer to figure 23.
Figure 20
>CD PLAYE 3. Rotate the VOLUME (ADJUST) Control to select SETUP: IR Codes
Figure 17 Alternate
the desired MA252 Input. Refer to figure 21.
Figure 23
RENAME: BAL SETUP: Data Port 4. Exit the SETUP Mode by several presses of the
>CD PLAYER Bal INPUT Control.
Figure 18 Figure 21
21. To save the new name, press and hold in the IN- 4. Exit the SETUP Mode by several presses of the
PUT Control until SETUP: CD PLAYER , ON / INPUT Control.
Rename appears on the Front Panel Information
Display. Refer to figure 19.

SETUP: CD PLAYER
On/Name(Hold IN)
Figure 19

21
 Setup, cont

IR Sensor Power Mode Factory Reset

The MA252 Front Panel Sensor, which receives the The MA252 incorporates an Auto Off Feature, which If it becomes desirable to reset all the adjustable set-
signals from the HR091 Remote Control, can be automatically places the preamplifier into the Power tings (Setup and Trim Settings) to the factory default
switched off to prevent interference when other Re- Saving Standby/Off Mode. This occurs approximately values, perform the following steps:
mote Control IR Signals are received. To de-activate 30 minutes after there has been an absence of user ac- 1. Press and hold in the INPUT Control to enter the
the Front Panel IR Sensor perform the following steps: tivity (includes changes to any of the Operation Func- SETUP MODE. Refer to figure 2 on page 19.
1. Press and hold in the INPUT Control to enter the tions such as source selection, volume adjustment, 2. Rotate the INPUT Control until FACTORY RE-
SETUP MODE. Refer to figure 2 on page 19. etc.) or absence of an audio signal. If it is desirable to SET, (Hold INPUT) appears on the Information
2. Rotate the INPUT Control until SETUP: Front disable the Auto Off Feature perform the following Display. Refer to figure 28.
IR, Enabled appears on the Information Dis- steps:
play. Refer to figure 24. 1. Press and hold in the INPUT Control to enter the FACTORY RESET
SETUP MODE. Refer to figure 2 on page 19. (Hold INPUT)
SETUP: Front IR 2. Rotate the INPUT Control until SETUP: Auto Figure 28
Enabled Off, Enabled appears on the Information Display. 3. Press and hold in the INPUT Control until FAC-
Figure 24 Refer to figure 26. TORY RESET, In Progress! appears on the Infor-
3. Rotate the VOLUME (ADJUST) Control to select mation Display, then release the INPUT Control.
Disabled. Refer to figure 25. SETUP: Auto Off Refer to figures 29 and 30.
Enabled
SETUP: Front IR Figure 26 FACTORY RESET
Disabled 3. Rotate the VOLUME (ADJUST) Control to select In Progress
Figure 25 Disabled. Refer to figure 27. Figure 29
4. Exit the SETUP Mode by several presses of the
INPUT Control. SETUP: Auto Off FACTORY RESET
Disabled Completed!
Figure 27 Figure 30
4. Press the INPUT Control to exit the Setup Mode. 4. Press the Front Panel STAND/BY Push-button to
switch On the MA252.

22
23
How to Operate the MA252
Power On and Off Tubes LED will be illuminated with the Amber then rotating it to select
The Red LED to the left of the VOLUME Control Color. Then sound will be heard and the LED the desired Trim Function.
lights to indicate the MA252 is in Standby mode. To illumination color of the Small Signal Vacuum Then use the VOLUME Ad-
switch ON the MA252, Press the VOLUME Control Tubes will change to the Green Color. just Control to change the
on the Front Panel or press the Push-button on the setting. The Remote Con-
trol TRIM Push-Button
Remote Control. The MA252 will go through a Tube
Warmup Initialization procedure. Refer to figure 50. UNBAL 1 15% together together with the
Directional Push-buttons
can also be used to select a
MA252 Figure 52
TRIM Function and make
Tube Warmup Trim settings. Refer to
Figure 50 PHONO 30% figures 51 and 54.
This is followed by the Front Panel Display indicating After approximately 5 seconds
the last used source and the volume setting indication Figure 53 the Display returns to indicate
starting at zero and then increasing to the last used the Source Selection and Vol-
volume setting. Refer to figures 51, 52 and 53. To Source Selection ume Level.
switch OFF the MA252, press the VOLUME Control Rotate the INPUT Control to select the desired source
on the Front Panel or press the Power Push-button or press the Input Push-button on the Remote Con- BALANCE
on the Remote Control. trol. Refer to figures 51 and 54. Listening balance varies with
Notes: 1. For an explanation of the Remote Control Push- different program sources, room
button functions, refer to pages 16 and 17. Volume Control acoustics and listening positions
2. During the Tube Warm-Up period of time no Rotate the Front Panel VOLUME Control or use the relative to the Loudspeakers.
sound will be heard. The Small Signal Vacuum + or - Push-buttons on the Remote Control for Use the Balance (Trim Function)
the desired listening level. Refer to as needed to achieve approxi-
figures 51 and 54. mately equal listening volume
levels in each Loudspeaker. To
Trim Functions adjust the Balance perform the
The MA252 has various Trim Selec- following: Figure 54
tions with Adjustments. The Trim 1. Press the TRIM Push-button
UNBAL 1 15%
Functions include Balance, Input repeatedly on the Remote Control until L BAL-
Trim Level, Tone Controls, Bass, Tre- ANCE R, || appears on the Front Panel Display.
INPUT VOLUME
ble and Display. The Trim Settings Refer to figure 55.
HEADPHONES
STANDBY are stored in memory independently
for each Input Source Selected. L BALANCE R
PUSH - TRIM PUSH - POWER
Note: Selection and Adjustment of all ||
Trim Functions may be per- Figure 55
formed by pressing the Front Note: The Front Panel INPUT/Trim Control may also
Panel INPUT Trim Control and be used.
Figure 51
24
 How to Operate the MA252

2. Rotate the VOLUME Control or press the listened to. The range of adjustment is 6.0dB in After approximately 6 seconds the Display returns to
(Left or Right) directional Push-buttons to make a half dB steps. Refer to figures 59 and 60. indicate the Source Selection and Volume Level.
change to the current Balance Setting to emphasize
the Right Channel (refer to figure 56) or the Left INPUT TRIM BASS
Channel (refer to figure 57). -2.5 dB The Intensity of the Low Frequencies in the music can
Figure 59 be increased or decreased by using the Trim Select
L BALANCE R and Trim Adjust Controls. To make an adjustment
INPUT TRIM perform the following:
Figure 56 +4.0 dB 1. Use the Front Panel INPUT/TRIM Control or press
Figure 60 the TRIM Push-button on the Remote Control until
L BALANCE R After approximately 6 seconds the Information BASS, 0 dB appears on the Front Panel Infor-
Display returns to indicate the Source Selection and mation Display. Refer to figure 63.
Figure 57 Volume Level.
BASS
The Front Panel Display indicates the relative Balance
TONE CONTROL 0 dB
changes. After approximately 6 seconds, the Display
The Tone Controls default setting is On. The TRIM Figure 63
returns to indicate the Source Selection and Volume
Level. To verify the Balance setting without changing TREBLE and BASS Settings may be adjusted for the 2. Rotate the VOLUME Control or press the
it, use the TRIM Push-button and select Balance. currently selected Input Source. When the Tone Con- (Left or Right) directional Push-buttons to increase
trols are Disabled the previous settings for Treble and (refer to figure 64) or decrease (refer to figure 65)
TRIM LEVEL Bass are bypassed from the signal path. To deactivate the volume level of the low frequencies.
Source Components can have slightly different volume Tone Controls perform the following:
1. Select the desired Input Source. BASS
levels resulting in the need to readjust the MA252
Volume Control when switching between different 2. Press the TRIM Push-button on the Remote Con- +10dB
trol until TONE CONTROLS, On appears on Figure 64
sources. The MA252 allows the adjustment of levels
for each Source, ensuring the same relative volume. To the Front Panel Display. Refer to figure 61.
BASS
adjust the Trim Level for the currently selected Input
TONE CONTROLS -10dB
Source perform the following steps:
On Figure 65
1. Select INPUT TRIM as indicated on the Front
Figure 61 The Front Panel Display indicates the Bass changes
Panel Information Display. Refer to figures 51, 54
and 58. 3. Press (Left) directional Push-button to deacti- in steps from +10dB to -10dB. After approximately
vate the Tone Controls. Refer to figure 62. 6 seconds the Display returns to indicate the Source
INPUT TRIM Selection and Volume Level.
0.0 dB TONE CONTROLS
Figure 58 Off TREBLE
Figure 62 The Intensity of the High Frequencies in the music can
2. Adjust the Trim Level of each Input to match the
Note: When the TONE CONTROLS Setting is Off, the be increased or decreased by using the Trim Select
average volume level of the Input most frequently BASS and TREBLE Controls will be inactive.
and Trim Adjust Control. To make an adjustment per-
25
How to Operate the MA252, cont
form the following: in steps from +10dB to -10dB. After approximately cate the Source Selection and Volume Level.
1. Use the Front Panel INPUT/TRIM Control or the 6 seconds the Display returns to indicate the Source
TRIM Push-button on the Remote Control until Selection and Volume Level. Trim
TREBLE, 0 dB appears on the Front Panel Press the Front Panel INPUT/TRIM Control to ac-
Information Display. Refer to figure 66. INFORMATION DISPLAY tivate the MA252 Trim Functions. Rotate the Front
2. Rotate the VOLUME Control or press the The MA252 Front Panel Information Display default Panel INPUT/Trim Control to select the desired Trim
setting is for the display to be Always On. The Function and then rotate the VOLUME Control to
TREBLE Auto Off setting is an option when the Display will vary or make changes. Refer to figure 51. The Remote
0 dB only be On during a change in the operational control Control (Left or Right) directional Push-buttons
Figure 66 settings. To active the Display Auto Off setting to may also be used to vary or make changes. Approx-
(Left or Right) directional Push-buttons to increase performing the following steps: imately 5 seconds after Trim Function Selection and/
(refer to figure 67) or decrease (refer to figure 68) 1. Use the Front Panel INPUT/TRIM Control or the or adjustments have stopped, the MA252 will switch
the volume level of the high frequencies. TRIM Push-button on the Remote Control until off the Trim Mode.
DISPLAY, Always On appears on the Front
TREBLE Panel Information Display. Refer to figure 69. Mute
+10dB Press the Mute Push-button on the Remote Con-
Figure 67 DISPLAY trol to Mute the Audio. The Front Panel Display will
Always On indicate the Source Name and with the word MUTE in
TREBLE Figure 69 place of the actual volume setting. Refer to figure 71.
-10dB 2. Rotate the VOLUME Control or press the
Figure 68 (Left or Right) directional Push-buttons to select UNBAL 1 MUTE
The Front Panel Display indicates the Treble changes DISPLAY, Auto Off as indicated on the Front
Panel Information Display. The Dis- Figure 71
play will be active during the time Press the Mute Push-button a second time or adjust
the Front Panel Controls or Remote the Volume and the MA252 will un-mute.
Control Operational Functions are
being changed. Then 8 seconds later Headphones Jack
UNBAL 1 15% the Display will be switched Off. Connect a pair of dynamic headphones to the Head-
Refer to figure 70. phone Jack with a 1/4 (0.635cm) stereo phone type
plug for private listening. The Loudspeakers connect-
INPUT VOLUME
DISPLAY ed to the MA252 will be automatically muted.
Auto Off Note: The Headphone Output is optimized for imped-
HEADPHONES
STANDBY

PUSH - TRIM PUSH - POWER

Figure 70 ances ranging from 20 to 600 ohms.
After approximately 5 seconds the
Information Display returns to indi- Power Guard
During normal operation, the Small Signal Vacuum
Figure 51
26
 How to Operate the MA252, cont

Tubes LED Illumination is the color green. During

peaks in the audio signals when the Power Guard Cir-
cuitry is activated, the LED Illumination will change
to the amber color.

Protection Circuitry
In the event the MA252 over heats, due to improper
ventilation, high ambient temperature and/or imped-
ance mismatch, the internal protection circuits will
activate. The small Signal Vacumn Tubes normal LED
Illuminated Color of Green, will change to an Amber
Color. The Audio Sound will also be muted at that
time.
When the MA252 has returned to a safe operating
temperature, normal operation will resume, Audio
Sound will be heard and the small Signal Vacuum
Tubes LED Illuminated Color of Green will become
active.

Reset of the Microprocesors

In the unlikely event the controls of the MA252 stop
functioning, the microprocessors can be reset by per-
forming the following:
1. Press and hold in the Front Panel VOLUME CON-
TROL until the STANDBY/ON LED Indicator
switches Off.
2. Then release the VOLUME CONTROL and the
MA252 will switch Off.
3. When the STANDBY/ON LED is illuminated
press the VOLUME CONTROL and the MA252
will resume normal operation.

27
28
Photos

29
 Specifications

Amplifier Specifications General Specifications

Power Output Stereo SUB (Mono) Output (for rated input) Power Requirements
Minimum sine wave continuous average power output 1.7V unbalanced (6V Maximun) Field AC Voltage conversion of the MA252 is not pos-
per channel, with both channels operating is: sible. The MA252 is factory configured for one of the
100 watts into 8 ohm load Signal To Noise Ratio (A-Weighted) following AC Voltages:
160 watts into 4 ohm load High Level - 97dB below rated output 100 Volts, 50/60Hz at 4.4 amps
Phono - 80dB below 5mV input 110 Volts, 50/60Hz at 3.7 amps
Output Load Impedance 120 Volts, 50/60Hz at 3.7 amps
8 or 4 ohms Input Impedance 220 Volts, 50/60Hz at 2.0 amps
High Level - 20K ohms 230 Volts, 50/60Hz at 1.9 amps
Rated Power Band Phono - 47K ohms; 50pF 240 Volts, 50/60Hz at 1.9 amps
20Hz to 20,000Hz Standby: Less than 0.5 watt
SUB (Mono) Output Impedance
Note: Refer to the rear panel of the MA252 for the cor-
Total Harmonic Distortion 200 ohms
rect voltage.
0.03% maximum with both channels operating from 250
milliwatts to rated power, 20Hz to 20,000Hz Maximum Input Signal Overall Dimensions
High Level - 4V unbalanced, 8V balanced Width is 12 inches (30.5cm)
Intermodulation Distortion Phono - 40mV Height is 7-5/8 inches (19.4cm) including feet
0.03% maximum, if the instantaneous peak power Depth is 18 inches (45.7cm) including the Cables
output does not exceed twice the rated power output Voltage Gain
for any combination of frequencies from 20Hz to High Level to Amp Output: 40db Weight
20,000Hz. High Level to Sub (Mono) Output: 15dB 28 pounds (12.7 kg) net, 37 pounds (16.8 kg) in shipping
Phono to Amp Output: 80dB carton
Dynamic Headroom Phono to Sub (Mono) Output: 55dB
1.8dB Shipping Carton Dimensions
Tone Controls Width is 22-1/4 inches (56.5cm)
Wide Band Damping Factor Bass 10dB (1dB steps) @ 70Hz Depth is 19-1/4 inches (48.9cm)
Greater than 200 - 8 ohm, Greater than 100 - 4 ohm Treble 10dB (1dB steps) @ 10,000Hz Height is 13-1/2 inches (34.3cm)

Power Guard Headphone Impedance

Less than 2% THD with up to 16dB overdrive at 20 to 600 ohms
1,000Hz
Power Control Output
Frequency Response 12VDC, 25mA
+0, -0.5dB from 20Hz to 20,000Hz
+0, -3dB from 10Hz to 100,000Hz

Sensitivity (for rated output/8 ohm load)

High Level - 300mV unbalanced, 600mV balanced
Phono - 3.0mV

30
 Packing Instructions

Packing Instructions
In the event it is necessary to repack the equipment
Warning Sheet Foam Top/Bottom
for shipment, the equipment must be packed exactly
as shown below. It is very important that the four feet
are attached to the bottom of the equipment. This will Foam Insert for Tubes
ensure the proper equipment location on the bottom and Tube Shields
foam pad. Failure to do this will result in shipping Accesories
damage.
To protect the tubes during shippment, the Foam
Insert removed from the MA252 needs to be re-insert-
ed. Follow the unpacking instructions on pages 4-5 in
the reverse order.
Use the original shipping carton and interior parts
only if they are all in good serviceable condition. If
Feet
a shipping carton or any of the interior part(s) are
needed, please call or write Customer Service Depart- Foam End Cap Bottom
Screws
ment of McIntosh Laboratory, refer to page 2. Please
see the Part List for the correct part numbers.

MA252 Packing Material List Corrugated Bottom Pad Foam End Cap Top

Quantity Part Number Description Foam Top/Bottom

1 034580 Shipping carton
2 034582 Foam Top/Bottom
1 034577 Foam End Cap Pad Top
1 034578 Foam End Cap Pad Bottom
1 034581 Corrugated Bottom Pad Shipping Carton
1 034579 Foam Insert (for protecting
the Tubes during shipping)
1 041855 Warning Sheet

4 400159 10-32 x 3/4 inch screw

4 163185 Feet

31
 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. 04175700