McIntosh MC303 audio amplifier
Contents
1. 10 7 8 12 3 8 Front View of the MC303 rare ee 27 62cm 31 43cm Mbntosh 17 3 8 44 15cm zZ N m JP KS Mi m O g aa af E m Rear View of the MC303 Lib ran j a sa x Mtinfosh mesos power ampuirien i 12 114 I 31 11cm 19 1 2 49 50cm i 18 meg y 1 5 8 ad 45 72cm 4 12cm Side View of the MC303 10 1 2 3 16 26 70cm 0 48cm Q COU AM LT 1 9 16 35 60cm 3 96cm Me Installation The MC303 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 MC303 when it is custom installed as outlined below The four feet together with the mounting screws should be retained for possible future use 1f the MC303 is removed from the custom installation and used free Installation sure to cut out a ventilation hole in the mounting shelf ac cording to the dimensions in the drawing When the MC303 is installed together with other McIntosh Components check clearances on all components before proceeding 17 9 16 44 62cm standing T2. 300 watts into a 2 ohm 4 ohm or 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 1 8dB Frequency Response 0 0 25dB from 20Hz to 20 000Hz 0 3dB from 10Hz to 100 000Hz Input Sensitivity for rated output 1 7 Volt Unbalanced 3 4 Volt Balanced Signal To Noise Ratio A Weighted 112dB below rated output Intermodulation Distortion 0 005 maximum if the instantaneous peak power output does not exceed twice the rated power output for any com bination of frequencies from 20Hz to 20 000H7 Wide Band Damping Factor Greater than 40 Input Impedance 10 000 ohms Power Guard Less than 2 THD with up to 14dB overdrive at 1 000Hz Power Control Input SVDC 12VDC Power Control Output 12V DC 25mA maximum delay 0 2 seconds 18 Specifications Power Requirements 100 Volts 50 60Hz at 12 Amps 110 Volts 50 60Hz at 11 Amps 120 Volts 50 60Hz at 10 Amps 220 Volts 50 60Hz at 6 Amps 230 Volts 50 60Hz at 6 Amps 240 Volts 50 60Hz at 6 Amps Standby Less than 1 watt Note Refer to the rear panel of the MC303 for the correct voltage Overall Dimensions Width is 17 3 4 inches 45 09cm Height is 12 3 8 inches 31 43cm including feet Depth is 22 inches 55 88cm including the Front Panel and Cables Weight 155 pounds
3. MC303 Owner s Manual McIntosh Laboratory Inc 2 Chambers Street Binghamton New York 13903 2699 Phone 607 723 3512 www mcintoshlabs com The lightning flash with arrowhead within an equilateral triangle is intended to alert the user to the presence of uninsulated danger ous voltage within the product s ka enclosure that may be of sufficient magpnitude to constitute a risk of electric shock to persons 10 WARNING TO REDUCE RISK OF FIRE OR ELECTRICAL SHOCK DO NOT EXPOSE THIS EQUIPMENT TO RAIN OR MOISTURE IMPORTANT SAFETY INSTRUCTIONS PLEASE READ THEM BEFORE OPERATING THIS EQUIPMENT Read these instructions Keep these instructions Heed all warnings Follow all instructions Do not use this apparatus near water Clean only with a dry cloth Do not block any ventilation openings Install in accordance with the manufacturer s instructions Do not install near any heat sources such as radia tors heat registers stoves or other apparatus including amplifiers that produce heat Do not defeat the safety purpose of the polarized or grounding type plug A polar zed plug has two blades with one wider than the other A ground ing type plug has two blades and a third ground ing 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 Pro
4. connected to another Loudspeaker 6 Prepare the Loudspeaker Hookup Cables that attach to the Amplifier by choosing one of the methods below Bare wire cable ends Carefully remove sufficient insulation from the cable ends refer to figures 1 2 amp 3 If the cable is strand ed carefully twist dh the strands together Lana as tightly as possible Note If desired the Figure 1 Figure 2 Figure 3 twisted ends can be tinned with solder to keep the strands together or attach spade lug and or banana connector Spade lug or prepared wire connection Insert the spade lug connector or prepared section of the cable end into the terminal side access hole and tighten the terminal cap until the cable is firmly clamped into 4 r the terminal so the u nn wires cannot slip out Refer to figures 4 5 amp 6 Banana plug connection Insert the banana plug into the hole at the top of the terminal Refer to figures A and B Note Banana Plugs are for use in the United States and Canada only Figure 6 Figure A Figure B 7 Connect the Loudspeaker hookup cables from a single Loudspeaker to the output terminals that match the impedance of OUPUT 1 being careful to observe the correct polarities Output impedance connections of 2 ohms 4 ohms and 8 ohms are provided Ifthe Loud speaker s impedance is in between the available con nections use the nearest lower impedance
5. manner connect a Loudspeaker to OUT PUT 2 and connect the remaining Loudspeaker to OUTPUT 3 9 Connect the MC303 Power Cord to a live AC outlet Me Meters indicate the Amplifier Power Output of Channels 1 3 POWER GUARD POWER QUTPUT Front Panel Displays and Switches LEDs indicate when Amplifier Channels 1 3 POWER GUARD circuits activate 5 mn METER LIGHTS OFF AUTO METER Switch selects Meter Illumination Auto On or Off POWER GUARD POWER GUARD co co z m aa E y g O i g O POWER QUTPUT POWER QUTPUT POWER Q REMOTE OFF ON MC303 POWER AMPLIFIER Standby Power On Indicator POWER Switch Turns AC Power On Off or On Remote How to Operate How to Operate Power On To have the MC303 automatically turn On or Off when an A V Control Center or Preamplifier turns on or off rotate the power switch to the REMOTE position For manual operation POWER rotate the power switch to the ON REMOTE or OFF position as desired Refer pa ON to figure 8 Note There must be a power con trol connection between the MC303 and the A V Control Center or Preamplifier in order for the remote power turn on to function Figure 8 Meters Rotate the METER LIGHTS Switch to select the Meter Il lumination Mode you desire Refer to figure 9 OFF Meter Illumination is switched OFF and the meters will con tinue to indicate the power output AUTO Meter Illumination is switched ON When Pow
6. refer to figures 1 2 amp 3 If the cable is strand ed carefully twist the strands together as tightly as possible Note If desired the 0 5 inches twisted ends can be tinned with solder to keep the strands together or attach spade lug and or banana connector Spade lug or prepared wire connection Insert the spade lug connector or prepared section of the cable end into the terminal side access hole and tighten the terminal cap until the cable s firmly clamped into the terminal so the wires r ji p Figure 1 Figure 2 Figure 3 cannot slip out Refer to figures 4 5 amp 6 Fer Figure 5 Banana plug connection Insert the banana plug into the hole at the top of the terminal Refer to figures A and B Note Banana Plugs are for use in the United States and Canada only Figure 6 Figure A Figure B 7 Connect the Loudspeaker hookup cables from a single Loudspeaker to the output terminals that match the impedance of OUPUT 1 being careful to observe the correct polarities Output impedance connections of 2 ohms 4 ohms and 8 ohms are provided If the Loud speaker s impedance is in between the available con nections use the nearest lower impedance connection Refer to General Information Note 5 on page 3 for additional information WARNING Loudspeaker terminals are hazardous live and present a risk of electric shock 8 In a similar
7. speakers e Special Power Supply A regulated Power Supply a very large Power Transformer and Capacitors ensure stable noise free operation even though the power line varies e Illuminated Power Meter The Illuminated Power Output Watt Meter on the MC303 is peak responding and indicates the power output of the amplifier The Front Panel Meter Illumination may be switched Off at any time e Fiber Optic Solid State Front Panel Illumination The even illumination of the Front Panel 1s accomplished by the combination of custom designed Fiber Optic Light Diffusers and extra long life Light Emitting Diodes LEDs e Glass Front Panel and Super Mirror Chassis Finish The famous McIntosh Illuminated Glass Front Panel and the Stainless Steel Chassis with Super Mirror Finish en sures the pristine beauty of the MC303 will be retained for many years ThermalTrakTM and ON Semiconductor are trademarks of Semicon ductor Components Industries LLC Dimensions Dimensions The following dimensions can assist in determining the best location for your MC303 There 1s additional informa tion on the next page pertaining to installing the MC303 into cabinets 17 3 4 45 09cm POWER GUARD POWER GUARD POWER GUARD fa Lk NG E p amp alos alo ofw Q lo
8. 70 3 kg net 180 pounds 81 6 kg in shipping carton Shipping Carton Dimensions Width is 31 inches 78 74cm Depth is 28 inches 71 12cm Height s 17 1 4 inches 43 82cm Packing Instructions Packing Instructions In the event it 1s necessary to repack the equipment 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 ensure the proper equipment location on the bottom foam pad Failure to do this will result in shipping damage Use the original shipping carton and interior parts only if they are all in good serviceable condition If a shipping carton or any of the interior part s are needed please call or write Customer Service Department of McIntosh Labo ratory Please see the Part List for the correct part numbers CARTON TOP TOP FOAM PAD FOAM RING 3 UNIT WITH 4 FEET ON BOTTOM COVER gt 4 gt ae Sang a 4 Sn pa x gt NG r a N A ee PI N ZA ZA CSS lt lt Ns p DI i SS 1 aH gt x 7 N lt I NG SS SS lt i WS gt i S i ka P 8 A P a 2 oS KA jg N m N u BOTTOM FOAM PAD CARTON BOTTOM a Quantity PartNumber Description 1 034105 Shipping carton top 1 034104 Shipping carton bottom 2 034439 Foam Pad top and bottom 3 034441 Foam Ring 4 018445 Feet USE BANDING STRAPS AS SHOWN IMPORTANT Read Above SEAL WITH PACKAG
9. ING TAPE 19 McIntosh Laboratory Inc 2 Chambers Street Binghamton NY 13903 www mcintoshlabs com The continuous improvement of its products is the policy of McIntosh Laboratory Incorporated who reserve the right to improve design without notice Printed in the U S A McIntosh Part No 04109800
10. PUT 3 Connections for 2 ohm 4 ohm or 8 ohm Loudspeaker Loudspeaker Connect the MC303 power cord to a live AC outlet Refer to the rear panel to determine the correct voltage OUTPUT 2 Connections for 2 ohm 4 ohm or 8 ohm OUTPUT 1 Connections for 2 ohm 4 ohm or 8ohm Loudspeaker Main Fuse holder refer to information on the back panel of your MC303 to determine the correct fuse size and rating When used in the USA and Canada refer to General Information note number 8 on page 4 How to Connect for Center and Surround Channels Caution The supplied AC Power Cord should not be connected to the Rear Panel of the MC303 Amplifier until after the Loudspeaker Connec tions have been made Failure to observe this could result in Electric Shock For additional instruction on making Loudspeaker Connec tions contact your McIntosh Dealer or McIn tosh Technical Support The connection instructions below together with the MC303 Connection Diagram located on the separate folded sheet Mc1A is an example of a typical audio video sys tem Your system may vary from this however the actual components would be connected in a similar manner For additional information refer to Connector and Cable In formation on page 4 1 For Remote Power Control connect a power control cable from the A V Control Center or Preamplifier Power Control Out to the Right Front Channel Power Amplifier Power Control In Connect a second power co
11. TRAK VOLTAGE AMP CURRENT SOURCE THERMAL SWITCHES MUTE TURN ON DELAY BALANCED BALANCED AMP PG ATTENUATOR UNBALANCED o PREDRIVER PREDRIVER gt gt NEGATIVE POSITIVE SENTRY MONITOR VOLTAGE LOG METER p AMP MONITOR n m F z NEGATIVE FEEDBACK Figure 12 Design Philosophy The design philosophy incorporated in the MC303 in volved several different techniques all based on sound scientific logic Refer to figure 12 Every stage of voltage or current amplification must be as linear as possible prior to the use of negative feedback McIntosh engineers know how to properly design negative feedback circuits so they contribute to the extremely low distortion performance expected from a McIntosh amplifier The typical McIntosh owner would never accept the approximately 100 times higher distortion of many non feedback designs All transistors are selected to have nearly constant cur rent gain over the entire current range they must cover The 12 Power Transistors used in each channel of the MC303 Power Output Circuitry have matched uniform current gain high current band width product and a large active re gion safe operat ing area Refer to figure 13 These Power Transistors are the very latest in semiconduc tor technology and incorporate a new design known as ThermalTrak Refer to figure 14 This allows for the instantaneous and accurate monitoring of the Power Transis tor T
12. alanced Outputs of the A V Control Center or Preamplifier Left Center and Right Front Channels to the MC303 BALANCED INPUTs 1 3 Ha An optional hookup is to use the UNBALanced IN PUTS with unbalanced cables instead of balanced However both type of connections for a given Input should not be used at the same time 4 Connect cables from the Balanced Outputs of the A V Control Center or Preamplifier Surround Channels to the Left and Right Surround Channel Power Amplifier When connecting Loudspeakers to the MC303 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 AA 25 feet 50 feet 100 feet p 7 62 meters 15 24 meters 30 48 meters Impedance or less or less or less 12AWG 10AWG 8AWG 4Ohms 14AWG 12AWG 10AWG 80hms 16AWG 14AWG 12AWG 5 This McIntosh MC303 Power Amplifier is designed for the connection of a single Loudspeaker per amplifier channel with an impedance of 2 ohms 4 ohms or 8 ohms Note The remaining Amplifier Loudspeaker Terminals should not be connected to another Loudspeaker 6 Prepare the Loudspeaker Hookup Cables that attach to the Amplifier by choosing one of the methods below Bare wire cable ends Carefully remove sufficient insulation from the cable ends
13. connection Refer to General Information Note 5 on page 3 for additional information WARNING Loudspeaker terminals are hazardous live and present a risk of electric shock 8 In a similar manner connect a Loudspeaker to OUT PUT 2 and connect the remaining Loudspeaker to OUTPUT 3 9 Connect the MC303 Power Cord to a live AC outlet How to Connect How to Connect for Left Center and Right Channels Caution The supplied AC Power Cord should not be connected to the Rear Panel of the MC303 Amplifier until after the Loudspeaker Connec tions have been made Failure to observe this could result in Electric Shock For additional instruction on making Loudspeaker Connec tions contact your McIntosh Dealer or McIn tosh Technical Support The connection instructions below together with the MC303 Connection Diagram located on the separate folded sheet Me1B is an example of a typical audio video sys tem Your system may vary from this however the actual components would be connected in a similar manner For additional information refer to Connector and Cable In formation on page 4 1 For Remote Power Control connect a power control ca ble from the A V Control Center or Preamplifier Power Control Out to the MC303 POWER CONTROL IN 2 Connect a second power control cable from the MC303 POWER CONTROL OUT to the Left and Right Sur round Channel Power Amplifier Power Control In 3 Connect cables from the B
14. emperature The MC303 Power Output Circuitry has a specially designed bias circuit to take full advantage of the ThermalTrakTM Power Transistors and thus precisely controls the power amplifier operation over a wide Figure 13 Figure 14 range of music conditions with the benefits of lower distor tion and cooler operation The MC303 can provide greater than 60 amperes peak output current to drive uneven speaker loads Some poor speaker designs have input impedance that dip to or 2 ohms at various frequencies and the MC303 has the output current reserve to drive them The high efficiency circuit design of the MC303 con tributes to low operating temperatures More than 2 100 square inches of heat sink area keep the MC303 operating safely with convection cooling No fans are needed Preci sion metal film resistors and low dielectric absorption film capacitors are used n all critical circuit locations Autoformers The output signal of the MC303 Power Amplifier Circuitry is coupled to the Loudspeaker via the unique McIntosh Output Autoformer Refer to figure 15 The unequaled ex pertise of McIn tosh in the design and manufactur ing of autoform ers 1s legendary in the high fidel ity industry All solid state power amplifier output circuits work best into what is called an optimum load This optimum load may vary consider ably from what a loudspeaker requires In the case of more than one Loudspeaker connected i
15. en 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 dis Emmm posal 7 For additional information on the MC303 and other McIntosh Products please vist the McIntosh Web Site at www mcintoshlabs com 8 When the MC303 is operated in the USA or Canada and the main fuse located on the rear panel is in need of replace ment use only the following part Bussman ABC 15 R or Littlefuse 314 015P K Connector and Cable Information XLR Connectors Below is the Pin configuration for the XLR Balanced Input Connectors on the MC303 Refer to the diagram for con nection PIN 1 Shield Ground PIN 2 Output PIN 3 Output PIN 3 Power Control Connector The MC303 s Power Control Inputs receive On Off signals of 5 volts An additional connection is for controlling the illumination of Power the MC303 Power Output Meters nn The 1 8 inch stereo mini phone plug Hunima on connects to a McIntosh A V Control Control Ground Center Power Control Output Note The Power Control Connecting Cable is available from the McIntosh Parts Department Data and Power Control Cable Part No 170 202 Six foot shielded 2 conductor with 1 8 inch stereo mini phone plugs on each end Introduction Now you can take advantage of traditional McIntosh standards of excellence in the MC303 Power Amplifier T
16. equipment to dripping or splashing and ensure that no objects filled with liq uids such as vases are placed on the equipment To completely disconnect this equipment from the a c mains disconnect the power supply cord plug from the a c receptacle The mains plug of the power supply cord shall remain readily operable Do not expose batteries to excessive heat such as sunshine fire or the like Thank You Your decision to own this McIntosh MC303 Power Ampli fier ranks you at the very top among discriminating music listeners You now have The Best The McIntosh dedica tion to Quality is assurance that you will receive many years of musical enjoyment from this unit Please take a short time to read the information in this manual We want you to be as familiar as possible with all the features and functions of your new McIntosh Please Take A Moment The serial number purchase date and McIntosh Dealer name are important to you for possible insurance claim or future service The spaces below have been provided for you to record that information Serial Number Purchase Date Dealer Name Technical Assistance If at any time you have questions about your McIntosh product contact your McIntosh Dealer who is familiar with your McIntosh equipment and any other brands that may be part of your system If you or your Dealer wish additional help concerning a suspected problem you can receive technical assistance f
17. er Control Input of the MC303 is connected to an A V Control Center or Preamplifier with Remote Meter Illumination Control the Meter Illumination will automatically be remotely controlled On Off The MC303 Meters respond to all the musical informa METER LIGHTS OFF AUTO Figure 9 tion being produced by the three Power Amplifier Circuits Refer to figure 10 They indicate to an accuracy of at least 95 of the power output with only a single cycle of a 2000Hz tone burst 030 30 301 30 300 POWER QUTPUT Figure 10 Power Guard During normal operation the Front Panel Power Guard Indicators will momentarily illuminate during peaks in the audio signals Refer to figure 11 In the event the MC303 overheats due Baer to improper ventilation and or high ambient temperature the internal protection circuits will activate The Front Panel Power Guard Indicators will continuously illuminate and the audio will be muted When the MC303 has returned to a safe operating tem perature normal operation will resume Figure 11 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 cre ated a power amplifier without compromise using the most advanced McIntosh circuit design concepts A continuous average power output rating of 300 watts per channel and with an output c
18. g the amplifier 1 The following Connecting Cable is available from the McIn tosh Parts Department Power Control Cable Part No 170 202 Six foot 2 conductor shielded with two 1 8 inch stereo mini phone plugs 2 For additional connection information refer to the owner s manual s for any component s connected to the MC303 3 The MC303 mutes the speaker output for approximately two seconds when first turned on 4 In the event the MC303 overheats due to improper ventilation and or high ambient temperature the protection circuits will activate The Front Panel Power Guard LEDs will continu ously indicate ON and the audio will be muted When the MC303 has returned to a safe operating temperature normal operation will resume 5 For the best performance it is important to minimize an im pedance mismatch An impedance mismatch can occur when a Loudspeaker of a given impedance rating is connected to the MC303 Output Terminals with a different impedance rating For example a Loudspeaker with an impedance rating of 2 Ohms is connected to the MC303 8 Ohm Output Terminals The impedance of a Loudspeaker actually varies as the Loudspeaker reproduces different frequencies As a result the nominal impedance rating of the Loudspeaker usually mea sured 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 General Information con t 6 Wh
19. he 300 watt high current output per channel will drive any high quality loudspeaker system to its ultimate per formance The MC303 reproduction is sonically transpar ent and absolutely accurate The McIntosh Sound is The Sound of the Music Itself Performance Features e Power Output The MC303 is a Power Amplifier with a capability of 300 watts per channel all channels driven into 2 4 or 8 ohm speakers with less than 0 005 distortion The Power Am Connector Information Introduction and Performance Features plifier circuitry uses Thermal Trak Output Transistors for lower distortion and cool operation e Balanced and Unbalanced Inputs Balanced connections guard against induced noise and al low long cable runs without compromising sound quality e 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 loudspeakers e Sentry Monitor and Thermal Protection McIntosh Sentry Monitor power output stage protection circuits ensure the MC303 will have a long and trouble free operating life Built in Thermal Protection Circuits guard against overheating e Patented Autoformer McIntosh designed and manufactured Output Autoformers provide an ideal match between the amplifier output stages and speaker loads of 2 4 and 8 ohms The Autoformers also provide perfect DC protection for your valuable loud
20. he required panel cutout ventilation cutout and unit dimen sions are shown Always provide adequate ventilation for your MC303 Cool operation ensures the longest pos sible operating life for any electronic instrument Do MC303 Front Panel Custom Cabinet Cutout POWER GUARD POWER GUARD POWER GUARD 030 30 3 300 es U 10 13 16 27 46cm METER LIGHTS OFF ___ AUTO POWER REMOTE C303 POWER AMPLIFIER not install the MC303 di rectly above a heat gener ating component such as a high powered amplifier If all the components are in stalled in a single cabinet a quiet running ventila tion fan can be a definite asset in maintaining all the system components at the coolest possible oper ating temperature A custom cabinet instal lation should provide the following minimum spac ing dimensions for cool operation Allow at least 6 inches 15 24cm above the top 2 inches 5 08cm below the bottom and 1 inch 2 54cm on each side of the Power Amplifier so that airflow is not ob structed Allow 19 1 2 inches 49 53cm depth behind the front panel Allow 1 5 8 inch 4 12cm in front of the mounting panel for clearance Be Opening MC303 Side View in Custom Cabinet MC303 Bottom View in Custom Cabinet 1 For purposes of clarity the above illustration is not drawn to scale Cabinet Fron
21. n 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 opti mum causes more output current to flow which results in extra heat being generated in the power output stage This Figure 15 13 Me increase in temperature will result in a reduced life expectancy for the amplifier The Autoformer creates an ideal match between the Power Amplifier Output Circuitry and the Loudspeaker There is absolutely no performance limitation with an Autoformer Its frequency response from below 20Hz to well beyond 20 000Hz exceeds the Power Output Circuitry Frequency Response and extends well beyond the audible range Its distortion level is so low it is virtually impossible to measure In the rare event of a power amplifier output circuit failure the McIntosh Autoformer provides absolute protection from possible damage to your valuable Loud speakers Protection Circuits The different types of protection circuits incorporated in the MC303 insure a long and safe operating life The MC303 incorporates the McIntosh Sentry Monitor output transistor protection circuit Refer to figure 16 There is absolutely no compromise in sonic performance with this circuit and it ensures safe operation of the amplifier under even the most extreme op erating conditions The MC303 also includes the unique patented McIntosh Power Guard Circuit Power Guard elimi nates the pos
22. ntrol cable from the Right Front Channel Power Amplifier Power Power Control Out to the Left Front Channel Power Amplifier Power Control In 2 Connect a power control cable from the Left Front Channel Power Amplifier Power Power Control Out to the MC303 POWER CONTROL IN 3 Connect cables from the Balanced Outputs of the A V Control Center or Preamplifier Left and Right Front Channels to the Left and Right Front Power Ampli fiers Note An optional hookup is to use the UNBALanced IN PUTS with unbalanced cables instead of balanced However both type of connections for a given Input should not be used at the same time 4 Connect cables from the Balanced Outputs of the A V Control Center or Preamplifier Center and Surround Channels to the MC303 BALANCED INPUTs 1 3 When connecting Loudspeakers to the MC303 it is very important to use cables of adequate size so there is little to no power loss in the cables The size 1s 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 Paga Kae 25 feet 50 feet 100 feet p 7 62 meters 15 24 meters 30 48 meters Impedance or less or less or less 5 This McIntosh MC303 Power Amplifier is designed for the connection of a single Loudspeaker per amplifier channel with an impedance of 2 ohms 4 ohms or 8 ohms Note The remaining Amplifier Loudspeaker Terminals should not be
23. ontrol Center When the A V Control Center is switched On a 5V signal operates the power relay in the MC303 The MC303 also has a remote Power Control Out Jack The Power Control signal from this jack is delayed by a frac tion 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 Theater System employing multiple Power Amplifiers 15 Wa We were teu rw tw ST Ma TT ll Ny SIE L wi TIL Ze ui ins en BEBEBE Melntosh POWER TRANSFORMER 750883 BLK BLK GRY GRY VIO LALA LO WHT tl AA il il I L da Melniosk McIntosh Melnfosh 16 AUDIO AUTOFORMER 750884 POWER OUTPUT OW into an 8 40 minimum sine wave c output per channel with a RATED POWER BAND 20Hz to 20 000Hz MONIC DISTORTION AUDIO AUTOFORMER 750884 AUDIO AUTOFORMER 750884 Precisio n Performance By Mcintosh Laboratory Inc Bingham Top View of the MC303 Made in U S A NCY RESPON from INPUT SENSITIVIT unbalance volts balanc MIC HEADROOM TO NOISE RATIO Photos Angle View of the MC303 INPUT 3 INPUT 1 UNBAL POWER CONTROL Ei INPUT 2 Rear View of the MC303 17 Specifications ower Outpu Minimum sine wave continuous average power output per channel all channels operating
24. or 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 2008 by McIntosh Laboratory Inc Table of Contents Sale by Insi UCT NA 2 Thank You and Please Take a Moment 000 3 Technical Assistance and Customer Service 3 Tole KA een 3 General Information ee ee each 3 4 Connector I OD One nee 4 Hala Kei YUL eeoa EEE EOUEEEFEOUHEN EEREEENIFEREREITEERRRR 4 Perlormance AN AE 4 AGNO ee ska a aaahh 5 AAAH Akda 6 Rear Panel Connections and Switch 200 00 7 How 0 CONN OL nee en een een 8 9 Connection Diagrams Separate Sheet MC1A and MCIB Front Panel Displays and Controls 10 How to OPT nenne 11 Technical Desctiption near 12 15 AA AA 16 17 BAE GANG a AAO 18 Packing Instruction ee 19 General Information Caution The MC303 Amplifier weight is 150 pounds 70 3 kilograms It requires two or more persons to safely handle when movin
25. sibility of ever overdriving the amplifier into clipping Refer to figures 17 18 and 19 An overdriven amplifier can produce both audible and inaudible distortion levels exceeding 40 The audible distortion is unpleas ant to hear but the inaudible ultrasonic distortion 1s also undesirable since it can damage valuable loudspeaker system tweeters You will never experience the harsh and damaging distortion due to clipping The Power Guard circuit is a waveform comparator moni toring both the input and out put waveforms Under normal operating conditions there are no differences between Normal oJojarsliisie Area Sentry Monitor Safaiy Arsa Output Transistor Failure Figure 16 Input Test Signal Figure 17 14 Without Power Guard the shape of these waveforms If an amplifier channel is overdriven there will be a dif ference between the two signal waveforms When the differ ence exceeds 0 3 the Power Guard activates the PG light and a dynamic electronic at tenuator at the amplifier input reduces the input volume just enough to prevent any further increase in distortion The Power Guard circuit acts so fast that there are absolutely no audible side effects and the sonic purity of the music reproduction is perfectly preserved The MC303 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 po
26. t Panel Support lt Shelf 21 32 67cm Note Center the cutout Horizontally on the unit 6 15 24cm Cutout Opening for Custom Mounting we for Ventilation Chassis Spacers ZO NG Cutout Opening for Ventilation Bo 14 35 56cm 4 S 2 54cm q 14 12 36 83cm Cutout Opening for Ventilation Rear Panel Connections and Switch UNBALANCED INPUT3 POWER CONTROL IN BALANCED INPUT 2 BALANCED INPUT 1 for an audio cable from an receives turn On Off signal for an audio cable from for an audio cable from A V Control Center or Pre from a McIntosh component an A V Control Center an A V Control Center amplifier audio output and the POWER CONTROL or Preamplifier audio or Preamplifier audio OUT sends a turn On Off output output signal to the next McIntosh Component BALANCED INPUT 3 UNBALANCED INPUT 2 UNBALANCED INPUT 1 for an audio cable from for an audio cable from an for an audio cable from an an A V Control Center A V Control Center or Pre A V Control Center or Pre or Preamplifier audio amplifier audio output amplifier audio output output POH Le HUA S S N NG Yj INPUT 3 POWER CONTROL O IN OUT CU EI IN 20 4Q McINTOSH LABORATORY INC BINGHAMTON NY 13903 MADE IN USA SUN N Gs MINANA 80 F15AH 125V OUT
27. tect the power cord from being walked on or pinched particularly at plugs convenience re ceptacles and the point where they exit from the apparatus CAUTION RISK OF ELECTRIC SHOCK DO NOT OPEN The exclamation point within an equilateral triangle is intended to alert the user to the presence of im portant operating and maintenance servicing instructions in the litera ture accompanying the appliance A AVI S RISQUE DE CHOC ELECTRIQUE NE PAS OUVRIR NO USER SERVICEABLE PARTS INSIDE REFER SERVICING TO QUALIFIED PERSONNEL To prevent the risk of electric shock do not remove cover or l1 12 13 14 gt 16 17 18 back No user serviceable parts inside Only use attachments accessories specified by the manufacturer Use only with the cart stand tripod bracket or table specified by the manufacturer or sold with the apparatus When a cart 1s used use caution when mov e ing the cart apparatus combination to avoid injury from tip over Unplug this apparatus during lightning storms or when unused for long periods of time 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 appara tus has been exposed to rain or moisture does not operate normally or has been dropped Do not expose this
28. urrent of greater than 60 amperes per channel making this one of the most ad vanced and powerful amplifiers McIntosh has ever manu factured The distortion limits for the MC303 are no more than 0 005 at rated power output for all frequencies from YG eS LAAL T Oe N 1 B8 N Ber 20Hz to 20 000Hz Typical performance at mid frequencies is less than 0 0002 The true distortion readings on the MC303 are so low it takes special measuring techniques to make accurate readings The MC303 can deliver the best possible performance from any type of high quality loudspeaker system Creating an amplifier with this level of performance did not come eas ly Many months of design testing and mea suring were required Extensive controlled listening tests the ultimate form of measuring were made before the final design was accepted 4 A G MA NG 91 Q 0 Oo on N N z32 823 3 a55 69033 12 Inside Bottom View of the MC303 Lira MS AAAA LA A A x sa DA 4 LANI LENI kb z Y padi 4 N F pons ih s Pa gt 5 y a i y G x N E AS r ae 4 E E pi 965990 20A OOL 4N 000 4Z a MET WE A 2151 Nil nii G LG IS LZy 2280 8s9 4sopujajll ma GZstaxizse lay OOL Er 11010101727 a Ba Technical Description PG PG POWER INDICATOR DRIVER GUARD Power Amplifier Block Diagram one channel shown VOLTAGE AMP
29. wer due to the McIntosh philosophy of conservative design Figure 18 With Power Guard Figure 19 Power Supply Circuits To compliment the design of the MC303 Power Amplifier Circuitry there is a high current high voltage power supply for the three channels Refer to figure 20 on page 15 The power amplifiers draw high current from the AC power line Therefore it is important that they plug directly into the wall outlet The MC303 incorporates a very large high current Main Power Transformer Refer to figure 21 It is enclosed in the legendary McIntosh Potted Enclosures and weighs 38 Ibs The super size multiple large main filter capacitors Technical Description con t POWER POWER SWITCH CONTROL LOW VOLTAGE SUPPLY INRUSH 120VAC POWER POWER MAIN O FUSE CURRENT 50 60Hz RELAY TRANSFORMER SUPPLY LIMITER Power Supply STANDBY STANDBY Block Diagram TRANSFORMER SUPPLY Figure 20 can store over 200 Joules of energy for the three amplifier channels necessary for the wide dynamic range Digital Audio demands Refer to figure 22 YV 8 gt e Oy rc 852 Son 3 ihep Enc Figure 22 There is also a fully regulated low voltage power supply to guarantee excellent signal to noise ratio Refer to figure 22 Also most owners desire one power switch for the whole audio system The MC303 is equipped with a circuit that provides remote Power Control from a McIntosh A V C
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