McIntosh Laboratory, Inc. 2 Chambers Street Binghamton, New York MC255 Power Amplifier Owner’s Manual 13903-2699 Phone: 607-723-3512 www.mcintoshlabs.
Important Safety Information is supplied in a separate document “Important Additional Operation Information Guide” Thank You Customer Service General Information Your decision to own this McIntosh MC255 Five Channel Power Amplifier ranks you at the very top among discriminating music listeners. You now have “The Best.” The McIntosh dedication to “Quality,” is assurance that you will receive many years of musical enjoyment from this unit. Please take a short time to read the information in this manual.
Cable Information, Introduction and Performance Features Performance Features Connector and Cable Information XLR Connectors Below is the Pin configuration for the XLR Balanced Input, Input/Output Connectors on the MC255. Refer IN to the diagram for connection: PIN 1: Shield/Ground PIN 2: + Input/Output PIN 2 PIN 1 PIN 3: - Input/Output PIN 3 Power Control Connector The MC255 Power Control Input receives an On/Off signal from +5 to +12 volts.
Dimensions Dimensions The following dimensions can assist in determining the best location for your MC255. Front View of the MC255 17-1/2" 44.5cm 8-7/8" 22.5cm 9-7/16" 24.0cm Side View of the MC255 18-1/4" 46.4cm 16-5/8" 42.2cm Rear View of the MC255 16-13/16" 43.0cm 5/8" 1.6cm 13/16" 2.1cm 3" 7.62cm 11-3/4" 29.9cm 4 3/16" 0.5cm 12" 30.5cm 2" 8-5/16" 21.1cm 5.
Installation Installation The MC255 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 MC255 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 MC255 is removed from the custom installation and used free standing.
Rear Panel Connections and Switch OUPUTS 2 Connections (ZONE B) for Left Surround Channel and for an 8 ohm or 4 ohm Loudspeaker OUPUTS 5 Connections for Right Front Channel and for an 8 ohm or 4 ohm Loudspeaker POWER CONTROL IN ZA (Zone A) receives a turn On/Off signal from a McIntosh component for all five channels POWER CONTROL OUT ZA (Zone A) sends a turn On/Off signal to the next McIntosh Component OUPUTS 1 Connections for Left Front Channel and for an 8 ohm or 4 ohm Loudspeaker OUPUTS 3 Connectio
How to Connect Input Connections and Output Terminals Connections Output Terminals When connecting the Loudspeaker Hookup Cables to the MC255 Power Amplifier Output Terminals please follow the steps below: 1. Rotate the top of the Output Terminal Post counterclockwise until an opening appears. Refer to figures A and B. 2. Insert the Loudspeaker hookup cable into the Output Terminal Opening Post opening or the cable spade Figure B Figure A lug around the center post of the Output Terminal. Refer to figure C.
How to Connect Output Terminals Connections, con’t 7. Referring to figure H, connect the Loudspeaker hookup cables with banana plugs into the MC255 hole at the top of the terminal Figure to theF Figure H Negative Output Terminal and the Positive Output Terminal indentified as 4Ω (ohm) or 8Ω (ohm) connection to match the impedance of the Loudspeaker, being careful to observe the correct polarities.
Front Panel Displays and Controls Meter indicates the Front Left Channel Output of the amplifier Meter indicates the Front Center Channel Output of the amplifier The LED indicates when the POWER GUARD Circuitry has activated for the Amplifier Center Channel (C4) The LEDs indicate when the POWER GUARD Circuitry has activated for Amplifier Channels, Right Front (RF5) and Right Surround (RS4) The LEDs indicate when the POWER GUARD Circuitry has activated for Amplifier Channels, Left Front (LF1) and Left Su
How to Operate How to Operate Power On There are two ways to have AC Power switched ON to the MC255: REMOTE Setting When the MC255 Power Control Connection (ZA and/or ZB) receives a Power Control Signal from a Preamplifier or A/V Control Center, it will turn On automatically when the MC255 POWER Control is set to the REMOTE Setting. Refer to figure 9. ON Setting When the MC255 POWER Control is set to the ON position, it will become active Zone A only. Refer to figure 10.
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. The MC255 has a continuous average power output rating of 250 watts and with a peak output current of 25 amperes per channel; making this one of the most advanced amplifiers available today.
Technical Description Block Diagram of the Power Amplifier (one channel shown) 4Ω/8Ω DISPLAY CONTROL ILUMETER POWER OUTPUT INDICATOR AUTO SENSE CONTROL ThermalTrak DC BIAS THERMAL SENSORS UNBALANCED INPUT BALANCED INPUT TO POWER SAVE CONTROL + - AMP POWER GUARD ATTENUATOR AMP MUTE Figure 18 Figure 16 All transistors are selected to have nearly constant current gain over the entire current range they must cover.
Technical Description, con’t Protection Circuits The MC255 incorporates the McIntosh Sentry Monitor Output Transistor Protection Circuit. Refer to Figure 20. There is absolutely no compromise in sonic performance with this circuit, and it Normal Operating Area ensures safe operation of the amplifier under even Sentry Monitor Output Safety Area Transistor the most extreme Failure operating condiFigure 20 tions.
Technical Description, con’t AC POWER CIRCUIT BREAKER Block Diagram of the Power Supply POWER RELAY POWER SAVE CONTROL Figure 24 It is enclosed in the legendary McIntosh Potted Enclosures and weighs 30 lbs. The six super size main filter capacitors can store over 350 Joules of energy which is necessary for the wide dynamic range that “Digital Audio” demands. Refer to figure 26. The power amplifier draws high current from the AC power line.
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Specifications Specifications Power Output (All Five Channels) Minimum sine wave continuous average power output per channel, all channels operating is: 200 watts into a 4 ohm or 8 ohm load Power Output (Three Front Channels) Minimum sine wave continuous average power output per channel operating is: 250 watts into a 4 ohm or 8 ohm load Output Load Impedance 8 and 4 ohms Rated Power Band 20Hz to 20,000Hz Total Harmonic Distortion 0.
Packing Instructions Packing Instructions In the event it is necessary to repack the equipment for shipment, the equipment must be packed exactly as shown below. It is very important that the four plastic feet are attached to the bottom of the equipment. Four 1/4 - 20 x 2-1/4 inch screws and washers must be used to fasten the unit securely to the bottom pad and shipping skid. This will ensure the proper equipment location on the bottom pad. Failure to do this will result in shipping damage.
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.
