McIntosh MC150 User manual

MC150
POWER
AMPLIFIER

MC150
POWER
AMPLIFIER

IMPORTANT
SAFETY
INSTRUCTIONS
THESE
INSTRUCTIONS
ARETOPROTECT
YOUANDTHE
MclNTOSH
INSTRUMENT.
BESURETO
FAMILARIZE
YOURSELF
WITHTHEM
Copyright1995© by
MclntoshLaboratory,Inc.
1.Readallinstructions- Readthesafetyandandoperatinginstructionsbeforeoperatingtheinstrument.
2.RetainInstructions- Retainthesafetyandoperatinginstructionsforfuturereference.
3.Heedwarnings- Adheretowarningsandoperatinginstructions.
4.FollowInstructions- Followalloperatinganduseinstructions.
WARNING:TOREDUCERISKOFFIREORELECTRICALSHOCK,DONOTEXPOSE
THISINSTRUMENTTORAINORMOISTURE.
5.PowerSources- Connectthepowersupplyonlytothetypedescribedintheoperatinginstructionsor
asmarkedontheunit
6.PowerCordProtection- Routepowersupplycordssothattheyarenotlikelytobewalkedonorpinched
byitemsplaceduponoragainstthem,payingparticularattentiontocordsatplugs,convenience
receptacles,andthepointwheretheyexitfromtheinstrument.
7.Ventilation- Locatetheinstrumentforproperventilation.Forexample,theinstrumentshouldnotbe
placedona bed,sofa,rug,orsimilarsurfacethatmayblockventilationopenings;or,placedinabuilt-in
installation,suchasa bookcaseorcabinet,thatmayimpedetheflowofairthroughtheventilation
openings.
8.Heat- Locatetheinstrumentawayfromheatsourcessuchasradiators,heatregisters,stoves,orother
appliance(includingamplifiers)thatproduceheat.
9.WallorCabinetMounting- Mounttheinstrumentina wallorcabinetonlyasdescribedintheowner's
manual.
10.WaterandMoisture- Donotusetheinstrumentnearwater- forexample,neara bathtub,washbowl,
kitchensink,laundrytub,ina wetbasementorneara swimmingpool,etc.
11.Cleaning- Cleantheinstrumentbydustingwithadrycloth.Cleanthepanelwitha clothmoistenedwith
awindowcleaner.
12.ObjectandLiquidEntry- Donotpermitobjectstofallandliquidstospillintotheinstrumentthrough
enclosureopenings.
13.NonusePeriods- UnplugthepowercordfromtheACpoweroutletwhenleftunusedfora longperiod
oftime.
14.DamageRequiringService- Servicemustbeperformedbyqualifiedservicepersonnelwhen:
A.Thepowersupplycordortheplughasbeendamaged;or
B.Objectshavefallen,orliquidhasbeenspilledintotheinstrument;or
C.Theinstrumenthasbeenexposedtorain;or
D.Theinstrumentdoesnotappeartooperatenormallyorexhibitsa markedchangeinperformanceor
E.Theinstrumenthasbeendropped,ortheenclosuredamaged.
15.Servicing- Donotattempttoservicebeyondthatdescribedintheoperatinginstructions.Allotherservice
shouldbereferredtoqualifiedservicepersonnel.
16.GroundingorPolarization- Donotdefeattheinherentdesignfeaturesofthepolarizedplug.Non-
polarizedlinecordadapterswilldefeatthesafetyprovidedbythepolarizedACplug.
17. CAUTION:TOPREVENTELECTRICALSHOCKDONOTUSETHIS(POLARIZED)
PLUGWITHANEXTENSIONCORD,RECEPTACLEOROTHEROUTLETUNLESSTHE
BLADESCANBEFULLYINSERTEDTOPREVENTBLADEEXPOSURE.
ATTENTION:POURPEVENIRLESCHOCSELECRIQUESPASUTILISERCETTE
FICHEPOLARISEEAVECUNPROLONGATEUR,UNEPRISEDECOURANTOUUNE
AUTRESORTIEDECOURANT,SAUFSILESLAMESPEUVENTETREINSEREESA
FONDSANSENLAISSERAUCUNEPARTIEA DECOUVERT.
Thelightningflashwitharrowhead,withinanequilateraltriangle,isintendedtoalerttheuser
tothepresenceofuninsulated"dangerousvoltage"withintheproduct'senclosurethatmaybe
ofsufficientmagnitudetoconstitutea riskofelectricshocktopersons.
CAUTION:TOPREVENTTHERISKOFELECTRICSHOCK,DO
NOTREMOVECOVER(ORBACK).NOUSER-SERVICEABLEPARTS
INSIDE.REFERSERVICINGTOQUALIFIEDPERSONNEL.
Theexclamationpointwithinanequilateraltriangleisintendedtoalerttheusertothepresence
ofimportantoperatingandmaintenance(servicing)instructionsintheliteratureaccompanying
theappliance.
WARNING:THISUNITISCAPABLEOFPRODUCINGHIGHSOUND
PRESSURELEVELS.CONTINUEDEXPOSURETOHIGHSOUND
PRESSURELEVELSCANCAUSEPERMANENTHEARINGIMPAIRMENT
ORLOSS.USERCAUTIONISADVISEDANDEARPROTECTIONIS
RECOMMENDEDWHENPLAYINGATHIGHVOLUMES.
2

YourdecisiontoownthispieceofMclntoshStereoEquipmentranksyouattheverytop
amongdiscriminatingmusiclisteners.Younowhave"TheBest".TheMclntoshdedicationto
"Quality",isassurancethatyouwillreceivethousandsofhoursofmusicalenjoymentfromthis
unit.
Pleasetakea shorttimetoreadtheinformationinthismanual.Wewantyoutobeas
familiaraspossiblewithallthefeaturesandfunctionsofyournewpieceofMclntosh.Thiswill
ensurethatyoureceivealltheperformancebenefitsthisinstrumentcanofferyou,andthat
itwillbecomea highlyvaluedpartofyourhomemusicsystem.
THANK
YOU
Theserialnumber,purchasedate,andMclntoshLaboratoryServiceContractnumberare
importanttoyouforpossibleinsuranceclaimorfutureservice.Recordthisinformationhere.
SerialNumberPurchaseDate
Uponapplication,MclntoshLaboratoryprovidesa ServiceContracttotheoriginal
purchaser.YourMclntoshAuthorizedServiceAgencycanexpediterepairswhenyouprovide
themwiththeServiceContract.
SERVICECONTRACT5
INTRODUCTION5
INSTALLATION5,6
FRONTPANEL6,7
REARPANEL7,8,9,10
CONNECTIONS11
TECHNICALDESCRIPTION12,13,14
SPECIFICATIONS15
CUSTOMINSTALLATIONDIAGRAM16
RECOMMENDEDVENTILATIONCUTOUTINMOUNTINGSHELF16
TABLEOF
CONTENTS
ServiceContractNumber
3

MclNTOSH
THREEYEAR
SERVICE
CONTRACT
YourMC150PowerAmplifierwillgiveyoumanyyearsofsatisfactoryperformance.Ifyou
haveanyquestions,pleasecontact,
MclntoshLaboratory,Inc.
2ChambersStreet
Binghamton,NY13903-2699
Phone:[phone]
AnapplicationtorA THREEYEARSERVICECONTRACTisincludedwiththismanual.
Thetermsofthecontractare:
1.Iftheinstrumentcoveredbythiscontractbecomesdefective.Mclntoshwillprovideallparts,
materials,andlaborneededtoreturnthemeasuredperformanceoftheinstrumenttothe
originalperformancelimitsfreeofanycharge.Theservicecontractdoesnotcoverany
shippingcoststoandfromtheauthorizedserviceagencyorthefactory.
2.AnyMclntoshauthorizedserviceagencywillrepairallMclntoshinstrumentsatnormal
servicerates.Toreceivethefreeserviceunderthetermsoftheservicecontract,theser-
vicecontractcertificatemustaccompanytheinstrumentwhentakentotheserviceagency.
3.Alwayshaveservicedonebya Mclntoshauthorizedserviceagency.Ifthe instrument is
modified or damaged as a result of unauthorized repair the service contract wilt be cancell-
ed. Damagebyimproperuseormishandlingisnotcoveredbytheservicecontract.
4.Theservicecontractisissuedtoyouastheoriginalpurchaser.Toprotectyoufrom
misrepresentationthiscontractcannotbetransferredtoa secondowner.
5.UnitsinoperationoutsidetheUnitedStatesandCanadaarenotcoveredbytheMclntosh
FactoryServiceContract,irrespectiveoftheplaceofpurchase.Norareunitsacquired
outsidetheUSAandCanada,thepurchasersofwhichshouldconsultwiththeirdealer
toascertainwhat,ifany,servicecontractorwarrantymaybeavailablelocally.
TAKEADVANTAGEOF3 YEARSOFCONTRACTSERVICE. . .
FILLINTHEAPPLICATIONNOW.
4

TheelectricalandmechanicaldesignoftheMC150poweramplifieristheresultofthe
manyyearsofengineeringandmanufacturingexperienceofthedesignstaffatMclntosh.
This"KnowHow",alongwiththemeticulousattentiontodesignandproductiondetails,makes
theMC150oneofthefinestamplifierseverproducedbyMclntoshLaboratory.
Theuseof6 complimentaryconnectedoutputtransistorsperchannel,allowsnotonlyfull
poweroutputintonormalloads,butextrahighcurrentoutputtodriveunevenspeakerloads.
Somespeakerdesignshaveimpedancecharacteristicsthatmaydiptoaslowas1 or2
ohmsatcertainfrequencies.ItispossiblefortheMC150todeliverasmuchas50amperes
peakcurrentintotheselowerimpedanceloads.
TheMC150providesthisextracurrentoutputwithcompletereliabilityduetotheuseof
MclntoshSentryMonitorprotectioncircuits.Somepoweramplifiermanufacturershave
claimedthattheirproductsdonotuseprotectioncircuitssincetheycompromiseperfor-
mance.TherealgeniusofMclntoshengineeringdesignhasrecognizedthesepotential
problemsandcompletelyeliminatedthem.Properlydesignedprotectioncircuitsassureyou
anamplifierthatwilloperateunderalltypesofuserconditionswithmaximumreliabilityand
freedomfrompossiblespeakeroramplifierdamage.Thebenefitsofthesedesignsmeanyou
ownanamplifierthatwillcontinuetooperatesafelyformanyyears.
TheMC150outputissodistortionfree,itisdifficulttomeasurewithconventionalinstru-
ments.Theperformancelimitis0.005%maximumdistortion,yetitistypicalforanamplifier
tomeasurelessthan0.002%atmidfrequencies.
ThepoweroutputwattmetersontheMC150arepeakresponding,andindicatetheTRUE
poweroutputoftheamplifier.TheMC150metercircuitsareconstantlymeasuringboth
voltageandcurrentdeliveredintothespeakerloads.A speakermayhavea differentload
impedanceatdifferentfrequencies,resultingina changeofoutputcurrent.TheMC150
metersproperlyreacttothisconditionandindicateRealOutputpower.
Otherdesirablefeaturesareincludedsuchashighcurrentgoldplatedoutputterminals.
AsinallMclntoshpoweramplifiers,thefamouspatentedMclntoshPOWERGUARDcir-
cuitisincluded.Youneverhavetobeconcernedwithamplifieroverdrivewhenplayingwide
dynamicrangeprogramsourcessuchascompactdiscs.
Refertothetechnicaldescriptionfora fullaccountofalltheoutstandingcircuitandper-
formancefeaturesofthissuperbpoweramplifier.
INTRODUCTION
TheMC150canbeplaceduprightona tableorshelf,standingonitsfourplasticfeet.
ItcanalsobeinstalledintheoptionalMclntoshL72equipmentcabinet.Followthe
mountinginstructionsenclosedwiththeL72cabinet.
TheMC150can becustomInstalledina cabinetofyourchoice.Themountingpanel
cutout,mountingshelfventilationcutoutandamplifierdimensionsareIncludedona
pagefurtherbackinthismanual.
itisessential tocutouta ventilation hole inthe mounting shelf according tothe
dimensions in the drawing.
Alwaysprovideadequateventilationfortheamplifier.Thetroublefreelifeofanyelectronic
instrumentisgreatlyextendedbyprovidingsufficientventilationforpropercooling.Ina
INSTALLATION
5

INSTALLATION
systemstack,thepoweramplifiershouldalwaysbeatthetop.Ifallthecomponentsare
installedina singlecabinet,a quietrunningventilationfancanbea definiteassetin
maintainingallthesystemcomponentsattheircoolestpossibleoperatingtemperatures.
Allowatleast1-1/2inches(3.8cm)abovetheheatsinkareatoallowthefreeflowofair.
Cutouta ventilationholeinthemountingshelfcorrespondingtothedimensionsinthedraw-
ing.Therecommendedminimumdepthformounting,includingclearanceforconnectorsis
16-1/2inches(41.9cm).Allow1-1/8inches(2.9cm)infrontofthemountingpanel forknob
clearance.
FRONT
PANEL
POWEROUTPUTMETERS
TheMC150poweroutputmetersrespond95%fullscaletoa singlecycleofa 2000Hz
tone.Bothvoltageandcurrentareelectronicallymeasuredandfedtoa specialcircuitthat
acceleratesthepointermovementintheupwarddirection.Whenthemeterpointerreaches
itspeak,itistimestretchedtopausejustlongenoughtoberead,andthendrops.
Theupperscaleonthemetersiscalibratedinaveragewattspower,andthelowerscale
indecibels.Themetercalibrationmarksreadingfromrighttoleft,startingatthe150watt
indication,areasfollows.
150
60
30
15
6
3
1.5
0.6
0.3
WattsIndicated
WattsIndicated
WattsIndicated
0.15WattsIndicated
0.06
0.03
15MilliwattsIndicated
6
3
1.5MilliwattsIndicated
0.6
0.3
Twoadditionalcalibrationmarksabove150wattsareonthemeters.Thefirstis300
watts,(+3dB),and600 watts,(+6dB).Thepoweramplifiercannotproducea continuous600
wattsofpower,butcanproducewellbeyond150wattsonprogrampeaks,especiallyinto
lowerimpedancespeakerloads.
METERWATTS/HOLD
IntheMETERWATTSposition,themetersrespondtoallthemusicalinformationbeing
producedbytheamplifierandreadtoanaccuracyofatleast95%ofthepoweroutputof
eitheramplifierchannel.
IntheMETERHOLDposition,themeterpointerislockedtothehighestpowerpeakin
asequenceofpeaks.Themeteriselectronicallyheldtothispowerleveluntilanotherhigher
powerpeakpassesthroughtheamplifier.Themeterpointerwillthenrisetothenewerhigher
indication.Ifnofurtherpowerpeaksarereached,themeterpointerwillveryslowlyreturnto
itsrestpositionorlowerpowerlevel.Thedecayrateisapproximately6 dBperminute.
6

POWERGUARD
ThepatentedMclntoshPOWERGUARDcircuitpreventstheMC150fromeverbeing
drivenintoclipping.Thisprotectsyoufromdistortionandpossiblespeakerdamage.The
POWERGUARDLEDneareachmeterwilllightwheneverPOWERGUARDisactivatedon
eitherchannel,andindicatesthatyouarebeingprotected.
POWER/OFF-REMOTE/ON
TurnontheMC150powerbyturningthefrontpanel POWERswitchtoON.Youcanalso
turntheMC150poweronwitha PowerControlsignalfromanaccessoryMclntoshcom-
ponentorControlCenterthatincludesa PowerControlOut.PlugtheMC150powercable
intoa walloutlet.Connecta datacablefromtheaccessorycomponentPowerControlOUT
totheMC150PowerControlINandsetthePOWERswitchtoOFF-REMOTE.Whenthe
accessorycomponentturnson,itwillsenda controlsignaltotheamplifiercausingittoturn
on.
FRONT
PANEL
HOWTOCONNECTINPUTS
CONNECTINGCABLES
Useshieldedcablestoconnectthesignalfromthepreamplifierorothersignalsource
tothepoweramplifier.Tominimizethepossibilityofhum,thecablesshouldbelocatedaway
fromspeakerconnectingcablesandACpowercords.
Usegoodqualitycables.Yourdealercanadviseyouonthetypeandlengthsofcables
thatwillbestsuityourinstallation.
STEREOOPERATION(UNBALANCEDINPUTS)
ConnecttwoshieldedcablesusingRCAconnectorsfromtheleftandrightunbalancedout-
putsofa PreamplifierorControlCentertotheMC150LEFTandRIGHT/MONOunbalancedinputs.
STEREOOPERATION(BALANCEDINPUTS)
Moderntechnologyhasmadeitpossibletobuildpreamplifiersandpoweramplifierswith
thehighsignaltonoiseratio necessarytoreproducethesoundqualitypresentoncompact
discsoranyotherwidedynamicrangesignalsource.
Itispossibleforconventionalinterconnectingcablestopickupelectricalinterference
fromotherequipment,ACcablesorelectricalappliances.Usingthebalancedinputspro-
videsanadditional40dBmoreprotectionagainstnoisepickup.
Use2 conductorshieldedcableswithXLRtypeconnectorstoconnectbetweenthepre-
amplifierandthepoweramplifier.Themaximumeffectofbalancedcablesisrealizedwhen
boththepreamplifierandpoweramplifierhavesimilarXLRbalancedconnectors.
Connecttheleftbalancedoutputcablefroma preamplifiertotheLEFTBALANCED
INPUTonthepoweramplifier.ConnecttherightoutputtotheRIGHTBALANCEDINPUT.
PinconfigurationfortheXLRINPUTconnectorsontheMC150.
PIN1:Shieldorground.
PIN2:+ input.
PIN3:- input.
InstereoInstallationswheretheamplifierandpreamplifierareclosetoeachotherand
requireinterconnectingcablesofsixfeetorless,usingqualityunbalancedconnectingcables
isusuallyequallysatisfactory.IftheunitsarefartherapartandrequirelongerInterconnecting
cables,usingbalancedcableswillgiveextraprotectionfromnoiseorInterference.
REAR
PANEL
7

MONOPHONICBRIDGEDORPARALLEL
ArearpanelMODEswitchallowstheamplifiertobeusedinnormalSTEREO,MONO
(BRIDGED)orMONO(PARALLEL).WhenswitchedtoeitherMONO(BRIDGED),orMONO
(PARALLEL)operation,theRIGHTBALANCEDandUNBALANCEDinputsaretheonlyones
usedforthemonoinputsignal.TheLEFTinputsareautomaticallydisconnected.
Connecttheappropriatecablefroma preamplifierorothermonosourcetothe
appropriateRIGHTUNBALANCEDorBALANCEDamplifierinput.
HOWTOCONNECTOUTPUTS
TheMclntoshoutputcircuit,superiorinitsperformance,demandsa superiormethodof
couplingtheamplifieroutputtotheloudspeakerload.TheMC150incorporatesMclntosh
designedandmanufacturedAutoformerstoinsurepeakperformanceandprotection,aswell
asoutstandingcompatibilitybetweenamplifierandspeakers.
TheMC150OutputAutoformershave3 differentoutputimpedancetapsforoptimum
matchingtotheparticularspeakerorcombinationofspeakersbeingused.Usethefollowing
tabletodeterminewhichtapshouldbeused.Itmaybedesirabletoconsultyourdealer,or
themanufacturerofyourspeakerforthebestimpedancetaptouse.
SPEAKERIMPEDANCEINOHMSAMPLIFIEROUTPUTCONNECTIONS
2to4 Commonand2 ohmoutput
4to8 Commonand4 ohmoutputs
8andupCommonand8 ohmoutputs
Usehighqualityspeakercables.Thetotalresistanceofthecablesmustbeaslowas
possible,solargerdiameter,(lowergaugenumber),cablesaremostdesirable.Thelonger
thespeakercableis,thelowerthegaugenumbermustbetokeepresistancelow.Consult
yourdealerforthebestcablesforyourparticularinstallation.
RECOMMENDATIONSFORSPEAKERCABLELENGTHSANDGAUGE(SIZE)
Thesespeakercablelengthsrepresenta resistanceequaltoapproximately5%ofthe
speakerimpedance.Thecablesizesaretheminimumthatshouldbeused.Ifthereisa
choice,thelargerdiametercables,(smallergaugenumber),shouldbeused.
4OHMSPEAKERS
FEET
15
25
40
60
100
METERS
4.6
7.6
12.2
18.3
30.5
8OHMSPEAKERS
FEET
30
50
80
120
200
METERS
9.1
15.2
24.4
36.6
61.0
CABLE
GAUGE
18
16
14
12
10
STEREOPHONICOPERATION
Set the rear panel MODE switch to STEREO
Connecta cablefromtheleftspeakercommonterminaltotheamplifierLEFTOUTPUT
COMterminal.Connecta cablefromtheleftspeakerhotterminaltotheamplifierLEFT
8
REAR
PANEL

OUTPUT(impedancetapdesired)terminal.Twoohms,4 ohmsand8 ohmsareprovided.
ConnecttherightspeakerinanidenticalmannertotheamplifierRIGHTOUTPUT
terminalsofthecorrectimpedanceforyourspeakers.
Iftheactualloadimpedanceofa speakerislowerthanthespecifiedimpedance,par-
ticularlyatdifferentpartsofthefrequencyrange,itwillcausenoproblems.Thehighcurrent
outputcapacityoftheMC150willproducetheextracurrentnecessarytoproperlydrivethe
speakerundertheseconditions.
Iftheimpedanceofthespeakerishigherthenthe8 ohmtap,nochangeinperformance
qualitywilloccur.Theavailablepoweroutputwillsimplybeslightlyless.
TheCOMMONandHOTterminalsofbothspeakersmustbeconnectedinanidentical
mannerto theproperamplifieroutputterminals.Thisis essentialforkeepingthespeakers
operatingINPHASE.Thismeansthatthespeakerdriversurfacesmovebackandforward
thesameineachspeaker.Almostallspeakershavetheirhotandcommonterminalscolor
coded,withredashot.
MONOPHONICBRIDGEDOPERATION
Set the rear panel MODE switch to MONO BRIDGED and use only a RIGHT/MONO
balancedor unbalanced Input.
TheMC150canbeusedasa singlechannelmonophonicpoweramplifierinbridged
configuration.ThetwoamplifierchanneloutputsaddtogetherinserieswhenusedinMONO
(BRIDGED).TheMODEswitchconnectstherightchannelinputstobothpoweramplifiers,with
thephaseoftheleftchannelinvertedtogetbridgedoperation.Thespeakerconnections,both
commonandhot,shouldbeconnectedonlytotheleftandrightamplifieroutputimpedancetaps
asshown.TheCOMmonamplifieroutputconnectionsarenotusedinMONO(BRIDGED)
configuration.Forexample,thetwo8ohmoutputswilladdtobecome16ohms,orthetwo4 ohm
outputswilladdtobecome8 ohms.
TomaintainthemonooutputoftheamplifierinphasewiththeinputsignalinMONO
(BRIDGED)operation,connecttheHotspeakerterminaltotheRIGHTchannelimpedancetap
andtheCommonspeakerterminaltotheLEFTchannelimpedancetap.
SPEAKERIMPEDANCEINOHMS
AMPLIFIEROUTPUTCONNECTIONS
4to8 LEFT2 andRIGHT2 (4ohmstotal)
8to16LEFT4 andRIGHT4 (8ohmstotal)
16andupLEFT8 andRIGHT8 (16ohmstotal)
MONOPHONICPARALLELOPERATION
Set the rear panel MODE switch to MONO (PARALLEL) and use only a RIGHT/
MONO balanced or unbalanced Input.
TheMC150alsocanbeusedasa singlechannelmonophonicpoweramplifierinparallel
configuration.Theamplifieroutputtapsarenowconnectedinparallelandtheimpedanceswill
beexactlyhalfwhatisstatedattheterminals.
Connecta cablefromthespeakercommonterminaltotheeithertheLEFTOUTPUTCOM
terminalortheRIGHTOUTPUTCOMterminal.(Theseterminalsarewiredtogetherinsidethe
amplifier).Connectthecablefromthehotspeakerterminaltotheimpedanceoutputdesiredon
eitherchannel.Alsowireacrosstotheotherchannelidenticalimpedancetap.Ineachcase,the
chosenoutputsofeachchannelmustbewiredtogether.
REAR
PANEL
9

SPEAKERIMPEDANCEAMPLIFIER
INOHMSOUTPUTS
1to2 LEFTCOM+ RIGHTCOMandLEFT2 + RIGHT2,(1ohm)
2to4 LEFTCOM+ RIGHTCOMandLEFT4 + RIGHT4,(2ohms)
4andUPLEFTCOM+ RIGHTCOMandLEFT8 + RIGHT8,(4ohms)
MAKESURETHEREARPANELMODESWITCHISSETTOMONO(PARALLEL)AND
USEONLYA RIGHTINPUT.ALWAYSPLACETHEMODESWITCHINTHECORRECT
POSITIONFORTHEMODEOFOPERATIONBEINGUSED.
TheMC150canbeusedtofeeda constantvoltageline,oftenusedinbackgroundmusic
applications.Fora 25voltline,usethe4 ohmoutputsontheamplifier.
BecausethecrosstalkbetweenchannelsontheMC150isalmostnonexistent,each
channelcanbeusedasa separatemonophonicamplifier.Anexamplewouldbeone
channelfeedingbackgroundmusictoa givenarea,andtheotherchannelusedforpaging
ina differentarea.
LEFTLEVEL
UsetheLEFTLEVELcontroltoadjusttheoutputintheleftchanneltothedesiredlisten-
inglevel.
RIGHTLEVEL(MONO)
UsetheRIGHTLEVELcontroltoadjusttheoutputintherightchanneltothedesired
listeninglevel,
Whentheamplifierisconnectedforeitherbridgedorparallelmonophonicoperation,the
RIGHTLEVELcontrolisusedtocontrolthecombinedmonophoniclevelofbothchannels.
The2.5V(detent)settingsarerecommendedforbestoperationwitha Mclntosh
ControlCenterorPreamplifier.
POWERCONTROL,IN/OUT
TheMC150ACpowercanbeturnedonandoffbya controlsignalfedtothePOWER
CONTROLIN connectorfromthePOWERCONTROLOUTconnectoron compatibleMclntosh
products.TheMC150POWERCONTROLOUTjackwillfeedthesamepowercontrolsignal
out,delayed0.2seconds,toturnonandoffanotheraccessorycomponentwitha compatible
PowerControlinput.
TheMC150POWERswitchmustbeintheOFF/REMOTEsettingforthepowercontrol
signalstoturntheMC150OnandOff.
The POWER CONTROL connectors are standard 1/8 inch mini phone plugs. Only the tip
(+) and sleeve (-) are used for connecting the plug to a single conductor shielded cable.
HOWTOCONNECTACPOWER
TheMC150isdesignedtooperateon120volts50/60Hz.PlugtheACpowercordeither
directlyintoa walloutletorintheamplifierACreceptacleonthebackofa preamplifier.Make
certainthattheACpoweroutletusedhasatleast7 amperescapacityavailable.
TheMC150candrawupto6.25amperesofcurrentfromtheACpowerlinewhenboth
channelsareproducingratedpoweroutput.Theamplifierusesonly0.5amperesofcurrent
whenidlingatnooutput.
FUSE
A6.25amperefuseprotectstheMC150circuits.
10
REAR
PANEL

11
CONNECTIONS

TheMC150isa stereopoweramplifierdesignedtooperatewithloudspeakershaving
anominalimpedanceof2,4 or8 ohms.
Itfeaturesa newcircuitdesignthatholdsharmonicdistortionfarbelowtheamplifier's
remarkablylownoisefloor.Onlybyusingspecialspectrumanalysismeasuringtechniques
isthedistortionmeasurableatall.
DESIGNPHILOSOPHY
Thesecrettothisperformancewillsoundverysimple,butitismoredifficulttocarryout
thanitmayseem.TheprincipleusedinthedesignoftheMC150wastoarrangeeverystage
ofvoltageorcurrentamplificationstobeaslinearaspossible.
Thislinearoperationisaccomplishedbyusingseveraldifferenttechniques.
1.Eachtransistorisselectedtohavenearlyconstantcurrentgain(Beta)overtheentire
rangeofcurrentsatwhichthetransistormustoperate.
2.Theloadimpedancepresentedtoeachamplificationstageismadetobeasuniforma
possibleforallsignallevels.
3.Theinputimpedanceofstagesinincreasedandlinearizedwherepossiblebyusing
emitterdegeneration.
4.Resistorsandcapacitorsinthesignalpathatcarefullyselectedtohaveexceedinglylow
voltagecoefficients(lowchangeofresistanceorreactancewithappliedvoltage).
Precisionmetalfilmresistorsandlowdielectricabsorptionfilmcapacitorsareusedin
allcriticalcircuitlocations.
5.Outputtransistorshavematcheduniformcurrentgain,highcurrentgain-bandwidth
product,lowoutputcapacitance,andlargeactive-regionsafeoperatingarea.These
characteristicsandtheautomatictrackingbiassystemeliminatescrossoverdistortion.The
distortiongraphsshowclearlythatdistortiondoesnotincreaseatlowpoweroutputlevels.
OVER58JOULESOFENERGYSTORAGE
Hugemainfiltercapacitorsareusedtoguaranteeanexcellentsignaltonoiserationand
theenergystoragenecessaryforthewidedynamicrangethat"DigitalAudio"demands.
ILLUMINATEDPEAKRESPONDINGOUTPUTWATTMETERS
TheMC150includesREALOUTPUTWATTMETERS.ThepoweroutputinWATTSofany
amplifierisdeterminedbymultiplyingtheoutputvoltage(E)bytheoutputcurrent(I),EI=W.
Outputmetersonotheramplifiersareonlyvoltmeters.Outputcurrentisnotconsidered.Cali-
brationisinwattsandisbasedonthefalsepremisethatallspeakershavea fixedimped-
anceregardlessoffrequency.Infact,theimpedanceofmanypoorspeakerdesignsvaries
byasmuchas4 to1.Fora specificoutputvoltage,thecurrentvariesinverselytothespeak-
erimpedance.Soifthespeakerimpedanceislower,theoutputcurrentandpowerare
higher.SinceMclntoshcannotcontrolothermanufacturersspeakers,wedecidedtoprovide
extraoutputcurrenttodrivethem.Therefore,themetercircuitintheMC150electronically
measuresbothvoltageandcurrent,multipliesthemanddisplaystheREALOUTPUTPOWER
INWATTS.
Anotherimportantfeatureoftheseoutputwattmetersistheirabilitytorespond95%full
scaletoa singlecycletoneburstat2kHz.Aftervoltageandcurrentaremeasuredand
multiplied,theproductisfedtoa specialcircuitthatacceleratesthemeterpointerinthe
upwarddirection.Whenitreachesitspeak,itpausesonlylongenoughforthehumaneye
toperceiveitsposition,thenreturnsto0.Responseisalmost10timesfasterthana pro-
fessionalVUmeter.
12
TECHNICAL
DESCRIPTION

AfrontpanelswitchisprovidedtochangethemeterstotheWATTSHOLDmodeof
operation,fastupwardmovementofthepointer,butgreatlyincreasedHOLDtimeatthepeak
ofitstravel.Thehighestpoweroutputofthesourcematerialisthusrecorded.
OUTPUTAUTOFORMERS
TheunequalledexpertiseofMclntoshinthedesignandmanufactureofoutputauto-
formersislegendaryintheHiFiindustry.IntheMC150,theyprovidepropermatchingfor
2,4 and8 ohmloads.Theyprotectyourspeakersfromdamageintheeventofanoutput
transistorfailure,providelowdistortionpowertransferatfrequencieswellbeyondhuman
hearinganddeliverpeakoutputcurrentsinexcessof53amperes.
PROTECTIONCIRCUITS
Somemanufacturesofpoweramplifiersadvertisedthattheirproductsdonotrequireor
useprotectioncircuitsandthatsuchcircuitscompromiseperformance.MclntoshLaboratory
agreesthatdiligentmeasuresarerequiredtoallowunrestrictedperformance,butwealso
insistthatprotectioncircuitsaredesirableandnecessarytopreventamplifierorloudspeaker
damageduetoabnormalcircumstanceandthattheyactuallyenhanceperformance.The
MC150incorporatessevenprotectioncircuitstoenhanceitsperformance,assureitsreliability
andtoprotectloudspeakers.
POWERGUARD
PowerGuard,a uniquefeatureofMclntoshamplifiers,assuresthateachchannelofthe
MC150willdeliverfullpowerfreeofclippingdistortion.Clippingiscausedwhenanamplifier
isaskedtoproducemorepoweroutputthanitsdesigniscapableofdeliveringwithlowdis-
tortion.Amplifiersthatareoverdrivenmaydeliverlargequantitiesofpowerwhentheyare
clipping,buttheymayhavemorethan40%harmonicdistortion.Inthismode,thesoundis
grosslydistortedandtheextraenergycontentoftheclippedsignalwilldamagemostloud-
speakers,TheMclntoshPowerGuardcircuitprotectsyourearsandyourspeakersfromthis
kindofdamage.
ThePowerGuardcircuitconsistsofa waveformcomparatorwhichmonitorsthewave
shapeoftheamplifierinputandoutputsignals.Normally,thereisnodisparitybetweenthese
signalsandthecomparatorproducesnooutput.Whentheamplifierisdrivenbeyondits
maximumpowercapacity,a differencewilldevelop.Ifthedisparityexceeds0.3%(equivalent
to0.3%totalharmonicdistortion),thecomparatoroutputcausestheamberPowerGuard
indicatortolight.Ifthereisa furtherincreaseinthedisparity,thecomparatoroutputcontrols
andelectronicattenuatorattheamplifierinputtoreducetheamplifiergain,thusholdingthe
amplifieroutputtoa lowdistortionvalue.Overdriveby14dBispossiblebeforetheoutput
distortionexceeds2%.
SENTRYMONITOR
Allpowertransistorshavelimitsforthemaximumamountofpowertheycanhandle.The
MC150outputtransistorsandpowersupplyhavebeendesignedtoallowveryhighcurrent
flowintoproperlymatchedloadimpedances.If,however,a shortcircuitorverylowvalueof
loadimpedanceisappliedtotheoutputoftheMC150,destructivecurrentlevelscouldbe
reachedifitwasnotcontrolledbytheSentryMonitor circuit.Thiscircuitsensesthedynamic
operatingtime,voltage,andcurrentoftheamplifieroutputsageandcontrolsthecurrentflow
confiningittonondestructivelimits.SentryMonitor doesnotlimitthepowerout-putavailable
fromtheamplifier.
13
TECHNICAL
DESCRIPTION

THERMALCONTROL
Allpowertransistorshavelimitsforthemaximumamountofheattheycantolerate.The
MC150usesa highlyefficientamplifyingcircuitwhichproducesrelativelylittleheatforthe
outputpowerproduced.Theamplifierhas4 oversizeheatsinkstodissipatetransistor
generatedheat,naturalconvectionairflowissufficientforcooloperation.Shouldthecooling
airbeblockedorshouldtheamplifieroperatingtemperaturebecometoohigh,thermalcut-
outswithintheamplifierwillturnoffthepowertotheamplifier.Whentheamplifierhascooled,
itwillautomaticallyturnonagain.
TURN-ONDELAY
TheMC150hasa turn-ondelaycircuitthatdelaysamplifieroperationforabout2
secondsafterpowerturn-on.Thispreventspopsorthumpsgeneratedinotherequipment
fromcausingannoyingnoisesordamagingyourloudspeakers.
DIRECTCURRENTFAILUREPROTECTION
Theautotransformerprotectsspeakersfromdamageintheeventofamplifierfailure.
Shoulda directcurrentcomponentappearintheoutput,itisshuntedbytheautotransformer
andDCcannotdamagethespeaker.
POWERLINEINRUSHPROTECTION
Turn-oninrushcurrentiscushionedbythermistorsinthepowertransformerprimary
circuit.A softstartisachievedthateliminatescomponentstressduringturn-on.
CIRCUITOPERATION
Theaudioinputpassesthroughthegaincontroltoa preamplifier.Theoutputamplifier
isdrivenbythepreamplifier.
Thepoweroutputamplifierusestwostagesofvoltageamplificationsfollowedbythree
stagesofcurrentamplifications.Allstagesarecomplementarybalanced,Evennumberhar-
monicsarecancelledbythebalancedcircuits.Thismeansthattheamplifyingstageshave
lesstotalharmonicdistortionandlessnegativefeedbackisrequiredtoachieveultralowdis-
tortion.
Thesignalisfedtooneinputofthebalanceddifferentialstage.Feedbackfromtheamp-
lifieroutputisappliedtotheotherinput.Thedifferentialamplifiersdrivea balancedcascode
connectedvoltageamplifierstage.Currentmirrorsarealsousedtoimprovebandwidthand
linearity.
ThecascodevoltageamplifieroutputfeedscomplementaryDarlingtonconnecteddriver
transistors.Thesesupplythesignalto6 complementaryconnectedoutputtransistorsper
channel.AncillarycomponentsforPowerGuard,SentryMonitor,PowerOutputMetersand
otherprotectioncircuitsinterconnectwiththeamplifiercircuits.Thepowersupplyusesa
massivepowertransformer,fullwavebridgerectifiers.Largefiltercapacitorshaving58joules
ofenergystorage.Fourlargeheatsinksprovidecoolingforthe12outputpowertransistors.
ThemechanicalandelectricaldesignoftheMC150istheresultofthemanyyearsof
engineeringandmanufacturingexperienceheldbythestaffatMclntoshThis"KnowHow",
themeticulousattentiontodesignandproductiondetails,makestheMC150oneofthefinest
amplifierseverproducedbyMclntoshLaboratory,Inc.
14
TECHNICAL
DESCRIPTION

POWEROUTPUT
STEREO
150wattsminimumsinewavecontin-
uousaveragepoweroutput,perchannel,
bothchannelsoperatinginto2 ohms,4
ohmsor8 ohmsloadimpedance.
OUTPUTLOADIMPEDANCE
2ohms,4 ohmsand8 ohms;separate
terminalsareprovidedforeachoutput.
RATEDPOWERBAND
20Hzto20,000Hz
TOTALHARMONICDISTORTION
0.005%maximumharmonicdistortionat
anypowerlevelfrom250 milliwattsto150
wattsperchannelfrom20Hzto20,000Hz,
bothchannelsoperating.
INTERMODULATIONDISTORTION
0.005%maximumharmonicifinstan-
taneouspeakpoweroutputis300 wattsor
lessperchannelwithbothchannelsoperat-
ingforanycombinationof frequencies,
20Hzto20,000Hz.
FREQUENCYRESPONSE
(ATONEWATTOUTPUT)
20Hzto20,000Hz+0,-0.25dB.
10Hzto100,000Hz+0,-3dB.
NOISEANDHUM(A-weighted)
110dBbelowratedoutput.
IHFDYNAMICHEADROOM
1.8dB
RATINGS
DAMPINGFACTOR
Greaterthan40.
INPUTIMPEDANCE
20,000ohms.
INPUTSENSITIVITY
1.4volt,levelcontrolprovidesforhigher
inputvoltages;2.5voltpositionatdetent.
POWERGUARD
ClippingispreventedandTHDdoes
notexceed2%withupto14dBoverdriveat
1kHz.
POWERREQUIREMENT
120volts,50/60Hz,0.5to6.5amperes
SEMICONDUCTORCOMPLEMENT
62silicondiodes.
2lightemittingdiodes.
72Bipolartransistors
7Integratedcircuits.
DIMENSIONS
Frontpanelmeasures17-1/2"(44.5cm)
wide,by5-3/8"(13.7cm)high.Depthbehind
mountingpanel includingclearancefor
connectors,19-3/4'(50.2cm).Knobclearance
requiredinfrontofmountingpanel,1-1/8"
(2.9cm).
WEIGHT
59lbs.(26.8Kg)net,75lbs.(34Kg)in
shippingcarton.
15
SPECIFICATIONS

RECOMMENDED
VENTILATION
CUTOUTIN
MOUNTING
SHELF
04040900
16
BE092204
CUSTOM
INSTALLATION
DIAGRAM