McIntosh MC500 User manual

MC500
POWER
AMPLIFIER

MC500
POWER
AMPLIFIER

IMPORTANT
SAFETY
INSTRUCTIONS
THESE
INSTRUCTIONS
ARE TO
PROTECT
YOUANDTHE
McINTOSH
INSTRUMENT.
BESURETO
FAMILIARIZE
YOURSELF
WITHTHEM.
Copyright©1996by
MclntoshLaboratory,Inc.
1.Readallinstructions- Readthesafetyandoperatinginstructionsbeforeoperating
theinstrument.
2. RetainInstructions- Retainthesafetyandoperatinginstructionsforfuturereference.
3.Heedwarnings- Adheretowarningsandoperatinginstructions.
4.FollowInstructions- Followalloperatinganduseinstructions
WARNING:TOREDUCERISKOFFIREORELECTRICALSHOCK,DONOT
EXPOSETHISINSTRUMENTTORAINORMOISTURE.
5.PowerSources- Connectthepowersupplyonlytothetypedescribedinthe
operatinginstructionsorasmarkedontheunit.
6PowerCordProtection- Routepowersupplycordssothattheyarenotlikelytobe
walkedonorpinchedbyitemsplaceduponoragainstthem,payingparticularattention
tocordsatplugs,conveniencereceptacles,andthepointwheretheyexitfromthe
instrument.
7.Ventilation- Locatetheinstrumentforproperventilation.Forexample,theinstrument
shouldnotbeplacedona bed,sofa,rug,orsimilarsurfacethatmayblockventilation
openings;or.placedina built-ininstallation,suchasa bookcaseorcabinet,thatmay
impedetheflowofairthroughtheventilationopenings.
8.Heat- Locatetheinstrumentawayfromheatsourcessuchasradiators,heat
registers,stoves,orotherappliance(includingamplifiers)thatproduceheat.
9.WallorCabinetMounting- Mounttheinstrumentina wallorcabinetonlyas
describedintheowner'smanual.
10.WaterandMoisture - Donotusetheinstrumentnearwater- forexample,neara
bathtubwashbowl,kitchensink,laundrytub,ina wetbasementorneara swimming
pool,etc.
11.Cleaning- Cleantheinstrumentbydustingwitha drycloth.Cleanthepanelwitha
clothmoistenedwitha windowcleaner.
12.ObjectandLiquidEntry- Donotpermitobjectstofailandliquidstospillintothe
instrumentthroughenclosureopenings
13.NonusePeriods- UnplugthepowercordfromtheACpoweroutletwhenleft
unusedfora longperiodoftime.
14.DamageRequiringService- Servicemustbeperformedbyqualifiedservice
personnelwhen:
A.Thepowersupplycordortheplughasbeendamaged;or
B.Objectshavefallen,orliquidhasbeenspilledintotheinstrument; or
C.Theinstrumenthasbeenexposedtorain;or
D.Theinstrumentdoesnotappeartooperatenormallyorexhibitsa markedchange
inperformanceor
E.Theinstrumenthasbeendropped,ortheenclosuredamaged.
15.Servicing- Donotattempttoservicebeyondthatdescribedintheoperating
instructions.Allotherserviceshouldbereferredtoqualifiedservicepersonnel.
16.GroundingorPolarization- Donotdefeattheinherentdesignfeaturesofthe
polarizedplug.Non-polarizedlinecordadapterswilldefeatthesafetyprovidedbythe
polarizedACplug.
17.CAUTION.TOPREVENTELECTRICALSHOCKDONOTUSETHIS(POLARIZED)
PLUGWITHANEXTENSIONCORD,RECEPTACLEOROTHEROUTLETUNLESSTHE
BLADESCANBEFULLYINSERTEDTOPREVENTBLADEEXPOSURE
2

ATTENTION:POURPEVENIRLESCHOCSELECRIQUESPASUTILISERCETTEFICHE
POLARISEEAVECUNPROLONGATEUR,UNEPRISEDECOURANTOUUNAUTRE
SORTIEDECOURANT,SAUFSILESLAMESPEUVENTETREINSEREESA FONDANS
ENLAISSERAUCUNEPARTIEA DECOUVERT
Thelightningflashwitharrowhead,withinanequilateraltriangle,isintended
toalerttheusertothepresenceofuninsulated"dangerousvoltage"within
theproduct'senclosurethatmaybeofsufficientmagnitudetoconstitutea
riskofelectricshocktopersons.
CAUTION:TOPREVENTTHERISKOFELECTRIC
SHOCK,DONOTREMOVECOVER(ORBACK).NO
USER-SERVICEABLEPARTSINSIDE.REFER
SERVICINGTOQUALIFIEDPERSONNEL
Theexclamationpointwithinanequilateraltriangleisintendedtoalertthe
usertothepresenceofimportantoperatingandmaintenance(servicing)
instructionsintheliteratureaccompanyingtheappliance.
WARNING:THISUNITISCAPABLEOFPRODUCINGHIGH
SOUNDPRESSURELEVELS.CONTINUEDEXPOSURETO
HIGHSOUNDPRESSURELEVELSCANCAUSEPERMANENT
HEARINGIMPAIRMENTORLOSS.USERCAUTIONIS
ADVISEDANDEARPROTECTIONISRECOMMENDEDWHEN
PLAYINGATHIGHVOLUMES.
LIGHTNING- Foraddedprotectionforthisproductduringa lightningstorm,orwhenitis
leftunattendedandunusedforlongperiodsoftime,unplugitfromthewalloutletand
disconnecttheantennaorcablesystem.Thiswillpreventdamagetotheproductdueto
lightningorpowerlinesurges.
OVERLOADING- Donotoverloadwalloutlets,extensioncordsorintegralconvenience
receptaclesasthiscanresultina riskoffireorelectricshock.
IMPORTANT
SAFETY
INSTRUCTIONS
THESE
INSTRUCTIONS
ARE TO
PROTECT
YOUANDTHE
McINTOSH
INSTRUMENT.
BESURETO
FAMILIARIZE
YOURSELF
WITHTHEM.
3

THANK
YOU
YourdecisiontoownthispieceofMclntoshStereoEquipmentranksyouatthevery
topamongdiscriminatingmusiclisteners.Younowhave"TheBest".TheMclntosh
dedicationto"Quality",isassurancethatyouwillreceivethousandsofhoursofmusical
enjoymentfromthisunit.
Pleasetakea shorttimetoreadtheinformationinthismanual.Wewantyoutobe
asfamiliaraspossiblewithallthefeaturesandfunctionsofyournewpieceofMclntosh.
Thiswillensurethatyoureceivealltheperformancebenefitsthisinstrumentcanoffer
you,andthatitwillbecomea highlyvaluedpartofyourhomemusicsystem.
Theserialnumberandpurchasedateareimportanttoyouforpossibleinsurance
claimorfutureservice.Recordthisinformationhere.
SerialNumberPurchaseDate
TABLEOF
CONTENTS
INTRODUCTION5
INSTALLATION5
FRONTPANELFEATURES5,6
HOWTOCONNECTINPUTS6
HOWTOCONNECTOUTPUTS7,8
CONNECTINGDIAGRAMS9.10
TECHNICALDESCRIPTION11,12,13
SPECIFICATIONS14
4

TheMclntoshMC500isa 500wattperchannelstereopoweramplifiercreatedina stun-
ningnewcontemporaryindustrialdesign.Two5-1/2inchTruePowerOutputmetersaremounted
behindthe1/2inchthickglassfrontpanel.ThehighefficiencyoftheMC500circuitstogether
withoversizeheatsinksutilizingconvectioncoolingeliminatestheneedforinternalcooling
fans.TypicalMclntoshattentiontodetailincludestheuseof1%metalfilmresistorsand
polypropylenecapacitorsthroughout.Internalheatsinkmoduleconnectorsusegoldplated
contactstoensurereliableoperation.
GoldplatedBalancedaswellasUnbalancedInputconnectorsensurereliablesignaltransfer.
ArearpanelMODEswitchisalsoprovidedtochangetheMC500outputconfigurationfrom
a500wattperchannelSTEREOamplifier toa 1000wattbridgedmonoamplifierThepatented
MclntoshPowerGuardcircuitineachchanneleliminatesthepossibilityofoverdrivingthe
MC500amplifier intoclippingdistortion.MclntoshSentryMonitorOutputprotectioncircuits
arealsoincluded.Youensuremaximumamplifierreliabilityandlongoperatinglifewithab-
solutelynosoniclimitationsorcompromises.
Eachchanneliscoupledtotheloudspeakerloadsbya MclntoshOutputAutoformerwith
matchedimpedancesof2,4 and8 ohms.EachchanneloftheMC500canproducea peak
currentoutputofmorethan112amperes,thehighesteverfora Mclntoshstereopower
amplifier.TheMC500cansuccessfullydriveanytypeofloudspeaker.Witha distortionlimit
oflessthan0.005%,theMC500poweramplifierisabsolutelytransparent,ensuringtotal
sonicaccuracy.
Mclntosh knows how to do it right.
INTRODUCTION
TheMclntoshMC500PowerAmplifierisdesignedasa freestandingunit.Itincludeslarge
paddedmountingfeetwhichallowtheamplifiertobeplacedona tabletop,shelforother
similarmountingsurface.
Alwaysprovideadequate ventilationfortheamplifier. Thetroublefreelifeofanyelectronic
instrumentisgreatlyextendedbyprovidingsufficientventilationforcooloperation.Allowat
least1-1/2inches(3.8cm)abovetheheatsinkareasoairflowisnotobstructed.Therecom-
mendedminimummountingdepth,includingclearanceforconnectorsis,20-1/8inches
(51.1cm).Thisdimensionincludesthehandleswhichextendfromthefrontpanel.
INSTALLATION
For detailed information on the operating features and circuit designs of the MC500,
please refer to the section in this manual titled TECHNICAL DESCRIPTION,
POWERLEVELMETERS
Thetwopoweroutputmetersindicatethepoweroutputinwattsofeachchannelofthe
MC500toanaccuracyof95%.
METER:WATTS/HOLD
IntheWATTSposition,themeterswillrespondcontinuouslytothepoweroutputproduced
byeachchannel.
POWER:OFF-REMOTE/ON
TheOFF-REMOTEswitchpositionallowstheMC500tobeturnedonremotelyfroma
FRONTPANEL
FEATURES
5

FRONT
PANEL
FEATURES
compatibleMclntoshControlCenterbysendinga signaltotheMC500POWERCONTROL
INconnectorontherearpanel.
TheONpositionturnsontheMC500aslongasitspowercordisconnectedtoa liveAC
outlet.
POWERGUARD
ThepatentedMclntoshPOWERGUARDcircuitpreventstheMC500fromeverbeingdriven
intoclipping.Thisprotectsyoufromdistortionandpossiblespeakerdamage.ThePOWER
GUARDLEDundereachmeterwilllightwheneverPOWERGUARDisactivated,andindicates
thatyouarebeingprotected.
HOW TO
CONNECT
INPUTS
CONNECTINGCABLES
Usehighqualityconnectingcables.YourMclntoshdealercanadviseyouonthetypes
andlengthsofcablesthatwillworkbestinyourinstallation.
The MC500 has input facilities for both Balanced and Unbalanced cables. Use either
type of input, but not both at the same time.
STEREO
Set the rear panel MODE Switch to the STEREO position.
STEREOUNBALANCEDINPUTS
ConnectshieldedcableswithRCAtypeconnectorsfromtheoutputsofa Preamplifier,Con-
trolCenterorsimilaraccessoryunittotheUnbalancedInputsoftheMC500
STEREOBALANCEDINPUTS
Itispossibleforunbalancedinterconnectingcablestopickupinterferencefromotherequip-
ment,ACcablesorelectricalappliances.UsingBalancedcableswillprovideanadditional
40dBofprotectionagainstsuchhumornoiseinterference.
IftwoMC500amplifiersareusedinBridgedMonoasa stereopair,usetheBalancedIn-
putstoavoidthepossibilityofgroundloophumpickup,
Use2 conductorshieldedcablewithXLRtypeconnectors.TheMC500BalancedInput
connectorsareFemale,requiringa Maleconnectorplug.
PinConfigurationfortheMC500BalancedXLRInputConnectors:
PIN1:ShieldorGround
PIN2:+ Input
PIN3:- Input
R/BRIDGED(MONO)
Set the rear panel MODE Switch to the BRIDGED position. Only the R/BRIDGED
(RIGHT) channel Balanced and Unbalanced Inputs are used in BRIDGED Mono
configuration.
R/BRIDGED(MONO)UNBALANCEDINPUT
Connecta shieldedcablewithanRCAtypeconnectortotheR/BRIDGED(RIGHT)UN-
BALANCEDInputontheMC500.
R/BRIDGED(MONO)BALANCEDINPUT
Connecta 2 conductorshieldedcablewithanXLRconnectortotheR/BRIDGED(RIGHT)
BALANCEDInputontheMC500.
6

SPEAKERCABLES
Usehighqualitycables,sincethisisanimportantlinkinyourstereosystem.
Selectionofthepropersizeandtypeofspeakercableisnecessaryforyoutoreceive
thebestpossibleperformancefromyouramplifierandloudspeakercombination.The
highpoweroutputcapabilityoftheMC500requiresheavygaugecabletohandlethe
currentrequirements.A sizeof14gaugeorheavierisrecommended.YourMclntosh
dealercanadviseyouonthetypeofcablethatwillworkbestinyourinstallation.
STEREOOUTPUTS
TheMC500incorporatesthelegendaryMclntoshdesignedandmanufactured
OutputAutoformers,toensurepeakperformance,speakerprotectionandoutstanding
amplifier-loudspeakercompatibilityTheMC500Autoformerusedoneachchannelhas
threedifferentoutputimpedanceconnectionsforoptimummatchingtotheparticular
loudspeakers,orcombinationofloudspeakersbeingused.Thefollowingtablewillhelp
determinewhichimpedanceconnectionwillbebestforyourloudspeakers.Youmay
finditdesirabletoconsultyourMclntoshdealerorthemanufacturerofyourloudspeaker
forfurtherinformationonthecorrectimpedancetouse.
HOW TO
CONNECT
OUTPUTS
SPEAKERIMPEDANCE
INOHMS
2to4 ohms
4to8 ohms
8ohmsandup
MC500AMPLIFIEROUTPUT
TERMINALCONNECTIONS
COMand2 (LandR)
COMand4 (LandR)
COMand8 (LandR)
ConnectcablesfromeachloudspeakerCommonorMinusterminaltotheMC500.
COM(Common)POWEROUTPUTterminals.Connectcablesfromeachloudspeaker
HotorPlusterminaltothedesiredMC5002,4,or8 (LandR)STEREOPOWER
OUTPUTterminals
Mostloudspeakershavetheirinputterminalsbothmarkedandcolorcoded.Usually
theCommonor(-)terminalisBLACK:andtheHotor(+)terminalisRED.
The MC500 Output signals are IN PHASE with the Input signals.
Theactualloadimpedanceofsomeloudspeakersmaydropbelowthespecified
impedanceatsomepointsintheaudiofrequencyrange.Thiswillbenoproblem.The
highcurrentoutputoftheMC500willproducetheextracurrentnecessarytoproperly
drivetheloudspeakerundertheseconditions.
Iftheimpedanceofa loudspeakersystemishigherthan8 ohms,nochangeinthe
qualityofperformancewilloccur.Theavailablepoweroutputdirectedtothe
loudspeakerswillsimplybeslightlyless.
BRIDGED(MONO)OUTPUT
In BRIDGED Mono configuration the outputs of the two channels of the MC500
will combine to produce 1000 watts. All performance specifications for the stereo
configuration will be exactly the same in BRIDGED Mono configuration, but with
double the power. In BRIDGED Mono Configuration, only the BRIDGED Output
terminals marked +4, +8, +16, -4, -8, and -16 are used. The COM (Common)
terminals are not used. 7

HOW TO
CONNECT
OUTPUTS
SPEAKERIMPEDANCE
INOHMS
4to8 ohms
8to16ohms
16ohmsandup
BRIDGEDMC500OUTPUT
TERMINALCONNECTIONS
+4and-4
+8and-8
+16and-16
TomaintaintheMC500OutputsignalINPHASEwiththeInputsignal,connectthe
Commonorminimum(-)loudspeakercabletoanMC500Minus(-)L BRIDGED
OUTPUTimpedanceterminal,andtheHotor(+)cabletoanMC500PLUS(+)R
BRIDGEDOUTPUTimpedanceterminal
IMPORTANT
BE SURE TO REPLACE THE PROTECTIVE POWER OUTPUT TERMINAL COVER
AFTER THE LOUDSPEAKERS ARE CONNECTED. THE MC500 CAN DELIVER
MORE THAN 126 VOLTS FROM THE BRIDGED (MONO) +16 AND -16 TERMINALS,
WHICH CAN BE A SHOCK HAZARD.
HOWTOCONNECTACPOWER
TheMC500isdesignedtooperateon120volts50/60HzACcurrent.Power
consumptionisratedat12amperesUL/CSA.Thiscurrentrequirementapplieswhenthe
amplifierisbeingusedfortypicalmusicreproduction.TheMC500willdrawhigher
currentwithsteadytesttonesignals.
PlugtheMC500intoa dedicatedACoutputwitha 15ampereorhighercurrent
capacityTurnthefrontpanelPOWERSwitchONorOFFasneeded
POWERCONTROLIN/OUT
TheMC500canbeturnedONandOFFremotelybymeansofa DCPOWER
CONTROLsignalfroma compatibleMclntoshControlCenterorPowerAmplifier.
Connecta cablefromthePOWERCONTROLOUTontheaccessoryMclntoshunit,to
thePOWERCONTROLINontheMC500.Whentheaccessoryunitisturnedon,the
PowerControlsignalwillthenturnontheMC500.ThePOWERCONTROLOUTonthe
MC500willfeedthesameturnoncontrolsignalout,timedelayed,toanadditional
MclntoshPowerAmplifierorcompatibleaccessory.
Whena pairofMC500amplifiersareconfiguredinBRIDGED(Mono)fora stereo
system,connecta cablefromtheControlCenterPOWERCONTROLOUTtothe
POWERCONTROLINononeoftheMC500amplifiers.Connecta secondcablefrom
thefirstMC500POWERCONTROLIN.ConnectthepowercordofeachMC500toa
separatededicated15ampereoutlet.
APOWER CONTROL cable uses single conductor shielded wire with 1/8 inch
miniphone plugs on each end. Connections are to the sleeve and tip of each plug.
DONOTPLUGTHEMC500POWERCORDINTOTHEBACKPANELACOUTLET
OFAPREAMPLIFIER,CONTROLCENTERORSIMILARACCESSORY.PLUGTHE
CORDDIRECTLYINTOAWALLSOCKETORHEAVYDUTYACPOWERSTRIPOR
RELAY.
8

CONNECTINGDIAGRAM
BRIDGED(MONO) CONNECTING
DIAGRAMS
CONTROLCENTER
WITHBALANCEDOUTPUT
POWER
CONTROL
POWERCONTROLOUT
TOPOWERCONTROLIN
TODEDICATED
15AMPERE
OUTLET
SETMODESWITCH
TOBRIDGED
8OHM
LOUDSPEAKER
BALANCEDOUTPUT
FROMPREAMPLIFIER
TOR/BALANCED
MC500INPUT
TODEDICATED
15AMPERE
OUTLET
SETMODESWITCH
TOBRIDGED
8OHM
LOUDSPEAKER
9

CONNECTING
DIAGRAMS
CONNECTINGDIAGRAM
STEREO
CONTROLCENTER
WITHBALANCEDOUTPUT
POWER
CONTROL
TODEDICATED
15AMPERE
OUTLET
4OHM
LOUDSPEAKER
BALANCED
INPUTS
SETMODESWITCH
TOSTEREO
4OHM
LOUDSPEAKER
10

DESIGNPHILOSOPHY
ThedesignphilosophyincorporatedintheMC500involvedmanydifferenttechniques,all
basedonsoundscientificlogic.Everystageofvoltageorcurrentamplificationisdesigned
tobeaslinearaspossible.Negativefeedbackisthenutilizedtoenhancetheperformance.
Mclntoshengineersknowhowtoproperlydesignnegativefeedbackcircuitssotheycon-
tributetotheextremelylowdistortionperformanceexpectedfroma Mclntoshamplifier.The
typicalMclntoshownerwouldneveraccepttheapproximately100timeshigherdistortion
ofmanysocallednon-feedbackdesigns.
Alltransistorsareselectedtohavenearlyconstantcurrentgain(Beta)overtheentirecur-
rentrangetheymustcover.Outputtransistorsinparticular,musthavematcheduniform
currentgain,highcurrent-bandwidthproductandlargeactiveregionsafeoperatingarea.
Resistorsandcapacitorsinthesignalpatharecarefullyselectedtohaveexceedinglylow
voltagecoefficients,(changeofresistanceorreactancewithappliedvoltage).Precisionmetal
filmresistors,lowdielectricabsorptionfilmcapacitorsandpremiumaudiogradeelectrolytics
areusedinallcriticalcircuitlocations.
PROTECTIONCIRCUITS
Somepoweramplifiermanufacturersclaimthattheirproductsdonotneedordonotuse
protectioncircuitsandthatsuchcircuitscompromiseperformance.Mclntoshfeelsthatpro-
tectioncircuitsaredesirableandnecessarytopreventamplifierorloudspeakerdamagedue
toabnormalcircumstances.ThegeniusofMclntoshengineeringhasresultedinprotection
circuitswhichdonoteffectorcompromisethenormalperformanceofa poweramplifier.
Sixdifferenttypes ofprotectioncircuitsareincorporatedintheMC500toinsureita long,
safeandtroublefreeoperatinglife.ThisisjustoneofthecharacteristicsofMclntoshpower
amplifiersthathavemadethemworldfamous.TheSENTRYMONITORcircuitisa good
example.
SENTRYMONITORCIRCUIT
Allpowertransistorshavelimitsforthemaximumamountofpowertheycanhandle.The
MC500outputtransistorsandpowersupplyhavebeendesignedtoallowveryhighcurrent
flowintoproperlymatchedloadimpedances.However,ifa shortcircuitorverylowloadim-
pedancewereconnectedtotheMC500outputs,destructivecurrentlevelscouldbereached
ifitwasnotcontrolledbytheMclntoshSENTRYMONITORcircuit.Thiscircuitsensesthe
dynamicoperatingtime,voltageandcurrentoftheoutputstage,andcontrolsittosafe
operatinglimits.TheSENTRYMONITORcircuitdoesnotlimitthepoweroutputavailablefrom
theamplifier.
Thereisabsolutelynocompromiseinsonicperformanceanditensuressafeoperation
oftheamplifierundereventhemostextremeoperatingconditions.
THERMALCONTROL
Allpowertransistorshavelimitstothemaximumamountofheattheycansafelytolerate.
TheMC500usesa highlyefficientamplifyingcircuitwhichproducesrelatively littleheatfrom
thepowertransistorsfortheoutputpowerproduced.Theamplifieruseslargeareaheatsinks
withanareaofmorethan2800squareinchestoefficientlydissipatethetransistorheat.Natural
convectionairflowissufficientforsafecooloperation.Coolingfansarenotrequired.
Ifthecoolingairisblocked,ortheamplifieroperatingtemperatureisforcedtoohigh,ther-
malcutoutswitcheswillturnofftheACpowertotheamplifier. Whentheproblemiscorrected
andtheamplifiercoolstoitsnormaloperatingtemperature,theACpowerwillturnbackon.
TECHNICAL
DESCRIPTION
11

TECHNICAL
DESCRIPTION
POWERGUARD
TheMC500includestheuniquepatentedMclntoshPOWERGUARDcircuitoneachchan-
nel.POWERGUARDeliminatesthepossibilityofeveroverdrivingtheamplifierintoclipping.
Clippingoccurswhenanamplifierisoverdrivenpastitsoutputdesigncapabilities.Anover-
drivenamplifiercanproducebothaudibleandultrasonicdistortionlevelsapproaching40%.
Theaudibledistortioniscertainlyunpleasant,buttheultrasonicdistortionisalsoundesirable,
sinceitcandamagetweeterloudspeakers.
TheMclntoshPOWERGUARDcircuitactsasa waveform comparator,monitoringboththe
inputandoutputsignalwaveforms.Undernormaloperatingconditionstherearenodifferences
betweenthesewaveforms.Whenanamplifierisoverdrivenbeyonditsmaximumdistortion
freeoutput,therewillbe a differencebetweenthetwosignalwaveforms.If thedifference
exceeds0.3%(equivalentto0.3%harmonicdistortion),theamberPOWERGUARDindicator
willlight.Ifthedifferencecontinuestoincrease,thePOWERGUARDcircuitcontrolsanelec-
tronicattenuatorattheinputoftheamplifiertoreducethegainjustenoughtopreventany
furtherincreaseindistortion.Distortionwillnotexceed2%withasmuchas14dBoverdrive.
WithoutPOWERGUARD,thedistortioncouldeasilyreach40%forthesameoperating
conditions.
AMclntoshpoweramplifier withPOWERGUARDwillalwaysdeliveritsmaximumdistortion-
freeoutput.ThispowerisalwayswellabovetheratedpowerduetotheMclntoshphilosophy
ofconservativedesign.Youwillneverexperiencetheharshanddamagingdistortiondueto
clippingwhenusinga MclntoshMC500amplifierwithPOWERGUARD.
THEVERSATILEMcINTOSHOUTPUTAUTOFORMER
Alltransistorpoweroutputcircuitsworkbestintowhatiscalledanoptimumload.Depend-
ingonthenumberandconfigurationoftransistorsused,thisoptimumloadmayvarycon-
siderablyfromwhata loudspeakerrequires.Inthecaseofmorethanoneloudspeakercon-
nectedinparallel,theimpedanceloadreflectedtothepoweramplifiermaydroptotwoohms
orevenless.
Apoweramplifierconnectedtoa loadthatislowerthanoptimumcausesextracurrent
toflowandextraheatingofthepowertransistors.Thismeanstheamplifierwillrunmuch
hotter,witha correspondingreductioninoperatinglife.
TheoutputsignalsfromthetwochannelsintheMC500arecoupledintotheautoforrner
atthepointonthewindingsthatisanoptimumimpedancematchforthetransistorsinthe
outputcircuit.TheMC500amplifier outputcircuitsarealwaysoperatingattheirhighestpossi-
bleefficiency.
TheMC500autoformersincludeoutputimpedancetapsforexactloudspeakermatches
of2 ohms.4 ohmsand8 ohms.LoudspeakerperformancewillalwaysbeatitsbestAny
Mclntoshpoweramplifierwithanautoformerisespeciallywellsuitedforstereoinstallations
thatrequiremultiplespeakers,sinceitispossibletohavea verycloseimpedancematch.
Thefrequencyresponseofa Mclntoshautoformerexceedsthatoftheoutputcircuititself,
andextendswellbeyondtheaudiorange.Itsdistortionlevelissolowitisvirtuallyimpossible
tomeasure.TheMclntoshAutoformerisquitesimplya significantengineeringadvancein
poweramplifier performanceandreliability.TheunequaledexpertiseofMclntoshinthedesign
andmanufacturingofautoformersislegendaryinthehighfidelityindustry.
Intherareeventofoutputcircuitfailure,theMclntoshautoformerwillconductanyspeaker
damagingDC(directcurrent),directlytocircuitground.Thiswillprotectyourvaluable
loudspeakersfrompossibledamage.
12

TRUEPOWEROUTPUTWATTMETERS
Twoilluminated5-1/2inchWATTmetersareprovidedontheMC500frontpanel.Themeters
arepeakrespondingandtheircircuitsareconstantlyreadingbothvoltageandcurrent
deliveredtotheloudspeakerloads.Theloadimpedanceofa loudspeakermaydifferatvarious
partsoftheaudiofrequencyrange,resultingina changeofoutputcurrentrequirements.
TheMC500metersreacttothesechangingcurrentandvoltageconditionsandindicatethe
trueamplifierpoweroutputofeachchannelatalltimes.
intheMETERWATTSposition,themetersrespondtothemusicalinformationandread
theamplifieroutputofeachchannelona continuousbasis.IntheMETERHOLDposition
themeterswilllocktothehighestpowerpeakina sequenceofpeaks.Ifnohigherpower
peaksarereachedthemeterpointerswillslowlyreturntothelowerpowerlevel.Ifthemusic
stops,themeterpointerswillreturntotherestposition.Themeterpointerdecayrateisap-
proximately6dBperminute.TheMC500outputmetersareextremelyaccurate,andwillres-
pondto95%offullscale,withonlya singlecycleofa 2,000Hztoneburst.
Theupperscaleonthemetersiscalibratedinaveragewattspower,andthelowerscale
indecibels.Themetercalibrationlinesreadingfromrighttoleft,startingatthe500watt
indicationareasfollows:
TECHNICAL
DESCRIPTION
500
200
100
50
20
10
5
2
1
(Indicated)
(Indicated)
(Indicated)
0.5
0.2
0.1
0.05
0.02
0.01
0.005
0.002
0.001
(Indicated)
(Indicated)
(Indicated)
Twoadditionalcalibrationmarksabove500wattsareonthemeters.Thefirstmarkis1000
watts(+3dB),andthesecondmarkis2000watts(+6dB)Theamplifiercannotproduce
acontinuous2000wattsofpower,butcanproducewellabove500wattsonprogrampeaks,
especiallyintolowerimpedanceloads.
InMONOoperation,thetwometerswillreadidenticalpowerlevels.Thetotalmonopower
outputoftheamplifierwillbethesumofthesereadings.
ADDITIONALFEATURES
Heavydutyhighcurrentgoldplatedoutputterminalswillacceptspeakercablesupto0.204
inches(5.18mm)indiameter.Itiseasytoconnectspeakersusinganyofthecurrentlypopular
speakercables
BothBalancedaswellasanUnbalancedinputjacksareprovidedforcompleteflexibility
inanyinstallation.
13

SPECIFICATIONS
POWEROUTPUT
500wattsperchannelintoan8,4 or2
ohmloadistheminimumsinewavecon-
tinuousaveragepoweroutput
1000wattsMonointoa 16,8 or4 ohm
loadistheminimumsinewavecontinuous
averagepoweroutput
RATEDPOWERBAND
20Hzto20,000Hz
TOTALHARMONICDISTORTION
0.005%maximumharmonicdistortionat
anylevelfrom250milliwattstoratedpower
output
DYNAMICHEADROOM
2.1dB
FREQUENCYRESPONSE
+0,-0.25dBfrom20Hzto20,000Hz
+0,-3.0dBfrom10Hzto100.000Hz
INPUTSENSITIVITY
2.2volts,StereoBalancedand
Unbalanced
2.2volts,MonoBalanced
3.2volts,MonoUnbalanced
A-WEIGHTEDSIGNAL-TO-NOISERATIO
85dB(115dBbelowratedoutput)
INTERMODULATIONDISTORTION,
SMPTE
0.005%maximumifinstantaneouspeak
poweroutputdoesnotexceedtwicetheout-
putrating
WIDEBANDDAMPINGFACTOR
200at8 ohmoutput
INPUTIMPEDANCE
10,000ohms
POWERGUARD
ClippingispreventedandTHDdoesnot
exceed2%withupto14dBoverdriveat
1000HZ
POWERREQUIREMENTS
120volts.50/60Hz,12amperesUL/CSA
SIZE
17-1/4inches(43.8cm)W,10-3/8inches
(26.4cm)H,20-1/3inches(51.1cm)D.in-
cludingfronthandles
WEIGHT
114pounds(51.7Kg)net,127pounds
(57.6Kg)shipping
14

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