McIntosh MC2200 User manual

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THEMclNTOSHMC2200SOLIDSTATESTEREOPOWERAMPLIFIER

YourMC2200StereoPowerAmplifier
willgiveyoumanyyearsofpleasant
andsatisfactoryperformance.Ifyou
haveanyquestions,pleasecontact:
CUSTOMERSERVICE
MclntoshLaboratoryInc.
2ChambersStreet
Binghamton,NewYork13903
Phone:[phone]
WARNING:TOPREVENTFIREORSHOCK
HAZARD,DONOTEXPOSETHISUNITTO
RAINORMOISTURE.
TakeAdvantageof3 years
ofFREEService. ..
FillintheApplicationNOW.
Contents
SERVICE
INSTALLATION
HOWTOCONNECT
FRONTPANELINFORMATION
REARPANELINFORMATION
PERFORMANCELIMITSANDRATINGS
PERFORMANCECHARTS
TECHNICALDESCRIPTION
BLOCKDIAGRAM
1
2
4
8
10
11
12
14
16
THREEYEARSERVICECONTRACT
Anapplicationfora FREETHREEYEARSERVICECONTRACTisincludedwiththismanual.
Thetermsofthecontractare:
1.Mclntoshwillprovideallparts,materialsand
laborneededtoreturnthemeasuredperform-
anceoftheinstrumenttotheoriginalper-
formancelimitsfreeofanycharge.The
SERVICECONTRACTdoesnotcoveranyship-
pingcoststoandfromtheauthorizedservice
agencyorthefactory.
2.AnyMclntoshauthorizedserviceagencywill
repairallMclntoshinstrumentsatnormal
servicerates.Toreceivethefreeserviceunder
thetermsoftheSERVICECONTRACT,the
SERVICECONTRACTCERTIFICATEmustac-
companytheinstrumentwhentakentothe
serviceagency.
3.Alwayshaveservicedonebya Mclntosh
authorizedserviceagency.Iftheinstrument
ismodifiedordamaged,asa resultofun-
authorizedrepairtheSERVICECONTRACT
willbecancelled.Damagebyimproperuse
ormishandlingisnotcoveredbytheSERV-
ICECONTRACT.
4.TheSERVICECONTRACTisissuedtoyouas
theoriginalpurchaser.Toprotectyoufrom
misrepresentationthiscontractcannotbe
transferredtoa secondowner.
5.ForyourprotectionMclntoshselectsonly
dealerswhohavetechnicalcompetenceto
guidepurchasersfairly,andprovideservice
whennecessary.ToreceivetheSERVICE
CONTRACTyourpurchasemustbemade
froma Mclntoshfranchiseddealer.
6.Yourcompletelyfilledinapplicationfora
SERVICECONTRACTmustbepostmarked
within30daysofthedateofpurchaseof
theinstrument.
7.ToreceivetheSERVICECONTRACTallin-
formationontheapplicationmustbefilled
in.TheSERVICECONTRACTwillbeissued
whenthecompletelyfilledinapplicationis
receivedatMclntoshLaboratoryIncorporated
inBinghamton,NewYork.
Copyright© 1976byMclntoshLaboratoryInc.1

TheMC2200canbehousedintheMclntoshL22cabinet,
installedina customcabinetor,withtheadditionofRACK
MOUNTINGADAPTERS(RMA7),mountedina standard19
inchrackpanel.TheMC2200weighs85pounds(38.6kg).
Inanyinstallationitisnecessarytoprovidepropersupport
fortheweight.Themountingmethodsdescribedandthe
amplifierhavebeendesignedtoaccommodatetheweight
sobesurethatthepanelanditsmountingcanalsohandle
theweight.
INSTALLATIONINMclNTOSHCABINET
Removetheinstrumentandhardwarepackagefromthe
carton.RemovetheMC2200fromitsplasticbagandplace
itupsidedownontheshippingpallet;unscrewthefour
plasticfeetfromthebottomofthechassis.Usethescrews
fromtheplasticfeettosecuretheinstrumenttothecabi-
net.Donotsubstitutelongerscrews.Longerscrewsmay
penetratetheelectroniccomponentsinthechassiswhich
wouldcauseseveredamage.Donotovertightenthescrews.
INSTALLATIONINA CUSTOMCABINET
Thetrouble-freelifeofanelectronicinstrumentis
greatlyextendedbyprovidingsufficientventilationtopre-
ventthebuildupofhighinternaltemperaturesthatcause
deterioration.Allowenoughclearancesothatcoolaircan
enteratthebottomofthecabinetandbeventedfromthe
top.Withadequateventilationtheinstrumentcanbe
mountedinanyposition.Therecommendedminimum
spaceforinstallationis15inches(38.1cm)deep,17inches
(43.2cm)wide,and8 inches(30.3cm)high.
VerticalmountingtheMC2200requirescarefulcon-
sideration.Thetotalweightistransmittedtothepaneland
shelfonwhichtheamplifieristobemounted.Thought
shouldbegiventoprovidinga meansforraisingtheMC
2200outofthepanel.Moreconsiderationshouldbegiven
toprovidingadequateventilationatthepanelinvertical
mounting.Theheatsinksareattherearofthechassis
permittingtheheattopassovertheentirechassis.Itisthen
trappedbehindthepanelcausingtheoveralltemperature
torise.Inanycase,airflowforcoolingcanbeimprovedby
theuseofa properlyinstalledlownoisefan.Adequate
coolingwillextendthelifeofthecomponents.
Fig.1.Topviewofthepanelcutoutandmountingshelf.
2
1/4"DIA.(2HOLES)
CUTOUT
FRONTPANEL
MTG.SURFACE

Fig.2.Viewsshowingmountingshelfinposition.
INSTALLATIONPROCEDURE
1.MarkforPosition
Markcabinetpanelwheretheinstrumentistobe
installed.ThesolidlinesinFig.2 representtheoutlineof
therectangularcutoutandalsorepresenttheoutside
dimensionsofthechassis.Makesuretheselinesclear
shelves,partitions,oranyequipment.Thebrokenline
representstheoutsidedimensionofthepanel.
2.DrillHoles
Usinga drillbitslightlywiderthanthetipofyoursaw
blade,drilloneholeateachoftwodiagonallyopposite
corners.Theholesshouldbarelytouchtheinsideedgeof
theoutline.
3.SawPanelCutout
Sawingcarefullyontheinsideofthelines,firstmake
thetwolongcutsandthenthetwoshort.Afterthe
rectangularopeninghasbeencutout,usea fileto
squarethecornersandsmoothanyirregularitiesinthe
cutedges.
4.ShelfInstallation
InstalltheshelfonwhichtheMC2200willsit.It
mustbecapableofsupportingthetotalweightofthe
instrument.Drillthetwo¼"holesshowninFig.1.
5.InstallInstrument
GuidetheACpowercordthroughthepanelopening
tothebackofthecabinet;then,slidetheinstrumentinto
theopeninguntilitsfrontpanelisflushwiththecabinet
panel.SecuretheMC2200totheshelfwith#10wood
screwsoftheproperlength.
½"thickshelf—use1"screws
5/8"thickshelf—use11/8"screws
¾"thickshelf—use1¼"screws
Donotusescrewslongerthanthisrecommended
length.Theymaypenetrateelectroniccomponents
insidethechassisandcauseseveredamage.Inany
event,thescrewlengthmustnotexceedtheshelf
thicknessbymorethan½".
Inserttwoproperlengthscrewsthroughthemount-
ingshelfandintotheholesinthebottomoftheampli-
fier.Donotovertightenthescrews.
INSTALLATIONINA 19INCHRACK
•TheRACKMOUNTINGADAPTERSinstalloneachendof
thefrontpanel.Oneachsideoftheamplifier,threescrews
securethefrontpanelbrackettothechassis.Thesethree
screwsareremoved,theRACKMOUNTINGADAPTER
placedoverthescrewholesandthescrewsreplaced.The
entireweightistransmittedthroughtheRACKMOUNTING
ADAPTERStotherack.Noweightiscarriedbythefront
panel.Additionalsupportfortheweightcanbeprovided
attherearofthechassisasdesired.
Fig.3.RackMountingAdaptersinstalled.
3
69/16"
DEPTHREQUIRED
15".
TOPOFSHELF& BOTTOM
OFCUTOUTSHOULDCOINCIDE.
SHELF
MOUNTINGSCREWS
DIFFERENCEBETWEENSCREW
LENGTH& TOTALSHELFTHICKNESS
MUSTNOTEXCEED1/2"
3"

INPUT
STEREOORTWINAMPLIFIEROPERATION
Useshieldedcablestoconnectthesignalfromthepre-
amplifierorsignalsourcetothepoweramplifierinput.To
minimizethepossibilityofhumtheshieldedcablesshould
berunparalleltoeachotherorlooselytwistedtogether.
LocatethecablesawayfromspeakerleadsandACpower
cords.Allconnectionsaremadeonthebackpanelofthe
MC2200.
Forstereooperation,theleftoutputofthepreamplifier
shouldbepluggedintotheLeftinputjackofthepower
amplifier.Therightoutputofthepreamplifiershouldbe
pluggedintotheRight(MONO)inputjackofthepower
amplifier.
Fortwinamplifieroperationa separatesignalsourcecan
beconnectedtoeachinput.Instereoortwinamplifier
operationtheMODESWITCHmustbeintheSTEREOposi-
tion.
MONOPHONICORSINGLECHANNELOPERATION
Ashieldedcablefromthesignalsourceispluggedinto
theRight(MONO)inputjackoftheMC2200only.The
MODESWITCHonthebackpaneloftheamplifiermustbe
placedintheMONOposition.IntheMONOpositionthe
rightchannelinputjackconnectstobothleftandright
poweramplifiers.Monooutputisobtainedbystrapping
bothoutputsinparallel.TheLeftINPUTisdisconnected.
OnlythesignalfedintotheRight(MONO)inputwillbe
amplified.
ShouldtheMODESWITCHbeleftintheSTEREOposition
andtheoutputtransformersremainstrappedfora mono-
phonicload,onechannelwillattempttodrivetheother
whichcauseshighcirculatingcurrentsandoverheating.Be
certainthattheMC2200isneveroperatedinthestereo
modewiththeoutputsconnectedformonophonicopera-
tion.
OUTPUT
BecertaintheloudspeakersconnectedtotheMC2200
arecapableofhandlingthepoweroutputoftheampli-
fier.
Formultiplespeakeroperation,runseparateleadsfrom
eachspeakertotheamplifier.Becauseofthehighpower
availablefromtheMC2200,largediameterspeakerleads
mustbeused.Uselampcord,bellwire,orwirewithsimilar
typeofinsulationtoconnectthespeakerstotheamplifier.
Inallcases,theleadstoandfromthespeakershouldbe
twinconductorortwistedtogether.Whenusing8 ohm
speakersandforthenormallyshortdistancesofunder30
feetbetweentheamplifierandspeaker,#18wireor
largercanbeused.Fordistancesover30feetbetweenthe
amplifierandspeakeruselargerdiameterwire.Selectthe
correctsizewireforthewiredistancefromthechart.Itis
recommendedthattheDCresistanceofthespeakerleads
belessthan5%ofthespeakerimpedance.Upto10%can
betolerated.Resistanceoftheleadsshouldbecomputedfor
thelengthofwirebothtoandfromthespeakerorspeakers.
Wire
Gauge
22
20
18
16
14
12
10
MAXIMUMWIRE
For4 OhmLoad
Feet
6
10
15
25
40
60
100
Meters
1.83
3.05
4.57
7.62
12.19
18.29
30.48
LENGTHS
For8
Feet
12
20
30
50
80
120
200
OhmLoad
Meters
3.66
6.10
9.14
15.24
24.38
36.58
60.96
Wirelengthsaboverepresentthewireresistanceequalto
5%ofthespeakersimpedance.Useofsmallerwiresizes
willproducemoreresistancewhichcausesmorepower
lossandlessloudspeakerdamping.
STEREOORTWINAMPLIFIEROPERATION
Checktheimpedanceofthespeakerwhichisusually
identifiedonthespeakeritselforinthespeakerowner's
manual.Connecta leadfromthecommonterminalofthe
leftspeakertotheamplifierLEFTOUTPUTterminalstrip
COMmonscrew.Connectanotherleadfromtheothertermi-
naloftheleftspeakertothescrewwiththenumber cor-
respondingtothespeakerimpedanceontheLEFTOUTPUT
terminalstrip.Therightchannelspeakerisconnectedin
thesamemanner ontheRIGHTOUTPUTterminalstrip.For
stereoortwinchanneloperationitisnotnecessarytouse
thesameimpedanceloudspeakeroneachoutput.Connect
4

eachchannelfortheimpedancedesired.Fullpowerwill
bedeliveredtoeachproperlyconnectedspeaker.
Whenmultiplespeakersaretobeconnectedtoeitheror
bothoutputs,thecombinedloadimpedancemustbecalcu-
lated.Theloadmustbeconnectedtotheappropriateim-
pedancetap.Usethistabletoaidinselectingthecorrect
impedancematch:
Load
impedance
inohms
0.8to1.6
1.6to3.2
Connectfor
1ohmoutput
2ohmoutput
Load
impedance
inohms
3.2to6.4
6.4andup
Connectfor
4ohmoutput
8ohmoutput
Ifa loadimpedanceisusedthatislowerthantheoutput
impedancetap,thenreducedpowerandpossibledistortion
willresult.Ifa loadimpedanceisusedthatishigherthan
theoutputimpedancetap,thenneitherthesignalnorthe
amplifierwillbeharmedbutthepoweravailableislimited.
FORSTEREOORTWINAMPLIFIERCONSTANTVOLTAGE
OPERATION:
Foroutput
voltageofConnectfor
25volts4 ohms
MONOPHONICORSINGLECHANNELOPERATION
WhentheMC2200isusedasa monophonicorsingle
channelpoweramplifierthetwochannelsarecombinedto
produceoutputupto400watts.Theoutputsmustbetied
togetherattheappropriateloadimpedancetap.Inconnect-
inga loadtotheMC2200forsinglechanneloperation
connectthecommonsideoftheloadtotheLEFTCHANNEL
OUTPUTterminalmarkedCOM.,theotherleadiscon-
nected:
FORMONOPHONICCONSTANTVOLTAGELINE
OPERATION
Foroutput
voltageofConnectedfor
25volts2 ohmoutput(mono)
Formultiplespeakeroperation,runseparateleadsfrom
eachspeakertotheamplifier.
ShouldtheMODESWITCHbeleftintheSTEREOposition
andtheoutputtransformersbestrappedfora monophonic
load,onechannelwillattempttodrivetheotherandcause
circulatingcurrentsandoverheating.Becertainthatthe
MC2200isneveroperatedinthestereomodewiththe
outputsconnectedformonophonicoperations.
ACPOWER
TheMC2200operateson120volts50/60Hz.Theaux-
iliaryACOUTLETontheMC2200isnotfusedorswitched.
Ifthespeaker
orload
impedanceis
0.5ohm
1ohm
2ohms
4ohms
Thehotside
ofthelineis
connectedto
Left1
Left2
Left4
Left8
Connecta
jumper
wirebetween
Left1 and
Left2 and
Left4 and
Left8 and
Right1
Right2
Right4
Right8
Donotconnectunequalimpedancetapstogether
Iftheloadimpedanceisbetweenanyoftheabovefig-
ures,selectthebestimpedancematchfrom:
Load
impedance
inohms
0.4to0.8
0.8to1.6
Connectfor
0.5ohmoutput
1ohmoutput
Load
impedance
inohms
1.6to3.2
3.2andup
Connectfor
2ohmoutput
4ohmoutput
5

FrontPanel
Information
LEFTGAIN
UsetheLEFTGAINcontroltoadjustthevolumeinthe
leftchanneltothedesiredlisteninglevel.Turnthecontrol
clockwisetoincreasethevolume.
RIGHT/MONOGAIN
UsetheRIGHT/MONOGAINcontroltoadjustthevolume
intherightchanneltothedesiredlisteninglevel.Turnthe
controlclockwisetoincreasethevolume.
MONO
WiththeoutputofMC2200connectedformonophonic
operationandtherearpanelMODESWITCHinMONOthe
volumeiscontrolledbytheRIGHT/MONOGAINcontrol
only.
LIMIT/NORMAL
TheNORMAL(green)andLIMIT(red)indicatorsarea
newMclntoshdevelopment.Aslongastheamplifier
operateswithoutoverloadtheNORMALindicatorillu-
8

minates.A waveformcomparatorintheMC2200con-
stantlycomparestheamplifierinputandoutputwaveform.
Waveformdifferenceoftheoutputwaveisconvertedto
avoltagewhichisusedasa controlsignalto"turnoff"the
NORMALindicatorandto"turnon"theLIMITindicator.
TheLIMITindicatorturnsonwheneverthewaveformdif-
ferenceexceeds0.5%.Generally,thesewaveformdiffer-
encesaretheresultofapplyingvoltagesattheinputin
excessofitsrating.Becausethelimitindicatorcircuitcan
showanoverloadconditionasshortasonecycleofa
20,000Hzsignala holdingcircuitkeepstheredindi-
catoronlongenoughfortheeyetosee.
HEADPHONES
TheoutputofthefrontpanelHEADPHONEjackhasbeen
designedtofeedlowimpedancedynamicstereohead-
phones.Electrostaticheadphonesgenerallyrequirehigher
powerthandynamicheadphones.Connectthemtothe
LEFTandRIGHTOUTPUTcontactsonthebackofthe
MC2200.Plugdynamicheadphonesintothefrontpanel
HEADPHONEjack.AdjustthefrontpanelLEFTGAINand
RIGHT/MONOGAINcontrolforcomfortableheadphone
listening.
POWER
ThepowerswitchturnstheMC2200ONorOFF.The
switchdoesnotcontrolthepoweroutletonthebackpanel.
IfyouwishtocontroltheACpowerfroma preamplifier
controlcenterleavetheswitchintheONposition.Besure
theACcordoftheMC2200ispluggedintothecontrolled
outletsontherearofthepreamplifiercontrolcenter.
OFF:IntheOFFpositiontheACpowertotheamplifier
isturnedoff.
9

RearPanelInformation
LEFTandRIGHTOUTPUT
Forstereooperation,outputimpedancesof1,2,4 and
8ohmshavebeenprovidedona secure,screwtypebarrier
strip.Formonophonicoperationproperinterconnection
provides0.5,1,2 and4 ohmsfromthesamebarrierstrips.
POWERGUARD
Amplifiersarecapableofdeliveringlargequantitiesof
powerwhentheyaredriventoclipping.Clippingis
causedwhentheamplifierisaskedtoproducemorepower
outputthanitcandeliverwithlowdistortion.A clipped
amplifiercanhavemorethan40%harmonicdistortion.
Theextraenergycontentoftheclippedsignalwilldam-
agemostspeakers.A newMclntoshadvancementhelps
toprotectyourspeakerfromthiskindofdamage.The
MC2200hasa builtin"waveformcomparator"thatcom-
paresthewaveshapeoftheinputsignalwiththeoutput
signal.Ifthenon-linearitybetweenthetwosignalsexceeds
0.5%a frontpanelsignalilluminatesinred(LIMIT}.With
thePOWERGUARDswitchintheNORMALposition,1.0%
distortionwillcausethePOWERGUARDcircuittooperate.
ThePOWERGUARDcircuitlimitstheinputdynamicallyso
thattheamplifiercannotbeoverdriven.Thiseliminates
amplifieroutputclipping.Recommendedoperationiswith
thePOWERGUARDswitchintheNORMALpositionatall
times.
MODESWITCH
TheMC2200canbeusedinthesedifferentmanners:
stereo(orasa twinamplifier)andmono.Becauseofthe
excellentchannelseparationoftheMC2200,itcanfulfill
allofthesefunctions.Whentheinstrumentisproperlycon-
nectedtheMODEswitchisusedtoselectthemethodof
operationdesired.
INPUT
Inthestereoortwinamplifiermodeofoperationboth
inputjacksacceptsignal.Inthemonomodeofoperation
theLeftchannelinputjackisdisconnectedandonlythe
Right(MONO)channelinputjackacceptssignal.
INPUTLEVEL
TheinputsensitivityoftheMC2200is0.75voltsor
2.5V dependingonthepositionoftheINPUTLEVELswitch.
WithindicatedvoltageappliedandtheGAINcontrolclock-
wise,theamplifierwilldeliveritsratedpower.AllMclntosh
preamplifiershavebeendesignedtodeliver2.5voltsout-
putwithratedinput.Forthebestsignaltonoiseratiowhen
usingMclntoshsourceequipment,alwayshavetheINPUT
LEVELswitchinthe2.5V positionandthefrontpanelLEFT
andRIGHT/MONOGAINcontrolsinthefullyclockwise
position.Ifmoregainisdesiredthe0.75V positionmaybe
used.ForsourceequipmentotherthanMclntoshsetthe
switchinthepositionnearesttothestatedoutputratingof
thesourceequipment.
ACPOWER
TheMC2200isratedfor120volts,50/60hertz.A
10amperefuseprotectstheMC2200electrically.An
auxiliaryACpoweroutlethasbeenprovided.Theauxiliary
outletisneitherfusednorswitched.
10

PerformanceLimitsandRatings
PERFORMANCEGUARANTEE
PerformanceLimitsarethemaximumdeviationfromper-
fectionpermittedfora MclntoshinstrumentWepromise
youthattheMC2200youbuymustbecapableofper-
formanceatorexceedingtheselimitsoryougetyour
moneyback,Mclntoshistheonlymanufacturerthatmakes
thisguarantee.
PERFORMANCE
Mclntoshaudiopowerratingsareinaccordancewiththe
FederalTradeCommissionRegulationofNovember4,1974
concerningpoweroutputclaimsforamplifiersusedinhome
entertainmentproducts.
POWEROUTPUT
STEREO
200wattsminimumsinewavecontinuous
averagepoweroutput,perchannel,both
channelsoperatinginto1 ohm,2 ohms,4
ohms,or8 ohmsloadimpedance,whichis:
14.1voltsRMSacross1 ohm
20.0voltsRMSacross2 ohms
28.3voltsRMSacross4 ohms
40.0voltsRMSacross8 ohms
MONO
400wattsminimumsinewavecontinuous
averagepoweroutputinto0.5ohm,1
ohm,2 ohms,or4 ohmsloadimpedance,
whichis:
14.1voltsRMSacross0.5ohm
20.0voltsRMSacross1 ohm
28.3voltsRMSacross2 ohms
40.0voltsRMSacross4 ohms
OUTPUTLOADIMPEDANCE
STEREO
1ohm, 2 ohms,4 ohms,and8 ohms;sepa-
rateterminalsareprovidedforeachoutput
MONO
0.5ohm,1 ohm,2 ohms,and4 ohms;ob-
tainedbyconnectingtogethertheappro-
priateterminalsofbothchannels
RATEDPOWERBAND
20Hzto20,000Hz
TOTALHARMONICDISTORTION
STEREO
0.1%maximumharmonicdistortionatany
powerlevelfrom250milliwattsto200
wattsperchannelfrom20Hzto20,000
Hz,bothchannelsoperating
MONO
0.1%maximumharmonicdistortionatany
powerlevelfrom250milliwattsto400
wattsfrom20Hzto20,000Hz
INTERMODULATIONDISTORTION
STEREO
0.1%maximumifinstantaneouspeakpoweroutputis400
wattsorlessperchannelwithbothchannelsoperatingfor
anycombinationoffrequencies,20Hzto20,000Hz
MONO
0.1%maximumifinstantaneouspeakpoweroutputis800
wattsorlessforanycombinationoffrequencies,20Hzto
20,000Hz
FREQUENCYRESPONSE(atonewattoutput)
20Hzto20,000Hz,+0-0.25dB
10Hzto100,000Hz+0-3.0dB
NOISEANDHUM
95dBbelowratedoutput
RATINGS
OUTPUTVOLTAGES
25voltsfordistributionlines
DAMPINGFACTOR
STEREO
16at1 ohmoutput,50at2 ohmsoutput,30at4 ohmsout-
put,16at8 ohmsoutput
MONO
16at0.5ohms,50at1 ohm,30at2 ohms,and16at4
ohmsoutput
INPUTIMPEDANCE
100,000ohms
INPUTSENSITIVITY
Switchable:0.75voltor2.5volts—Levelcontrolprovided
forhigherinputvoltages
GENERALINFORMATION
POWERREQUIREMENTS
120volts50/60Hz,70to550watts
SEMICONDUCTORCOMPLEMENT
43silicontransistors
24siliconrectifiersanddiodes
2integratedcircuits
MECHANICALINFORMATION
SIZE
Frontpanelmeasures16incheswide(40.7cm)by6 31/32
incheshigh(17.7cm).Chassismeasures145/8inches
wide(37.2cm)by6 9/16incheshigh(16.7cm)by141/2
inchesdeep{36.8cm),includingconnectors.Knobclear-
ancerequiredis1 1/2inches(3.8cm)infrontofmounting
panel
FINISH
Frontpanelisanodizedgold.Chassisischromeandblack
Weight
73pounds(38.6kg)net,87pounds(44.0kg)inshipping
carton
11

Technical
Description
INPUTAMPLIFIER
Separateinputamplifiersareusedfortherightand
leftchannels.Eachinputamplifierisa twotransistorfeed-
backamplifierwhichhasunitygain.Theyareusedtopro-
videhighinputimpedanceandlowoutputimpedancefor
drivingthepoweramplifiersections.Inaddition,impe-
dancematchingisprovidedforthePOWERGUARDsystem
inputattenuator.
WhentheMODEselectorisswitchedtoMONO,onlythe
rightchannelinput,GAINcontrol,POWERGUARDattenua-
tor,andinputamplifierisusedtodrivebothpoweram-
plifiers.
POWERAMPLIFIER
Therearetwoidenticalpoweramplifiersections.Atthe
inputtoeachpoweramplifierisa monolithicdifferential
transistorselectedforlownoise.Themonolithicdesign
yieldscloselymatchedtransistorsforlowdistortion.The
inputandthefeedbacksignalsareappliedtothisdifferen-
tialamplifier.Thesecondstageisa classA voltageampli-
fierusinga singletransistorwithfeedback.
Thepredriver,driver,andoutputsectionsfollowandare
fullycomplimentarywithhighefficiencyandnegligibledis-
tortion.Thepredriverisa complimentarytransistorpair
biasedtonearlyclassA operationforlowcrossoverdis-
tortion.Biasissuppliedbya transistorwhichservesas
atemperaturetrackingcircuitsothepredriverisproperly
biasedregardlessoftemperature.Thepredriverhasa
generousamountofemitterdegenerationforlowdistortion.
Anothercomplimentarypairofpowertransistorsbiased
forclassABoperationmakeuptheoutputdriverstages.
Theirbiasisdevelopedacrossa termistorwhichholdsthe
biascurrentstableregardlessoftemperature.
Theoutputstageconsistsof6 ruggedcomplimentary
powertransistorsconnectedinsingleendedpush-pull
parallel.Thisstageisconnectedasa balancedemitterfol-
lowerwhichallowsgreatstabilityandlowdistortion.Due
toa uniquearrangementoftheoutputbiasnetwork,the
outputtransistorsareoperatedclassB freeofcrossover
distortion.Heatisnotproducedbythesetransistorswhen
thereisnooutput.Thebiasnetworkfortheoutputstage
istemperaturecompensatedassuringclassB operation
atanytemperatureorpowerlevel.
Theoutputtransistorsanddriversaremountedongener-
oussizedblackanodizedaluminumheatsinks.Thefree
flowofroomtemperatureairthatpassesthroughtheover-
sizedheatsinksprovidesthecoolingnecessaryforthelong
lifeofcomponents.
TheMC2200hastransientfreeturnonandturnoff
characteristics.Thisisbecausetheoutputoftheamplifieris
switchedbya heavydutyrelaytotheoutputautotrans-
former.Therelayisdrivenbya transistorswitch.Thecon-
troltothistransistorisderivedfroma longtimeconstant
capacitorchargingnetwork.Theswitchturnsontherelay
approximatelytwosecondsaftertheMC2200isturnedon.
Thesamecircuithasa shortturn-offtimeconstantwhich
turnsofftherelaybeforetheamplifier'smainpowersupply
hashada chancetodrop.Theoutputsignalisfedthrougha
matchingnetworktothefrontpanelHEADPHONEjack.The
HEADPHONEoutputisdesignedtofeedlowimpedance
dynamicstereoheadphones.
Theamplifieroutputsignalisfedtotheoutputterminals
throughtheautotransformer.TheMclntoshdesignedinter-
leavedmultifilarwoundautotransformerisusedtoproperly
matchtheamplifiertoanyoutputimpedancetap.TheMC
2200willdeliverfullpowerovertheentireaudiofrequency
rangeatanyoftheseimpedances.TheMC2200willnot
overheatwhendrivinglowimpedanceloads{1ohm,2
ohmsor4 ohms).Theautotransformeralsoprotectsspeak-
ersfromdamageintheeventofamplifierfailure.Shoulda
directcurrentcomponentappearintheoutputitisshunted
bytheautotransformerandcannotdamagethespeaker.
TheMclntoshpatentedSentryMonitoringcircuitcon-
stantlymonitorstheoutputsignalandinstantlyreactsto
preventoverloadoftheoutputtransistors.Atsignallevels
uptoratedoutputthiscircuithashighimpedanceandhas
noeffectupontheoutput.Ifthepoweroutputexceeds
designmaximum,theSentrymonitoringcircuitoper-
atestolimitthesignaltotheoutputtransistors.Inthe
eventofa shortcircuitacrosstheamplifieroutputor
severeimpedancemismatchtheSentryMonitoring
circuitwillprotecttheoutputtransistorsfromfailure.
Thepositiveandnegativehalvesoftheoutputsignalare
monitoredindependently.
LIMITINDICATORANDPOWERGUARD
ThefrontpanelNORMAL(green)andLIMIT(red)indica-
torsareactivatedbya newlydesignedMclntoshcircuit.The
MC2200hasa builtin"waveformcomparator."Thewave-
formcomparatorelectricallycomparestheamplifier'sout-
putwaveformwiththeinputwaveform.Shouldthewave-
formdifferencesreach0.5%,theredLIMITindicatoronthe
frontpanelisturnedonandtheNORMALindicatoris
turnedoff.Ifthedifferencesincreaseto1%thePOWER
GUARDcircuitisactivated.POWERGUARDprovidesan
unusualmarginofsafetyforloudspeakersbythepreven-
tionofamplifierclippingyetpermitstheamplifiertode-
liverdesignedmaximumpower.
14

Theinputwaveformandtheoutputwaveformare
comparedinanintegratedcircuitdifferentialamplifier.
Anydifferences,duetodistortionoftheoutputwaveform,
areconvertedtoa controlvoltage.Thiscontrolvoltageis
applieddifferentiallytoa highgainoperationalamplifier
whereitisamplifiedabout100times.Theamplified
controlvoltageisdetectedbya fullwavebridgerectifier
thenentersa Schmidttriggerwhichisprogrammedto
sequencethefrontpanelindicatorsfromNORMAL(green)
toLIMIT(red}ata presetdistortionlevel.Alsobuiltinto
thetriggercircuitisa timing capacitorwhichholdsthe
LIMITindicatoronlongenoughtobevisibleevenwhenthe
durationoftheoverloadismuchshorter.TheLIMITindica-
torwillbeilluminatedforanoverloadconditionasshort
asonecycleofa signalat20,000Hz.
ThesamecontrolvoltageusedtoactivatetheLIMIT
indicatoralsoactuatesthePOWERGUARDsystem.Ifthe
controlvoltageisgreaterthanisneededtoilluminate
theLIMITindicationthenthePOWERGUARDbeginsop-
erating.Thecontrolvoltageisusedtooperatea light
emittingdiode/lightdependentresistor(LOR)network.
TheLDRispartofanattenuatorbetweenthevolumecon-
trolandtheinputamplifier.Theinputtothepoweram-
plifiercanbeattenuatedtoaslittleasonetenth,ifneces-
sary,inordertomaintainlowdistortionintheeventof
excessiveinputsignal.
ThePOWERGUARDcircuitisactivatedwhentherear
panelswitchisintheNORMALposition.POWERGUARD
protectionisdisabledintheOUTposition.TheLIMITindi-
catoroperatesregardlessofthepositionofthePOWER
GUARDswitch.
15

MclNTOSHLABORATORYINC.
2CHAMBERSST.,BINGHAMTON,N.Y.13903
607-723-3512
Designsubjecttochangewithoutnotice.
PrintedinU.S.A.
038-910