McIntosh MC-7300 User's Manual
Contents
1.2. 7300 DIGITAL ER AMPLIFIER STEREO E INPUT SENSITIVITY E INPUTS terr LEFT OUTPUT RIGHT OUTPUT EE e P R2 Ra L Unmacanceo 77 m S 4 OHM SPEAKER PLACE INPUT SENSITIVITY SWITCH AT 2 5V 8 CONNECTING DIAGRAM NA The McIntosh output circuit superior in its performance demands a superior method of coupling the amplifier output to the loudspeaker load The MC 7300 incorporates McIntosh designed and manufactured Autotransformers to insure peak performance and protection as well as outstanding compatibility between amplifier and speakers The MC 7300 Output Autotransformers have 3 dif ferent output impedance taps for optimum matching to the particular speaker or combination of speakers being used Use the following table to determine which tap should be used It may be desirable to consult your dealer or the manufacturer of your Speaker for the best impedance tap to use SPEAKER IMPEDANCE AMPLIFIER OUTPUT IN OHMS CONNECTIONS 1 6 to 32 Common and 2 ohm outputs 3 2 to 6 4 Common and 4 ohm outputs 6 4 and up Common and 8 ohm outputs Use high quality speaker cables The total resistance of the cables must be as low as possible so larger diameter lower gauge number cables are most desirable The longer the speaker cable is the lower the gauge number must be to keep resistance Aow RECOMMENDATIONS FOR SPEAKER CABLE
3. IMPORTANT SAFETY INSTRUCTIONS THESE INSTRUCTIONS ARE TO PROTECT YOU AND THE McINTOSH INSTRUMENT BE SURE TO FAMILIARIZE YOURSELF WITH THEM 1 Read all instructions Read the safety and operating instructions before operating the instrument Retain Instructions Retain the safety and operating instructions for future reference Heed warnings Adhere to warnings and operating instructions 4 Follow Instructions Follow all operating and use instructions WARNING TO REDUCE RISK OF FIRE OR ELECTRICAL SHOCK DO NOT EXPOSE THIS INSTRUMENT TO RAIN OR MOISTURE Power Sources Connect the power supply only to the type described in the operating instructions or as marked on the unit Power Cord Protection Route power supply cords so that they are not likely to be walked on or pinched by items placed upon or against them paying particular attention to cords at plugs convenience receptacles and the point where they exit from the instrument Ventilation Locate the instrument for proper ventilation For example the instrument should not be placed on a bed sofa rug or similar surface that may block ventilation openings or placed in a built in installation such as a bookcase or cabinet that may impede the flow of air through the ventilation openings Heat Locate the instrument away from heat sources such as radiators heat registers stoves or other appliance including amplifiers that produce heat Wa
4. LENGTHS AND GAUGE SIZE These speaker cable lengths represent a resistance equal to approximately 5 of the speaker im pedance The cable sizes are the minimum that should be used If there is a choice the larger diameter cables Lower gauge number should be used For 4 Ohm Load For 8 Ohm Load Wire Feet Meters Feet Meters Gauge 15 4 6 30 9 1 18 25 7 6 50 15 2 16 40 12 2 80 24 4 14 60 18 3 120 36 6 12 100 30 5 200 61 0 10 STEREOPHONIC OPERATION Connect a cable from the left speaker common ter minal to the amplifier LEFT OUTPUT LC terminal Connect a cable from the left speaker hot terminal to the amplifier LEFT OUTPUT L impedance tap desired terminal Connect the right speaker in an identical manner to the amplifier RIGHT OUTPUT terminals of the cor rect impedance for your speakers If the actual load impedance of a speaker is lower than the specified impedance particularly at dif ferent parts of the frequency range it will cause no problems The high current output capacity of the MC 7300 will produce the extra current necessary to properly drive the speaker under these conditions If the impedance of the speaker is higher than the 8 ohm tap no change in performance quality will occur The available power output will simply be slightly less The common and hot terminals of both speakers in a stereo installation must be connected in an identical manner to the proper amplifier output terminals This is essent
5. not limit the power output available from the amplifier THERMAL CONTROL power transistors have limits for the maximum amount of heat they can tolerate The MC 7300 uses a highly efficient amplifying circuit which produces relatively little heat for the output power produced The amplifier has 4 oversized heatsinks to dissipate tran sistor generated heat Natural convection air flow is suf ficient for cool operation Should the cooling air be blocked or should the amplifier operating temperature become too high thermal cutouts within the amplifier will turn off the power to the amplifier When the amplifier has cooled it will automatically turn on again TURN ON DELAY The MC 7300 has a turn on delay circuit that delays amplifier operation for about 2 seconds after power turn on This prevents pops or thumps generated in other equipment from causing annoying noises or damaging your loudspeakers DIRECT CURRENT FAILURE PROTECTION The autotransformer protects speakers from damage in the event of amplifier failure Should a direct current component appear in the output it is shunted by the autotransformer and DC cannot reach the speaker POWER LINE INRUSH PROTECTION Turn on inrush current is cushioned by thermistors in the power transformer primary circuit A soft start is achieved that eliminates component stress during turn on CIRCUIT OPERATION The audio input passes through the gain control to a preamplifier The out
6. output of the amplifier in phase with the input signal in MONO BRIDGE opera tion connect the hot speaker terminal to the RIGHT channel impedance tap and the common speaker ter minal to the LEFT channel impedance tap SPEAKER IMPEDANCE AMPLIFIER OUTPUT IN OHMS CONNECTIONS 3 2 to 6 4 L2 and R2 4 ohms total 6 4 to 10 L4 and R4 8 ohms total 10 and higher L8 and R8 16 ohms total MAKE SURE THE REAR PANEL MODE SWITCH IS SET TO MONO BRIDGE AND USE ONLY A RIGHT INPUT MONOPHONIC PARALLEL OPERATION The MC 7300 also can be used as a single channel monophonic power amplifier in parallel configura tion The amplifier output taps are now connected in parallel and the impedances will be exactly half what is stated at the terminals Connect a cable from the speaker common ter minal to either the LEFT OUTPUT LC terminal or the RIGHT OUTPUT RC terminal These terminals are wired together inside the amplifier Connect the cable from the hot speaker terminal to the im pedance output desired on either channel Also wire across to the other channel identical impedance tap In each case the chosen outputs of each channel must be wired together SPEAKER IMPEDANCE AMPLIFIER OUTPUT IN OHMS 0 8 to 1 6 LC RC and L2 R2 1 ohm 1 6 to 3 2 LC RC and 14 4 2 ohms 3 2 and up LC RC and 18 4 ohms MAKE SURE THE REAR PANEL MODE SWITCH IS SET TO MONO PARALLEL AND USE ONLY A RIGHT INPUT ALWAYS BE CERTAIN TO PLA
7. safety provided by the polarized AC plug 17 CAUTION TO PREVENT ELECTICAL SHOCK DO NOT USE THIS POLARIZED PLUG WITH AN EXTENSION CORD RECEPTACLE OR OTHER OUTLET UNLESS THE BLADES CAN BE FULLY INSERTED TO PREVENT BLADE EXPOSURE ATTENTION POUR PREVENIR LES CHOCS ELECTRIQUES PAS UTILISER CETTE FICHE POLARISEE AVEC UN PROLONGATEUR UNE PRISE DE COURANT OU UNE AUTRE SORTIE DE COURANT SAUF SI LES LAMES PEUVENT ETRE 5 INSEREES FOND SANS EN LAISSER AUCUNE PAR TIE A DECOUVERT A The lightning flash with arrowhead within equilateral triangle is intended to alert the user to the presence of uninsulated dangerous voltage within the product s enclosure that may be of sufficient magnitude to constitute a risk of electric shock to persons CAUTION RISK OF ELECTRIC SHOCK DO NOT OPEN CAUTION TO PREVENT THE RISK OF ELECTRIC SHOCK DO NOT REMOVE COVER OR BACK NO USER SERVICABLE PARTS INSIDE REFER SERVICING QUALIFIED PERSONNEL A 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 E go The serial number purchase date and McIntosh Laboratory Service Contract number are important to you for possible insurance claim or future service Record this information here Serial Number p ys Purchase
8. strips previously mounted 7 install the Instrument Guide the AC power cord through the panel opening to the back of the cabinet then slide the instrument into the opening carefully so that the rails on the bottom of each side of the chassis engage the tracks on the mounting brackets Continue to slide the in strument into the cabinet until the front panel is flush with the cabinet panel Turn the PANLOC but tons at the lower left and right corners of the instru ment panel clockwise to lock the unit firmly in the cabinet Turn the PANLOC buttons counterclockwise to unlock the instrument It can then slide outward to permit the removal of the instrument from the cabinet INSTALLATION 5 CONNECTING CABLES Use shielded cables to connect the signal from the preamplifier or other signal source to the power amplifier To minimize the possibility of hum the cables should be located away from speaker connect ing cables and AC power cords Use good quality cables Your dealer can advise you on the type and lengths of cables that will best suit your installation STEREO OPERATION UNBALANCED INPUTS Use shielded single conductor cable with RCA type plugs Connect the cable from the left channel out put of a preamplifier to the LEFT UNBALANCED IN PUT on the power amplifier Connect the right chan nel output to the RIGHT MONO UNBALANCED INPUT Set the MODE switch to STEREO STEREO OPERATION BALANCED INPUT Modern tec
9. CE THE MODE SWITCH IN THE CORRECT POSITION FOR THE MODE OF OPERATION BEING USED HOW TO CONNECT AC POWER The MC 7300 is designed to operate on 120 volts 50 60 Hz Plug the AC power cord directly into a wall outlet Make certain that the AC power outlet has at least 12 amperes capacity available If you choose to connect the amplifier AC power to the back AC outlet on a preamplifier or other accessory make certain it can supply 12 amperes of current The MC 7300 can draw up to 12 amperes of cur rent from the AC power line when both channels are producing rated power output The amplifier uses only 0 6 amperes of current when idling at no output The AC auxiliary outlet on the amplifier rear panel will provide up to 100 watts 1 ampere and is not fused or switched FUSE A 15 ampere fuse protects the MC 7300 circuits The fuse does not protect additional equipment con nected to the rear panel auxiliary AC outlet ardt 10 HOW TO CONNECT OUTPUTS jPOWER OUTPUT METERS The MC 7300 power output meters respond 9596 full scale to a single cycle of a 2 000Hz tone burst Both voltage and current are electronically measured and fed to a special circuit that accelerates the pointer movement in the upward direction When the meter pointer reaches its peak it is time stretch ed to pause just long enough to be read and then drops The upper scale on the meters is calibrated in average watts power and the lower scale
10. Date Service Contract Number Upon application McIntosh Laboratory provides a Service Contract to the original purchaser Your McIntosh Authorized Service Agency can expedite repairs when you provide the Service Contract with the instrument for repair Copyright 1991 by McIntosh Laboratory Inc Contents INTRODUCTION 3 INSTALLATION 4 5 HOW CONNECT INPUTS 6 CONNECTING DIAGRAMS 7 8 HOW TO CONNECT OUTPUTS 9 10 FRONT PANEL CONTROLS 11 REAR PANEL 12 PERFORMANCE LIMITS 13 PERFORMANCE CHARTS 14 TECHNICAL DESCRIPTION 15 16 BLOCK DIAGRAM 17 Take Advantage of 3 Years of Contract Service Fill in the Application NOW Your MC 7300 Power Amplifier will give you many years of satisfactory performance If you have any questions please contact CUSTOMER SERVICE McIntosh Laboratory Inc 2 Chambers Street Binghamton New York 13903 2699 Phone 607 723 3512 McINTOSH THREE YEAR SERVICE CONTRACT An application for A THREE YEAR SERVICE CONTRACT is included with this manual The terms of the contract are 1 If the instrument covered by this contract becomes defective McIntosh will provide all parts materials and labor needed to return the measured perform ance of the instrument to the original performance limits free of any charge The service contract does not cover any shipping costs to and from the authorized service agency or the factory 2 Any McIntosh authorized se
11. ITY SWITCH to the 2 5V position and turn the front panel GAIN controls to maximum The 1 4V sensitivity can be us ed when additional gain is needed for special applications BALANCED AND UNBALANCED INPUTS SPEAKER OUTPUTS AC OUTLET FUSE Refer to other sections of this manual for the proper connections and operations of the inputs and outputs CAUTION zorne Mit Infosh mc7300 ee mono DIGITAL DYNAMIC STEREO POWER AMPLIFIER STEREO LABORATORY INC BINGHAMTON NY 13903 MADE IN U S A TYPE AND RATING FUSE ATLENTIQN SERIAL NO REMPLACER PAR UN FUSIBLE DE TYPE AMPERAGE INPUT SENSITIVITY ET VOLTAGE WARNING aisk or HAZARDOUS ENERGY SEE OPERATING MANUAL DO NOT OPERATE WITHOUT OUT PUT TERMINAL COV R IN PLACE AVERTISSEMENT ENERGIE ELECTRIQUE K DANGEREUSE LA NOTICE DE FONCTIONNEMENT BRIOGE R MONO INPUTS 120V LEFT RIGHT MONO 50 60Hz 100W or 1A MAX B A ENS LEFT OUTPUT fe z L4 L BALANCED 12 REAR PANEL Rajz Performance limits the maximum deviation from perfection permitted for a McIntosh instrument We promise you that when you purchase a new MC 7300 from a McIntosh franchised dealer it will be capable of or can be made capable of perfor mance at or exceeding these limits or you can return
12. allows not only full power output into normal loads but extra high current out put to drive uneven speaker loads Some speaker designs have impedance characteristics that may dip to as low as 1 or 2 ohms at certain frequencies It is possible for the MC 7300 to deliver as much as 85 amperes peak current into these lower impedance loads The MC 7300 will supply this extra current output with complete reliability due to the use of McIntosh Sentry Monitor protection circuits Some power amplifier manufacturers have claimed that their pro ducts do not use protection circuits since they com promise performance The real genius of McIntosh engineering design has recognized these potential problems and completely eliminated them Properly designed protection circuits assure you an amplifier hat will operate under all types of user conditions with maximum reliability and freedom from possible speaker or amplifier damage The benefits of these designs mean you own an amplifier that will con tinue to operate safely for many years The MC 7300 output is so distortion free it is dif ficult to measure with conventional instruments The performance limit is 0 005 maximum distortion yet it is typical for an amplifier to measure less than 0 00296 at mid frequencies The power output watt meters on the MC 7300 are peak responding and indicate the TRUE power out put of the amplifier The MC 7300 meter circuits are constantly measuri
13. for installation is 17 inches 43 2 cm wide 16 inches 40 7 cm deep including connectors and 8 inches 20 3 cm high Allow 1 inch 2 54 cm in front of panel for knob clearance CUSTOM INSTALLATION The PANLOC system of installing equipment conveniently and securely is a product of McIntosh research The PANLOC buttons on the front panel will lock the unit firmly in place when turned ap proximately one quarter turn clockwise A one quarter counterclockwise turn of the PANLOC but tons unlocks the chassis from its mounting To install the instrument in a McIntosh cabinet follow the instructions that are enlcosed with the cabinet For any other type of installation follow these instructions 1 Unpack from Carton Open the carton and remove the PANLOC brackets hardware package and mounting template Remove the instrument from its plastic bag and place it up side down on the shipping pallet Unscrew the four plastic feet from the bottom of the chassis 2 Mark the Cabinet Panel Tape the mounting template in position on the cabinet panel where the instrument is to be install ed The broken lines that represent the outline of the rectangular cutout also represent the outside dimensions of the chassis Make sure these lines clear shelves partitions or any equipment With the template in place first mark the six A and B holes and the four small holes that locate the corners of the cutout Then join the four corner ma
14. hnology has made it possible to build preamplifiers and power amplifiers with the high signal to noise ratio necessary to reproduce the sound quality present on compact discs or any other wide dynamic range signal source It is possible for conventional interconnecting cables to pick up electrical interference from other equipment AC cables or electrical appliances Using the balanced inputs provides an additional 40dB more protection against such noise pickup Use 2 conductor shielded cables with XLR type connectors to connect between the preamplifier and the power amplifier The maximum effect of balanc ed cables is realized when both the preamplifier and power amplifier have similar XLR balanced connectors Connect the left balanced output cable from a preamplifier to the LEFT BALANCED INPUT on the power amplifier Connect the right output to the RIGHT BALANCED INPUT Pin configuration for the XLR INPUT connectors on the MC 7300 PIN 1 Shield or ground PIN 2 output PIN 3 output In stereo installations where the amplifier and preamplifier are close to each other and require in terconnecting cables of six feet or less using quality unbalanced connecting cables is usually perfectly satisfactory If the units are farther apart and require longer interconnecting cables using balanced cables will give extra protection from noise or interference MONOPHONIC BRIDGE OR PARALLEL A rear panel MODE switch allows the a
15. ial for keeping both speaker systems operating IN PHASE This means that the driving surfaces of each channel speaker system will move back and forth together Almost all speakers have their hot and com mon terminals color coded with red usually as hot BE SURE THE REAR PANEL MODE SWITCH 15 SET TO STEREO The MC 7300 can be used to feed a constant voltage line often used in background music ap plications For a 25 volt line use the 2 ohm outputs on the amplifier Because the crosstalk between channels on the MC 7300 is almost non existent each channel can be used as a separate monophonic amplifier An exam ple would be one channel feeding background music to a given area and the other channel used for pag ing in a different area MONOPHONIC BRIDGE OPERATION The MC 7300 can be used as a single channel monophonic power amplifier in bridge configuration The two amplifier channel outputs add together in series when used in MONO BRIDGE The MODE switch connects the right channel inputs to both power amplifiers with the phase of the left channel inverted to get bridge operation The speaker con nections both common and hot should be con nected only to the left and right amplifier output im pedance taps as shown The common amplifier out put connections are not used in MONO BRIDGE configuration For example the two 8 ohm outputs will add together to become 16 ohms HOW TO CONNECT OUTPUTS 9 To maintain mono
16. in decibels The meter calibration marks reading from right to left starting at the 300 watt indication are as follows 300 Watts Indicated 120 Milliwatts 120 60 60 30 Indicated 30 Indicated 12 12 6 6 3 Indicated 3 Indicated 1 2 12 0 3 0 6 0 3 Indicated Two additional calibration marks above 300 watts on the meters The first is 600 watts and the second is 1200 watts 6dB The power amplifier cannot produce a continuous 1200 watts of power but can produce well beyond 300 watts on program peaks especially into lower impedance speaker loads In MONO operation the two meters will read iden tical power levels The total mono power output of the amplifier will be the sum of these readings METER WATTS HOLD In the METER WATTS position the meters respond to all the musical information being produced by the amplifier and read to an accuracy of at least 9596 of the power output of either amplifier channel In the METER HOLD position the meter pointer is locked to the highest power peak in a sequence of peaks The meter is electronically held to this power level until another higher power peak passes through the amplifier The meter pointer will then rise to the newer higher indication If no further power peaks are reached the meter pointer will very slowly return to its rest position or lower power level The decay rate is approximately 6dB per minute LEFT GAIN Use the LEFT GAIN co
17. ll or Cabinet Mounting Mount the instrument in a wall or cabinet only as described in the owners manual 10 Water and Moisture Do not use the instrument near water for example near a bathtub washbowl kitchen sink laundry tub in a wet basement or near a swimming pool etc 11 Cleaning Clean the instrument by dusting with a dry cloth Clean the panel with a cloth moistened with a window cleaner 12 Object and Liquid Entry Do not permit objects to fall and liquids to spill into the instrument through enclosure openings 9 S e so 13 Nonuse Periods Unplug the power cord from the AC power outlet when left unused for a long period of time 14 Damage Requiring Service Service must be performed by qualified service personnel when A The power supply cord or the plug has been damaged or 4 B Objects have fallen or liquid has been spilled into the instrument or C The instrument has been exposed to rain or D The instrument does not appear to operate nor mally or exhibits a marked change in performance or E The instrument has been dropped or the enclosure damaged 15 Servicing Do not attempt to service beyond that described in the operating instructions other service should be referred to qualified service personnel 16 Grounding or Polarization Do not defeat the bs inherent design features of the polarized plug Non polarized line cord adaptors will defeat the
18. m Output 040 FOU EE EDS vs 035 be Qi 030 De Des Pbi 025 ae ops Lasts 020 EE PERCENT DISTORTION 200 300 0 2 0 3 04 10 77 100 1000 5 14 PERFORMANCE CHARTS Ke tem ni me 020 l x up 015 E DS M Vm m em Em Tis xis PERCENT DISTORTION Ec T ET o 7 1 10 100 220209 090 POWER IN WATTS Output Power vs Load Impedance m Continuous ak A n n ect d t TEE AVERAGE POWER IN WATTS E ere E 100 0 1 1 0 10 LOAD IMPEDANCE IN OHMS Output Power vs Load Impedance 20mS Dynamic 10k ak bisce non crees Ma tee Aha Pee E AVERAGE POWER IN WATTS 04 10 10 LOAD IMPEDANCE IN OHMS GUARD Power Guard a unique feature of McIntosh amplifiers assures that each channel of the MC 7300 will deliver full power free of clipping distortion Clipping is caused when an amplifier is asked to pro duce more power output than its design is capable of delivering with low distortion Amplifiers that are overdriven may deliver large quantities of power when they are clipping but they may have more than 4096 harmonic distortion In this mode the sound is grossly distorted and the extra energy con tent of the clipped signal will damage most loud speakers The McIntosh Power Guard circuit pro
19. mplifier to be used in normal STEREO MONO BRIDGE or MONO PARALLEL When switched to either MONO BRIDGE or MONO PARALLEL operation the RIGHT BALANCED and UNBALANCED inputs are the only ones used for the mono input signal The LEFT inputs are automatically disconnected Connect the appropriate cable from a preamplifier or other mono source to the appropriate RIGHT UNBALANCED or BALANCED amplifier input 6 HOW TO CONNECT INPUTS 14 2 5 SENSITIVITY SWITCH AT 2 5V PLACE MODE SWITCH MONO IN STEREO UN PARALLEL STEREO CONNECTIONS INPUT SENSITIVITY PLACE INPUT McINTOSH PREAMPLIFIER DIGITAL DYNAMIC STEREO POWER AMPLIFIER EIN USA Cr cr 3 oa 000000 gy LEFT OUTPUT RIGHT OUTPUT 12 u LEFT 8 OHM 8 OHM SPEAKER SPEAKER E MONO BRIDGE CONNECTIONS INPUT SENSITIVITY PLACE INPUT NON 14 2 5 SENSITIVITY BRID SWITCH AT 2 5V PLACE MODE SWITCH 2 ira m IN MONO BRIDGE PARALLEL McINTOSH PREAMPLIFIER o DIGITAL DYNAMIC STEREO POWER AMPLIFIER ex I ecce cr gt e 900000 LEFT OUTPUT RIGHT OUTPUT 2 aa 8 OHM SPEAKER CONNECTING DIAGRAMS 7 MONO PARALLEL CONNECTION MONO BRIDGE MONO INPUT SENSITIVITY 1 4 2 5 PLACE MODE SWTICH IN MONO PARALLEL
20. ng both voltage and current delivered into the speaker loads A speaker may have a different load impedance at different frequencies resulting in a change of output current The MC 7300 meters properly react to this condition and indicate Real Output power Other desirable features are included such as high current gold plated output terminals that will accept cable up to 0 204 inches in diameter Balanced input connectors are also provided in addition to the nor mal RCA inputs As in all Mcintosh power amplifiers the famous patented McIntosh POWER GUARD circuit is includ ed You never have to be concerned with amplifier overdrive when playing wide dynamic range program sources such as compact discs Refer to the technical description for a full account of all the outstanding circuit and performance features of this superb power amplifier INTRODUCTION 3 LOCATION The MC 7300 may be installed in a McIntosh cabinet or custom installed in furniture of your choice Always provide adequate ventilation The trouble free life of an electronic instrument is greatly extended by providing sufficient ventilation This prevents the build up of high internal temperatures that cause deterioration of circuit components Allow enough clearance so cool air can enter at the bottom of the cabinet and be vented from the top Allow at least 1 1 2 inches 3 8 cm above the amplifier so the airflow is not obstructed The recommended minimum space
21. ntrol to adjust the output in the left channel to the desired listening level RIGHT MONO GAIN Use the RIGHT MONO control to adjust the output in the right channel to the desired listening level When the amplifier is connected for monophonic operation the RIGHT MONO GAIN control is used to control the combined monophonic outputs of both channels FOR THE BEST SIGNAL TO NOISE RATIO WHEN USING McINTOSH PREAMPLIFIERS PLACE THE IN PUT SENSITIVITY SWITCH ON THE REAR PANEL OF THE AMPLIFIER TO THE 2 5V POSITION AND TURN BOTH FRONT PANEL GAIN CONTROLS TO THE MAX IMUM OR FULLY CLOCKWISE POSITIONS If your needs require more input sensitivity from the amplifier slide the INPUT SENSITIVITY switch to the 1 4 volt position and adjust the GAIN controls as needed In the 1 4 volt position turning the gain controls halfway will result in the same amplifier sen sitivity as the 2 5 volt position with full gain POWER The POWER switch turns the MC 7300 ON or OFF The switch does not control the auxiliary AC outlet on the rear panel If you wish to control the MC 7300 AC power from another source such as a preamplifier or switching relay leave the switch in the ON position FRONT PANEL CONTROLS 11 MODE SWITCH Provides STEREO MONO BRIDGE or PARALLEL operation INPUT SENSITIVITY SWITCH Provides an amplifier sensitivity of 1 4V or 2 5V When the MC 7300 is being used with a McIntosh preamplifier set the INPUT SENSITIV
22. ow how the meticulous atten tion to design and production details makes the MC 7300 one of the finest amplifiers ever produced by McIntosh Laboratory S1ndino SLNdLNO A431 210 zno rie M 0384315 DIWVNAG 00625 3ALLVO3N 504 HOLIMS uoivinoss 2H09 05 cid VAGI 184 5 NIV Al ddns BOVLIOA S3HOLIMS WWH3HL SANAN o 4 wanna HOLVOIONI 9 1861 HOLIMS ALAHISNaS HOLVNNBLLY 108110 YILAN AiN3uHno 3AILVD3N HOLIMS 300W 901 dW SLANI 1431 Q39NvYG U3MOd Horai Dd 1431 iN3Huno BLOCK DIAGRAM 17
23. put amplifier is driven by the preamplifier The power output amplifier uses two stages of voltage amplification followed by three stages of cur rent amplification All stages are complementary balanced Even number harmonics are cancelled by the balanced circuits This means that the amplifying stages have less total harmonic distortion and less negative feedback is required to achieve ultra low distortion The signal is fed to one input of the balanced dif ferential stage Feedback from the amplifier output is applied to the other input The differential amplifiers drive a balanced cascode connected voltage amplifier stage Current mirrors are also used to improve bandwidth and linearity The cascode voltage amplifier output feeds com plementary Darlington connected driver transistors These supply the signal to 10 complementary con nected output transistors per channel Ancillary com ponents for Power Guard Sentry Monitor Power Output Meters and other protection circuits inter TECHNICAL DESCRIPTION 15 connect with the amplifier circuits The power supply uses a massive power transformer full wave bridge rectifiers and large filter capacitors having 227 joules of energy storage Four large heatsinks provide cool ing for the 20 output power transistors The mechanical and electrical design of the MC 7300 is the result of the many years of engineer ing and manufacturing experience held by the staff at McIntosh This kn
24. rkings with pencil lines using the edge of the template as a straightedge 3 Drill Holes Use a drill with a 3 16 inch 5 mm bit held perpen dicular to the panel and drill the six A and B holes Then using a drill bit slightly larger than the tip of your saw blade drill one hole at each of two diagonally opposite corners The holes should barely touch the inside edge of the penciled outline Before taking the next step make sure that the six A and B holes have been drilled ud 4 Saw the Panel Cutout First make the two long cuts and then the two short cuts After the rectangular opening has been cut out use a file to square the corners and smooth any irregularities in the cut edges 5 Install the Mounting Strips In the hardware package are two mounting strips and two 4 40 x 1 1 4 31 8 mm black screws that have a flat head Use these screws one on each end to fasten the mounting strips They are attached through the center hole marked on the template Make sure the screw heads are drawn flush or slight ly into the wood before attaching the PANLOC brackets 6 Attach the PANLOC Brackets Using two 6 32 x 1 1 4 31 8 mm screws in the A holes on each side attach the PANLOC brackets to the cabinet panel the short flange is mounted against the front face of the cabinet panel The screws pass through the PANLOC bracket flange the cabinet panel and then through the mounting
25. rvice agency will repair all McIntosh instruments at normal service rates To receive the free service under the terms of the service contract the service contract certificate must accompany the instrument when taken to the service agency 3 Always have service done by a McIntosh authorized service agency If the instrument is modified or damaged as a result of unauthorized repair the service contract will be cancelled Damage by improper use or mishandling is not covered by the service contract 4 The service contract is issued to you as the original purchaser To protect you from misrepresentation this contract cannot be transferred to a second owner 5 Units in operation outside the United States and Canada are not covered by the McIntosh Factory Service Contract irrespective of the place of purchase Nor are units acquired outside the USA and Canada the purchasers of which should consult with their dealer to ascertain what if any service contract or warranty may be available i locally The electrical and mechanical design of the MC 7300 power amplifier is the result of the many years of engineering and manufacturing experience of the design staff at McIntosh This Know How along with the meticulous attention to design and production details makes the MC 7300 one of the finest amplifiers ever produced by McIntosh Laboratory The use of 10 complimentary connected output transistors per channel
26. tects your ears and your speakers from this kind of damage The Power Guard circuit consists of a waveform comparator which monitors the wave shape of the amplifier input and output signals Normally there is no disparity between these signals and the com parator produces no output When the amplifier is driven beyond its maximum power capacity a dif ference will develop If the disparity exceeds 0 3 equivalent to 0 39 total harmonic distortion the comparator output causes the amber Power Guard indicator to light If there is a further increase in the the comparator output controls an elec onic attenuator at the amplifier input to reduce the amplifier gain thus holding the amplifier output to a low distortion value Overdrive by 14dB is possible before the output distortion exceeds 296 SENTRY MONITOR All power transistors have limits for the maximum amount of power they can handle The MC 7300 out put transistors and power supply have been design ed to allow very high current flow into properly matched load impedances If however a short cir cuit or very low value of load impedance is applied to the output of the MC 7300 destructive current levels could be reached if it was not controlled by the Sentry Monitor circuit This circuit senses the dynamic operating time voltage and current of the amplifier output stage and controls the current flow confining it to nondestructive limits Sentry Monitor does
27. the unit and get your money back STEREO POWER OUTPUT 300 watts into 8 4 or 2 ohm loads is the minimum _ sine wave continuous average power output per channel from 20Hz to 20 000Hz with both channels operating The output RMS voltage is 49 0 across 8 ohms 34 6 across 4 ohms 24 5 across 2 ohms MONO BRIDGE POWER OUTPUT 600 watts into a 16 8 or 4 ohm load is the minimum sine wave continuous average power output from 20Hz to 20 000Hz The output RMS voltage is 98 0 across 16 ohms 69 3 across 8 ohms 49 0 across 4 ohms MONO PARALLEL POWER OUTPUT 600 watts into a 4 2 or 1 ohm load is the minimum sine wave continuous average power output from 20Hz to 20 000Hz The output RMS voltage is 49 0 across 4 ohms 34 6 across 2 ohms 24 5 across 1 ohm OUTPUT LOAD IMPEDANCE STEREO 8 4 or 2 ohms by connecting to the proper out put terminals MONO 16 8 4 2 or 1 ohms by connecting to proper out put terminals TOTAL HARMONIC DISTORTION STEREO 0 005 maximum harmonic distortion at any power level from 250 milliwatts to rated power per channel from 20Hz to 20 000Hz both channels operating MONO 0 005 maximum harmonic distortion at any power level from 250 milliwatts to rated power from 20Hz to 20 000Hz INTERMODULATION DISTORTION STEREO 0 005 maximum if instantaneous peak per output does not exceed twice the output rating per channel with both channels operating for any combination of frequencies from 20Hz
28. to 20 000Hz MONO 0 005 maximum if instantaneous peak power out put does not exceed twice the output rating for any combination of frequencies from 20Hz to 20 000Hz FREQUENCY RESPONSE at one watt output 0 0 254 from 20Hz to 20kHz 0 3 0dB from 10Hz to 100kHz HUM AND NOISE A weighted 105dB below rated output IHF DYNAMIC HEADROOM 1 9dB DAMPING FACTOR Greater than 40 INPUT IMPEDANCE 20 000 ohms Unbalanced 40 000 ohms Balanced INPUT SENSITIVITY Switchable for either 1 4 or 2 5 volts POWER REQUIREMENTS 120 volts 50 60Hz 0 6 to 12 amperes MECHANICAL INFORMATION SIZE 16 3 16 inches wide 41 1 cm by 7 1 8 inches high 18 1 cm by 15 9 16 inches deep 40 0 cm including connectors Knob clearance required is 1 inch 2 54 cm in front of mounting panel FINISH The front panel is a combination of glass and black anodized aluminum The chassis is black WEIGHT 79 pounds 35 8 kg net 97 pounds 44 kg in shipping carton Harmonic Distortion vs Frequency 300 Watts Per Channel 8 Ohm Load Harmonic Distortion vs Power 040 938 bo caini A 030 8 Ohm Output PERCENT DISTOHTION 100 200 300 ik 2k 4k 10k 20k FREQUENCY IN HERTZ Frequency Response at 8 Ohm Output 1 Watt INPUT SENSITIVITY 2 5V 140 AUDIO OUTPUT IN dB 10 100 1k 10k 100k FREQUENCY IN HERTZ Intermodulation Distortion vs Power 8 Oh
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