McIntosh MC7100 User manual

MC7100
POWER
AMPLIFIER

MC7100
POWER
AMPLIFIER

1.Readallinstructions- Readthesafetyandoperatinginstructionsbeforeoperatingtheinstrument.
2.RetainInstructions- Retainthesafetyandoperatinginstructionsforfuturereference.
3.Heedwarnings- Adheretowarningsandoperatinginstructions.
4.FollowInstructions- Followalloperatinganduseinstructions.
WARNING:TOREDUCERISKOFFIREORELECTRICALSHOCK,DONOTEXPOSETHISIN-
STRUMENTTORAINORMOISTURE.
5.PowerSources- Connectthepowersupplyonlytothetypedescribedintheoperatinginstructions
orasmarkedontheunit.
6.Power-CordProtection- Routepower-supplycordssothattheyarenotlikelytobewalkedonor
pinchedbyitemsplaceduponoragainstthem,payingparticularattentiontocordsatplugs,
conveniencereceptacles,andthepointwheretheyexitfromtheinstrument.
7.Ventilation- Locatetheinstrumentforproperventilation.Forexample,theinstrumentshouldnot
beplacedona bed,sofa,rug,orsimilarsurfacethatmayblockventilationopenings;or,placed
ina built-ininstallation,suchasa bookcaseorcabinet,thatmayimpedetheflowofairthrough
theventilationopenings.
8.Heat- Locatetheinstrumentawayfromheatsourcessuchasradiators,heatregisters,stoves,or
otherappliance(includingamplifiers)thatproduceheat.
9.WallorCabinetMounting- Mounttheinstrumentina wallorcabinetonlyasdescribedintheowner's
manual.
10.WaterandMoisture- Donotusetheinstrumentnearwater- forexample,neara bathtub,washbowl,
kitchensink,laundrytub,ina wetbasement,orneara swimmingpool,etc.
11.Cleaning-Cleantheinstrumentbydustingwitha drycloth.Cleanthepanelwitha clothmoistened
witha windowcleaner.
12.ObjectandLiquidEntry- Donotpermitobjectstofallandliquidstospillintotheinstrumentthrough
enclosureopenings.
13.NonusePeriods- UnplugthepowercordfromtheACpoweroutletwhenleftunusedfora longperiod
oftime.
14.DamageRequiringService- Servicemustbeperformedbyqualifiedservicepersonnelwhen:
A.Thepowersupplycordortheplughasbeendamaged:or
B.Objectshavefallen,orliquidhasbeenspilledintotheinstrument;or
C.Theinstrumenthasbeenexposedtorain;or
D.Theinstrumentdoesnotappeartooperatenormallyorexhibitsa markedchangeinperformance;
or
E.Theinstrumenthasbeendropped,ortheenclosuredamaged.
15.Servicing- Donotattempttoservicebeyondthatdescribedintheoperatinginstructions.Allother
serviceshouldbereferredtoqualifiedservicepersonnel.
16.GroundingorPolarization- Donotdefeattheinherentdesignfeaturesofthepolarizedplug.Non-
polarizedlinecordadaptorswilldefeatthesafetyprovidedbythepolarizedACplug.
17.CAUTION: TO PREVENTELECTRICALSHOCK DONOTUSE THIS(POLARIZED)PLUG
WITHANEXTENSIONCORD,RECEPTACLEOROTHEROUTLETUNLESSTHEBLADESCAN
BEFULLYINSERTEDTOPREVENTBLADEEXPOSURE.
ATTENTION:POURPREVENIR LES CHOCSELECTRIQUES PAS UTILISERCETTE
FICHEPOLARISEEAVECUNPROLONGATEUR,UNEPRISEDECOURANTOUUNEAUTRE
SORTIEDECOURANT,SAUFSILESLAMESPEUVENTETREINSEREESA FONDSANSEN
LAISSERAUCUNEPARTIEA DECOUVERT.
IMPORTANT
SAFETY
INSTRUCTIONS
THESE
INSTRUCTIONS
ARETOPROTECT
YOUANDTHE
McINTOSH
INSTRUMENT.
BESURETO
FAMILIARIZE
YOURSELF
WITHTHEM
Copyright1992© by
MclntoshLaboratoryInc.
2
WARNING:THISUNITISCAPABLEOFPRODUCINGHIGHSOUND
PRESSURELEVELS.CONTINUEDEXPOSURETOHIGHSOUND
PRESSURELEVELSCANCAUSEPERMANENTHEARINGIMPAIRMENT
ORLOSS.USERCAUTIONISADVISEDANDEARPROTECTIONIS
RECOMMENDEDWHENPLAYINGATHIGHVOLUMES.
Theexclamationpointwithinanequilateraltriangleisintendedtoalerttheusertothe
presenceofimportantoperatingandmaintenance(servicing)instructionsintheliterature
accompanyingtheappliance.
CAUTION: TO PREVENTTHERISK OF ELECTRICSHOCK, DO NOT
REMOVECOVER(ORBACK).NOUSER-SERVICABLEPARTSINSIDE.
REFERSERVICINGTOQUALIFIEDPERSONNEL.
Thelightningflashwitharrowhead,withinanequilateraltriangle,isintendedtoalertthe
usertothepresenceofuninsulated"dangerousvoltage"withintheproduct'senclosure
thatmaybeofsufficientmagnitudetoconstitutea riskofelectricshocktopersons.

Theserialnumber,purchasedate,andMclntoshLaboratoryServiceContractnumberare
importanttoyouforpossibleinsuranceclaimorfutureservice.Recordthisinformationhere.
SerialNumberPurchaseDate
ServiceContractNumber
Uponapplication,MclntoshLaboratoryprovidesa ServiceContracttotheoriginalpurchaser.
YourMclntoshAuthorizedServiceAgencycanexpediterepairswhenyouprovidetheSer-
viceContractwiththeinstrumentforrepair.
SERVICECONTRACT4
INTRODUCTION5
INSTALLATION5,6,7
HOWTOCONNECTINPUTS8
HOWTOCONNECTOUTPUTS8,9
CONNECTINGDIAGRAMS10
SPECIFICATIONS11
PERFORMANCECHARTS12
TECHNICALDESCRIPTION13,14
BLOCKDIAGRAM15
TABLEOF
CONTENTS
3

TAKEADVANTAGEOF3 YEARSOFCONTRACTSERVICE.. .
FILLINTHEAPPLICATIONNOW.
YourMC7100PowerAmplifierwillgiveyoumanyyearsofsatisfactoryperformance.Ifyou
haveanyquestions,pleasecontact,
MclntoshLaboratoryInc.
2ChambersStreet
Binghamton,NewYork13903-2699
Phone:[phone]
McINTOSH
THREEYEAR
SERVICE
CONTRACT
AnapplicationforA THREEYEARSERVICECONTRACTisincludedwiththismanual.
Thetermsofthecontractare:
1.Iftheinstrumentcoveredbythiscontractbecomesdefective,Mclntoshwillprovideallparts,
materials,andlaborneededtoreturnthemeasuredperformanceoftheinstrumenttothe
originalperformancelimitsfreeofanycharge.Theservicecontractdoesnotcoverany
shippingcoststoandfromtheauthorizedserviceagencyorthefactory.
2.AnyMclntoshauthorizedserviceagencywillrepairallMclntoshinstrumentsatnormal
servicerates.Toreceivethefreeserviceunderthetermsoftheservicecontract,theser-
vicecontractcertificatemustaccompanytheinstrumentwhentakentotheserviceagency.
3.Alwayshaveservicedonebya Mclntoshauthorizedserviceagency.Iftheinstrumentis
modifiedordamagedasa resultofunauthorizedrepairtheservicecontractwillbecancell-
ed.Damagebyimproperuseormishandlingisnotcoveredbytheservicecontract.
4.Theservicecontractisissuedtoyouastheoriginalpurchaser.Toprotectyoufrom
misrepresentationthiscontractcannotbetransferredtoa secondowner.
5.UnitsinoperationoutsidetheUnitedStatesandCanadaarenotcoveredbytheMclntosh
FactoryServiceContract,irrespectiveoftheplaceofpurchase.Norareunitsacquired
outsidetheUSAandCanada,thepurchasersofwhichshouldconsultwiththeirdealer
toascertainwhat,ifany,servicecontractorwarrantymaybeavailablelocally.
4

TheelectricalandmechanicaldesignoftheMC7100PowerAmplifieristheresultofthe
manyyearsofengineeringandmanufacturingexperienceofthedesignstaffatMclntosh.
This"KnowHow",alongwiththemeticulousattentiontodesignandproductiondetails,makes
theMC7100oneofthefinestamplifierseverproducedbyMclntoshLaboratory.
Theuseof4 complimentaryconnectedoutputtransistorsperchannel,allowsnotonlyfull
poweroutputintonormalloads,butextrahighcurrentoutputtodriveunevenspeakerloads.
Somespeakershavedesigncharacteristicsthatcausethemtodipbelowtheirratedim-
pedancesatcertainfrequencies.ItispossiblefortheMC7100todeliverasmuch as18
amperespeakcurrentintotheselowerimpedanceloads.
TheMC7100providesthisextracurrentoutputwithcompletereliabilityduetotheuseof
MclntoshSentryMonitorprotectioncircuits.Somepoweramplifiermanufacturershaveclaimed
thattheirproductsdonotuseprotectioncircuitssincetheycompromiseperformance.The
realgeniusofMclntoshengineeringdesignhasrecognizedthesepotentialproblemsandcom-
pletelyeliminatedthem.Properlydesignedprotectioncircuitsassureyouanamplifierthat
willoperateunderalltypesofuserconditionswithmaximumreliabilityandfreedomfrom
possiblespeakeroramplifierdamage.Thebenefitsofthesedesignsmeanyouownanamplifier
thatwillcontinuetooperatesafelyformanyyears.
TheMC7100outputissodistortionfree,itisdifficulttomeasurewithconventional in-
struments.Theperformancelimitis0.005%maximumdistortion,yetitistypicalforanamplifier
tomeasureaslowas0.002%atmidfrequenciesinto8 ohms.
AsinallMclntoshpoweramplifiers,thefamouspatentedMclntoshPOWERGUARDcir-
cuitisincluded.Youneverhavetobeconcernedwithpossibleamplifieroverdrive.Youwill
notexperienceamplifierclippingwithitsharshspeakerdamagingdistortionwhenplaying
widedynamicrangeprogramsourcessuchascompactdiscs.
Manyotherdesirablefeaturesareincludedsuchasgoldplatedoutputterminals,DCout-
putprotection,thermalprotectionanda turnondelaycircuit.A Toroidalwoundpower
transformerpermitsa lowprofiledesignwithquietcooloperation.
RefertothesectioninthismanualtitledTECHNICALDESCRIPTIONfordetailedinforma-
tiononalltheoutstandingcircuitandperformancefeaturesoftheMC7100.
INTRODUCTION
LOCATION
TheMC7100maybeinstalledona shelfortable,ina Mclntoshcabinet,orcustominstall-
edinfurnitureofyourchoice.Alwaysprovideadequateventilationfortheamplifier.Thetrou-
blefreelifeofanyelectronicinstrumentisgreatlyextendedbyprovidingsufficientventila-
tion.Thispreventsbuild-upofinternaltemperaturesthatcancausedeteriorationofcircuit
components.TheMclntoshcabinetdesignallowsforproperventilation.
Allowenoughclearancesocoolaircanenteratthebottomofthecabinetandbevented
fromthetop.Provideatleast1 1/2inches(3.8cm)abovetheamplifierheatsinkareasoairflow
isnotobstructed.Therecommendedminimumspaceforinstallationis181/2inches(47cm)
wide,141/2inches(36.8cm)deep,(including connectors)and4 1/2inches(11.5cm)high.
Allow1 inch(2.54cm)infrontofthemountingsurfaceforpanelclearance.
McINTOSHPANLOCMOUNTINGSYSTEM
ThePANLOCsystemofinstallingequipmentisa productofMclntoshresearch.Twosteel
PANLOCmountingshelvesareattachedtothefrontpanelateachsideofthepanel cutout,
usingthescrewsandbracketsprovided.Theamplifierhasrunnersonthebottomofitschassis,
INSTALLATION
5

INSTALLATION
allowingittoslideintotheshelves.Whentheunithasbeenpositionedcompletelyintothe
cabinetanditsfrontpanelisagainstthecabinetpanel,itcanbelockedintoposition.Turn
eachPANLOCbuttonapproximatelyone-quarterturnclockwisetolock.TurnthePANLOCbutton
one-quarterturncounterclockwisetounlocktheunitsoitcanberemovedfromthecabinet.
UNPACKING
OpenthecartonandremovethePANLOCshelves,thehardwarepackageandthemount-
ingtemplate.Lifttheamplifierupofftheshippingpalletandremovetheplasticbag.The
amplifierisnowreadyforshelfortabletopinstallation.
Iftheamplifieristobeinstalledina Mclntoshcabinetorcustominstallation,placeitcarefully
upside-downona flatsurfaceandunscrewthefourplasticfeetfromthebottomoftheamplifier
chassis.
INSTALLINGINA McINTOSHCABINET
GuidetheamplifierACpowercordthroughthefrontpanelopeningtothebackofthecabinet.
Slidetheamplifierintotheopening,makingsuretherailsonthebottomofeachsideofthe
amplifierchassisengagethetracksonthePANLOCshelves.Slidetheamplifiercompletely
intothecabinetuntilthebacksideofitsfrontpanelispressinggentlyagainstthefrontof
thecabinetpanel.TurnthePANLOCbuttonsapproximatelyone-quarterturnclockwisetolock
theamplifierintothecabinet.Turnthebuttonsone-quarterturncounterclockwisetounlock
andremovetheamplifier.
CUSTOMINSTALLATION
1.MARKTHECABINETFRONTPANEL
Tapetheplasticmountingtemplatetothecabinetpanelinthepositionwheretheamplifier
istobemounted.Thebrokenlinesthatrepresenttheoutlineoftherectangularcutoutalso
representtheoutsidedimensionsoftheamplifierchassis.Makesuretheselinesclearany
shelves,partitionsoranyotherequipmentmountedinthesamecabinet.Withthetemplate
inplace,firstmarkthesixA andB holes,andthefoursmallholesthatlocatethecorners
ofthecutout.Thenjointhefourcornermarkingswitha rulerorstraightedge.
2.DRILLTHEHOLES
Usea drillwitha 3/16inch(5mm)bit.DrillperpendiculartothefrontpanelthesixA and
Bholes.Then,usinga drillbitslightlylargerthanthetipofyoursawblade,drilloneholeat
eachoftwodiagonallyoppositecorners.Theholesshouldbarelytouchtheinsideedgeofthe
penciledoutline.Beforetakingthenextstep,besurethesixA andB holeshavebeendrilled.
6

3.SAWTHEPANELCUTOUT
Firstmakethetwolonghorizontalcuts.Thenmakethetwoshortverticalcuts.Afterthe
cutoutisfinished,usea filetosquarethecornersandsmoothanyroughedges.
4.INSTALLTHEPANLOCMOUNTINGSTRIPS
Thehardwarepackageincludestwo
mountingstripsandtwoblackflathead
6/32x 1 1/4inch(31.8mm)screwsandtwo
6/32x 1 1/4inch(31.8mm)fillisterhead
screws.Placea mountingstripbehind
eachedgeofthecutoutandsecureitto
thebacksideofthepanelinsertinga black
flathead6/32screwthroughthecenter
holesmarkedB onthetemplate.Make
surethescrewsaredrawnflushorslightlyintothewoodbeforeattachingthePANLOCshelves.
5.ATTACHTHEPANLOCSHELVESPositionthePANLOCshelvesinsidethe
cutoutwiththeshortflangeagainstthe
frontfaceofthecabinetpanel.Fastenthe
shelvesbyinsertingtwofillisterhead6/32
screwsthroughtheholesineachofthe
PANLOCshelfflanges,throughthefront
panelandintothethreadedreceptacleon
themountingstrips.
6.INSTALLTHEAMPLIFIER
GuidetheamplifierACpowercord throughthepanelopeningtothebackofthecabinet.
Slidetheamplifierintotheopening,makingsuretherailsonthebottomofeachsideofthe
amplifierchassisengagethetracksonthePANLOCshelves.Slidetheamplifiercompletely
intothecabinetuntilthebacksideofitsfrontpanelispressinggentlyagainstthefrontof
thecabinetpanel.TurnthePANLOCbuttonsapproximatelyone-quarterturnclockwisetolock
theamplifierinthecabinet.TurnthePANLOCbuttonsone-quarterturncounterclockwiseto
unlockandremovetheamplifier.
7
INSTALLATION

INPUTCABLES
Useshieldedcablestoconnectthesignalsfromthepreamplifierorothersignalsource
tothepoweramplifier.Tominimizethepossibilityofhumpickuporinterference,locatethe
cablesawayfromACpowercordsorloudspeakercables.
Usegoodqualitycables.YourMclntoshdealercanadviseyouonthetypesandlengths
ofcablesthatwillworkbestinyourinstallation.
STEREOOPERATION
UseshieldedsingleconductorcablewithRCAtypeconnectors.Connecta cablefromthe
LEFTchannelofa preamplifieroutputtotheL (left)INPUTjackontheMC7100.Connect
theRIGHTchannelpreamplifieroutputtotheR (right)INPUTjackontheMC7100.
MONOPHONIC(BRIDGED)OPERATION
ArearpanelMODEswitchallowstheMC7100tobeusedasa normalstereoamplifier,
orasa bridgedmonoamplifier.
Connecta shieldedcablefroma monosignalsourcetotheR (right)/MONOinputjack
ontheMC7100.SetthemodeswitchtoMONO.OnlytherightchannelLEVELcontrolfunc-
tionsinMONOoperation.TheoutputsmustbeconnectedasindicatedinHOWTOCONNECT
OUTPUTSforpropermonooperation.
INPUTLEVELCONTROLS
Thesecontrolsadjusttheinputvolumelevelsofeachchannel.WhentheLEVELcontrols
areinthe12o'clockorDETENTposition,theamplifierinputsensitivityfortherated100watts
outputis2.5volts.
THE2.5VOLTSENSITIVITYSETTINGISRECOMMENDEDFORBESTOPERATIONWITHA
McINTOSHPREAMPLIFIER.
TurningtheLEVELcontrolsfullyon,(clockwise),willgivea higheramplifiersensitivityof
1.4voltswhichmayberequiredforotherapplications.
HOW TO
CONNECT
OUTPUTS
SPEAKERCABLES
Usehighqualityspeakercablessincethisisanimportantlinkinyourstereosystem.Selec-
tionofthepropersizeandtypeofspeakercableisnecessaryforyoutoreceivethebest
possibleperformancefromyouramplifierandspeakercombination.ConsultyourMclntosh
dealerforrecommendationsonthecablesthatwillbestfittheneedsofyourstereoinstallation.
STEREOOPERATION
(SETTHEMODESWITCHSETTOSTEREOPOSITION)
TheoutputsoftheMC7100aredirectcoupled,andmatchspeakerloadsfromfour
to eightohmsandhigher.
Connecta cablefromtheLEFTspeakerCOMMONterminaltotheamplifierL (Left)- (minus)
OUTPUTterminal.Connecta cablefromtheLEFTspeakerHOTterminaltotheamplifierL
(Left)+ (Plus)OUTPUTterminal.Connecttherightspeakertotherightchanneloutputter-
minalsina similarmanner.
TheCOMMONandHOTterminals,(-and+),ofbothspeakersmustbeconnectedinan
identicalmannertotheproperamplifieroutputterminalssotheywilloperateINPHASE.This
meansthatthespeakerdriversurfacesmovebackandforththesameineachspeaker
HOW TO
CONNECT
INPUTS
8

system.Almostallloudspeakersystemshavetheirhotandcommonterminalscolorcoded,
withredusuallyashotorplus.TheoutputsignalsofallMclntoshpoweramplifiersarealways
INPHASEwiththeinputsignals.
ThecrosstalkbetweenchannelsontheMC7100isalmostnoneexistent,soeachchannel
canbeusedasa separatemonophonicamplifier.Anexamplewouldbeonechannelfeeding
backgroundmusictoa givenarea,andtheotherchannelfeedinga differentprogramsignal
toanotherarea.
MONOPHONIC(BRIDGED)OPERATION
(SETTHEMODESWITCHTOMONOPOSITION)
Connecta cablefromthemonophonicspeakerCOMMONterminaltotheMONO- (Minus)
amplifieroutputterminal.Connecta cablefromthespeakerHOTterminaltotheamplifier
MONO+ (Plus)terminal.
TheMC7100amplifiermonophonicoutputsignalwillbeinphasewiththeinputsignalwhen
thespeakerisconnectedasindicated.
Itisrecommendedthatspeakerloadsnolowerthan8 ohmsbeusedwiththe
amplifierinthebridgedMonophonicconfiguration.
HOWTOCONNECTACPOWER
TheMC7100isdesignedtooperateon120volts50/60Hzcurrent.Plugthepowercord
intoa switchedACreceptacleonthebackofa preamplifierorotheraccessorycomponent.
Theplugbladesarepolarized;sobecertaintheplugisfullyinsertedintheoutlettoprevent
bladeexposure.(TheMC7100hasnoACpowerswitch,soitmustbeswitchedonandoff
bya preamplifierorotheraccessorycomponent.)MakecertainthattheACoutletusedcan
supplyatleast6 amperes ofcurrent.Theamplifiercandraw upto5 amperes fromtheAC
powerlinewhenbothchannelsareproducingratedpoweroutput.
TheauxiliaryACoutletontheamplifierrearpanelwillprovideupto600watts(5amperes)
current,andisnotfusedorswitched.
CAUTION: TO PREVENT ELECTRIC SHOCK, DO NOT CONNECT THE POLARIZED AC
PLUG ON THIS UNIT TO AN EXTENSION CORD OR OTHER AC OUTLET THAT IS NOT
DESIGNED TO ACCEPT POLARIZED PLUGS. THE PLUG MUST BE FULL Y INSERTED
TO PREVENT BLADE EXPOSURE AND MAINTAIN LINE POLARITY.
FUSE
A5 ampere fuseprotectstheMC7100circuits.Thisfusedoesnotprotecttheauxiliary
ACoutlet.
FRONTPANEL
Thefrontpanelisthe"ClassicMclntosh"blackglasswithbacklightednomenclature.
TheREDACpowerindicatoraswellasthetealcoloredpanel nomenclaturewillilluminate
whenACpowerison.TheamberPOWERGUARDindicatorswillflashwheneverthePOWER
GUARDcircuitisactivated.
HOW TO
CONNECT
OUTPUTS
9

STEREO
CONNECTION
BRIDGED
MONOPHONIC
CONNECTION
LEFT
SPEAKER
4OR8
OHMS
RIGHT
SPEAKER
4OR8
OHMS
MUSTBEIN
STEREOPOSITION
FORSTEREOPROGRAMS
PREAMPLIFIER
8OHM
SPEAKER
MUSTBEIN
MONOPOSITION
FORMONOPROGRAMS
MONO
INPUT
SIGNAL
10
STEREO
MONO
STEREO MONO

PERFORMANCELIMITS
Performancelimitsarethemaximum
deviationfromperfectionpermittedfora
Mclntoshinstrument.Wepromiseyouthat
whenyoupurchasea newMC7100froma
MclntoshFranchisedDealer,itwillbe
capableofperformanceatorbetterthan
theselimits.
STEREOPOWEROUTPUT
150wattsinto4 ohmloadsor100watts
into8 ohmloadsminimumsinewavecon-
tinuousaveragepoweroutputperchannel,
bothchannelsoperating.
TheoutputRMSvoltageis:
28.3Vacross8 ohms
24.5Vacross4 ohms
MONOPHONIC(BRIDGED)
300wattsintoan8 ohmloadminimum
sinewavecontinuousaveragepoweroutput.
TheoutputRMSvoltageis:49voltsacross
8ohms.
OUTPUTLOADIMPEDANCE
STEREO
8or4 ohms
MONOPHONIC
8ohms
RATEDPOWERBAND
20Hzto20,000Hz
TOTALHARMONICDISTORTION
0.005%maximumharmonicdistortionat
anypowerlevelfrom250milliwattstorated
poweroutput.
IHFDYNAMICHEADROOM
8ohms,1.7dB
4ohms,2.1dB
FREQUENCYRESPONSE
+0,-0.25dBfrom20Hzto20.000Hz
+0,-3.0dBfrom10Hzto100,000Hz
INPUTSENSITIVITY
1.4volts(2.5voltsatgaincontrolcenter
detent)
A-WEIGHTEDSIGNAL-TO-NOISERATIO
95dB(115dBbelowratedoutput)
INTERMODULATIONDISTORTION.SMPTE
0.005%maximumifinstantaneouspeak
poweroutputdoesnotexceedtwicetheout-
putpowerrating.
RATINGS
WIDEBANDDAMPINGFACTOR
8ohms,200
4ohms,100
INPUTIMPEDANCE
20,000ohms
POWERGUARD
ClippingispreventedandTHDdoesnot
exceed2%withupto14dBoverdriveat
1000Hz.
POWERREQUIREMENTS
120volts,50/60HZ,3.0ampsUL/CSA
MECHANICAL
SIZE
Frontpanel:171/2inches(44.5cm)wide,
by3 5/8inches(9.2cm)high.
Chassis:143/4inches(37.5cm)wide,by
23/8inches(6cm)high,by141/2inches
(36.9cm)deep,(frombackoffrontpanel),in-
cludingconnectors.Panelclearancere-
quiredinfrontofthemountingsurfaceis1
inch(2.54cm).
FINISH
Glasswithspecialgold/tealnomenclature
illumination.Chassisandchassiscoverare
black.
WEIGHT
24pounds(11Kg)net;35pounds(15.9Kg)
inshippingcarton.
SPECIFICATIONS
11

PERFORMANCE
CHARTS
12

DESIGNPHILOSOPHY
TheMC7100stereopoweramplifierisdesignedtooperateloudspeakerswitha nominal
impedanceof4 to8 ohms.Itfeaturesa newcircuitdesignthatkeepsdistortionlevelsso
lowittakesspecialtestgearforaccuratemeasurements.
Thedesignphilosophythatresultedintheoutstandingperformanceofthisamplifierin-
volvedseveraldifferenttechniques.Everystageofvoltageorcurrentamplificationwasdesign-
edtobeaslinearaspossiblepriortotheuseofnegativefeedback,
1.Eachtransistorisselectedtohavenearlyconstantcurrentgain(Beta)overitsentire
operatingrange.
2.Theloadimpedancepresentedtoeachamplificationstageismadeasuniformaspossi-
bleforallsignallevels.
3.Theinputimpedanceofeachamplifierstageisincreasedandmademorelinearbyus-
ingemitterdegenerationwheneverpossible.
4.Resistorsandcapacitorsinthesignalpatharecarefullyselectedtohaveexceedingly
lowvoltagecoefficients(changeofresistanceorreactionwithappliedvoltage).Precision
metalfilmresistorsandlowdielectricabsorptionfilmcapacitorsareusedinallcriticalcir-
cuitlocations.
5.Outputtransistorshavematcheduniformcurrentgain,highcurrentgain-bandwidthpro-
duct,lowoutputcapacitanceandlargeactive-regionsafeoperatingarea.Thesecharacteristics
togetherwiththeautomatictrackingbiassystemeliminatecrossoverdistortion.
PROTECTIONCIRCUITS
Somemanufacturersofpoweramplifiersclaimthattheirproductsdonotneedorusepro-
tectioncircuitsandthatsuchcircuitscompromiseperformance.Mclntoshfeelsthatprotec-
tioncircuitsaredesirableandnecessarytopreventamplifierorloudspeakerdamagedue
toabnormalcircumstances.ThegeniusofMclntoshengineeringhasresultedinprotection
circuitswhichhavenoeffectorcompromiseonthenormalperformanceofa poweramplifier.
TheSENTRYMONITORcircuitisa goodexample.TheMC7100incorporatessevenspecific
protectioncircuitstoenhanceitsperformance,increaseitsreliabilityandprotectloudspeakers.
SENTRYMONITORCIRCUIT
Allpowertransistorshavelimitsforthemaximumamountofpowertheycanhandle.The
MC7100outputtransistorsandpowersupplyhavebeendesignedtoallowveryhighcurrent
flowintoproperlymatchedloadimpedances.However,ifa shortcircuitorverylowloadim-
pedanceisconnectedtotheMC7100outputs,destructivecurrentlevelscouldbereached
ifitwasnotcontrolledbytheSENTRYMONITORcircuit.Thiscircuitsensesthedynamic
operatingtime,voltageandcurrentoftheoutputstage,andcontrolsittosafeoperatinglimits.
TheSENTRYMONITORcircuitdoesnotlimitthepoweroutputavailablefromtheamplifier.
THERMALCONTROL
Allpowertransistorshavelimitstothemaximumamountofheattheycansafelytolerate.
TheMC7100usesa highlyefficientamplifyingcircuitwhichproducesrelativelylittleheat
fortheoutputpowerproduced.Theamplifieruseslargeareaheatsinkstoefficientlydissipate
whatheatitdoesgenerate.Naturalconvectionairflowissufficientforsafecool operation.
Ifthecoolingairisblocked,ortheamplifieroperatingtemperatureisforcedtoohigh,ther-
malcutoutswitcheswillturnoffthespeakers.BothPOWERGUARDindicatorswilllightcon-
tinuouslytoshowthatthermalprotectionisoperating.Whentheproblemiscorrectedand
13
TECHNICAL
DESCRIPTION

TECHNICAL
DESCRIPTION
theamplifiercoolsdowntoitsnormaloperatingtemperature,thespeakerswillbeturned
backon.
DIRECTCURRENTFAILUREPROTECTION
Aprotectioncircuitisprovidedthatturnsoffthespeakersifforanyreasona DCvoltage
shouldappearattheoutputterminals.Thispreventspossiblespeakerdamage.
POWERGUARD
AuniqueandpatentedfeatureofMclntoshpoweramplifiersinsuresthateachchannel
oftheMC7100willdeliverfullpower,freeofclippingdistortion.Clippingoccurswhenan
amplifierisoverdrivenpastitsoutputdesigncapabilities.Anoverdrivenamplifiercanpro-
ducebothaudibleandultrasonicdistortionlevelsapproaching40%.Theaudibledistortion
iscertainlyunpleasant,buttheultrasonicdistortionisalsoundesirable,sinceitcandamage
tweeterloudspeakers.
ThePOWERGUARDcircuitactsasa waveformcomparator,monitoringboththeinput
andoutputwaveforms.Undernormaloperatingconditions therearenodifferencesbetween
thesewaveforms.Whenanamplifierisoverdrivenbeyonditsmaximumdistortionfreeout-
put,thentherewillbea differencebetweenthetwowaveforms.Ifthedifferenceexceeds
0.3%(equivalentto0.3%harmonicdistortion),theamberPOWERGUARDindicatorwilllight.
Ifthedifferencecontinuestoincrease,thePOWERGUARDcircuitcontrolsanelectronic
attenuatorattheinputtoreducethegainoftheamplifierjustenoughtopreventanyfurther
increaseindistortion.Distortionwillnotexceed2%withasmuch as14dBoverdrive.
AMclntoshpoweramplifierwithPOWERGUARDwillalwaysdeliveritsmaximumdistor-
tionfreeoutput.ThispowerisalwayswellabovetheratedpowerduetotheMclntosh
philosophyofconservativedesign.Youwillneverexperiencetheharshanddamagingdistor-
tionduetoclippingwhenusinga MclntoshPOWERGUARDamplifier.
14

BLOCKDIAGRAM
15

039942