McIntosh MR 71 User manual

FMSTEREO
TUNER MR71
CONTENTS
TABLEOFCONTENTS
OWNER'SMANUAL
INTRODUCTION
TECHNICALDESCRIPTION
FRONTPANELINFORMATION
BACKPANELINFORMATION
INSTALLATION
CONNECTING
AudioOutputs
StereophonicFMMultiplex
MonophonicFM
RemoteAmplifiers
Off-The-AirRecording
AntennaConnections
OPERATINGINSTRUCTIONS
StereophonicFMMultiplex
MonophonicFM
ADJUSTMENTS
MutingThreshold
DialPanelLights
OutputAdjust
GUARANTEE
MR71
1
2
6
8
8
9
9
9
9
9
9
9
11
11
11
12
12
12
12
13

THANKYOU
Judgingfromthestereoequipmentyouown,yourankhigh
amongdiscriminatingmusiclisteners.Youareprobablyno
freshmanwhenitcomestostereo.Never-the-lessweaskyou
toreadandcarefullyfollowtheseinstructionstoinsurea
successfulpartnershipbetweenyouandyournewstereo
equipment.
Younowhave"THEBEST."Usedproperlyyouareinfor
thousandsofhoursofmusicalenjoyment.
Ifyouareina hurry,readpage3 first.Thisgivesyoua brief
outlineofwhateachcontrolandindicatordoes.Readingtime
forthismanualis30minutes.Thisistimewellspent.
MR71FMSTEREOTUNER
INTRODUCTION
TheMclntoshMR71isa precisionengi-
neered,highlysensitiveFMMultiplexTuner.
TheresearchstaffofMclntoshLaboratory
hasdevelopedfivenewtunercircuitimprove-
mentsfortheMR71.
1.Automaticstereo-monoswitchingthat
is"clickless"andcompletelyelectronic.
(Patentappliedfor.)
2.Multipathindicatortoeliminatemulti-
pathreceptionbyshowingwhenyouranten-
naisrotatedtothecorrectpositionformini-
mummultipathdistortion.
3.Doubletunedinputcircuitsbeforethe
firstR.F.amplifiertoreducespuriousre-
sponses.
4.NewD'Arsonvalmovementmetersof
increasedsensitivitywhichdonotneedzero
settingadjustments.
5.A newcomputerdesignedfiltertore-
ducenoisefromstationsbroadcastingsub-
carrierauxiliarymusicservices.Noother
tunerusessucha filter.
TheMR71alsousestheexclusiveMc-
lntoshPANLOCmethodofinstallation.The
PANLOCsystemgivesyouabsoluteeaseof
installation,operation,andmaintenance.
PANLOCisthefirstprofessionalinstallation
techniquetobeusedonstereoinstruments.
InthePANLOCsystema metalshelfis
mountedfirst.Thetunerslidesintoposition
onthisshelf.DepressingthePANLOCbut-
tonsonthefrontpanellocksthetunerfirmly
intoplacefornormaloperation.Tounlock
thetunerdepressthePANLOCbuttonsa
secondtime.Thetunercannowslidefrom
thefrontpanel.Thetunerwilllockintothis
position,preventingaccidentalreleaseof
thetunerfromtheinstallation.Depressing
theholdinglatchesallowsthetunertobe
takenoutofthePANLOCshelfortoslide
backintopositionagainstthemountingpanel.
ThefinestpossiblereceptionofFMmono-
phonicandFMmultiplexstereophonicbroad-
castsisassuredbytheMclntoshMR71
tuner.
Onceyouhaveenjoyedtheoutstanding
performanceoftheMR71,youwillunder-
standwhyMclntoshproductshaveearned
theirreputationas"THEBEST."YourMc-
lntoshMR71tunerwillgiveyouyearsofthe
finestpossibleFMreception,andwillbea
valuedpartofyourhomemusicsystem.
1

TECHNICALDESCRIPTION
TheMR71tunerhasa 6DS4high-grain
NuvistorforthefirstRFamplifier.TheNuvis-
tor(triode)operatesintoa secondtriodetube
toforma cascadeamplifier.Carefuldesign
oftheoperatingcharacteristicsallowsthe
cascadeamplifiertohandlea widedynamic
rangeofsignalswithexcellentsignal-to-
noiseratio.
Adouble-tunedRFinputcircuitcombined
withtheNuvistor-tubecascadeamplifier
reducesspurioussignalstoanextremelylow
value.Sensitivityisincreasedtothehighest
possiblerating,whilestillretaininghigh
selectivity.
AnewlydevelopedAutomaticFrequency
Control(AFC)circuitgreatlysimplifiestuning.
Asthetuningknobismoved,theAFCcircuit
automaticallycutsoffforsharpesttuning.
Afterthestationistunedin,theAFCcircuit
graduallycomesintooperationovera 3
secondinterval.TheAFCactionautomatically
bringsthetuningtominimumdistortion.This
automatictuningrepeatsitsactioneach
timethetuningdialismovedtoa newsta-
tion.TheamountofAFCactionisfullyad-
justablewitha frontpanelcontrol.
TheAFCcircuitisunique.Itusesa silicon
diodeinplaceofa conventionaltube.The
silicondiodeimprovestheoverallAFCper-
formance.Itisunaffectedbytemperature
changes.Ithasnowarm-updriftandelimi-
natesthechanceoftubefilamenthum.A
temperature-compensatednarrowbandde-
tectorsuppliesoperatingsignalstotheAFC
circuit.ThisinsurespositiveAFCaction.The
narrowbanddetectoralsooperatestheFM
tuningmeteramplifierandtheultrasonic
mutingcircuit.
TheMclntoshdevelopedultrasonicmuting
circuitautomaticallysuppressesallintersta-
tionnoise,includingthenoisesusuallyheard
tuninginandoutofa station.Weakordistant
stationsthatcan'toverridethebackground
noiseandinterferencearesuppressedbythe
muting.A frontpanelswitchallowsmutingto
becutoffforlisteningtoweakandnoisy
stations.A backpaneladjustcontrolisfac-
torysettothecorrectmutingthresholdlevel.
Themixeroutputisamplifiedthroughfive
intermediatefrequencystageswithflat-
toppedhighlyselectiveresponsecurves.
TheIFtransformershavewidebandre-
sponsewithmaximumadjacentchannel
rejection.ConstructionoftheIFtransformers
assureselectricalstabilityandresistanceto
mechanicalshockandvibration.Morethan
adequategainisprovidedtooperateboth
limitersontheweakestsignals.Twocom-
pletelimitersareusedforthebestpossible
signal-to-noiseratio.
Aseparatewidebanddetectorhandles
onlyaudiofrequenciesforlowdistortionand
widefrequencyresponse.
BoththeRFandIFcircuitsarecompletely
shieldedinexcessofFCCrequirementsfor
suppressionofradiationoftheFMoscillator
andIFfrequencies.
TheMR71multiplexdecoderusesa
Mclntoshdevelopeddetector.Theadvantage
ofthiscircuitistheeliminationofcritical
adjustmentsnecessarywithcommonlyused
multiplexmatrixingmethods.TheL-R(left
minusright)stereosidebandsaredetected.
ThenautomaticallycombinedwiththeL+R
maincarriersignal.Theleftandrightchan-
nelsignalsarethenproducedwithexcellent
separation.
Atemperaturestabilized19KCamplifier
locksina highlystable38KCsynchronous
oscillator.Thismethodgivesexceptional
noiseimmunity.Balanceddetectorscancel
the38KCsignalcomponentsintheoutput,
providinglowdistortionandreducedsus-
ceptibilitytospurioussignals.Taperecord-
inginterferenceisminimizedbythismethod.
Ahighlyselectivecomputerdesignedfilter
reducesnoisefromstationsbroadcasting
auxiliarymusicservices.Thefilterreduces
thefrequencybandfrom63-74KCapproxi-
mately50db.Thefilterresponseslopeis
275dbperoctave.Thenoiseiseliminated
withoutaffectingnormalprogrammaterial.
TheMR71hasa multiplexstereoindicator
whichlightswhenthedialpointercrossesa
stationbroadcastingmultiplexstereo.A
uniquecircuitusinga transistoroperatesthe
2

YourMclntoshMR71tunerwillgiveyoumanyyearsofpleasant
andsatisfactoryperformance.Ifyouhaveanyquestionsconcern-
ingtheoperationormaintenanceofthistunerpleasecontact:
CustomerService
MclntoshLaboratoryInc.
2ChambersStreet
Binghamton,NewYork
Ourtelephonenumberis723-5491.
Thedirectdialareacodeis607.
GUARANTEE
MclntoshLaboratoryIncorporatedguar-periodof90daysfromdateofpurchase,
anteesthisequipmenttoperformasadver-Thisguaranteedoesnotextendtocompo-
tised.Wealsoguaranteethemechanicalandnentsdamagedbyimproperusenordoesit
electricalworkmanshipandcomponentsofextendtodamageincurredduringtranspor-
thisequipmenttobefreeofdefectsfora tationtoandfromMclntoshLaboratory,Inc.
3-YEARFACTORYSERVICECONTRACT
Anapplicationfora FREE3-YEARFAC-finedinthe3-yearfactoryservicecontract.
TORYSERVICECONTRACTisincludedintheIftheapplicationisnotmailedtoMclntosh
pocketinthebackcoverofthismanual.TheLaboratory,onlytheservicesofferedunder
FREE3-YEARFACTORYSERVICECONTRACT thestandard90-dayguaranteewillapplyon
willbeissuedbyMclntoshLaboratoryuponthisequipment.TAKEADVANTAGEOF3
receiptofthecompletelyfiledoutapplica-YEARSOFFREEFACTORYSERVICEBY
tionform.Thetermofthiscontractisde-FILLINGINTHEAPPLICATIONNOW.
Designsubjecttochangewithoutnotice.
13

MPXstereoindicatorlamp.Thetransistoris
controlledbya noise-rejectingdifferential
detectingbridgecircuit.Thecircuitdiscrimi-
natesbetweennoiseandthe19KCmultiplex
pilotsignal.Theindicatorwilllightonlyon
the19KCsignalpresentina multiplexstereo
broadcast.
TheMR71usesa newMclntoshdeveloped
automaticmono-stereoswitchingcircuit.
(Pat.Pend.)Theswitchingiselectronicwith-
outswitchingclicksortransients.
Thecircuitswitchessmoothlyandsilently
whenthe19KCmultiplexcarrierispresent.
Themultipathsignalindicatoronthetun-
ingdialisanelectronraytube.Thisisan
exclusiveMclntoshdevelopment.Multipath
signalreceptioncausesmoderatetosevere
distortionandpoorstereochannelsepara-
tion.Byknowingthepresenceofmultipath
reception,a directionalFMantennamaybe
rotatedtoreduceoreliminatethemultipath
signal.TheMR71multipathindicatorshows
iftherearemultipathsignalspresentby
rapidfluctuationoftheelectronraybeams.
Withtheantennacorrectlypositioned,the
indicatorbeamsremainrelativelysteady,
showingthatmultipathdistortionhasbeen
eliminated.
Twopairsofaudiooutputjacksareonthe
backpanel.Onepairofjacksiscontrolled
onlybythefrontpanelvolumecontrol.The
otherpairofjacksiscontrolledonlybythe
backpaneloutputadjustcontrols.Twostage
feedbacktypepreamplifiersonbothchan-
nelsprovidelowimpedanceoutputs.More
thansufficientoutputvolumeisavailableto
feedpoweramplifiersaswellaspreamplifiers.
Anewtypeofmechanicaltuningassembly
givestheMR71extremelysmoothflywheel
tuningaction.Thetuningcapacitorisdriven
directly,andinturndrivesthepointer.Back-
lashiseliminatedwiththisdesign.A teflon
linedpointercarriageandnylonpulleysre-
ducefrictionandweartogiveanunusually
smoothandquietdialaction.
IFYOUAREINA HURRY
Turnantennasotheeyeissteady.Willlightonlyonstations
broadcastingMPXstereo,Tuning. . . select
desiredstation
Tuneforcenterofblackarea.
In...eliminatesinterstation
noise.Out. . . usetoreceive
weakstations.
3
Continuouslyvariable,use
Max.positionforMPXreception.
automaticallyfromstereotomono.
Poweroff.Usestereo-auto
position:willswitch
TuneforMax.reading.
Adjusttodesiredvolume.

SPECIFICATIONS
UseableSensitivity
2.5microvoltsat100%modulation(±75KC
deviation)forlessthan3%totalnoiseand
harmonicdistortioninaccordancewith
IHFstandards.
AudioFrequencyResponse
Within½dbfrom20to20,000cycles.
Distortion
Lessthan0.5%at100%modulation±75KC
deviation
CaptureRatio
1.5dbat100%modulation.
Muting
IFinjectedultrasonicmuting:atleast60db
noisereductionbetweenstations.
OscillatorDrift
Lessthan25KCwithAFCdisabled;negli-
giblewithAFCinoperation.
ImageRejection
Betterthan80dbat90MC;betterthan
70dbat105MC.
Hum
Betterthan70dbbelow100%modulation.
Output
Approximately2.5volts;lowimpedance.
AntennaInputs
300ohmsbalanced;75ohmsunbalanced.
RFAmplifier
Cascodewith6DS4Nuvistorinfirststage.
IFStages
Five,with200KCbandwidth,flattop
response.
Limiters
Two.
Radiation
SubstantiallybelowFCCrequirements.
MultiplexChannelSeparation
Betterthan30db at1000cycles.
MultiplexFilter
Greaterthan48dbsuppressionof19KC
pilotand38KCcarrier.
MultiplexIndicator
Frontpanelmultiplexstereolightactivated
by19KCcarrier-only.
MultiplexType
Peak-detecting,selfmatrixingdetector.
SCAFilter
50dbdownat67KCto74KC275dbper
octaveslope.
AutomaticMono-StereoSwitch
AnexclusiveMclntoshdevelopment;all-
electronicautomaticmono-stereoswitch-
ingcircuit.(Pat.Pend.).
TubeandSemiconductorComplement
1-6DS4Nuvistor,1stRF.
1-12AT7,2ndRFandMixer.
1-6BN4A,Oscillator.
1-6AU6,1stIF.
1-6AU6,2ndIF.
1-6AU6,3rdIF.
1-6AU6,4thIFand1stLimiter.
1-6CS6,5thIF2ndLimiterandMuting.
1—6BN8,MutingAmplifier,Muting
Detector,AVCClamper.
2-6BL8,LeftandRight,1stand2nd
AudioAmplifiers.
1-6U8, MPX Amplifier, MPX Indicator
Control.
1-6HU6/EM87MultipathIndicator.
1-12AU7,MPXOscillator.
1-ST2-275,VoltageReference.
1-MA113 (Transistor), MPX Indicator
LampSwitch.
2-1N542 Diodes,WideBand
Discriminator.
2—1N542Diodes,NarrowBand
Discriminator.
4-1N542 Diodes,Balanced MPX
Detector.
2-1N542Diodes,BalancedDetectorfor
MPXIndicator.
2—SeleniumRectifiers,HighVoltage
PowerSupply.
1-No.1850Lamp,MPXIndicator.
Power Consumption
70watts,105to125volts,50to60cycles.
Dimensions
FrontPanel;16incheswideby57/16inches
high;chassis(includingPANLOCshelf)15
incheswideby5 incheshighby13inches
deep,includingconnectors;clearancein
frontofmountingpanelincludingknobs.
1½inches.
Weight
Chassisonly,27pounds.
Inshippingcarton,37pounds.
4

5
BLOCK
DIAGRAM
MR71

FRONTPANELINFORMATION
TUNINGDIALSCALES
TheMR71hastwodialscales,the88to
108scalemarkedinmegacyclesandthe
0-100loggingscale.Thedialscalemarked
inmegacyclesindicatesthepositionsofFM
stationsinthe88to108megacycleband.
Theloggingscalewithlineardivisionsfrom
0-100islocateddirectlybeneaththe88to
108scale.Theloggingscalecanbeusedto
accuratelyretuneanystation.Youmayfind
iteasiertokeepa recordofyourfavorite
stationsbyuseoftheloggingscale.
INDICATORS
TheMR71hasfourindicatorsonthe
dialpanel:MULTIPATHindicator,SIGNAL
STRENGTHindicator,STEREOindicator,and
theTUNINGindicator.
MULTIPATHINDICATOR
TheMR71MULTIPATHindicatorisanex-
clusiveMclntoshdevelopment.
TheMR71MULTIPATHindicatormakesit
possibletoimproveFMreceptionwith
preciseFMantennapositioning.
Reducenoiseduetomultipathreception.
Reducedistortionduetomultipathrecep-
tion.
Improvestereoseparationandtheaccu-
racyofyourSTEREOINDICATORbyreducing
multipathreception.
TheMR71MULTIPATHINDICATORshows
distortionfrommultipathsignalreception.
Multipathreceptioncausesthetwobeamson
theindicatortofluctuaterapidly.Whenthe
antennaisrotatedtothecorrectposition,
theindicatorbeamswillremainsteady.The
directionalantennaispickinguponlythe
desiredsignalandrejectingthereflected
multipathsignals.Insomelocations,itis
possiblethatthebestreceptionwilloccuron
astrongreflectedsignalratherthanthe
directsignal.Whenyoutunetoa different
station,themultipathindicatorwilltellyou
ifmultipathispresent.Multipathisinde-
pendentofsignalstrength.
STEREOINDICATOR
Thestereoindicatorwilllightwhenthedial
pointercrossesa stationbroadcastingmulti-
plexstereo.Thespecialcircuitusedwilllight
ONLYonthe19KCmultiplexcarrier.The
indicatorwillnotlightonnoisepulsesor
interference.
TUNINGINDICATOR
AnFMstationiscorrectlytunedwhenthe
indicatorisintheblackareaofthetuning
indicator.TheactionoftheTUNINGindicator
isindependentofstationsignalstrength.
VOLUME
Controlsvolumelevelwhenthetuneris
connectedtothepairofjacksmarked
FRONTPANELCONTROLLED.
6

MODESELECTOR
POWEROFF
TurnsoffthetunerACpowerandtheAC
outletonthetunerbackpanel.
MONO
ProvidesmonophonicFMatbothpairsof
leftandrightchannelaudiooutputjacks.
bringsthetuningtominimumdistortion.The
AFCactionrepeatsitselfeachtimethetuning
dialismovedtoa differentstation.
TheamountofAFCactionisadjustable
withtheAUTOFREQ.CONTROL.Fullleft
(MIN)positionofthecontrolcutsoffAFC
action.Fullright(MAX)positiongivesmaxi-
mumAFCaction.
Normally,thebesttuningoccurswiththe
AUTOFREQ.CONTROLsetatornearMAX
position.Ifseveralstationsareveryclose
togetheronthedial,orifa desiredstationis
veryclosetoa muchstrongerstation,a lower
AFCsettingisusuallyneededforbesttuning.
MUTING
STEREOAUTO
TheSTEREOAUTOpositionprovidesboth
monophonicFMandFMmultiplexstereoat
theleftandrightchannelaudiooutputjacks.
AssumeyouhavetheMR71MODESELEC-
TORintheSTEREOAUTOposition.Youare
listeningtoa stationbroadcastingFMmono-
phonic.ThestationswitchestoMPXstereo
broadcast.TheMULTIPLEXindicatorwill
light.TheMR71willautomaticallyswitchto
FMmultiplexstereooperation.Ifmono
broadcastingisresumedtheMR71will
automaticallyswitchtoFMmonophonic.
AUTOFREQ.CONTROL
TheAutomaticFrequencyControl(AFC)
circuitmakesFMtuningeasier.Iteliminates
thepossibilityoftunerdrift.TheAFCcircuit
intheMR71iselectronicallydelayedinits
action.ThisisanexclusiveMclntoshdevel-
opment.Whenthetuningdialismoved,the
AFCcircuitistemporarilycutoff.Whenthe
dialpointercomestorestona stationthe
AFCgraduallycomesintooperation.This
takesthreeseconds.TheAFCautomatically
OUT
OUT—Thispositionturnsoffthemutingto
allowconventionaltuningwithinterstation
noisepresent.Usethissettingtolistento
weakordistantstationsthathavenoiseor
interference.
IN—Thispositionturnsonthemutingcir-
cuit.Mutingsuppressesallbackgroundhiss
andnoiseusuallyheardwhentuningbe-
tweenstations.Weakordistantstationsthat
cannotoverridethebackgroundnoiseand
interferencearesuppressedbythemuting.
PANLOCBUTTONS
Atthebottomofthefrontcornersarethe
PANLOCbuttons.Aftera tunerisinstalledon
thePANLOCshelf,depressingthePANLOC
buttonswilllockthetunerfirmlyinposition.
DepressingthePANLOCbuttonsa second
time(aswitha ball-pointpen>willreleasethe
tuner.Thetunercanthenbeslidforwardto
theinspectionandadjustmentposition.The
PANLOCsystemgivesyouabsoluteeaseof
installation,operationandmaintenance.
7

BACKPANELINFORMATION
TP2
TestpointTP2 isprovidedfortunercircuit
alignment.Itisalsousedinconjunctionwith
theMclntoshMl2 orMl3.
OUTPUTADJ
Thisdualconcentriccontroladjuststhe
outputvolumelevelsattheleft-handpairof
AUDIOOUTPUTJACKS.Thecentershaft
adjuststheLEFTchanneloutput,andthe
outersleeveadjuststheRIGHTchannelout-
put.Theseoutputcontrolsettingsfortheleft
pairofjacksarenotaffectedbytheMR71
frontpanelvolumecontrol.
MUTINGADJ
Adjusttheoperatingthresholdoftheultra-
sonicmutingcircuit.
AUDIOOUTPUT-LEFT-RIGHT
Theleft-handpairofAUDIOOUTPUTjacks
providesaudiosignalsunaffectedbythe
MR71frontpanelVOLUMEcontrol.Thedual
concentricOUTPUTADJUSTcontrolssetthe
volumelevels.Usetheseoutputjackstocon-
nectthetunertoa stereocontrolpreampli-
fierwhichhasitsownmastervolumecontrol.
TherighthandpairofAUDIOOUTPUT
jacksprovidesaudiosignalcontrolledbythe
MR71frontpanelVOLUMEcontrol.Use
theseoutputjackstoconnecttoexternal
poweramplifier,taperecorders,orany
equipmentwhichrequirescontinuousfront
panelcontroloftuneroutputvolume.
300OHM-75OHMANTENNA
TerminalforconnectingFMantennasto
theMR71.
1ASLOBLOFUSE
A1 amp"Slo-Blo"fuseprotectsthetuner
circuits.Thisfusedoesnotprotectadditional
equipmentconnectedtothebackpanelAC
outlet.
ACOUTLET
Provides117voltACpowerupto350watts
maximumforadditionalequipmentsuchas
turntables,orothertuners.Thisoutletisnot
fused.Itturnsonandoffwiththefrontpanel
MODESELECTORswitch.
PANELLIGHTSWITCH
Adjuststhepanellightstobrightordim.
INSTALLATION
TheMclntoshMR71tunermaybein-
stalledona table,ona shelf,ina custom
built-incabinet,orina professionalequip-
mentrack.Forbestappearanceinanopen
installation,mounttheMR71intheattrac-
tiveMclntoshL11cabinet.TheL12isoiled
walnut.TheL11islacqueredwalnut.
TheMR71tunerisinstalledbythenew
exclusiveMclntoshPANLOCmethod.Refer
tothespecialPANLOCSYSTEMINSTALLA-
TIONinstructionsincludedwithyourMR71.
Allowatleast13¾inchesbehindthemount-
ingpanelfortheMR71chassis.Thisin-
cludesclearanceforleadsandconnectors.
Allowinsidedimensionsofatleast16½
inchesinwidthand6 inchesinheightfor
adequateaircirculation.Thebackofthe
MR71cabinetshouldbeasopenaspossible
forthebestventilation.Avoidmountingthe
tunerdirectlyovera poweramplifier.The
heatfromtheamplifiermaychangethe
precisiontunercalibration.Adequateventila-
tionwillgiveyourtunerlongtrouble-freelife.
8

CONNECTING
AUDIOOUTPUTS
UsetheFIXEDOUTPUTjacks(left-hand
pairofjacksnexttoOUTPUTADJ)toconnect
toa conventionalcontrolpreamplifierwhich
hasitsownvolumecontrol.Fulltuneroutput
isavailableatalltimesfromtheFIXED
OUTPUTjacks.
UsetheFRONTPANELCONTROLLEDjacks
toconnecttoa conventionalcontrolpre-
amplifierwhencontinuousfrontpanelcon-
troloftunervolumeisdesired.Thesejacks
maybeusedtoconnecttoexternalequip-
mentsuchaspoweramplifiersortape
recorderswherecontroloftunervolumeis
necessary.Thereisnodifferenceinthe
signalqualityoroutputlevelsavailableat
eachpairofoutputjacks.
STEREOPHONICFMMULTIPLEX
Connecta shieldedcablefromthetuner
LEFTchannelAUDIOOUTPUTjacktothe
controlpreamplifierLEFTchanneltuneror
auxiliaryinputjack.
Connecta secondshieldedcablefromthe
RIGHTchanneltunerAUDIOoutputjackto
thecontrolpreamplifierRIGHTchannel
tunerorauxiliaryinputjack.WhentheMR71
modeselectorissettoMONOorSTEREO
AUTOposition,a monophonicbroadcastwill
automaticallybepresentatbothleftand
rightoutputs.Fora stereobroadcastsetthe
MODESELECTORin theSTEREOAUTO
position.
MONOPHONICFM
TheMR71canbeusedstrictlyformono-
phonicreception.
Connecta shieldedcablefromeitherthe
leftorrightaudiooutputjacktothemono-
phoniccontrolpreamplifierauxiliaryortuner
inputjack.WiththeMR71MODESELECTOR
settoMONO,themonophonicFMsignal
appearsatboththeleftandrightchannel
AUDIOOUTPUTjacks.
REMOTEAMPLIFIERS
Thepairofaudiooutputjacksnotbeing
usedinaninstallationmaybeconnectedto
externalorremoteamplifiers.AnFMpro-
SEEDIAGRAM
gramcanthenbefedtospeakersystems
apartfromthemainsoundsystem.
OFFTHEAIRRECORDING
Taperecordersortapedeckswithrecord-
playbackpreamplifiersarenormallycon-
nectedtotheTapeOutputjacksonthecon-
trolpreamplifier.AnyFMprogramcoming
throughthetunerintothepreamplifiercan
berecordedontape.Youmayalsoconnect
theextrapairoftuneraudiooutputjacks
directlytotherecorderinputsifdesired.
ANTENNACONNECTIONS
SatisfactoryFMmultiplexstereoreception
requires10timesasmuchsignalasFM
monophonicreception.Monophonicinstalla-
tionsthatweresatisfactorywithanindoor
FMantennamayrequireanoutsideordirec-
tionalFMantennaforsatisfactorymultiplex
stereoreception.A gooddirectionalantenna
witha rotatormakesitpossibletoeliminate
orminimizemultipathdistortion.TheMR71
multipathindicatorshowsthecorrectan-
tennapositionforreceptionwithminimum
multipathdistortion.
INDOORFLEXIBLEFMDIPOLE
AconvenientflexibleindoorFMdipole
(300ohm)antennaissuppliedwiththe
MR71tuner.Thisantennaiseasytoinstall.
Itissuitablefora goodFMreceptioninhigh
signalareas.
Connectthetwoleadsofthedipolean-
tennatothetwoterminalsmarked300
OHMontheMR71backpanel.
Theflexibilityofthethinflatwireallowsthe
dipoletobeeasilylocatedbehindtheequip-
mentenclosureoranypositionnearthe
tuner.Openthedipoleintoa "T."Extendthe
NEXTPAGE
9

10

armsasstraightaspossible.Thedipole
antennaissomewhatdirectional.Itshouldbe
positionedforbestreceptionofthedesired
stations.
Experimentingwiththedipolepositionmay
benecessarytoreducemultipathdistortion
oncertainstations.Sinceitisnotconvenient
tocontinuallychangethepositionofthe
dipole,youmayhavetosetitforminimum
multipathonyourfavoritestation.
IMPORTANT
Keepthedipoleawayfromlarge
metalobjectsorsurfaces.Theyinter-
ferewiththeefficiencyoftheantenna.
AnoutdoorFMantennaisrecommended
forbestFMreceptionunderallconditions.
Infringeareas,a highlydirectionalFMan-
tennausedwitha rotatorwillgivethefinest
possibleFMreception.Rotatetheantenna
untilitpointsinthedirectionofthestationor
untilitreceivesthebestpossiblesignal.Use
themultipath,signalstrengthandtuning
indicatorstopositiontheantennacorrectly.
75OHMANTENNA
OUTDOORFMANTENNA
Anunbalanced75ohmFMantennacanbe
usedwiththeMR71.A BNCconnectoris
provided.Connecta MaleBNCconnector
tothefemaleBNCconnectorontherear
paneloftheMR71.
OPERATINGINSTRUCTIONS
STEREOPHONICFMMULTIPLEX
1.TurntheMODESELECTORtoSTEREO
AUTO.
2.TurnMUTINGtoIN.
3.TurntheFMTUNINGdialtothedesired
station.
TheTUNINGindicatorpointershouldbein
theblackareaofthetuningindicatormeter.
WhentheMPXSTEREOindicatorislit,the
stationisbroadcastinga 19KCcarrierfor
multiplexstereo.TheMR71willautomati-
callyswitchtostereoMode.Ifa stationis
broadcastingmonophonicFMprogram,the
MPXSTEREOindicatorwillremainoffand
thetunerwillautomaticallyswitchtoMono
Mode.
4.Adjustthevolumecontroltodesired
listeninglevel.
Ifthefixedaudiooutputjacksareused,the
tunervolumecontrolwillnotaffectvolume.
MONOPHONICFM
1.TurntheMODESELECTORtoMONOto
listenonlytomonophonicFM.
Note:Ifyouwishtoreceivemonophonic
FMandhavetheMR71automaticallyswitch
toa stereobroadcastavailableonthesame
stationsettheMODESELECTORtoSTEREO
AUTO.
2.TurntheMUTINGtoIN.
3.TurntheFMTUNINGKNOBtothe
desiredstation.TheTUNINGindicatorpointer
shouldbeintheblackareainthecenterof
theindicator.
4.Rotatethedirectionalantennaforbest
receptionasshownbythesignalstrength
andmultipathindicators.
5.AdjusttheVOLUMEcontroltodesired
listeninglevel.
11

ADJUSTMENTS
MUTINGTHRESHOLD
TheMR71ultrasonicmutingcircuitsup-
pressesallnoisebetweenstations.Itsup-
pressesallweakerstationsnotstrong
enoughtooverridethebackgroundnoise.
Themutingthresholdsettingdetermines
thestrengthofthesignalwhichcanbeheard
withmutinginoperation.Themutingthresh-
oldiscarefullyadjustedtooptimumatthe
factoryusingprecisiontestinstruments.
Casualadjustmentofthemutingthreshold
isnotrecommended.
Ifitisnecessarytoadjustthemuting
threshold,usetheMUTINGADJcontrolto
theRIGHT(clockwise)tolowerthemuting
threshold.Thisallowsweakerstationsto
beheardwiththeMUTINGINSETTING.
TurntheMUTINGADJcontroltotheLEFT
(counterclockwise)toraisethemutingthresh-
old.Thisallowsonlythemorepowerful
stationstobeheardwiththeMUTINGIN
setting.
DIALPANELLIGHT
Adjustthebrightnessofthedialpanel
lightsbymeansofthePANELLIGHTswitch
onthetunerbackpanel.Settheswitchto
BRIGHTformaximumpanellight.Setthe
switchtoDIMforlessdiallightandextended
lamplife.
OUTPUTADJUST
ThedualconcentricOUTPUTADJcontrols
(onthetunerbackpanel)adjusttheoutput
volumelevelofthelefthandpairofAUDIO
OUTPUTJACKS.Thecentershaftofthe
controladjuststheleftchanneloutput.The
outersleeveofthecontroladjuststheright
channeloutput.
Beforemakingtheadjustment,connect
thelefthandAUDIOOUTPUTjackstothe
tunerinputsofthecontrolpreamplifier.Set
thepreamplifierselectortophono.Setthe
volumecontroltonormallisteninglevelfor
astereodiscrecording.Switchthepreampli-
fierselectorbacktotuner.SettheMR71
MODESELECTORtoMONO.Tuneina local
station.TunetheOUTPUTADJcontrols
untilthelevelsofbothchannelsareequal,
andequaltothevolumelevelofthephono
recording.Youcannowswitchthepreampli-
fierselectorfromtheMR71tootherpro-
gramsourceswithoutreadjustingthemain
volumecontrol.
12

FMSTATIONLOG
STATION
DIAL
FREQ.
LOG
SCALELOCATION CITY,STATEANTENNA DIRECTION
REMARKS
MONO-STEREO-TIME-DATE

FMSTATIONLOG
STATIONDIAL
FREQ.
LOG
SCALE
LOCATION
CITY,STATEANTENNA
DIRECTION
REMARKS
MONO— STEREO— TIME—DATE

FMSTATIONLOG
STATION
DIAL
FREQ.
LOG
SCALELOCATION
CITY,STATEANTENNA DIRECTION
REMARKS
MONO— STEREO— TIME— DATE

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Phone-AreaCode607-723-5491
038-029
BE022003
PrintedinU.S.A.
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