McIntosh MX113 User manual

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Price$1.25
THEMclNTOSHMX113FM/FMSTEREO-AMTUNER-PREAMPLIFIER

YourMX113AM-FM/FMstereotuner
andstereopreamplifierwillgiveyou
manyyearsofpleasantandsatisfactory
performance.Ifyouhaveanyquestions
pleasecontact—
CUSTOMERSERVICE
MclntoshLaboratoryInc.
2ChambersStreet
Binghamton,NewYork13903
Phone:[phone]
WARNING:TOPREVENTFIREOR
SHOCKHAZARD,DONOTEXPOSE
THISUNITTORAINORMOISTURE.
TakeAdvantageof3 years
ofFREEService...
FillintheApplicationNOW.
THREEYEARSERVICECONTRACT
Anapplicationfora FREETHREEYEARSERVICECONTRACTisincludedwiththismanual.
Thetermsofthecontractare:ormishandlingisnotcoveredbytheSERV-
ICECONTRACT.
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
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© 1971byMclntoshLaboratoryInc.
CONTENTS
ServiceContract1
Installation2,3
HowtoConnect4,5
WhattheControlsDo
AndHowtoUseThem6,7
UsingthePushbuttons7
BalancingYourStereo8
ListeningtoYourStereo9
PerformanceLimitsand
Ratings10,11
PerformanceCharts12,13,14
TechnicalDescription15,16,17
BlockDiagrams18,19
StationLog20
1

Adequateventilationextendsthetrouble-freelifeof
electronicinstruments.Itisgenerallyfoundthateach10°
centigrade(18°F)riseintemperaturereducesthelifeof
electricalinsulationbyonehalf.Adequateventilationisan
inexpensiveandeffectivemeansofpreventinginsulation
breakdownthatresultsfromunnecessarilyhighoperating
temperatures.Thedirectbenefitofadequateventilation
islonger,trouble-freelife.
Allowatleast15inchesdeepx 17½incheswidex 6
incheshighformountingtheMX113.Alwaysallowforair
flowbyeitherventilationholesorspacenexttothebottom
oftheinstrumentanda meansforwarmairtoescapeat
the top.
Withadequateventilation,theMX113canbemounted
inanyposition.
TopreparetheMX113forinstallationremovethepro-
tectivecovering.TurntheMX113upsidedownsothatit
restsonitstopontheshippingpallet.Removethefour
plasticfeetfastenedtothebottomofthechassis.
Next,placethemountingbrackets,thepartsbagandthe
mountingtemplateathand.
ThePANLOCprofessionalmountingdesigneliminates
theneedforanyshelforbrackettosupporttheMX113.It
iscompletelysupportedbyitsownmountingbrackets.
Thedesignofthemountingtemplateallowsyoutoposi-
tionorlocatethecutoutfromthefrontorrearofthepanel
towhichtheinstrumentistobemounted.Positiontheplas-
ticmountingtemplateovertheareaofthepaneltobecut
outforinstallation.
Ifthecutoutistobelocatedfromthefrontofthepanel,
beginat2.Ifthecutoutistobelocatedfromtherearofthe
panel,beginhere.
1.Onthebackofthecabinetpanel,scribea verticalcen-
terlinethroughtheexactcenteroftheareainwhichthe
cutoutistobemade.
Placethetemplateagainstthebackofthepaneland
matchthetemplatecenterlinewiththecenterlineon
thecabinetpanel.
Makesurethatthereisatleast¼ inchclearancebe-
tweenthebottomofthedashedlineofthecutoutarea
onthetemplateandanyshelforbracebelowthepro-
posedcutout.
Markthetwolocatingholes("C"holesonthemounting
template).
Drillthetwolocatingholes.Becertainthedrillisper-
pendiculartothepanel.
Nowpositionthetemplateonthefrontofthepanelby
aligningthe"C"locatingholesonthetemplatewiththe
drillholes.
2.Ifthecutoutistobelocatedfromthefrontofthepanel:
Withthetemplateinplaceagainstthecabinetpanel,
markthe"A"and"B"drillholesandthefoursmall
holesthatidentifythecornersofthecutout.Jointhe
cornermarkswitha pencil.Theedgeofthetemplate
canbeusedasa straightedge.
2

IMPORTANT:DRILLTHE6 HOLESBEFOREMAKING
THECUTOUT.
Accuratelydrillthethreeholesoneachsideofthecut-
outareawitha 3/16inchdrill.
WiththesawontheINSIDEOFTHEPENCILLINES
carefullycutouttherectangularopening.
Securethemountingstripstotherearofthecabinet
panelusingtwoscrewsfromthehardwarepackage.
Insertthescrewsinthecenterholesofcabinetpanel
("B"holesonthetemplate)andtighten.Thescrewhead
shouldpullintothewoodslightly.(Usetwo¾ inchlong
screwsforpanelsunder½ inch,ortwo1¼inchlong
screwsforpanels½ inchthickandlarger.)
Attachthemountingbracketstothecabinetpanelusing
fourscrews.
Placethetemplateoverthemountingscrews.The
mountingscrewsshouldbecenteredinthe"A"and"B"
holesonthetemplate.Thesidesofthemountingbrackets
shouldmatchtheverticaldashlinesonthetemplate.If
necessary,loosenthescrewsandpushthebracketsinto
alignmentandretighten.
Insertthepowercordthroughtheopening.Carefully
slidetheMX113intotheopeningsotherailsonthebot-
tomoftheequipmentslideinthetrackofthemounting
brackets.Slidetheinstrumentinuntilitstopsattheadjust
positionlatches.Pressthelatchesinandcontinuetoslide
theinstrumentinuntilthefrontpanelisagainstthe
cabinetpanel.Atthebottomcornersofthefrontpanelare
thePANLOCbuttons.DepressingthePANLOCbuttons
willlocktheinstrumentfirmlyintheinstallation.Depress-
ingthePANLOCbuttonsa secondtimewillreleasethe
instrument.Youcanthenslidetheinstrumentforwardto
theinspection-adjustmentposition.Depressingtheinspec-
tion-adjustmentpositionlatcheswillallowtheinstrument
toslidecompletelyoutoftheinstallation.

HowtoConnect
CONNECTINGA RECORDPLAYERTOPHONO1
Connectthecablefromtheleftchanneloftherecord
playerintotheL PHONO1 inputjack.
Connectthecablefromtherightchanneloftherecord
playerintotheR PHONO1 inputjack.
PHONO2 isprovidedfortheuseofa secondrecord
player.
Connectthecablefromtheleftchanneloftherecord
playerintotheL PHONO2 inputjack.
Connectthecablefromtherightchanneloftherecord
playerintotheR PHONO2 inputjack.
AUX
Anyhighlevelprogramsourcesuchasanothertuneror
aTVsetcanbeconnectedtotheinputjacksmarkedAUX.
CONNECTINGA TAPERECORDER
ToRecord
Connecta cablefromtheL TAPEOUTPUTjacktothe
lefthighlevelinputofa taperecorder.
Connecta cablefromtheR TAPEOUTPUTjacktothe
righthighlevelinputofthetaperecorder.
ToPlayback/Monitor
Connectthecablefromtheleftchanneloutputofa tape
recordertothehighlevelinputs. . . L TAPE.
Connectthecablefromtherightchanneloutputofa
taperecordertothehighlevelinputs.. . R TAPE.
CONNECTINGTHEMX113TOPOWERAMPLIFIERS
ConnecttheMAINOUTPUTjackstotheinputofa stereo
poweramplifier.TheL jackisconnectedtotheleftampli-
fierinputjack.TheR jackisconnectedtotherightampli-
fierinputjack.
TheoutputsourceimpedanceattheMAINOUTPUTis
200ohms.Longercablesthansuppliedcanbeusedbe-
tweentheMX113andtheamplifier.Thelengthofthe
cableislimitedbythecapacityofthecable.Thetotal
capacitymustnotexceed1,000pF.Forinstance:cables
witha capacityof25pFperfootmaybe40feetlong.
13.5pFperfootcablemaybe75feetlong.Theinput
impedanceoftheamplifiersshouldbe47,000ohmsor
greater.
L+ R OUTPUT
UsetheL + R OUTPUTtofeedleftplusrightsignaltoa
separatepoweramplifierformonophonicbackground
musicorfora centerchannelspeaker.
CONNECTINGANFMANTENNA
Satisfactorystereowheremonoreceptionhasbeen
satisfactoryrequiresabouttentimesasmuchsignalfrom
theantenna.Monophonicreceptionthatissatisfactory
onanindoorantennamayrequiretheuseofanoutdoor
antennaforstereoreceptionofequivalentquality.
WiththeMX113oneofthreeantennasystemscanbe
used:(1)theindoordipolesuppliedwiththeMX113,
(2)anoutdoorFMantenna,or(3)anallchannel(UHF-VHF-
FM)antenna.Infringeareasbestresultswillprobablybe
obtainedwiththeuseofanoutdoorFMantenna.Inmany
areastheindoordipolemaybesatisfactory.
CONNECTINGANINDOORDIPOLEANTENNA
Theflexiblefoldeddipoleantenna(300ohm)supplied
withtheMX113isforindooruseinurbanorhighstrength
signalareas.
Connectthetwoleadsfromthedipoletotheterminals
markedFMANT(red).Theflexibilityofthethinflatwire
assemblypermitsittobeplacedundera rug,tackedbehind
thestereo...or,placedinanyotherconvenientlocation.
Insomecases,itmaybenecessaryto"position"thean-
tennaforbestsignalreception.Thisshouldbedonebefore
itispermanentlylocatedortackeddown.Keeptheantenna
awayfrommetalobjects.Donotattachtoa metalsurface.
CONNECTINGANOUTDOORFMANTENNA
Anoutdoorantennaisrecommendedforoptimumper-
formanceinallareas.Infringe(outlying)areas,bestresults
willbeobtainedwitha highlydirectionalFMantennaused
inconjunctionwitha rotator.Rotatetheantennauntilthe
bestreceptionisobtained.Connectthe300ohmantennato
theterminalsmarkedFMANT(red).
CONNECTINGA 75OHMCOAXIALANTENNA
Anunbalanced75ohmantennacanbeconnectedtothe
MX113withcoaxialcable.Connectthecenterconductor
totherightFMANT(red)connector.Theshieldisconnected
totheGND(black)connector.
CONNECTINGANAMANTENNA
Ahigh-qualityloopstickantennaisprovided.Itcanbe
rotatedthroughnearly180°inalldirectionsformaximum
performance,optimumsignalreceptionorminimuminter-
ference.Withthismobilityyouwillnotsufferlossofsen-
sitivityregardlessoftheangleatwhichtheinstrumentis
mounted.A backpanelantennajackisprovidedforcon-
nectinganexternalantennaifdesired.
ACPOWEROUTLETS
TherearetwoblackACpoweroutlets,andoneredAC
poweroutlet.TheACpowertotheblackoutletsiscontrolled
bythefrontpanelswitch.Usetheseoutletsfora poweram-
plifier,ortaperecorder,etc.Theredreceptableisonatall
times.Usetheredoutletfora turntableorrecordchanger.
Theturntableisprotectedbythisarrangement.Itisneces-
sarytoturnofftheturntableorrecordchangerwithits
ownACpowerswitch.
GROUNDCONNECTION
Asinglegroundpostisprovided.Groundsforturntables,
recordchangers,tapedecks,etc.shouldbeconnectedto
thispost.Theleftandrightprogramcablesandtheground
wirefromthatsourceshouldbelooselytwistedtogether.
Toavoidhum,makesurethegroundwiredoesnotmake
anycontacttotheshieldsoftheleftandrightprogram
cablesbetweentheprogramsourceandtheMX113.
4

LEFTSPEAKERRIGHTSPEAKER
TO120VACOUTLET
POWER
AMPLIFIER
TURNTABLE
TAPERECORDER
AMANTENNA
FMANTENNA
5

WhattheControlsDoandHowtoUseThem
INPUTSELECTOR
Selectanyoneoffiveprogramsources:
AUX:Connectstheoutputfromanyhighlevelprogram
sourcerequiringflatamplificationtothehighlevel
inputstage.IntheAUXpositionthegainis20dBto
theMAINoutputsand0 dBtotheTAPEoutputs.Thein-
putimpedanceis250,000ohms.
TAPE:Connectstheoutputfroma completetapere-
cordertothehighlevelinputstageoftheMX113.The
TAPEpositionhasflatamplification.Thegainis20dB
totheMAINoutputs.Thegainis0 dBtotheTAPE
outputs.
AM:ConnectstheAMtunerportionoftheMX113to
theoutputjacks.
FM:ConnectstheFMtunerportionoftheMX113to
theoutputjacks.
PHONO1:Connectstheoutputofanymagneticphono
cartridgetothelowlevelinputstage.Theresponseof
thelowlevelstageshasbeenshapedtoconformto
RIAAstandards.Thegamat1000Hzis62dBtothe
MAINoutputs;42dBtotheTAPEoutputs.Theinput
impedanceis47,000ohms.
PHONO2:SameasPHONO1
BASS
TheBASSisa concentriccontrol.Theouterknobcontrols
thelowfrequencyresponseintherightchannel.Thecenter
knobcontrolsthelowfrequencyresponseintheleftchan-
nel.Thetwoknobsarefrictioncoupled.Thispermitsthem
tobeadjustedtogetherorindependently.Clockwiserota-
tionincreaseslowsandcounterclockwisedecreaseslows.
Turnthecontroltothecenterpositionforflatresponse.
TREBLE
TheTREBLEisa concentriccontrol.Theouterknobcon-
trolsthehighfrequencyresponseintherightchannel.The
centerknobcontrolsthehighfrequencyresponseinthe
leftchannel.Thetwoknobsarefrictioncoupled.Thisper-
mitsthemtobeadjustedtogetherorindependently.
Clockwiserotationincreaseshighsandcounterclockwise
decreaseshighs.Turnthecontroltothecenterpositionfor
flatresponse.
BALANCE/LOUDNESS
TheBALANCE/LOUDNESSisa concentriccontrol.The
outerknobcontrolsthebalancebetweenchannels.The
centerknobisa switchthataddsloudnesscompensation
forlowvolumelistening.
BALANCE
TheBALANCEcontroladjustsforunequalvolumein
eithertheleftorrightchannels.Thevolumeofeachchan-
nelcanbevariedrelativetotheotherwithoutaffecting
theircombinedloudness.
LEFT. . . turningthecontroltotheleftaccentstheleft
channelbyreducingtherightchanneloutput
RIGHT. . . turningthecontroltorightaccentstheright
channelbyreducingtheleftchanneloutput.
LOUDNESS
TheLOUDNESScontrolautomaticallyprovidesthecor-
rectamountofbassrequiredtocompensateforthechange
inresponseofthehumanearatlow-loudnesslevels.
Whenthevolumeisreduced,themusicwillseemtolose
muchofitsbassandsomeofitstreble.Thiseffectisdue
tothesensitivitycharacteristicofhumanhearing.There-
sponseofthehumaneartobassandtreblepitchdecreases
6

morerapidlythanitsresponsetopitchcenteredinthemid-
tonalrange.TheLOUDNESSswitchconvertsthevolume
controltoa loudnesscompensatedcontrol.UseLOUDNESS-
INtolistenatlowvolumeandstillhearfull-frequencyrange.
VOLUMEON/OFF
TheVOLUMEcontrolregulatestheloudnessinboth
channels.TheVOLUMEcontrolhasbeenprecisiontracked
throughoutthelisteningrange(0to-65dB)foraccurate
stereobalance.Whenrotatedtothecounterclockwiseposi-
tiontheACpowertotheMX113isturnedoff.
UsingthePushbuttons
MODESELECTOR
Stereo
WiththepushbuttonattheOUTpositiontheleftchannel
isheardfromtheleftloudspeakerandtherightchannelis
heardfromtherightloudspeaker.
Mono(L+ R)
WiththepushbuttonattheINpositiontheleftandright
channelsareaddedtogetherandareheardfromboth
loudspeakers.
LFFILTER
WiththepushbuttonattheINpositionthelowfrequency
responseisattenuatedbelow50Hz.Theslopeis12dB
peroctave.UseoftheLFfilterreducesunwantedlowfre-
quencynoisesuchasrumble.Withthepushbuttonreleased,
theresponseoftheMX113isflat.
HFFILTER
WiththepushbuttonattheINpositionhighfrequency
responseisattenuatedabove5000Hz.Theslopeis12dB
peroctave.UseoftheHFfilterreducesunwantedhighfre-
quencynoiselikehissorscratch.Withthepushbuttonre-
leased,theresponseoftheMX113isflat.
TAPE
TheTAPEpushbuttonallowsinstantaneouscomparison
ofrecordedmaterialandtheprogramsource.Withthepush-
buttonattheINposition,therecordedtapeisheard.With
thepushbuttonattheOUTpositiontheprogrambeing
recordedisheard.
IMPORTANT:WhentheMX113isoperatedwiththe
TAPEpushbuttonattheINposition,signalfromany
othersourcewillnotbeheardfromtheloudspeakers.
Tohearanyotherprogramsource,thepushbuttonmust
beattheOUTposition.
MUTING
MUTINGsuppressesthebackgroundnoiseandhiss
normallyheardbetweenFMstations.Withthepushbutton
attheINpositionthemutingisturnedon.Weakstations
thatmaynotoverridenoiseandinterferencearealsosup-
pressedbythemuting.WiththepushbuttonattheOUT
position,themutingisturnedoff.Thisallowsconventional
FMtuningwiththebetweenstationnoiseandinterference
present.
SELECT
WiththeSELECTpushbuttonattheINpositiontheselec-
tivityoftheMX113isincreasedinbothFMandAM.The
sidesoftheIFcurvearecompressedwhichincreasesthe
abilityofthetunertoseparatea weak(distant)station
froma strong(local)stationonadjacentchannels.
PANLOC
MclntoshdevelopedPANLOCmountingbringsprofes-
sionalinstallationtechniquetostereo.Depressingthe
PANLOCbuttonswilllocktheinstrumentfirmlyinthe
installation.DepressingthePANLOCbuttonsa secondtime
willreleasetheinstrument.Itcanthenbepulledtoward
youtothe"adjustment"position.Inthispositionthetop
panelcontrolscanbeadjusted.
7

BalancingYourStereo
Theperformanceandenjoymentofa stereosystemis
greatlyincreasedwhenthesoundisproperlybalanced.
Thebalanceofthestereosystemisaffectedbymanythings
includingroomacoustics,furnitureplacement,roomshape,
smalldifferencesinloudspeakers,etc.Toassistyouin
balancingyourstereosysteminyourroom,hereisthe
proceduretodeterminecorrectphaseandprogramloudness.
TOADJUSTPHASE
1.Playa familiarrecord.
2.PresstheMODEpushbuttontotheMONOposition.
3.TurnBALANCEcontrolto12o'clockposition.
4.Standabout10feetinfrontofandmidwaybetweenthe
loudspeakers.Thesoundshouldappeartocomefrom
directlyinfrontofyou.Ifthesoundisnotdirectlyin
frontofyouwiththephaseswitchinthe0°NORMAL
position,reversetheleadsononeloudspeaker.When
thesoundcomesfromdirectlyinfrontofyouthe
speakersareinPHASE.UsethePHASEswitchtocorrect
foroutofphaseprogramsources.
TOBALANCELOUDNESS
1.PresstheMODEpushbuttontotheMONOposition.
2.Playa familiarrecording,
3.TurntheBALANCEcontroltothe12o'clockposition.
4.Whiletheprogramisplaying,standbetweenthetwo
loudspeakers.Listenfora differenceinloudnessbe-
tweenspeakers.Balancethesystembyadjustingthe
controlsonthepoweramplifiers.Next,settheMODE
selectortoSTEREO.Ifthereisthena differenceinloud-
nessturntheBALANCEcontroltowardthespeakerthat
isnotasloud.AdjusttheBALANCEcontroluntilthe
soundissatisfactorybetweenbothspeakers.
8

ListeningtoYourStereo
LISTENINGTOA STEREORECORD
TurntheINPUTSELECTORtoPHONO1 orPHONO2,
whicheverisconnectedtotherecordplayeryouwish
tohear.
MakecertaintheMODEPUSHBUTTONisintheOUTor
STEREOposition.
AdjusttheVOLUMEcontroltodesiredvolume.
LISTENINGTOA MONOPHONICRECORD
TurntheINPUTSELECTORtoPHONO1 orPHONO2,
whicheverisconnectedtotherecordplayeryouwish
tohear.
PushtheMODEpushbuttonINtoMONO.
AdjusttheVOLUMEcontroltodesiredvolume.
LISTENINGTOA STEREOTAPERECORDER
TurntheINPUTSELECTORtoTAPE.
SettheMODEpushbuttontoSTEREOorMONO,depend-
ingontheprogramonthetape.
AdjusttheVOLUMEcontroltodesiredvolume.
TORECORDONA STEREOTAPERECORDER
AllprogramsourcesareavailableattheTAPEOUTPUT
jacks.Theprogrammaterialisunaffectedbyallfrontpanel
controlsexcepttheINPUTSELECTOR,andtheuseofthe
SELECTbuttononAMandFM.
Tomonitorwhilerecording,thetaperecordermusthave
separaterecordandplaybackormonitorheads.TheTAPE
pushbuttonpermitsmonitoringthetaperecordingswhile
intheprocessofrecording.WhentheTAPEpushbuttonis
attheINpositionitwillplaythesoundfromthetapeas
itpassestheplaybackhead,a momentafteritisrecorded.
Therecordingprocesscontinuesasusual.WhentheTAPE
pushbuttonisattheOUTpositiontheprogrambeingre-
cordedisheard.
LISTENINGTOAM
TurntheINPUTSELECTORtoAM.
Rotatethetuningknobtothestationofyourchoice.
Adjustthevolumetoa comfortablelevel.
Separationof a weakstationfroma strongadjacent
stationcanbeimprovedwiththeSELECTbuttonatthe
INposition.
LISTENINGTOFMORFMSTEREO
TurntheINPUTSELECTORtoFM.
Rotatethetuningknobtothestationofyourchoice.
Separationofa weakstationfroma strongadjacent
stationcanbeimprovedwiththeSELECTbuttonat
theINposition.
WhentheSTEREOindicatorislighted,thestationis
broadcastinga 19,000Hzpilotsignalforstereoandthe
MX113willautomaticallyswitchtostereo.Ifa stationis
nottransmittingthe19,000Hzpilotsignalforstereo,
theSTEREOindicatorwillremainoffandthetunerwill
automaticallyswitchtomono.TheMX113usesa new
Mclntoshdevelopedautomaticmono-stereoswitchingcir-
cuit.Thecircuitactioniselectronicandpreventsswitching
clicksortransients.
Theultrasonicmutingcirciutsuppressesallnoisebe-
tweenFMstations.Italsosuppressesallweakerstations
notstrongenoughtooverridethebackgroundnoise.The
mutingthresholdsettingdeterminesthestrengthofthe
signalwhichcanbeheardwithmutinginoperation.Casual
adjustmentofthemutingthresholdisnotrecommended.
WhiletuningFMyoumaynoticethatthetuningmeter
willshowa stationyetnoprogramisheardfromthe
speakers.Themutingcircuitinthetunerhasrejectedthe
stationbecausethereisobjectionablenoisewiththeweak
signalfromthestation.PushtheMUTINGpushbuttonto
theOUTpositionandthestationwillbeheard.Mostpro-
gramsthatcanbetunedinthismannerareofpoorquality
duetointerferingnoise.
Theabilityto separatea weakstationfroma strongsta-
tionwillbeimprovedbytheuseoftheSELECTpush-
button.WiththepushbuttonattheINpositiona Mclntosh
developedcircuitcompressesthesidesoftheIFcurve
whichimprovestheseparationofweakstationsfromstrong
stationsonadjacentchannels.
9

PerformanceLimitsandRatings
Performancelimitsarethemaximumdeviationfrom
perfectionpermittedfora Mclntoshinstrument.Wepromise
youthattheMX113youbuymustbecapableofperform-
anceatorexceedingtheselimitsoryougetyourmoney
back.Mclntoshistheonlymanufacturerthatmakesthis
guarantee.
FM
USEABLESENSITIVITY
2.5microvoltsat100%modulation(±75kHzdeviation)
forlessthan3%totalnoiseandharmonicdistortion
SIGNALTONOISERATIO
70dBat100%modulation
HARMONICDISTORTION
Mono:0.3%at100%modulation±75kHzdeviation
Stereo:0.5%at100%modulation±75kHzdeviation
FREQUENCYRESPONSE
±1dBfrom20Hzto15,000Hzwithstandardde-emphasis
CAPTURERATIO
1.5dB
SPURIOUSREJECTION
90dBIHF
IMAGEREJECTION
95dB;88to108MHz (IHF)
STEREOSEPARATION
35dBat 1000 Hz
SELECTIVITY
AdjacentChannel—6dBIHFwithSELECTbuttonin
normal;15dBIHFwithSELECTbuttonattheIN
position
AlternateChannel—58dBIHFwithSELECTbuttonin
normal;88dBIHFwithSELECTbuttonattheIN
position
TUNINGINDICATOR
D'Arsonvalmovementmeter
STEREOINDICATOR
Stereolightactivatedby19,000Hzpilotsignalonly
AM
SENSITIVITY
75microvoltsat1,000kHz(usingexternalantenna
input)
SIGNALTONOISERATIO
45dB
HARMONICDISTORTION
1%at30%modulation
FREQUENCYRESPONSE
Down6 dBat3,500Hz
ADJACENTCHANNELSELECTIVITY
35dBwithSELECTbuttonattheOUTposition
45dBwithSELECTbuttonattheINposition
IMAGEREJECTION
65dB;540kHzto 1600 kHz
PREAMPLIFIER
FREQUENCYRESPONSE
±0.5dB,20to20,000Hz
DISTORTION
0.1%at2.5voltsoutput,20to20,000Hz
INPUTSENSITIVITY
PHONO1 andPHONO2:2 millivoltsfor2.5voltsoutput
at 1,000 Hz
AUXandTAPE:0.25voltsfor2.5voltsoutput
INPUTIMPEDANCE
PHONO1 andPHONO2:47,000ohms
AUXandTAPE:250,000ohms
VOLTAGEAMPLIFICATION
PHONO1,PHONO2 toMAINoutput62dB,toTAPE
output42dB
AUXandTAPEtoMAINoutput20dB;toTAPEoutput0dB
HUMANDNOISE
PHONO1 andPHONO2:72dBbelow10millivolt
input;equivalenttolessthan3 microvoltsattheinput
terminals.
AUXandTAPE;85dBbelow2.5voltsoutput,un-
weighted
BASSCONTROL
-18dBto+16dBat20Hz
TREBLECONTROL
±20dBat20,000Hz
LFFILTER
Flatorrolloffbelow50Hz,down12dBat20Hz
HFFILTER
Flatorrolloffabove5,000Hz,down12dBat20,000Hz
OUTPUT
Main:2.5voltswithratedinput.Upto10voltscanbe
developedwithoutincreaseindistortion.FMandAM
willproduce10voltsoutputat100%modulation.
Tape:0.25voltswithratedinput.Phonoinputsignalof
10

10millivoltsproduces1.2voltsoutput.FMand
willproduce1.2voltsoutputat100%modulation.
L+ R:2 voltswithratedinput
GENERAL
TRANSISTORCOMPLEMENT
2-JFET
3—MOSFET
30—SiliconPlanar
31—Diodes
2IntegratedCircuits—(eachcontainstheequivalentof
16transistorsand8 diodes)
POWERREQUIREMENTS
120volts,50/60Hz,30watts
FACILITIESANDFEATURES
VOLUMECONTROL:Precision"tracked"atalllistening
levels.(0to-65dB).Doesnotchangestereobalanceas
loudnessischanged.TheACpowerON/OFFswitchis
coupledwiththiscontrol.
BALANCECONTROL:Naturalbalanceatcenterposition,
attenuationofleftorrightchannelbyrotatingcontrol.
LOUDNESS:Loudnesscompensatedorfatresponse—
Loudnesspositionboostslowfrequenciesforlowlevel
listening.Operatesasa functionofvolumecontrolposition.
Fullcompensationisobtainedatlowervolumelevelsand
flatresponseisobtainedatfullvolume.
SELECTIVITY:Increasestheabilityofthetunertoseparate
aweak(distant)stationfroma strong(local)stationon
adjacentchannels.
MUTING:Suppressesthebackgroundnoiseandhissnor-
mallyheardbetweenFMstations.
TAPEMONITOR:Pushbutton;comparesrecordedtapewith
programsourcewhilerecording.
MODE:Selectseitherstereoormonooperation.
PHASECONTROL:Electronicallyreversesphaseintheleft
channeltocorrect"outofphase"programsources.
MUTINGADJUST:Modifiesthenoiserejectionthreshold
onFM
DIALSCALEINTENSITY:Modifiesthebrightnessofthe
illuminationofthefrontpanel
WEIGHT:26pounds(11.79kg)net,38pounds(17.24kg)
inshippingcarton.
FINISH:Frontpanel:Anodizedgoldandblackwithspecial
gold/tealpanelnomenclatureillumination.
CHASSIS:Chromeandblack.
MOUNTING:MclntoshdevelopedprofessionalPANLOC.
MECHANICAL
SIZE:Frontpanel:16incheswide(40.64cm)by5-7/16
incheshigh(13.81cm);Chassis:15incheswide(38.1cm)
by13inchesdeep(33.02cm),includingPANLOCshelf
andbackpanelconnectors;KnobClearance:1½inches
(3.81cm)infrontofmountingpanel.
11

Performance
Charts
FMSIGNALPERFORMANCE
12
FREQUENCYINKILOHERTZ
-100 0 100200300400
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
20100100010000
FREQUENCYINHERTZ
3
2
1
0
FMHARMONICDISTORTION
RFINPUTSIGNALINMICROVOLTSACROSS300OHMS
0.11.0101001K10K
0
10
20
30
40
50
60
70
FM-IF CHARACTERISTIC
RELATIVEOUTPUT
INdB
AMPLITUDE
RESPONSE
ENdB
PER
CENT
HARMONIC
DISTORTION

13
AMFREQUENCYRESPONSE
0
-10
-20
-30
-40
RELATIVE
OUTPUT
INdB
AMSELECTIVITYAT1000kHz
RELATIVEOUTPUT
INdB
FREQUENCYINHERTZ
2010010001000020000
FREQUENCYINkHz
1030102010101000 990980970
0
-20
-40
-60
-80
-85
-100

PHONOEQUALIZATION
14
Response
indB
Response
indB
Response
indB
FREQUENCYINHERTZ
2010010001000020000
15
10
5
0
-5
-10
-15
-20
LOUDNESSANDFILTERCHARACTERISTICS
FREQUENCYINHERTZ
2010010001000020000
20
15
10
5
0
-5
-10
-15
-20
TONECONTROLS
FREQUENCYINHERTZ
2010010001000020000
20
15
10
5
0
-5
-10
-15
-20

TechnicalDescription
TUNINGMECHANISMANDDIALDRIVE
IntheMX113,theuniquedesignandcarefulmanufac-
tureofthemechanicalassemblygivessmoothflywheel
tuning.
Bycontrollingtherelationshipofmassandmechanical
resistance,andbydividingtheworkloadsinthedialdrive
system,itbecomesnearlyimpossibletodetectanybacklash.
Yet,theentiredialdriveisa modelofmechanicalstability.
Foraddedeaseandincreasedtuningaccuracy,a section
ofthedialpointerisilluminated.
FMSECTION
TheRadioFrequency(RF)sectionhousesthecomplete
FM-RFfront-endandpartoftheAMRFcircuit.
Aseven-sectionvariablecapacitoristheheartoftheRF
section.Foursectionsofthevariablecapacitorareinthe
FMfrontendandtheremainingthreeareintheAMsection.
Byinterleavingthesections(AM-FM-AM-FM-etc.)spurious
responsesaresignificantlyreduced.ThefourFMsections
ofthevariabletuningcapacitorprovidesa highdegreeof
RFselectivityandexcellentspuriousrejection.Usingthe
latest"stateoftheart"fieldeffecttransistorswitha well-
designedvariabletuningcapacitorhasprovidedthe
MX113withanexcellentRFfront-end.
Adualinsulatedgatemetaloxidesiliconfieldeffect
transistor(MOS-FET)isusedasfirstandsecondRFampli-
fier.Eachgateofthetransistorisinternallyprotectedby
back-to-backdiodesagainstincomingtransientsthatmay
occurduetosevereexternalconditions.UseofMOS-FET's
greatlyreducesthecross-modulationproductsovera
widerdynamicrange.A widerdynamicrangepermitsthe
inputcircuitstoacceptextremelystrongsignalswithout
overload.SincebothRFamplifiershaveinsulatedgate
configurations,externalneutralizationisnotrequired.
Thisdesignresultsina verystableRFamplifiercircuit.
LowtemperaturecoefficientcomponentsfortheFMlocal
oscillatorpreventfrequencydrift.Thefrequencystability
inherentinthelocaloscillatormakesautomaticfrequency
control(AFC)unnecessary.Therateofdriftofthelocal
oscillatorislessthantenpartspermillionperdegree
centrigrade.
Themixerdesignusesa JFETforhighsensitivityand
freedomfromoverload.Themixerdeliversthecomposite
FMsignalatthe10.7MHzintermediatefrequency.The
pathoftheIFsignaliscontrolledbythefrontpanel
SELECTivitypushbutton.
AttheOUTposition,theSELECTivityswitchdirectsthe
signalthroughanIFpreamplifierstage,thatusesa J-FET
anda double-tunedIFtransformer.Thesignalthengoesto
theFM-IFanddiscriminatormoduleforfurtheramplifica-
tion.ActivatingtheSELECTivitypushbuttonroutesthe
signaltotwodouble-tunedtransformers,a ceramicfilter
network,anda single-gateMOS-FET.ThesidesoftheIF
curvearecompressedbythiscircuitnarrowingtheIFband-
pass.Inthismodeofoperationweakstationsadjacentto
strongstationscanbetunedwithsurprisingclarity.
AlloftheRFcircuits,includingtheselectivitycircuit
andtheAMsectionsofthevariablecapacitorareencased
ina metalmodule.EachFM-RFsectionisisolatedina
separatecompartmentbymetalshielding.Carefuldesign
andmanufacturingincreasetheprotectionagainstradiation
andinterference.TheMX113exceedstheFCCrequire-
mentsforsuppressionoflocaloscillatorradiation.
Antennaconnectionsforeither300ohmtwinleadtrans-
missionlineor75ohmcoaxialcableareprovidedonthe
backpaneloftheMX113.Thenormalinputimpedanceof
theRFamplifieris75ohms.Impedancematchto300ohms
isprovidedbya Mclntoshdesigned,negligibleloss,balun
transformer.Connectionsforboth300ohmtwinleadand
75ohmcoaxialcablearemadewithpushtypeterminals.
FM-IFANDDISCRIMINATORSECTION
TheMX113useslinear-phaseIFfilters.Eachfilterwas
designedfroma FORTRANcomputerprogramforminimum-
phaseandconstantdelay.Themathematicalcomplexityof
thefilterdesignprocedureisalmostbeyondbelief.Using
numericalintegrationintheS-Plane,an"IBM"1130high
speedcomputerspenteighteenminutesonthemathematics
forthedesignoftheIFfilter.Itwouldhavetakena human
engineer,workingtwenty-fourhoursa day,sevendaysa
week,andworkingerror-freethree-hundredyearstoper-
formthesamemathematicalcalculations!
TheIFfilterhasequaltimedelayinitspassbandregion.
AnyerrorintimedelaycausesFMdistortion.AllotherIF
filtershavedelaydistortion,someasmuchas100%of
the10.7MHztransitdelay.TheMX113haslessthan1.0%
delaydistortionfromantennainputtodiscriminatoroutput!
Thismakespossibletheoveralllowdistortionperformance
limitfortheFMtunerandmultiplexsectionoftheMX113.
Amplificationoftheintermediatefrequencysignalis
providedbytwohighgainintegratedcircuits,eachcontain-
ing16transistors,3 zenerdiodes,5 diodes,and23re-
sistors,allona signalmonolithicsiliconchip.Theexcep-
tionallyhighgainoftheintegratedcircuitassures"hard
limiting"atverylowlevelsofinputsignals.
ParallelingthemainsignalpaththroughtheFM-IFand
detectormodule,a secondaryamplifyingandde-modulat-
ingprocessisusedtoactivatethetuningmeterandtopro-
videtestpointTP1andTP2witha signaltobeusedwith
theMclntoshMaximumPerformanceIndicator.
FMSTEREOMULTIPLEXSECTION
Mclntoshhasdevelopeda specialdetectingcircuitused
inthemultiplexsection.A particularadvantageofthis
circuitistheeliminationofthecriticaladjustmentsneces-
sarywithcommonlyusedmatrixingcircuits.Thecircuit
detectstheL - R sidebands,thenautomaticallymatrixes
15

therecoveredinformationwiththeL + R carriersignal.
Thisyieldstheleftandrightprogramoutputwithmaximum
separation.
The19,000Hzpilotsignal,broadcastbyanFMstation,
isfilteredfromthecompositestereoinputsignal,ampli-
fiedbya speciallimitingamplifier,doubledtothe38,000
Hzcarrierfrequency,andthenamplifiedagainbya limit-
ingamplifier.Thecompositesignalminusthe19,000Hz
pilotiscombinedwiththe38,000Hzcarriersignal.
Thenewcombinationofsignalsisfedtothespecialdetector
circuitmentionedabove.Balancedfullwavedetectors
areusedtocancelthe38,000Hzcomponentsintheout-
put.TheSCA(SubsidiaryCommunicationAuthorization)
signalmustberemovedfromthecompositeoutput.This
isaccomplishedbytheuseofa new"ImageParameter"
bandeliminationfilterthathasbeencomputerdesigned.
TheSCAfilterrejectsSCAsignalswithoutimpairingstereo
performance.
Whenthe19,000Hzcarrierofa stereosignalisre-
ceived,theautomaticFMstereoswitchingcircuitactivates
themultiplexdecodingcircuit.Thislightsthestereoindi-
cator.Thecircuitswitchingisalldoneelectronicallywith
noclicks.Theautomaticstereoswitchingcanbedefeated
bydepressingthemodeselectorswitchtoMONO.(Inthis
positionthestereoindicatorwillstilllighttoindicatethe
presenceofa stereosignal.)Onmonophonictransmissions
thestereoswitchingisinactiveatalltimes,assuring
optimumsignaltonoiseratio.Thestereoswitchingcircuit
hasbeendesignedsothatnoisewillnotactivateit.
FMmutingintheMX113operatesbydetectingultra-
sonicnoisewhichispresentwhentuningbetweenstations
orwhenreceivinga weakstation.Themutingcircuitcan
beactivatedordefeatedbytheuseofthemutingbutton
onthefrontpanel.Thethresholdofmutingdesiredcanbe
adjustedbythemutinglevelcontrolonthetoppanel.
Varyingthemutingcontroladjuststhethresholdatwhich
themutingtakeseffect.
AMSECTION
TheAM-RFamplifiercircuitincludesa threesection
variabletuningcapacitorinthemetalenclosedshielded
RFmodulewhichalsohousestheFM-RFfrontend.A three
sectionvariablecapacitorisusedforgreaterspurious
rejection.TheRFamplifierisunique.Thecircuithascon-
stantsensitivity,constantselectivity,highimagerejection
acrossthecompleteAMband.OrdinaryAM-RFcircuits
cannotdoallofthesesimultaneously.Thiscircuitdesign
achievesequalsensitivityevenatthelowendoftheband.
Spurious,image,andintermediatefrequencyrejectionare
allsuperior.Thesamecircuitdeliversequalselectivity
acrosstheentireband.TheMclntoshcircuitisuniqueina
superheterodyneAMreceiver.
In addition,thereis no lossof audiofrequencyresponse
atthelowendoftheband,commoninAMreceivers.An-
otheradvantageoftheMclntoshcircuitisfreedomfrom
cross-modulationandoverloadingbystronglocalstations.
Ahigh-qualityloopstickantennaisprovided.Itcanbe
rotatedformaximumperformance,optimumsignalrecep-
tionorminimuminterference.IneachMX113theloop-
sticksareindividuallytunedforoptimumperformance.
Aftertuning,theloopstickisthensealed.Thiscustom
matchingoftheloopsticktotheAM-RFfrontendmaxi-
mizestheperformanceoftheloopstickantenna.Thean-
tennaisrotatablethroughnearly180degreesinalldirec-
tions.Withthismobilityyouwillnotsufferlossofsensitivity
regardlessoftheangleatwhichtheinstrumentismounted.
Abackpanelantennaconnectorisprovidedforconnecting
anexternalantennaifdesired.
Tomaintaintheexcellentimagerejectionandlackof
spuriouscrossmodulationoftheAM-RFamplifieranauto-
dyneconvertercircuitwasusedinproducingtheAM-IF.
AM-IFusestwodoubletunedIFtransformersdesigned
toobtaina highdegreeofselectivityyetallowinggood
audiofidelity.WiththeSELECTbuttonINa narrowband
ceramicfilterisaddedbetweentheAM-IFamplifierandthe
detector.
A10,000Hzactivefiltereliminatesthe10,000Hz
whistleandirritating"MonkeyChatter"causedbyan
adjacentstation.Thefrequencyresponseofallstationsis
nearlyflatfrom20Hztoaround3,500Hz,thenrolloff
begins.Becauseanactivefilterisused,theoutput levelat
10,000Hz,orthewhistlefrequency,isdownover20dB
oronehundredthofwhatitwouldbewithoutfiltering.
WiththeselectbuttonIN,theactivefiltercutofffrequency
islowered.Thefiltertheneffectivelysuppressesthe5,000
Hzwhistlefromnearbytelevisionreceivers.
TheAVC(automaticvolumecontrol)systemwasde-
signedtopreventburstingorthumpswhentheAMis
tunedthrougha strongsignal.Distortionatlowaudiofre-
quenciesisminimizedbyusingtwoAVCfiltersections
insteadoftheconventionalone.
PHONOPREAMPLIFIER
Therearethreetransistorsineachchannelofthephono
preamplifier.Theoutputofthethirdtransistorisconnected
bya negativefeedbacklooptotheemitteroftheinput
transistor.Thefeedbackloopreducesnoiseanddistortion.
ItalsoprovidesprecisionRIAAfrequencycompenation
requiredformagneticphonographcartridges.Feedback
remainsineffectevenat20Hz,wheregainishighest.
Thenegativefeedbackalsoprovidesa lowoutputimped-
anceforthetapeoutput.
Phonoinputoverloadisvirtuallyimpossible.Forex-
ample,at1,000Hz,thephonoinputcanaccept150
millivoltsofsignalwithoutoverload.Tenmillivoltsofsignal
atthephonoinputat1,000Hzwillproduce1.2voltsat
thetapeoutput.
Theselectorswitchconnectseithertheoutputofthe
phonoamplifier,theFMtunersection,theAMtuner
sectionoroneoftwohighlevelinputs(TAPEorAUX)
tothemainpreamplifier.Theinputimpedanceofthehigh
levelinputis250,000ohms.Thehighlevelinputsfeed
16

directlytothevolumecontrol.A loudnesscircuitiscon-
nectedtoa taponthevolumecontroltoprovideloudness
compensation.Compensationcanbeswitchedinorout.
Thehighlevelsignalthenfeedstoa pairoftransistors
connectedashighgainamplifiers.Negativefeedbackis
usedaroundthispairoftransistorstoreducenoiseand
distortion.Thenegativefeedbackprovidesthelowimped-
anceneededtodrivethehighlyselectivefilternetworks
whichfollow.
Intheleftchannelthesecondtransistorisconnected
ina balancedoutputarrangement.Thiscircuitprovides
equalamplitudesignalsbutofoppositephaseforthephase
switch.
Thefilternetworkscanbeswitchedinorout.Thehigh-
frequencyfilternetworkreducestrebleresponseabove
5,000Hz.Thelow-frequencyfilterreducesbassresponse
below50Hz.Theslopeofthefiltersisselectedformaxi-
mumrejectionofcommonlyencounterednoise.Careful
designkeepsthelossofuseableprogrammaterialtoa
minimum.
Theoutputfromthefiltercircuitsisfedtothebalance
control.Theoutputofthebalancecontroldrivesthefirst
stageofthetonecontrolsection.Theremainingtwotran-
sistorsareconnectedasa high-gainamplifierstage.The
high-gainofthisstageisusedtoadvantageforthetone
controlnegativefeedbackcircuits.Negativefeedbackin
thetonecontrolcircuitsassureslowdistortionandaccurate
shapeofthetone-controlresponsecurves.Negativefeed-
backismaintainedatallfrequencies,evenwithtonecon-
trolsturnedtofullboost.Overalldistortionislowatall
frequenciesincludingfrequeniceswheremaximumboost
occurs.Thenegativefeedbackalsoprovidesthelowim-
pedanceoutputrequiredforthemainpreamplifieroutputs.
L+ R AMPLIFIER
TheL + R amplifierconsistsofa singletransistorcon-
nectedasa voltageamplifier.Negativefeedbackisused
aroundthesummingamplifiertomaintainlowdistortion
andprovidea lowimpedanceforthecenterchanneloutput.
POWERSUPPLY
ThepowersupplyoftheMX113hasreceivedveryspe-
cialattention.
Threeseparaterectifiercircuitsareused.First,a full-
waverectifiersuppliesDCtoallaudiocircuits.Thesecond
full-waverectifiersuppliedDCtoalltunerandmultiplex-
decodercircuits.ThethirdsupplyprovidesDCtotheAM
circuit.
Thepowersuppliesareelaborateindesign.Theyuse
electronicfilteringtoinsurethelowestpossibleback-
groundhumlevel,maximumstability,andextremelygood
regulation.
17

18
FM-AMBLOCKDIAGRAM