McIntosh MC 2500 User manual

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THEMclNTOSHMC2500STEREOPOWERAMPLIFIER

VARIOUSREGULATORYAGENCIESREQUIRETHATWEBRINGTHEFOLLOWING
INFORMATIONTOYOURATTENTION.PLEASEREADITCAREFULLY.
TheMclntoshMC2500isanex-
tremelyhighpoweramplifier.
Becauseofthehighpoweravailable
itisnecessarytoemphasizesome
prudentandsafeoperatingcondi-
tions.
1.Loudspeakerscanbedamagedor
destroyedbythehighpower
availablefromtheMC2500.Never
connectordisconnectinputsor
outputswhiletheamplifieristurn-
edon.
2.Neveroperatetheamplifierwith
thepowercordpluggedintoan
auxiliaryACpoweroutleton
sourceequipment.Theamplifier
draws15amperesandcandamage
thesourceequipment.
3.Donotoperatetheinstrumentplug-
gedintoanordinaryextension
cord.A heavydutyextensioncord
(14ga.orheavier)isrequired.
4. Be cautiouswhenliftingtheinstru-
ment.Itweighs129pounds.Make
certainthatwhatitisplacedon
cansupporttheweight.
5.Theamplifiercoolingfanscanbe
thermostaticallycontrolledwhen
thefanswitchontherearpanelis
placedinthethermallyswitched
positions.Whensooperated,the
fanswillnotrunwhentheamplifier
iscool,aswhentheamplifieris
firstturnedon.Asheatdevelops,
oneorbothfanswillautomatically
turnonasconditionsrequire.This
operatingbehaviorisnormal.
WARNING:TOPREVENTFIREORSHOCK
HAZARD,DONOTEXPOSETHISUNITTORAIN
ORMOISTURE.
TheMclntoshyouhavepurchasedisa Model
MC2500.Ithasa serialnumberlocatedontherearpanel
ofthechassis.Recordthatserialnumberhere:
Themodel,serialnumberandpurchasedateareimpor-
tanttoyouforanyfutureservice.Recordthepurchase
datehere:
Uponapplication,MclntoshLaboratoryprovidesa
Three-YearServiceContract.YourMclntoshauthorized
ServiceAgencycanexpediterepairswhenyouprovide
theServiceContractwiththeinstrumentforrepair.To
assist,recordyourServiceContractnumberhere:
SerialNumber
Purchasedate
ServiceContractNumber

YourMC2500StereoPowerAmplifier
cangiveyoumanyyearsof
satisfactoryperformance.Ifyou
haveanyquestions,pleasecontact:
CUSTOMERSERVICE
MclntoshLaboratoryInc.
2ChambersStreet
Binghamton,NewYork13903-9990
Phone:[phone]
Contents
SERVICECONTRACTINFORMATION1
INSTALLATION2
HOWTOCONNECT3
FRONTPANELINFORMATION8
REARPANELINFORMATION10
PERFORMANCELIMITS12
PERFORMANCECHARTS13,14
TECHNICALDESCRIPTION15
BLOCKDIAGRAM17
MclNTOSHTHREEYEARSERVICECONTRACT
AnapplicationforA THREEYEARSERVICECONTRACTisincludedwiththismanual.
Thetermsofthecontractare:
1 Mclntoshwillprovideallparts,materials
andlaborneededtoreturnthemeasured
performanceoftheinstrumenttothe
originalperformancelimits.TheSER-
VICECONTRACTdoesnotcoverany
shippingcoststoandfromtheauthoriz-
edserviceagencyorthefactory.
2.AnyMclntoshauthorizedserviceagency
willrepairMclntoshinstrumentsatnor-
malservicerates.Toreceiveservice
underthetermsoftheSERVICECON-
TRACT,theSERVICECONTRACTCER-
TIFICATEmustbepresentedwhenthe
instrumentistakentotheserviceagency.
3.Alwayshaveservicedonebya
Mclntoshauthorizedserviceagency.If
theinstrumentismodifiedordamaged
asa resultofunauthorizedrepair,the
SERVICECONTRACTwillbecancelled.
Damagebyimproperuseormishandl-
ingisnotcoveredbytheSERVICE
CONTRACT.
4.TheSERVICECONTRACTisissuedto
youastheoriginalpurchaser.Topro-
tectyoufrommisrepresentation,this
contractcannotbetransferredtoa se-
condowner.
5.ToreceivetheSERVICECONTRACT,
yourpurchasemustbemadefroma
Mclntoshfranchiseddealer.
6.Yourcompletelyfilledinapplicationfor
theSERVICECONTRACTmustbepost-
markedwithin30daysofthedateof
purchaseoftheinstrument.
7.ToreceivetheSERVICECONTRACT,all
informationontheapplicationmustbe
filledin.TheSERVICECONTRACTwill
beissuedwhenthecompletelyfilledin
applicationisreceivedbyMclntosh
LaboratoryIncorporatedinBinghamton,
NewYork.
8.UnitsinoperationoutsidetheUnited
StatesandCanadaarenotcoveredby
theMclntoshFactoryServiceContract,
irrespectiveoftheplaceofpurchase.
Norareunitsacquiredoutsidethe
U.S.A.andCanada,thepurchasersof
whichshouldconsultwiththeirdealer
toascertainwhat,ifany,servicecon-
tractorwarrantymaybeavailablelocally.
Copyright1981© byMclntoshLaboratoryInc.
-1-
TakeAdvantageof3 years
ofContractService...
FillintheApplicationNOW.

Installation
InstallationoftheMC2500requirescareful
thoughtaboutthreeimportantfactors.Theyare:the
electricalpowertooperatetheunit,theweight,and
theheatgeneratedwhentheMC2500isoperating.
TheMC2500draws15ampereswhenoperatedat
fullpowerwhenamplifyingmusicorspeech.Donot
useordinaryextensioncords.Ifanextensionisused
thenitmustbeheavydutyand14ga.orheavier.
PlugtheACpowercorddirectlyintoa walloutlet.
MakecertainthattheACpoweroutlethasatleast
15amperescapacity.DonotplugtheMC2500into
anauxiliaryACpoweroutletona preampliferor
othersourceequipment.Ifremotepoweroperation
isrequired,anexternalrelayarrangementmustbe
made.
Theweightoftheinstrumentis129pounds.Make
certainthatthestructureonwhichitistobe
mountedcansupportthatweight.
Adequateventilationextendsthetrouble-freelife
ofelectronicinstruments.Itisgenerallyfoundthat
each10°centigrade(18°F)riseintemperature
reducesthelifeofelectricalinsulationbyonehalf.
Adequateventilationisaninexpensiveandeffective
meansofpreventinginsulationbreakdownthat
resultsfromunnecessarilyhighoperatingtempera-
tures.Thedirectbenefitofadequateventilationis
longer,trouble-freelife.Theheatgeneratedinthe
operationoftheMC2500isexhaustedfromtheunit
bytwotemperaturecontrolledlownoise,longlife
fans.
CoolinginputairisdrawnintotheMC2500
throughtheventilationholesonthesidesandbot-
tomoftheamplifier.Theairpassesoverthe
transformers,outputtransistorheatsinks;and,is
blownoutthebackoftheinstrumentbythefans.It
isrecommendedthatatleast2 inchesofclearspace
beprovidedoneachsideandbottom.
Topermitthefanstooperatebest,provideatleast
5inchesofspaceattherearoftheinstrument.A
sourceforinputairanda meanstoexhaustthe
heatedairisnecessarysothattheheatedairdoes
notrecirculatethroughtheMC2500.
RACKINSTALLATION
TheMC2500maybemountedina standard19"
rackbyremovingthealuminumsiderails.Whenrack
mounted,theMC2500requires10½inchesofpanel
space.Allowtwoinchesinfrontofthepanelforthe
knobs.A depthof17inchesplusventilationspaceis
required.
TheMC2500canbeslidemountedina rack.
Tappedweld-nutsandinternalstructurebracinghas
beenaddedtobothsidesoftheMC2500forusewith
ModelCTS-116sidemountedslideassemblies
manufacturedby
GeneralDevicesCo.
Chassis-TrakDiv.
525S.WebsterAve.
Indianapolis,IN46219
-2-

HowtoConnect
INPUT
Stereooperation:
Useshieldedcablestoconnectthesignalfrom
thepreamplifieroranyothersignalsourcetothepo-
weramplifier.Allconnectionsaremadeontheback
paneloftheMC2500.
Forstereooperation,theleftoutputofthepre-
amplifiershouldbeconnectedtotheLeftINPUTof
thepoweramplifier.Therightoutputofthepreamp-
lifiershouldbeconnectedtotheRight/MONOIN-
PUTofthepoweramplifier.TheMODESWITCH
mustbeplacedintheSTEREOposition.
Tominimizethepossibilityofhumtheshielded
leadsshouldberunparallelorlooselytwistedtoget-
her.LocatethecablesawayfromACpowercords.
Monophonicoperation:
Ashieldedcablefromthesignalsourceiscon-
nectedtotheRight/MONOinputoftheMC2500.The
MODEswitchonthebackpaneloftheamplifier
mustbeplacedinoneofthetwoMONOpositions.In
theseMONOpositionstheoutputoftherightchan-
nelinputamplifierisfedtobothleftandrightpower
amplifiers.TheLeftINPUTisdisconnected.Onlythe
signalfedintotheRight/MONOinputwillbeampli-
fied.
OUTPUT
Stereooperation:
Toconnecttheleftspeakerfirstchecktheimpe-
danceofthespeakerwhichisusuallyidentifiedon
thespeakeritselforintheowner'smanual.Connect
oneleadfromthecommonterminalofthespeaker
totheLEFTOUTPUTterminalstripscrewCOMmon.
Connecttheotherterminalofthespeakertothe
screwwiththenumbercorrespondingtothespeaker
impedanceontheLEFTOUTPUTterminalstrip.The
rightchannelspeakerisconnectedinthesame
mannerontheRIGHTOUTPUTterminalstrip.Figure
1showstheconnectionsforstereooperation.
STEREOLOAD
OHMSVOLTS
122.4
231.6
444.7
863.2
STEREOOPERATION
CONNECTLOW
SIDEOFLOADS
TOTERMINALS
LEFT
COM
COM
COM
COM
RIGHT
COM
COM
COM
COM
CONNECTHIGH
SIDEOFLOADS
TOTERMINALS
LEFT
1W
2W
4W
8W
RIGHT
1W
2W
4W
8W
Whenmultiplespeakersaretobeconnectedto
eitherorbothoutputs,thecombinedloadimpe-
dancemustbecalculatedandtheloadconnectedto
theappropriateimpedancetap.ThefollowingFigure
2willaidinselectingthecorrectimpedancematch.
Load
impedance
inohms
0.9to1.8
1.8to3.6
Connect
to
1W
2W
Load
impedance
inohms
3.6to7.2
7.2to14.4
Connect
to
4W
8W
Figure1
Figure2
Ifa loadimpedanceisusedthatislowerthanthe
outputimpedancetap,thenreducedpower,increas-
edheating,andpossibledistortionwillresult.Ifa
loadimpedanceisusedthatishigherthantheout-
putimpedancetap,thenthemaximumavailableout-
putislimited.
Makeallspeakerconnectionsattheamplifieron-
ly.Formultiplespeakeroperation,paralleltheleads
fromthespeakerstotheamplifier.
Becauseofthehighpoweravailablefromthe
MC2500,besuretouselargediameterspeaker
leads.Inallcases,theleadstoandfromthespeaker
shouldbetwinconductorortwistedtogether.
Lampcordorwirewithsimilartypeofinsulation
canbeusedtoconnectthespeakerstotheampli-
fier.Forthenormallyshortdistancesofunder20
feetbetweentheamplifierand8 ohmspeakers#18
wireorlargercanbeused.Fordistancesover20feet
betweentheamplifierandspeakeruselargerdiame-
terwire.Selectthecorrectsizewireforthewire
distancefromthechart(Figure5 page4).Itisrecom-
mendedthattheDCresistanceofthespeakerleads
notbeover5%oftheloadimpedance.Resistanceof
theleadsmustincludethelengthofwirebothtoand
fromthespeakerorspeakers.
-3-

MONOLOAD
OHMSVOLTS
244.7
463.2
889.4
16126.5
MONOBRIDGEOPERATION
CONNECTLOW
SIDEOFLOAD
TOTERMINALS
L1W
L2W
L4W
L8W
CONNECTHIGH
SIDEOFLOAD
TOTERMINALS
R1W
R2W
R4W
R8W
INBRIDGEOPERATIONTHEOUTPUTISBALANCEDTO
GROUNDANDNEITHEROUTPUTLEADISATGROUND
POTENTIAL
MONOPARALLELOPERATION
CONNECTLOW
SIDEOFLOADTO
MONOLOADBOTHTERMINALS
OHMSVOLTS
1/222.4L COM& R COM
131.6LCOM&RCOM
244.7L COM& R COM
463.2L COM& R COM
CONNECTHIGH
SIDEOFLOADTO
BOTHTERMINALS
L1W & R 1W
L 2W & R 2W
L4W& R 4W
L8W& R 8W
DONOTOPERATEAMPLIFIERWITHMODESWITCHINTHE
STEREOORMONOBRIDGEPOSITIONWITHTHEOUTPUTS
PARALLELEDASABOVE
Figure3 Figure4
Monophonicoperation:
WhentheMC2500isusedasa monophonicor
singlechannelpoweramplifierthetwochannelsare
combinedtoproduceanoutputpowerof1000watts.
Theleftandrightoutputsmustbetiedtogetherat
theappropriateloadimpedancetaps.Figure3
showstheconnectionsforMONOBRIDGEopera-
tionandFigure4 showstheconnectionsforMONO
PARALLELoperation.
Makeallspeakerconnectionsattheamplifieron-
ly.Formultiplespeakeroperation,paralleltheleads
fromthespeakerstotheamplifier.
ACPOWER
TheMC2500isdesignedtooperateon120volts
50/60Hz.PlugtheACpowercorddirectlyintoa wall
outlet.MakecertainthattheACpoweroutlethasat
least15amperecapacitywithnothingelseconnec-
tedtothecircuit.DonotplugtheMC2500intoan
auxiliaryACpoweroutletona preamplifierorother
sourceequipmentunlessitisknownthereisade-
quatecurrentcapacity.Ifremotepoweroperationis
required,anexternalrelayarrangementmustbe
made.Ifanextensioncordisusedmakecertainthat
ithas15amperecurrentcapacity.
TheMC2500draws15amperesAClinecurrent
whenamplifyingmusicorspeechatratedoutputon
programpeaks.Theamplifierusesonly0.7ampere
whileidlingatnooutput.Iftheamplifierisdrivento
ratedoutputusingsinewavesignalsitwilldraw22
amperes.TheMC2500isdesignedforcontinuous
andreliableoperationatanypowerleveltoitsrated
500 wattscontinuousaveragepoweroutputper
channelor1000wattsasa monoamplifier.Forcon-
tinuoussinewaveoperationtheACsourcemustbe
capableofsupplyingtherequired22amperes.
-4-

Stereophonic
Connections
-5-

Mono-Bridge
Connections
-6-

Mono-Parallel
Connections
-7-

FrontPanelInformation
METERS
Outputpowermonitormetersindicatetheoutput
powerofeachchannel.Eachmeterhastwoprimary
scales:WATTSandDECIBELS.WhentheMETER
RANGEswitchinoneofthedecibel(dB)positions,
peaksignalreadingsareindicatedonthelowerDE-
CIBELscale.WhentheMETERRANGEswitchinthe
WATTSposition,directpowerinwattsisreadfrom
theupperWATTSscale.Themetersarecalibratedto
readaveragewatts.Theintermediatemarkingsbet-
weenthecalibrationsrepresent,beginningwith500
watts,200watts,100watts,theindicated50watts,
20watts,10watts,theindicated5 watts,2 watts,1
watt,theindicated0.5watt,0.2watt,0.1watt,thein-
dicated0.05watt,0.02watt,0.01watt,theindicated
0.005watt,0.002wattand0.001watt.Althoughthe
metercalibrationsareinaveragewattsfora sine
wavesignal,themeterselectricallyrespondtosig-
nalpeaks.Themetersarevoltageactuatedandindi-
catepoweraccuratelywhentheamplifierisoper-
atedintoratedoutputloadimpedances.
Themetersrespondtothepeakoutputofeach
channel.Ordinarymeterslackthecapabilityofindi-
catingtheshortintervalinformationina sound
wave.Themassofthemetermovementistoogreat
torespondtothenearlyinstantaneouschangesin
musicprogrammaterial.Shortintervalinformation
canhavea durationasshortashalfa thousandthof
asecond.Ordinarily,a meterpointermovingoverits
scaleinsucha shorttimewouldnotbeseen.
Mclntoshhasdevelopedcircuitsthatdrivetheme-
terstorespondtotheshortintervalinformationina
soundwavetoanaccuracyof90%.Theelectrical
pulsethatdrivesthemeterpointeristimestretched
longenoughsothatthepeakpositionofthepointer
canregisterinthepersistenceofvisioncharacteris-
ticoftheretinaofthehumaneye.
LEFTGAIN
TheLEFTGAINcontroladjuststhevolumeinthe
leftchanneltothedesiredlisteninglevel.Turnthe
controlclockwisetoincreasethevolume.
RIGHT/MONOGAIN
TheRIGHT/MONOGAINcontroladjuststhevol-
umeintherightchanneltothedesiredlisteninglev-
el.Turnthecontrolclockwisetoincreasethevol-
ume.WhentheoutputoftheMC2500isconnected
formonophonicoperationandtherearpanelMODE
SWITCHintheMONOposition,thevolumeiscon-
trolledbytheRIGHT/MONOGAINcontrolonly.
-8-