McIntosh MC152

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McIntosh Laboratory, Inc. 2 Chambers Street Binghamton, New York 13903-2699 Phone: 607-723-3512 www.mcintoshlabs.com MC152 Power Amplifier Owner’s Manual 2 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 en - closure 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. 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. 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 instruc- tions. 8. Do not install near any heat sources such as radiators, heat registers, stoves, or other appa- ratus (including amplifiers) that produce heat. 9. Do not defeat the safety purpose of the polar- ized 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 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 manu - facturer, or sold with the appa- ratus. When a cart is used, use caution when moving the cart/ apparatus combination to avoid injury from tip-over. 13. Unplug this apparatus during lightning storms or when unused for long periods of time. 14. Refer all servicing to qualified service person - nel. 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. 18. Do not expose batteries to excessive heat such as sunshine, fire or the like. 19. Connect mains power supply cord only to a mains socket outlet with a protective earthing connection. IMPORTANT SAFETY INSTRUCTIONS! PLEASE READ THEM BEFORE OPERATING THIS EQUIPMENT. 3 2. The MC152 mutes the speaker output for approxi- mately two seconds when first turned on. 3. For the best performance and safety it is important to always match the impedance of the Loudspeaker to the Power Amplifier connections. Refer to “How to Connect” pages 8 thru 11. Note: The impedance of a Loudspeaker actually var- ies as the Loudspeaker reproduces different frequencies. As a result, the nominal impedance rating of the Loudspeaker (usually measured at a midrange frequency) might not always agree with the impedance of the Loudspeaker at low frequencies where the greatest amount of power is required. Contact the Loudspeaker Manufac- turer for additional information about the actual impedance of the Loudspeaker before connecting it to the McIntosh MC152. 4 . In the event the MC152 over heats, due to improper ventilation and/or high ambient temperature, the protection circuits will activate. The Front Panel Power Guard LED will continuously indicate ON and the audio will be muted. When the MC152 has returned to a safe operating temperature, normal operation will resume. 5. When discarding the unit, comply with local rules or regulations. Batteries should never be thrown away or incinerated but disposed of in accordance with the local regulations concerning battery disposal. 6. For additional information on the MC152 and other McIntosh Products please visit the McIn- tosh Web Site at www.mcintoshlabs.com. 1. For additional connection information, refer to the owner’s manual(s) for any component(s) connected to the MC152. Thank You Please Take A Moment Technical Assistance If at any time you have questions about your McIntosh product, contact your McIntosh Dealer who is familiar with your McIntosh equipment and any other brands that may be part of your system. If you or your Dealer wish additional help concerning a suspected problem, you can receive technical assistance for all McIntosh products at: McIntosh Laboratory, Inc. 2 Chambers Street Binghamton, New York 13903 Phone: 607-723-1545 Fax: 607-724-0549 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: 607-723-3515 Fax: 607-723-1917 Copyright 2014 © by McIntosh Laboratory, Inc. Table of Contents Your decision to own this McIntosh MC152 Power Amplifier ranks you at the very top among discrimi- nating 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 pos- sible with all the features and functions of your new McIntosh. 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: ________________________________ Safety Instructions ......................................................2 Thank You and Please Take a Moment .......................3 Technical Assistance and Customer Service ..............3 Table of Contents ........................................................3 General Information ...................................................3 Connector and Cable Information ..............................4 Introduction .................................................................4 Performance Features .................................................4 Dimensions .................................................................5 Installation ..................................................................6 Rear Panel Connections and Switch ...........................7 Output Terminals and How to Connect .................. 8-9 Output Terminals and How to Connect for Bi-Amp ......................................................... 10-11 Front Panel Displays and Controls ............................12 How to Operate ......................................................... 13 Technical Description .......................................... 14-17 Specifications ............................................................ 18 Packing Instruction ................................................... 19 General Information 4 XLR Connectors Below is the Pin configuration for the XLR Balanced Input Connectors on the MC152. Refer to the diagram for connection: PIN 1: Shield/Ground PIN 2: + Input/Output PIN 3: - Input/Output Power Control Connector The MC152 Power Control Input receives an On/Off signal from +5 to +12 volts. The Power Control Output will in turn provide a +12 volt Output Signal with a total cur- rent up to 50mA. An additional connection is for controlling the illumination of the MC152 Power Output Meters. The 3.5mm stereo mini phone plug connects to a McIntosh Preamplifier or A/V Control Center Power Control Output. Output Terminal Connector When cables with spade lugs are used for Loudspeaker Connection, the spade lugs need an opening of at least 3/10 inch (7.6mm) Cable Information, Introduction and Performance Features Connector and Cable Information Introduction Now you can take advantage of traditional McIntosh standards of excellence in the MC152 Power Ampli- fier. The 150 watts high current output per channel will drive any high quality Loudspeaker. The MC152 reproduction is sonically transparent and absolutely accurate. The McIntosh Sound is “The Sound of the Music Itself.” Performance Features • Power Output The MC152 is a Power Amplifier with a capability of 150 watts per channel into 2, 4 or 8 ohm speakers with less than 0.005% distortion. The Power Amplifier Circuitry uses Thermal Trak 1 Output Transistors for lower distortion and cool operation. • Patented Autoformer McIntosh designed and manufactured Output Auto- formers provide an ideal match between the amplifier output stages and speaker loads of 2, 4 and 8 ohms. The Autoformers also provide perfect DC protection for your valuable loudspeakers. • Balanced and Unbalanced Inputs Balanced connections guard against induced noise and allow long cable runs without compromising sound quality. • Power Guard The patented McIntosh Power Guard circuit prevents the amplifier from being over driven into clipping, with its harsh distorted sound that can also damage your valuable loudspeaker. • Sentry Monitor and Thermal Protection McIntosh Sentry Monitor power output stage protec- tion circuits ensure the MC152 will have a long and trouble free operating life. Built-in Thermal Protection Circuits guard against overheating. • Special Power Supply A very large Power Transformer and Large Capaci- tors ensure stable noise free operation even though the power line varies. • Illuminated Power Meters The Illuminated Power Output Watt Meters on the MC152 are peak responding, and indicates the power output of the amplifier. The Front Panel Meter Illu- mination may be controlled On/Off by comtemporary McIntosh Preamplifiers and Audio/Video Control Centers. • Auto Off The MC152 incorporates a Power Save Feature to automatically switch power Off to the Power Ampli- fier approximately 30 minutes after there has been an absence of an audio input signal. • McIntosh Custom Binding Posts McIntosh patent pending gold plated output terminals deliver high current output. They accept large diam- eter wire and spade lugs. Banana plugs may also be used only in the United States and Canada. • Glass Front Panel with Solid State Illumination The famous McIntosh Illuminated Glass Front Panel is evenly Illuminated by the combination of custom designed Fiber Optic Light Diffusers and extra long life Light Emitting Diodes (LEDs). Trigger Control Ground Meter Illumination Control 1 ThermalTrak™ and ON Semiconductor are trademarks of Semi- conductor Components Industries, LLC 3/10 of an inch (7.6millimeters) PIN 2 PIN 1 PIN 3 5 Dimensions The following dimensions can assist in determining the best location for your MC152. Dimensions 17-1/2" 44.5cm 13 -1/4" 33.7cm 17-1/8" 43.5cm 3/16" 0.5cm 13/16" 2.1cm 12-5/8" 32.1cm 17-3/16" 43.7cm 3" 7.6cm Front View of the MC152 Rear View of the MC152 Side View of the MC152 6" 15.2cm 5-3/8" 13.7cm 4-9/16" 11.6cm 4-3/4" 12.1cm 18-15/16" 48.1cm BAL R BAL L UNBAL 12-1/4" 31.1cm 1-9/16" 4.0cm 6 Installation Installation The MC152 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 MC152 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 MC152 is removed from the custom installation and used free standing. The required panel cutout, ventila- tion cutout and unit dimensions are shown. Always provide adequate ventilation for your MC152. Cool operation ensures the longest possible operating life for any electronic instrument. Do not install the MC152 directly above a heat generating component such as a high powered amplifier. If all the compo- nents are installed in a single cabinet, a quiet running ventilation fan can be a definite asset in maintaining all the system components at the coolest possible oper- ating temperature. A custom cabinet installation should provide the fol- lowing minimum spacing dimensions for cool opera- tion. Allow at least 6 inches (15.24cm) above the top, 2 inches (5.08cm) below the bottom, 3 inches (7.62cm) behind the rear panel and 2 inches (5.08cm) on each side of the Power Amplifier, so that airflow is not obstructed. Allow 2-1/2 inches (6.35 cm) in front of the mounting 1 panel for clearance. Be sure to cut out a ventilation hole in the mounting shelf according to the dimensions in the drawing. 1 When the MC152 is installed together with other McIn- tosh Components, check clearances on all components before proceeding. MC152 Front Panel Custom Cabinet Cutout MC152 Side View in Custom Cabinet MC152 Bottom View in Custom Cabinet 17-3/16" 43.66cm Cutout Opening for Custom Mounting Cabinet Front Panel 10-3/4" 27.3cm Opening for Ventilation Cabinet Front Panel 6" 15.2cm Opening for Ventilation Cutout Opening for Ventilation Cutout Opening for Ventilation Support Shelf Chassis Spacers Note: Center the cutout Horizontally on the unit. For purposes of clarity, the above illustration is not drawn to scale. 7" 17.8cm 15-5/8" 39.6cm 9" 22.8cm 16" 40.6cm 13" 33cm 3" 7.6cm 15-1/16" 38.3cm 7 BAL R BAL L UNBAL Connect the MC152 power cord to a live AC outlet. Refer to the rear panel to determine the correct voltage PoWeR ConTRoL IN receives turn On/Off signals from a McIntosh component UNBALanced IN- PUTS for an audio cable from a Preampli- fier or A/V Control Center audio output INPUT MODE switch se- lects between BALanced or UNBALanced Input BALanced R INPUT for audio cables from a Preamplifier or A/V Control Center audio output Rear Panel Connections and Switch Fuse holder, refer to information on the rear panel of your MC152 to determine the correct fuse size and rating RIGHT OUTPUT Connections for a 2 ohm, 4 ohm and 8 ohm Loudspeaker PoWeR ConTRoL OUT sends turn On/Off signals to the next McIntosh Com- ponent AUTO OFF Power Save Feature is either DISabled or ENAbled LEFT OUTPUT Connections for a 2 ohm, 4 ohm and 8 ohm Loudspeaker BALanced L INPUT for audio cables from a Preamplifier or A/V Control Center audio output 8 3. Prepare the Loudspeaker Hookup Cable for attach- ment to the MC152 Power Amplifier: Bare wire cable ends: Carefully remove sufficient insulation from the cable ends, refer to figures 2, 3 & 4. If the cable is stranded, carefully twist the strands together as tightly as possible. Notes: 1. If desired, the twisted ends can be tinned with solder to keep the strands together. 2. The prepared bare wire cable ends may be inserted into spade lug connectors. 3. Banana plugs are for use in the United States and Canada only. Banana Plugs are for use in the United States and Canada only: 4. Attach the previously prepared bare wire cable ends into the banana plugs and secure the connections. Refer to figure F. 5. Rotate the top of the Output Terminal Post clockwise until it is finger tight. Refer to figure G. Then using the McIntosh Wrench, rotate the top of the Output Terminal one quarter of a turn (90° ). Do not over tighten. Refer to figure E. 6. Referring to figure H, connect the Loudspeaker hookup cables with ba- nana plugs into the hole at the end of the MC152 Negative and Positive How to Connect 1. For Remote Power Control, connect a power control cable from the Audio Preamplifier or A/V Control Center Power Control Output 1 to the Amplifier PoWeR ConTRoL IN. Note: When a Power Control Cable is connected between the MC152 and Preamplifier (or A/V Control Center), the AUTO OFF Feature is bypassed. Refer to page 13. 2. Connect XLR cables from the Balanced Output 1 (L&R) of an Audio Preamplifier or A/V Control Center to the Amplifier BALanced INput (Right and Left). Place the INPUT MODE Switch in the BALanced Position. Note: An optional hookup is to use unbalanced cable and place the INPUT MODE Switch in the UNBALanced Position. This McIntosh MC152 Power Amplifier is designed for Loudspeakers with an impedance of 2 ohms, 4 ohms or 8 ohms. Connect a single Loudspeaker only to the Right and Left Output Terminals. When connecting Loudspeakers to the MC152 it is very important to use cables of adequate size, so there is little to no power loss in the cables. The size is specified in Gauge Numbers or AWG (American Wire Gauge). The smaller the Gauge number, the larger the wire size: Loudspeaker Cable Distance vs Wire Gauge Guide Loudspeaker Impedance 25 feet (7.62 meters) or less 50 feet (15.24 meters) or less 100 feet (30.48 meters) or less 2 Ohms 12AWG 10AWG 8AWG 4 Ohms 14AWG 12AWG 10AWG 8 Ohms 16AWG 14AWG 12AWG Caution: Do not connect the AC Power Cord to the MC152 Rear Panel until after the Loudspeaker Connections are made. Failure to observe this could result in Electric Shock. The connection instructions below, together with the MC152 Connection Diagram located on the separate folded sheet “ Mc1A ”, is an example of a typical audio system. Your system may vary from this, however the actual components would be connected in a similar manner. For additional information refer to “Connec- tor and Cable Information” on page 4. Figure 2 Figure 3 Figure 4 Figure F Figure H Output Terminals When connecting the Loudspeaker Hookup Cables to the MC152 Power Amplifier Output Terminals please follow the steps below: 1. Rotate the top of the Output Terminal Post coun- terclockwise until an opening appears. Refer to figures A and B. 2. Insert the Loudspeaker hookup cable into the Output Terminal Post opening or the cable spade lug around the center post of the Output Terminal. Refer to figure C. 3. Rotate the top of the Output Terminal Post clockwise until it is finger tight. Refer to figure D. 4. Place the supplied McIntosh Wrench over the top of the Out- put Terminal and rotate it one quarter of a turn (90° ) to secure the Loudspeaker Cable Connec- tion. Do not over tighten. Refer to figure E. Figure G Figure A Opening Figure B Figure C Figure D Figure E 9 Note: The illustration on separate sheet “ Mc1A ” is connections for 8Ω (ohms) Loudspeakers. If the Loudspeaker’s impedance is in-between the available connections, use the nearest lower imped- ance connection. Refer to “General Information” Note 3 on page 3 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. 9. Connect the MC152 power cord to an active AC outlet. Output Terminals. The terminals are indentified as 2Ω (ohms), 4Ω (ohms) or 8Ω (ohms) connection to match the impedance of the Loudspeaker, being careful to observe the correct polarities. Note: The illustration on separate sheet “ Mc1A ” is connections for 8Ω (ohms) Loudspeakers. If the Loudspeaker’s impedance is in-between the available connections, use the nearest lower imped- ance connection. Refer to “General Information” Note 3 on page 3 for additional information. WARNING: Loudspeaker terminals are hazardous live and present a risk of electric shock. For additional instruction on making Loudspeaker Connections contact your McIntosh Dealer or McIntosh Techni- cal Support. 7. Connect the MC152 power cord to an active AC outlet. Spade Lug or Wire Connections: 8. Connect the Loudspeaker hookup cables to the MC152 Negative Output Terminal and Positive Output Terminal indentified as 2Ω (ohms), 4Ω (ohms) or 8Ω (ohms) connection to match the impedance of the Loudspeaker, being careful to observe the correct polarities. Insert the spade lug connector or prepared section of the cable end into the terminal side access hole, and tighten the terminal cap until the cable is firmly clamped into the terminals so the lugs or wire cannot slip out. Refer to figures 7 and 8. Output Terminals and How to Connect Figure 7 Figure 8 10 Loudspeaker Cable Distance vs Wire Gauge Guide Loudspeaker Impedance 25 feet (7.62 meters) or less 50 feet (15.24 meters) or less 100 feet (30.48 meters) or less 2 Ohms 12AWG 10AWG 8AWG 4 Ohms 14AWG 12AWG 10AWG 8 Ohms 16AWG 14AWG 12AWG 5. Prepare the Loudspeaker Hookup Cable for attach- ment to the MC152 Power Amplifier: Bare wire cable ends: Carefully remove sufficient insulation from the cable ends, refer to figures 2, 3 & 4. If the cable is stranded, carefully twist the strands together as tightly as possible. Notes: 1. If desired, the twisted ends can be tinned with solder to keep the strands together. 2. The prepared bare wire cable ends may be inserted into spade lug connectors. 3. Banana plugs are for use in the United States and Canada only. Banana Plugs are for use in the United States and Canada only: 6. Attach the previously prepared bare wire cable ends into the banana plugs and secure the connections. Refer to figure F. 7. Rotate the top of the Output Terminal Post clockwise until it is finger tight. Refer to figure G. Then using the McIn - tosh Wrench, rotate the top of the Output Terminal one quarter of a turn (90° ). Do not over tighten. Refer to figure E. How to Connect for Bi-Amp 1. For Remote Power Control, connect a power control cable from the Audio Preamplifier or A/V Control Center Power Control Output 1 to Amplifier One PoWeR CoNTRoL IN. Note: When the Power Control Cable is connected between the MC152 and Preamplifier or A/V Control Center, the AUTO OFF Power Save Feature is automatically disabled. 2. Connect a power control cable from AudioPream- plifier power control Output 2 to Amplifier Two PoWeR CoNTRoL IN. 3. Connect XLR cables from the Balanced Output 1 (L&R) of an Audio Preamplifier or A/V Control Center to the MC152 BALanced INput (Right and Left) on Amplifier One. Place the INPUT MODE Switch in the BALanced Position. Note: An optional hookup is to use unbalanced cable and place the INPUT MODE Switch in the UNBALanced Position. 4. Connect XLR cables from the Balanced Output 2 (L&R) of an Audio Preamplifier or A/V Control Center to the MC152 Balanced INput (Right and Left) on Amplifier Two. Place the INPUT MODE Switch in the BALanced Position. Note: An optional hookup is to use unbalanced cable and place the INPUT MODE Switch in the UNBALanced Position. This McIntosh MC152 Power Amplifier is designed for Loudspeakers with an impedance of 2 ohms, 4 ohms or 8 ohms. Connect a single Loudspeaker only to the Right and Left Output Terminals. When connecting Loudspeakers to the MC152 it is very important to use cables of adequate size, so there is little to no power loss in the cables. The size is specified in Gauge Numbers or AWG (American Wire Gauge). The smaller the Gauge number, the larger the wire size: Caution: Do not connect the AC Power Cord to the MC152 Rear Panel until after the Loudspeaker Connections are made. Failure to observe this could result in Electric Shock. The connection instructions below, together with the MC152 Connection Diagram located on the separate folded sheet “ Mc1B ”, is an example of a typical audio system. Your system may vary from this, however the actual components would be connected in a similar manner. For additional information refer to “Connec- tor and Cable Information” on page 4. Figure 2 Figure 3 Figure 4 Figure F When connecting the Loudspeaker Hookup Cables to the MC152 Power Amplifier Output Terminals please follow the steps below: 1. Rotate the top of the Output Terminal Post counterclock- wise until an opening appears. Refer to figures A and B. 2. Insert the Loudspeaker hookup cable into the Output Terminal Post opening or the cable spade lug around the center post of the Output Terminal. Refer to figure C. 3. Rotate the top of the Output Terminal Post clockwise until it is finger tight. Refer to figure D. 4. Place the supplied McIntosh Wrench over the top of the Out- put Terminal and rotate it one quarter of a turn (90° ) to secure the Loudspeaker Cable Connec- tion. Do not over tighten. Refer to figure E. Output Terminals Figure A Opening Figure B Figure C Figure D Figure E 11 How to Connect for Bi-Amp terminal cap until the cable is firmly clamped into the terminals so the lugs or wire cannot slip out. Refer to figures 7 and 8. Note: The illustration on separate sheet “ Mc1B ” is connections for 8Ω (ohms) Loudspeakers. If the Loudspeaker’s impedance is in-between the available connections, use the nearest lower imped- ance connection. Refer to “General Information” Note 3 on page 3 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. 11. Connect the MC152 power cord to an active AC outlet. 8. Referring to figure H, connect the Loudspeaker hookup cables with banana plugs into the hole at the top of the MC152 Negative and Positive Output Terminals. The terminals are indentified as 2Ω (ohms), 4Ω (ohms) or 8Ω (ohms) connection to match the impedance of the Loud- speaker, being careful to observe the correct polarities. Note: The illustration on separate sheet “ Mc1B ” is connections for 8Ω (ohms) Loudspeakers. If the Loudspeaker’s impedance is in-between the available connections, use the nearest lower imped- ance connection. Refer to “General Information” Note 3 on page 3 for additional information. WARNING: Loudspeaker terminals are hazardous live and present a risk of electric shock. For additional instruction on making Loudspeaker Connections contact your McIntosh Dealer or McIntosh Techni- cal Support. 9. Connect the MC152 power cord to an active AC outlet. Spade Lug or Wire Connections: 10. Connect the Loudspeaker hookup cables to the MC152 Negative Output Terminal and Positive Output Terminal indentified as 2Ω (ohms), 4Ω (ohms) or 8Ω (ohms) connection to match the impedance of the Loudspeaker, being careful to observe the correct polarities. Insert the spade lug connector or prepared section of the cable end into the terminal side access hole, and tighten the Figure 7 Figure 8 Figure H Figure G 12 Front Panel Displays and Controls Standby Power On Indicator POWER Push-button switches AC Power On and Off METER Push-button switches Meter Illumination On and Off Meter indicates the Right Channel Output of the amplifier LED indicates when the LEFT Channel Amplifier POWER GUARD circuit activates Meter indicates the Left Channel Output of the amplifier LED indicates when the RIGHT Channel Amplifier POWER GUARD circuit activates 13 Power On/Off Momentarily press the POWER Push-button to switch the MC152 On or Off. Refer to figure 8. Note: There must be a power control connection between the MC152 and the Audio Preamplifier or A/V Control Center, in order for the remote power turn-on to function. Auto Off The MC152 incorporates a Power Save Feature to automatically switch power Off to the Power Ampli- fier approximately 30 minutes after there has been an absence of an audio input signal. Note: If the Power Save Feature has activated and switched the MC152 Off, the Power Save Fea- ture can be reset by momentarily pressing the POWER Push-button. When there is a Power Control Connection be- tween the MC152 and a McIntosh Preamplifier or (A/V Control Center), the Power Save Feature in the MC152 is bypassed. With the MC152 connected (via Power Control) to a McIntosh Preamplifier (or A/V Control Center) with the Power Save Feature and the feature is active, the MC152 will switch Off with the Preamplifier (or A/V Control Center) after a period of inactivity. There may be times when it would be desirable to bypass the Power Save Feature, which by default is ac- tive. This can be implemented by placing the “AUTO OFF” Switch, located on the MC152 Rear Panel, in the DIS (Disable) position. Refer to figure 9: How to Operate How to Operate Input Mode Switch The Input Mode Switch, which is located on the Rear Panel of the MC152, allows selec- tion of either the BALanced or UN- BALanced Input. Refer to figure 12. Power Meter By default the Power Output Meters are illuminated when the MC152 is On. To switch Off the Meter Illumination, mo- mentarily press the METER LIGHT Push-button. Refer to figure 10. The Power Output Meters will continue to indicate the power output even with the Illumination Off. Note: When Power Control Input of the MC152 is connected to an Audio Preampli- fier or A/V Control Center with Remote Meter Illumination Control, the Meter Illumination will automatically be remotely controlled (On/Off). The meters respond to all the musical information being produced by the amplifier. It indicates to an ac- curacy of at least 95% of the power output with only a single cycle of a 2000Hz tone burst. Refer to figure 11. Figure 8 BAL L Figure 9 Figure 11 Figure 10 Figure 12 14 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 compro- mise, using the most advanced McIntosh circuit design concepts. The MC152 has a continuous average power output rating of 150 watts per channel and with a peak output current of 40 amperes; making this one of the most advanced amplifiers available today. The distortion limits for the MC152 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 read- ings on the MC152 are so low, it takes special measuring tech- niques to make accurate read- ings. The MC152 can deliver the best possible performance from any type of high quality loud- speaker system. Refer to figure 13. Creating an amplifier with this level of performance did not come easily. Many months of de- sign, testing and measuring were required. Extensive controlled listening tests, the ultimate form of measuring, were made before the final design was accepted. Design Philosophy The design philosophy incor- porated in the MC152 involved several different techniques, all based on sound scientific logic. Every stage of voltage or current amplification must be as linear as possible prior to the use of nega- tive feedback. Refer to figure 14. 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. The Balanced Push-Pull design is used from input to output. Each channel of the amplifier contains com- plimentary balanced circuitry. Refer to figure 15. All transistors are selected to have nearly constant current gain over the entire current range they must cover. Output transistors in particular, have matched uniform current gain, high current bandwidth product and large active region safe operating area. These Power Transistors are the very latest in semiconductor technology and incorpo- rate a new design known as Thermal- Trak™. Refer to figure 16. This allows for the instantaneous and accurate monitor- ing of the Power Transistor Temperature. The MC152 Power Output Circuitry has a specially designed bias circuit to take full advantage of the ThermalTrak™ Power Transistors and thus precisely controls the power amplifier operation over a wide range of music conditions with the benefits of lower distortion and cooler operation. Precision metal film resistors and low dielectric absorption film ca- pacitors are used in all critical circuit locations. Technical Description Figure 16 Figure 14 Figure 13 15 The output signal of the amplifier circuit is coupled into the unique McIntosh MC152 Output Autoformer. It provides low distortion power transfer at frequen- cies from below 20Hz to well beyond 20,000Hz with optimum impedance points of two ohms, four ohms and eight ohms. The unequaled expertise of McIntosh in the design and manufacturing of autoformers is leg- endary in the high fidelity industry. Refer to figure 17. The Autoformer creates an ideal match between the power am- plifier output stage and the loudspeaker. Refer to figure 18. There is absolutely no performance limitation with an Autoformer. Its frequency response ex- ceeds 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. The high efficiency circuit design of the MC152 contributes to low operating temperatures. More than 800 square inches of heat sink area keep the MC152 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 op- timum 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 out- put stage. This increase in temperature will result in a reduced life expectancy for the amplifier. Technical Description Figure 18 Block Diagram of the Power Amplifier (one channel shown) Figure 15 ThermalTrak DC BIAS OUTPUT MUTE THERMAL SENSORS BALANCED AMP POWER GUARD ATTENUATOR INPUT MODE SWITCH - AMP + AMP UNBALANCED INPUT BALANCED INPUT + - com Figure 17 16 In the rare event of a power amplifier output circuit failure, the McIntosh Autoformer provides absolute protection from possible damage to your valuable loudspeakers. The unequaled expertise of McIntosh in the design and manufacturing of Autoformers is legendary in the high fidelity industry. McIntosh engi- neers know how to do it right. Power Output Meter The McIntosh MC152 has large Output Watt Meters responding to 95% full scale to a single cycle tone burst at 2kHz. Refer to figure 19. The Ampli- fier Outputs are electronically measured and fed to a special circuit that accelerates the pointer movement in the upward direction. Refer to figure 26 on the next page. When the pointer reaches its peak it pauses only long enough for the human eye to perceive its position, then drops. It is almost 10 times faster than a profes- sional VU meter. will never experience the harsh and damaging dis- tortion due to clipping. The Power Guard circuit is a waveform comparator, monitoring both the input and output waveforms. Under normal operating conditions, there are no differences between the shape of these waveforms. If the amplifier is overdriven, there will be a differ- ence between the two signal waveforms. When the difference exceeds 0.3%, the Power Guard activates the PG light and a dynamic electronic attenuator at the ampli- fier 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 MC152 Power Amplifier with Power Guard is not limited to just the rated power output, but will actu- ally produce distortion free output well above its rated power due to the McIntosh philosophy of conservative design. Protection Circuits The MC152 incorporates the McIntosh Sentry Moni- tor Output Transistor Protection Circuit. Refer to Figure 20. There is absolutely no com- promise in sonic performance with this circuit, and it ensures safe opera- tion of the ampli- fier under even the most extreme operating condi- tions. The different types of protection circuits incorporated in the MC152 insure a long and safe operating life. This is just one of the many char- acteristics of McIntosh Power Amplifiers that make them world famous. The MC152 also includes the unique patented McIntosh Power Guard circuit. Power Guard elimi- nates the possibility of ever overdriving the amplifier into clipping. Refer to figures 21, 22 and 23. 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 undesir- able, since it can damage valuable loudspeaker system tweeters. You Figure 22 Without Power Guard Figure 21 Input Test Signal (14kHz & 15kHz) Figure 23 With Power Guard Figure 20 Normal Operating Area Sentry Monitor Safety Area Output Transistor Failure Technical Description, con’t Figure 19 17 Technical Description, con’t Figure 24 Block Diagram of the Power Supply INRUSH CURRENT LIMITER AC Power MAIN RELAYS BACKUP POWER SUPPLY CONTROL LOGIC LIGHTING CONTROL POWER CONTROL Power Supply Circuits To compliment the design of the MC152 Power Am- plifier Circuitry, there is a high current high voltage power supply. Refer to figures 24 and 26. The very large Power Transfomer can supply over 6 amps of current. Refer to figure 25 (golf ball is for size com- parsion). It is enclosed in the legendary McIntosh Pot - ted Enclosures and weighs 18 lbs. There are two super size main filter capacitors sup- pling all of the 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. Therefore, it is important that they plug directly into the wall outlet. Also, most owners desire one power switch for the whole audio system. The MC152 is equipped with a circuit that provides remote Power Control from a Mc- Intosh A/V Control Center. Refer to figure 14 on page 14. When the A/V Control Center is switched On, a (5-12V) signal operates the power relay in the MC152. The MC152 also has a Power Control Out Jack. The Power Control signal from the jack is delayed by a fraction of a second so that the turn on power surge of the next power amplifier occurs at a later time. This helps prevent power circuit overload that could trip circuit breakers or blow fuses, a very important feature in a high power Home Systems employing multiple MC152 Power Amplifiers. Figure 26 Figure 25 18 Specifications Specifications Power Output Minimum sine wave continuous average power output per channel, with both channels operating is: 150 watts into 2 ohm load 150 watts into 4 ohm load 150 watts into 8 ohm load Output Load Impedance 2, 4 or 8 ohms Rated Power Band 20Hz to 20,000Hz Total Harmonic Distortion 0.005% maximum harmonic distortion at any power level from 250 milliwatts to rated power, 20Hz to 20,000Hz Dynamic Headroom 2dB Frequency Response +0, -0.25dB from 20Hz to 20,000Hz +0, -3.0dB from 10Hz to 100,000Hz Input Sensitivity (for rated output) 2.4 Volts Balanced 1.2 Volts Unbalanced Signal To Noise Ratio (A-Weighted) 95dB Balanced (118dB below rated output) 93dB Unbalanced (115dB below rated output) Intermodulation Distortion 0.005% maximum, if the instantaneous peak power output does not exceed twice the rated power output for any combination of frequencies from 20Hz to 20,000Hz. Wide Band Damping Factor Greater than 40 Input Impedance 22,000 ohms Balanced 22,000 ohms Unbalanced Voltage Gain 23dB, 2 Ohms 26dB, 4 Ohms 29dB, 8 Ohms Power Guard Less than 2% Total Harmonic Distortion with up to a 14dB overdrive signal Power Control Input 5-15VDC, less than 1mA Power Control Output 12VDC, 50mA maximum Output is delayed 0.2 seconds from turn On Power Requirements Field AC Voltage conversion of the MC152 is not possible. The MC152 is factory configured for one of the following AC Voltages: 100V ~ 50/60Hz at 4.4 Amps 110V ~ 50/60Hz at 3.7 Amps 120V ~ 50/60Hz at 3.7 Amps 220V ~ 50/60Hz at 2.0 Amps 230V ~ 50/60Hz at 1.9 Amps 240V ~ 50/60Hz at 1.9 Amps Standby: less than 0.3 watt Note: Refer to the rear panel of the MC152 for the cor- rect voltage. Overall Dimensions Width is 17-1/2 inches (44.5cm) Height is 6 inches (15.2cm) including feet Depth is 21 inches (50.8cm) including the Front Panel and Cables Weight 75 pounds (34 kg) net, 85 pounds (38.6 kg) in shipping carton Shipping Carton Dimensions Width is 27 inches (68.6cm) Height is 12-1/2 inches (31.8cm) Depth is 25 inches (63.5cm) 19 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. Two #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. Use the original shipping carton and interior parts only if they are all in good serviceable condition. If a shipping carton or any of the interior part(s) are needed, please call or write Customer Service Depart- ment of McIntosh Laboratory. Refer to page 3. Please see the Part List for the correct part numbers. Quantity Part Number Description 1 03383600 Inner carton 1 03372500 Top pad 1 03430100 Bottom pad 1 03448000 Shipping skid 4 01793700 Foot 4 40015900 10-32 x 3/4 screw 4 40408000 #10 flat washer 1 03383800 Shipping carton 2 03383700 Foam Pad (end cap sides) 2 40120400 #10 x2-1/2 cap screw 2 40403300 #10 x 1-3/4 washer 2 01721800 Plastic foot spacer TOP PAD END CAP (2) INSIDE CARTON SHIPPING CARTON WOOD SKID BOTTOM PAD PLASTIC FOOT SPACERS (2) PLASTIC FOOT (4) UNIT WITH (4) FEET ON BOTTOM COVER INSIDE CARTON #10 x 2-1/2“ SCREW (2) #10 x 1-3/4" WASHER (2) 10-32 x -3/4" SCREW WITH WASHER (4) IMPORTANT (Read Above) IMPORTANT (Read Above) 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 Laboratory, Inc. 2 Chambers Street Binghamton, NY 13903 www.mcintoshlabs.com McIntosh Part No. 04151400