McIntosh MR 77 User manual

THEMclNTOSHMR77SOLIDSTATEFM/FMSTEREOTUNER
ReadingTime:24Minutes
Price$1.25

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TakeAdvantageof3 years
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FillintheApplicationNOW.
CONTENTS
SERVICECONTRACT...1
INSTALLATION...2,3
HOWTOCONNECT... 4
BACKPANELINFORMATION...5,6
FRONTPANELINFORMATION...6,7
LISTENINGTOTHEMR77...7
TECHNICALDESCRIPTION...8,9
PERFORMANCELIMITSANDRATINGS...9
PERFORMANCECHARTS...10,11
BLOCKDIAGRAM...12
Anapplicationfora FREETHREEYEARSERVICECONTRACTisincludedwiththismanual.
Thetermsofthecontractare:ormishandlingisnotcoveredbytheSER-
VICECONTRACT.
1.Mclntoshwillprovideallparts,materialsand
laborneededtoreturnthemeasuredperform-
anceoftheinstrumenttotheoriginalper-
formancelimitsfreeofanycharge.The
SERVICECONTRACTdoesnotcoveranyship-
pingcoststoandfromtheauthorizedservice
agencyorthefactory.
2.AnyMclntoshauthorizedserviceagencywill
repairallMclntoshinstrumentsatnormal
servicerates.Toreceivethefreeserviceun-
derthetermsoftheSERVICECONTRACT,the
SERVICECONTRACTCERTIFICATEmustac-
companytheinstrumentwhentakentothe
serviceagency.
3.Alwayshaveservicedonebya Mclntosh
authorizedserviceagency.Iftheinstrument
ismodifiedordamagedasa resultofun-
authorizedrepairtheSERVICECONTRACT
willbecancelled.Damagebyimproperuse
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
whenthecompletelyfilledinapplication
isreceivedatMclntoshLaboratoryIncor-
poratedinBinghamton,NewYork.
Copyright© 1970ByMclntoshLaboratoryInc.
MclntoshLaboratoryInc.
2ChambersStreet
Binghamton,NewYork13903
Phone:[phone]
CUSTOMERSERVICE
YourMR77FM/FMStereoTunerwillgive
youmanyyearsofpleasantand
satisfactoryperformance.Ifyouhave
anyquestions,pleasecontact:
THREEYEARSERVICECONTRACT
1

Installation
Adequateventilationextendsthetrouble-freelifeof
electronicinstruments.Itisgenerallyfoundthateach
10°centigrade(18°F)riseintemperaturereducesthe
lifeofelectricalinsulationbyonehalf.Adequateventi-
lationisaninexpensiveandeffectivemeansofprevent-
inginsulationbreakdownthatresultsfromunneces-
sarilyhighoperatingtemperatures.Thedirectbenefit
ofadequateventilationislonger,trouble-freelife.
Allowatleast15inchesdeepx 17½incheswidex 6
incheshighformountingtheMR77.Alwaysallowforair
flowbyeitherventilationholesorspacenexttothe
bottomofthetuneranda meansforwarmairto
escapeatthetop.
ItisrecommendedthattheMR77bemountedina
normalorhorizontalposition.However,withadequate
ventilationthetunercanbemountedinanyposition.
TopreparetheMR77forinstallationremovethe
plasticprotectivecovering.TurntheMR77upsidedown
sothatitrestsonitstopontheshippingpallet.Remove
thefourplasticfeetfastenedtothebottomofthe
chassis.
Next,placethemountingbrackets,thepartsbag
andthemountingtemplateathand.
ThePANLOCprofessionalmountingdesignelimi-
natestheneedforanyshelforbrackettosupportthe
MR77.Itiscompletelysupportedbyitsownmounting
brackets.
Thedesignofthemountingtemplateallowsyouto
positionorlocatethecutoutfromthefrontorrearof
thepaneltowhichtheinstrumentistobemounted.
Positiontheplasticmountingtemplateovertheareaof
thepaneltobecutoutforinstallation.
Ifthecutoutistobelocatedfromthefrontofthepanel,
beginatstep2.Ifthecutoutistobelocatedfromthe
rearofthepanel,beginhere.
1.Onthebackofthecabinetpanel,scribea vertical
centerlinethroughtheexactcenteroftheareain
whichthecutoutistobemade.
Placethetemplateagainstthebackofthepaneland
matchthetemplatecenterlinewiththecenterlineon
thecabinetpanel.
Makesurethatthereisatleast¼ inchclearancebe-
tweenthebottomofthedashedlineofthecutout
areaonthetemplateandanyshelforbracebelow
theproposedcutout.
Markthetwolocatingholes("C"holesonthe
mountingtemplate).
Drillthetwolocatingholes.Becertainthedrillis
perpendiculartothepanel.
Nowpositionthetemplateonthefrontofthepanel
byaligningthe"C"locatingholesonthetemplate
withthedrillholes.
2

2.Ifthecutoutistobelocatedfromthefrontofthe
panel:
Withthetemplateinplaceagainstthecabinet,mark
the"A"and"B"drillholesandthefoursmallholes
thatidentifythecornersofthecutout.Jointhecor-
nermarkswitha pencil.Theedgeofthetemplate
canbeusedasa straightedge.
IMPORTANT:DRILLTHE6 HOLESBEFOREMAKING
THECUTOUT.
Accuratelydrillthethreeholesoneachsideofthe
cutoutareawitha3/16inchdrill.
WiththesawontheINSIDEOFTHEPENCILLINES
carefullycutouttherectangularopening.
Securethemountingstripstotherearofthecabinet
panelusingtwoscrewsfromthehardwarepackage.
Insertthescrewsinthecenterholesofthecabinet
panel("B"holesonthetemplate)andtighten.The
screwheadshouldpullintothewoodslightly.(Usetwo
¾inchlongscrewsforpanelsunder½ inch,ortwo1¼
inchlongscrewsforpanels½ inchthickandlarger.)
Attachthemountingbracketstothecabinetpanel
usingfourscrews.
Placethetemplateoverthemountingscrews.The
mountingscrewsshouldbecenteredinthe"A"and
"B"holesonthetemplate.Thesidesofthemounting
bracketsshouldmatchtheverticaldashlinesonthe
template.Ifnecessary,loosenthescrewsandpushthe
bracketsintoalignmentandretighten.
Insertthepowercordthroughtheopening.Carefully
slidetheMR77intotheopeningsotherailsonthebot-
tomoftheequipmentslideinthetrackofthemounting
brackets.Slidetheinstrumentinuntilitstopsatthe
adjustpositionlatches.Pressthelatchesinandcon-
tinuetoslidetheinstrumentinuntilthefrontpanelis
againstthecabinetpanel.Atthebottomfrontcorners
ofthePANLOCinstrumentsarethePANLOCbuttons.
DepressingthePANLOCbuttonswilllocktheinstru-
mentfirmlyintheinstallation.DepressingthePANLOC
buttonsa secondtimewillreleasetheinstrument.You
canthenslidetheinstrumentforwardtotheinspection-
adjustmentpositionlatcheswillallowtheinstrumentto
beslidcompletelyoutoftheinstallation.
3

HowtoConnect
AUDIOOUTPUTS
UsetheFIXEDOUTPUTjackstoconnecttoa con-
ventionalcontrolpreamplifierwhichhasitsownvolume
control.TheVOLUMECONTROLdoesnotaffectthe
outputofthetunerattheFIXEDOUTPUTjacks.
TheoutputimpedanceattheFIXEDOUTPUTSis
600ohms.Longercablesthanarenormallysupplied
canbeusedtointerconnecttheMR77withotherequip-
ment.Thelengthofthecableislimitedbythecapacity
ofthecable.Thetotalcapacitymustnotexceed1600
pF.Forinstance:cableswitha capacityof32pFper
footmaybe50feetlong;16pFperfootcablemaybe
100feetlong.
UsetheFRONTPANELCONTROLLEDjackstocon-
necttoa conventionalcontrolpreamplifierwhenuseof
thetunervolumecontrolisdesired.Thesejacksmay
beusedtoconnecttoexternalequipmentsuchaspower
amplifiersortaperecorderswherecontrolofvolumeat
thetunerisnecessary.Theloadimpedanceconnected
tothefrontpanelcontrolledpacksshouldnotbeless
than47,000ohms.Thereisnodifferenceinthesignal
qualityormaximumoutputlevelsavailableateachpair
ofoutputjacks.
CONNECTINGANFMANTENNA
Oneofthreeantennasystemscanbeused:(1)an
outdoorFMantenna,(2)a VHF-TVantenna,or(3)the
indoordipolesuppliedwiththeMR77.
Anoutdoorantennaisrecommendedforoptimum
performanceinallareas.Infringe(outlying)areas,best
resultswillbeobtainedwitha highlydirectionalFM
antennausedinconjunctionwitha rotator.Rotatethe
antennauntilthebestreceptionisobtained.Connect
the300ohmantennatothe300WANT(red)terminals.
CONNECTINGA 75OHMANTENNA
Anunbalanced75ohmantennacanbeconnected
totheMR77.A "typeF"connectorisusedtoconnect
the75ohmcoaxialcabletothebackpanel75WANT
input.
AVHF-TVantennaisofteneffectivebutthean-
tennamustbedesignedforbothFMandTVreception.
ConnecttheleadsfromtheVHF-TVantennatothe
300ohmANT(red)terminals.
CONNECTINGANINDOORDIPOLEANTENNA
Theflexiblefoldeddipoleantenna(300ohm)isfor
useinurbanorhighstrengthsignalareas.
Connectthetwoleadsfromthedipoletothe300W
ANT(red)terminals.Theflexibilityofthethinflatwire
assemblypermitsittobeplacedundera rug,tacked
behindthestereo...or,placedinanyotherconven-
ientlocation.Insomecases,itmaybenecessaryto
"position"theantennaforbestsignalreception.This
shouldbedonebeforeitispermanentlylocated.Avoid
locatingthisantennanexttootherwiresormetalob-
jects.Thisantennamaynotproveeffectiveinhouses
havingmetalsidingormetal-cladinsulation.
4

FMANTENNA
OPTIONAL
75W
ANTENNA
LEAD-IN
POWERAMPLIFIERPREAMPLIFIER
LEFTSPEAKER
RIGHTSPEAKER
BackPanelInformation
TP1andTP2
TestpointTP1andTP2isusedwiththeMclntosh
MaximumPerformanceIndicator.
117V.ACOUTLET
Provides117voltACpowerupto350wattsforaddi-
tionalequipmentsuchasamplifiers,etc.Thisoutlet
isnotfused.Itturnsonandoffwiththefrontpanel
ACpowerswitchontheVOLUMEcontrol.
ACPOWERCORD
ConnecttheACpowercordtoa 117volt,50to60Hz
powerlinereceptacle.ThepowerusedbytheMR77is
35watts.
FUSE
A0.5AMPfuseprotectsthetunercircuits.Thisfuse
doesnotprotectadditionalequipmentconnectedto
thebackpanelACoutlet.
ANTENNACONNECTIONSTRIP
Provideseasypushtypeconnectorsfor300ohmFM
antennaanda groundconnection.
FMANTENNA—75OHM
Providesa "typeF"connectorfora 75ohmun-
balancedFMantenna.
AUDIOOUTPUTS
Theleft-handpairofAUDIOOUTPUTjacksprovides
FIXEDOUTPUTaudiosignals.Theprogramatthese
jacksisunaffectedbytheMR77frontpanelVOLUME
control.Usetheseoutputjackstoconnectthetuner
5

toa stereocontrolpreamplifierwhichhasitsown
mastervolumecontrol.
TherighthandpairofAUDIOOUTPUTjacks,pro-
videsFRONTPANELCONTROLLEDaudiosignal.The
programatthesejacksiscontrolledbytheMR77front
panelVOLUMEcontrol.Usetheseoutputjackstocon-
necttoexternalpoweramplifier,taperecorders,or
anyequipmentwhichrequirescontinuousfrontpanel
controloftuneroutputvolume.
TUNINGDIAL
TheMR77hastwodialscales:
1.FM—Marked88to108MHz
2.Loggingscale—Marked0 to100
Theloggingscalecanbeusedtoaccuratelyretune
anystation.Youmayfinditeasiertokeepa recordof
yourfavoritestationsbyuseoftheloggingscale.
Asmallportionofdialpointerhasbeenilluminated
toincreasetheeaseoftuning.
INDICATORS
TherearefourindicatorsontheMR77dialpanel.
Theyare:STEREOindicator,MULTIPATHindicator,
SIGNALSTRENGTHmeter,andtheTUNINGmeter.
MULTIPATHINDICATOR
TheMULTIPATHindicatorisanexclusiveMclntosh
development.
TheproperuseoftheMULTIPATHindicatormakes
itpossibletoimproveFMreceptionwithpreciseFM
antennapositioning.
Anelectronrayindicatorisusedtoshowmultipath
reception.Itoperatesbymovementofelectronbeams
insidea vacuumtube.Whenrotatingtheantenna,ob-
servationofthemultipathindicatorwillshowbest
orientationfortheFMstationbeingreceived.Multipath
distortioncausesthetwobeamsontheindicatorto
fluctuaterapidly.Whentheantennaisrotatedtothe
bestposition,theindicatorbeamstendtoremain
steady.Thedirectionalantennaisthenpickinguponly
thedesiredsignalandrejectingthereflectedmultipath
signals.Insomelocationsitispossibleforthebest
receptiontooccurwhenpickingupa strongreflected
signalratherthanthedirectsignal.Multipathdistortion
ispracticallyindependentofsignalstrength.
STEREOINDICATOR
TheSTEREOindicatorlightsredwhenthedial
pointeristunedtoorcrossesa stationbroadcasting
the19kHzcarrierforstereo.Thespecialcircuitused
willlightonlywhenthe19kHzmultiplexcarrieris
presentinthesignal.Theindicatorwillnotlighton
noisepulsesorinterference.
SIGNALSTRENGTHMETER
TheSIGNALSTRENGTHmeterindicatesthestrength
ofthesignalasreceivedfromtheantenna.Thehigher
theindication,thestrongeristhesignal.
FMTUNINGMETER
AnFMstationiscorrectlytunedwhenthemeter
needleisintheblackareaoftheFMTUNINGmeter.
TheactionoftheTUNINGindicatorisindependentof
stationsignalstrength.
MODESELECTOR
Selectsoneofthreeoperatingconditions:
FM-MONO— Inthispositionallbroadcastswillbe
heardmonophonically.Thispositionbypassesthe
automaticstereoswitching.Thestereoindicator
willstilllightwhena stationistransmittingstereo,
6
FrontPanelInformation

buttheprogramheardfromtheloudspeakerswill
bemono.
AUTO— TheFMpositionprovidesmonophonicFM
orFMstereoattheleftandrightchannelaudio
outputjacksautomatically.WiththeMODESE-
LECTORintheFMpositiona stationbroadcast-
inga monophonicprogramwillbeheardinmono.
Whenthestationswitchestostereobroadcast,or
thetunerischangedtoa stereostation,thestereo
indicatorwilllightandtheMR77willautomatic-
allyswitchtostereooperation.Ifmonobroadcast-
ingisresumedtheMR77willautomaticallyswitch
tomono.
STEREO— Onlystationsbroadcastingstereocan
beheardinthisposition.Allmonophonicstations
andbackgroundnoisesaresuppressed.The
TUNINGmeterandSIGNALSTRENGTHmeter
functionnormally.
STEREOFILTER
TheSTEREOFILTERreducesnoiseonweakstereo
stations.
Position1 reducesnoisebyapproximately10dB.
Position2 reducesnoisebyapproximately20dB.
FMMUTING
Mutingsuppressesthebackgroundnoiseandhiss
normallyheardbetweenstations.Turnthecontrolto
eitherLOCALorDISTANTpositionformuting.Weak
stationsthatmaynotoverridenoiseandinterference
arealsosuppressedbythemuting.IntheACOUTposi-
tion,themutingisturnedoff.Thisallowsconventional
FMtuningwiththenoiseandinterferencepresent.
VOLUME
TheVOLUMEcontrolhasbeenprecisiontracked
throughoutthelisteningrange(0to—65dB)foraccurate
stereobalance.
ItadjuststheoutputlevelofthetunerFRONT
PANELCONTROLLEDAUDIOOUTPUTjacks.The
FIXEDOUTPUTjacksarenotaffectedbythevolume
control.
ACPOWERON/OFF
TheACpowerswitchispartoftheVOLUMEcontrol.
Turningthevolumecontroltotallycounterclockwise
turnstheACpowertotheMR77off.
PANLOCBUTTONS
Atthebottomofthefrontpanelcornersarethe
PANLOCbuttons.Aftera turnerisinstalledonthe
PANLOCshelf,depressingthePANLOCbuttonswill
lockthetunerfirmlyinposition.Depressingthe
PANLOCbuttonsa secondtimewillreleasethetuner.
Thetunercanthenbeslidforwardtotheinspection
LISTENINGTOMONOPHONICFM
TurntheMODESELECTORtoFMMONOtolisten
onlytomonophonicFM.
TurntheSTEREO-FILTERtoOUT.
TurntheMUTINGcontroltoDISTANT.
Turnthetuningknobtothedesiredstation.The
stationisproperlytunedwhentheFMTUNINGmeter
pointercomestorestanywhereintheblackareaofthe
meterscale.Whiletuningacrossthedialyoumaynotice
movementofthetuningmeter,withouthearinga station.
Thisiscausedbya stationsoweakordistantthatit
doesnotover-ridethebackgroundnoise.Extremely
weakstationscanbeheardbyturningtheMUTING
switchtoOUT.
Rotatethedirectionalantennaforbestreceptionas
shownbytheSIGNALSTRENGTHandMULTIPATH
indicators.
AdjusttheVOLUMEcontroltodesiredlisteninglevel.
LISTENINGTOSTEREOFM
IfyouwishtohavetheMR77automaticallyswitch
toa stereobroadcast,settheMODESELECTORtoFM
AUTO.
WhentheSTEREOindicatorislighted,thestation
isbroadcastinga 19kHzcarrierforstereoandthe
MR77willautomaticallyswitchtostereo.Ifa station
isbroadcastingmonophonicFMprogram,andisnot
transmittingthe19kHzcarrierforstereo,theSTEREO
indicatorwillremainoffandthetunerwillautomatically
switchtomono.
RepeatthesameprocedureasforMonophonicFM
butsettheMODESELECTORtoFMAUTO.
WhenMR77MODEselectorissettoSTEREOonly
stereostationswillbereceived.Monostationsand
backgroundnoisebetweenstationwillbemuted.
Thestereofilterswitchreducesnoiseonweak
stationsinposition1 and2.
ListeningtotheMR77
andadjustmentposition.ThePANLOCsystemgives
youabsoluteeaseofinstallation,operationandmain-
tenance.
SECONDARYCONTROLS
Onthetopofthechassisbehindthefrontpanelis
theDIALSCALEINTENSITYswitch.
DIALSCALEINTENSITY
Adjustthebrightnessofthedialpanellightsby
meansofthisswitchonthetunertoppanel.Setthe
switchtoBRIGHTformaximumpanellight.Setthe
switchtoDIMforlowerdiallight.
7

TechnicalDescription
TheMR77FMtuneristheendresultofovernine
yearsofintensiveresearch.
TwentyyearsagoMclntoshdevelopedthefirstlow
distortionpoweramplifier.Now,theworld'sfirstlow
distortionFMtuner— TheMR77— hasarrived.Justas
oldconceptswereabandonedinordertoachievethe
improvementinamplifierperformance,sohaveold
ideasbeenforgottenincreatingtheMR77.
Hereisa descriptionofthesemonumentalchanges
thathaveproducedsucha superiorproduct.
FRONTEND
FMsignalsenterthetunerthroughtheantenna
terminals.A coaxialcableisusedtoconductthesignal
tothefrontend.Inthefrontendthestationsaresepa-
rated,amplified,andconvertedtoa common10.7MHz
IFfrequency.Insteadofusinga conventionaleasily
overloadedsmalltransistororFETasa straightRF
amplifier,theMR77takesa differentapproach.A
ruggedJunctionFieldEffectTransistorisusedasanim-
pedanceconvertertodrivea real5-wattpowertransistor.
Thisheftycombination(calleda cascodecircuit)makes
theRFamplifiervirtuallyimpossibletooverloador
crossmodulate.Asanexample,ifyouaretunedtoa 3-
micro-voltsignalat96.3MHz,theMR77willrejectsig-
nalselsewhereonthedialwhichareatleast4,000,000
timesstronger.Forexample,a 12-voltsignalreceivedat
104.3MHzwouldnotbotherthesignalat96.3MHzatall.
And,whentunedto104.3MHz,yourtunerwillnotover-
load.AllMR77tunersmustpassthe12-voltoverload
test.
Asix-gangtuningcapacitorisusedwiththispower-
fulRFamplifier.Thispermitsover100dBrejectionof
spurioussignals(IHF).
AnotherdesignfirstintheMR77frontendisthe
integratedcircuitbalancedmixer.Thismixerisimmune
tooverload,oscillatorpulling,crossmodulation,and
othertypesofdistortionsocommoninordinarytran-
sistororFETmixers.A balancedbifilartransformer
couplesthe10.7MHzmixeroutputtotheIFamplifier.
CompletingtheMR77frontendistheoscillator.It
usesa balancedtankcircuit.Theoscillatorisfreefrom
spuriousradiations,andoperatesathighefficiency.
AFCisnotrequired.
IFAMPLIFIER
TheMR77usesthefirstlinearphaseIFfilters.The
filter,designedfroma FORTRANcomputerprogram,is
forminimum-phaseandconstantdelay.Themathe-
maticalcomplexityofthefilterdesignprocedureis
almostbeyondbelief.Usingnumericalintegrationin
theS-Plane,an"IBM"1130highspeedcomputerspent
eighteenminutesonthemathematicsforthedesignof
theMR77IFfilter.Itwouldhavetakena humanengi-
neer,workingtwenty-fourhoursa day,sevendaysa
week,andworkingerror-freethree-hundredyearsto
performthesamemathematicalcalculations!
Ordinary"wide-band"IFfilterconceptsnolonger
applywiththeadventofthisnewfilter.TheMR77has
thenarrowestIFbandwidtheverusedina stereotuner
-only150kHzwideatthe6 dBpoints.Thisisenough
widthtoletjustoneFMstationsqueezethrough.
WithtremendousselectivityoftheMR77(480kHz
wideat60dBdown)youwillhearstationsloudandclear
thatareabsolutelyinaudibleontheothertuners!
TheIFfilterhasflattimedelayinitspassband
region.AnyerrorintimedelaycausesFMdistortion.
AllotherIFfiltershavedelaydistortion,someasmuch
as100%.TheMR77filterhaslessthan1.0%delaydis-
tortionfromantennainputtodiscriminatoroutput!
LINEARPHASEBRIDGEDISCRIMINATOR
TheadvantagesoftheIFfilterwouldbelostifithad
toworkintoanordinaryFMdetector.Thus,a newdetec-
torhadtobedeveloped.Itisthelinearphasebridge
discriminator.Thelinearphasebridgediscriminator
usesa balancedtransmissionlinebridgeinconjunction
witha differentialvoltage-doublingrectifiertoachieve
nearlydistortionlessdemodulationofFMsignals.A U.S.
PatentispendingonthisnewFMdetector.
STEREODECODER
Anintegratedcircuitaudioamplifierwithover120
dBofnegativefeedbackintwoloopsisusedtodrive
thestereodemodulator.Thisnewcircuitkeepsthe
distortionlowinthestereomodeofoperation.Highly
stablepilotrecoverycircuitsareusedtominimize19
kHzintermodulationbeats.Youwillhearcrystal-clear
stereoontheMR77.
Muting,stereoonly,andautomaticstereo/mono
switchingarefunctionsalsoperformedwithinthestereo
decoder.
AUDIOPREAMPLIFIERSECTION
Theaudioamplifierincreasesthelevelofthepro-
gramadequatetodrivea preamplifierorotheraccessory
equipment.Itconsistsoftwo,threetransistoramplifiers,
oneforeachchannel.Thedesignusesconsiderablenega-
tivefeedbacktohelpachievelowdistortion,widefre-
quencyresponse,andexcellentstability.Eachaudio
8

amplifierdelivers2.5voltstotheFIXEDOUTPUTjacks.
Asecondpairofoutputsareavailablewherelevelcanbe
variedbytheVOLUMEcontrol.
TheSTEREOFILTERisconnectedintheaudio
amplifiertoreducenoisewhenlisteningtoweakstereo
stations.Carefuldesignpermitsanidealcompromise
betweenchannelseparationandnoiserejectionwhen
usingtheSTEREOFILTER.
POWERSUPPLY
Specialdesignattentionhasbeengiventothepower
supplysection.Threeseparatepowercircuitsareused.
Thefirstisa 24voltregulatedsupply.This24voltregu-
latorisveryelaborateindesign,usinga speciallyse-
lectedtransistorandassociatedcircuit.Theregulator
useselectronicfilteringtoinsurethelowestpossible
backgroundhumlevel,maximumstabilityandextremely
goodregulation.Allsignalstagesarepoweredfromthis
regulator.
Thesecondcircuitisa halfwaverectifierandfilter
fortheDChighvoltageneededfortheanodeofthe
multipathindicator.Thethirdpowercircuitisa half
waverectifierwithelectronicfilterwhichsuppliesDC
tothemultiplexdecoder.
PerformanceLimits
PERFORMANCEGUARANTEE—Performancelimitsare
themaximumdeviationfromperfectionpermittedfora
Mclntoshinstrument.WepromiseyouthattheMR77
youbuymustbecapableofperformanceatorexceed-
ingtheselimitsoryougetyourmoneyback.Mclntosh
istheonlymanufacturerthatmakesthisguarantee.
SENSITIVITY:2µVfor35dBofquieting;2.5µAat100%
modulation(±75kHzdeviation)for3%totalnoiseand
harmonicdistortion
SIGNALTONOISERATIO:75dBbelow100%modu-
lation
HARMONICDISTORTION:0.2%monoorstereoat100%
modulation,20Hzto15,000Hz.Typically,0.05%at
1,000 Hz
DRIFT:25,000Hzinfirsttwominutes;thereafter5,000
Hzat25°Cin24hours
FREQUENCYRESPONSE:±1dB20Hzto15,000Hz
withstandardde-emphasis,(75µS)and19,000Hz
pilotfilter
CAPTURERATIO:0.25dBdetectoronly;2.5dB
completetuner
SELECTIVITY:Adjacentchannel6 dBIHF,carrier47
dBdown;Alternatechannel50dBIHF,carrier90dB
down
SPURIOUSREJECTION:100dBIHF
IMAGEREJECTION:100dB;88to108MHz(IHF)
MAXIMUMSIGNALINPUT:12voltsacross300ohms
antennaterminalswillnotincreaseharmonicorin-
termodulationdistortion
INTERMODULATIONDISTORTION:0.2%monoor
stereoforanycombinationoffrequenciesfrom20
Hzto15,000Hzwithpeakmodulationequalto100%
orless.Typically0.1%
AUDIOHUM:75dBdownfrom100%modulation
MUTING:70dBnoisereductionbetweenstations
MUTINGTHRESHOLD:Position1;5µV;Position2,
20µV
SCAFILTER:50dBdownfrom67kHzto74kHz;275
dBperoctaveslope
STEREOSEPARATION:40dBat1,000Hz
STEREOFILTER:10dBnoisereductioninposition1;
20dBnoisereductioninposition2
ANTENNAINPUTS:300ohmsbalanced;75ohmsun-
balanced
AUDIOOUTPUT:2.5voltsinto47,000ohms;1 volt
into600ohmsfromfixedoutput
POWERREQUIREMENT:120volts,50/60Hz.35watts
IFSYSTEM:8-PoleRimoFilter,2 IC's,1 J-Fet,and
push-pulloverlaypowertransistorstagedrivinga
linearphasebridgediscriminator
STEREOINDICATOR:Frontpanelstereolightactivated
by19,000Hzonly
AUTOMATICMONO-STEREOSWITCH:Mclntoshde-
veloped;allelectronicautomaticmono-stereo
switchingcircuit
SEMICONDUCTORCOMPLEMENT:21Transistors,24
Diodes,4 IntegratedCircuits,1 IndicatorTube
MECHANICALINFORMATION
SIZE:Frontpanelmeasures16incheswide(40.64cm)
by5-7/16incheshigh(13.81cm).Chassismeasures
15incheswide(38.1cm)by13inchesdeep(33.02
cm),includingPANLOCshelfandbackpanelcon-
nectors.Knobclearancerequiredis1½inches(3.81
cm)infrontofmountingpanel
FINISH:Frontpanelisanodizedgoldandblackwith
specialMclntoshgold/tealpanelnomenclatureillu-
mination.Chassisischromeandblack
MOUNTING:ExclusiveMclntoshdevelopedprofes-
sionalPANLOC
WEIGHT:27pounds(12.25kg)net,39pounds(17.69
kg)inshippingcarton
9

IFAMPLITUDERESPONSEANDTIMEDELAYCHARACTERISTICS
Performance
Charts
FREQUENCYINKILOHERTZ
INTERMODULATIONDISTORTION(STEREOANDMONO)
ft(TEST1000FREQUENCYINHERTZ)
10
20000 10000
1000
100
20
0
0.1
%IM
DISTORTION
0.2
0.3
20
100
FREQUENCYINHERTZ
1000
20000 10000
0
01
%
HARMONICDISTORTION
0.2
0.3
400
300
200 100
0
HARMONICDISTORTION(STEREOANDMONO)
-100
0.93
0.96
NORMALIZEDTIME
DELAY
0
-10
-20
-30
-40
-50
-60
-70
-8O
-90
AMPLITUDE
RESPONSE
INdB
1.0
1.04
1.02

0
-10
-20 -30
-40 -50
-60
-70
-75
11
AUDIOOUTPUTINdB
0.1µV1.0µV10µV
100µV
1mV
10mV100mV1.0V
10V
SIGNAL
PERFORMANCE
R.F.
INPUTSIGNAL
IN
VOLTS
ACROSS
300W

BlockDiagram
12

MclNTOSHLABORATORYINC.
2CHAMBERSST.,BINGHAMTON,N.Y.13903
607-723-3512
Designsubjecttochangewithoutnotice.
PrintedinU.S.A.
038-912
BE042003