McIntosh MPI 4 User manual

THEMclNTOSHMPI4 MAXIMUMPERFORMANCEINDICATOR
ReadingTime40Minutes
Price$1.25

YourMPI4 MaximumPerformance
Indicatorwillgiveyoumanyyearsof
pleasantandsatisfactoryperformance.
Ifyouhaveanyquestionsconcerningthe
operationormaintenanceofthis
instrument,pleasecontact:
CUSTOMERSERVICE
MclntoshLaboratoryInc.
2ChambersStreet
Binghamton,NewYork13903
Phone:[phone]
TakeAdvantageof3 years
ofFREEFactoryService. . .
FillintheApplicationNOW.
contents
GUARANTEE...1
GENERAL...2
INSTALLATION...2,3
HOWTOCONNECT. . . 3-5
FRONTPANELINFORMATION...6-8
LEVELSETPANELINFORMATION...8
REARPANELINFORMATION...9
INITIALSETUP...9,10
HOWTOUSETHEMPI4 ... 10-18
PERFORMANCELIMITS...18,19
TECHNICALDESCRIPTION...19,20
BLOCKDIAGRAM...21
Guarantee
MclntoshLaboratoryIncorporatedguaranteesthisinstrument
tobecapableofperformanceasadvertised.Wealsoguarantee
themechanicalandelectricalworkmanshipandcomponentsto
befreeofdefectsfora periodof90daysfromdateofpurchase.
Ifsuchdefectsoccur,MclntoshLaboratoryoroneofitsauthorized
agencieswillrepairthedefectatnocosttothepurchaser.This
guaranteedoesnot extendtocomponentsdamagedbyimproper
usenordoesitextendtotransportationtoandfromthefactory
orserviceagency.
THREEYEARFACTORYSERVICECONTRACT
Anapplicationfora FREETHREEYEARFACTORYSERVICE
CONTRACTisincludedwiththismanual.Thetermsofthecontract
are:
ForThreeYearsfromdateofpurchase—
1.Mclntoshwillprovideallparts,materialsandlaborneeded
toreturnthemeasuredperformanceoftheinstrumenttothe
originalperformancelimitsfreeofanycharge.TheSERVICE
CONTRACTdoesnotcoveranyshippingcoststoandfrom
theauthorizedserviceagencyorthefactory.
2.AnyMclntoshauthorizedserviceagencywillrepairallMc-
lntoshinstrumentsatnormalservicerates.Toreceivethefree
serviceunderthetermsoftheSERVICECONTRACT,the
SERVICECONTRACTCERTIFICATEmustaccompanythein-
strumentwhentakentotheserviceagency.
3.Alwayshaveservicedonebya Mclntoshauthorizedservice
agency.Iftheinstrumentismodifiedordamaged,asa result
ofunauthorizedrepairtheSERVICECONTRACTwillbecan-
celled.Damagebyimproperuseormishandlingisnot covered
bytheSERVICECONTRACT.
4.TheSERVICECONTRACTisissuedtoyouastheoriginal
purchaser.Toprotectyoufrommisrepresentationthiscontract
cannotbetransferredtoa secondowner.
5.TheSERVICECONTRACTisgiventopurchaserswholive
inthe50UnitedStatesorCanadaonly.
6.ForyourprotectionMclntoshselectsitsdealerscarefully.
Onlyonedealerintenqualifiesfora Mclntoshfranchise,
ToreceivetheSERVICECONTRACTyourpurchasemustbe
madefroma Mclntoshfranchiseddealer.
7.Yourcompletelyfilledinapplicationfora SERVICECON-
TRACTmustbepostmarkedwithin30daysofthedateof
purchaseoftheinstrument.
8.ToreceivetheSERVICECONTRACTallinformationonthe
applicationmustbefilledin.TheSERVICECONTRACTwill
beissuedwhenthecompletelyfilledinapplicationisre-
ceivedatMclntoshLaboratoryIncorporatedinBinghamton,
NewYork,IftheapplicationisnotreceivedatMclntosh
Laboratory,onlytheserviceofferedunderthe90-dayguar-
anteewillapply.
Copyright© 1973ByMclntoshLaboratoryInc.
1

General
installation
TheMPI4 isa laboratory-gradeinstrument.Itprovides
thefacilitytocontinuouslymonitorthequalityoftheper-
formanceofa stereosystem.TheMPI4 cansampleanddis-
playsignalsfromthetuner,preamplifierandpowerampli-
fierwithoutreconnectingcables.Signalsaredisplayesonan
oscilloscopescreencalibratedwithscalesfortuning,
measuringandtesting.
Asa tuningaid,theinstrumentisa guidetoexactFM
stationselectionandprecisetuning.Thescreendisplays
FMsignalstrength,modulationpercentageandmulitpath
interference.Audiosignalsmaybeviewedforstereobal-
ance,strength,phaseandchannelseparation.Outputpower
ofthepoweramplifiercanbeseenatanyinstantduring
programperformance,orstoredtodevelopa trendover
severalminutes.
Withtheadditionoftestrecords,theMPI4 canshow
complianceandtrackabilityofa phonopickup,frequency
responseofthepreamplifierandpoweramplifier,audio
distortionandstereospeakerbalance.
Inoneofitsoperationalmodes,theMPI4 becomesa
"dualtrace"oscilloscope.Whenoperatedinthedualtrace
modetheleftandrightstereochannelsappearsimul-
taneouslyandseparatelyonthescreenfordirectcompari-
son.Theinstrumentalsohas"triggeredsweep."Itpermits
theviewertochoosea singletoneandlockitonthescreen
forcarefulinspection.
Ina searchforconvenientequipment-mountingtech-
nique,MclntoshdevelopedthePANLOCsystem.Pressing
thetwoPANLOCbuttonsonthefrontpaneloftheMPI4
releasestheunittoslideinoroutofitsmounting.This
allowseasyaccesstocableconnectionsattherear.It
bringstoppanelcontrolsintoviewforeasyadjustments,
adjustments.
Ventilationextendsthetrouble-freelifeofaninstru-
mentbypreventingexcessiveinternaltemperatureand
insulationbreakdown.Toaccomplishthis,allowcoolair
toenteratthebottomoftheinstrumentandwarmairto
escapeatthetop.TheMPI4 MaximumPerformanceIn-
dicatormaybemountedinanyposition.Itrequiresa
mountingspace15inchesdeep(38.1cm),17½inches
wide(44.45cm),and6 incheshigh(15.24cm).
TomountintheMclntoshcabinetfollowtheinstruc-
tionsenclosedwiththecabinet.Foranyotherinstallation,
removetheinstrument,PANLOCbrackets,partsbagand
mountingtemplatefromthecarton.RemovetheMPI4
fromtheplasticbagandplaceitupsidedownonthe
shippingpallet.Thenremovethefourplasticfeetfastened
tothebottomofthechassis.
1.POSITIONTEMPLATEANDMARK
Positiontheplasticmountingtemplateovertheareaof
thecabinetpanelwheretheMPI4 istobeinstalled.
Besurethattheedgesoftheequipmentmarkedonthe
templateclearsanyshelves,partitionsorexisting
equipmentlocatedbehindthepanel.Withthetemplate
inplacemarkthesix"A"and"B"holesandfoursmalt
holeslocatingthecornersofthecutout.Next,jointhe
fourcornermarkswithpencillines.Theedgeofthe
templateisusedasa straightedge.
2.DRILLHOLES
Withthedrillperpendiculartothepanel,drillthe
six"A"and"B"holesusinga 3/16inchdrill.THE
SIXHOLESMUSTBEDRILLEDBEFOREMAKING
THECUTOUT.
2

3.SAWCUTOUT
Carefullycuttherectangularopeningontheinsideof
thepencilledrectangle.
4.SECUREMOUNTINGSTRIPS
Installthemountingstrips(suppliedinthehardware
package)ontheinsideofthecabinetpanel.Insert
twoscrews(suppliedinthehardwarepackage)into
thecenterholes("B"holesonthetemplate).Usethe
¾-inchlongscrewsforpanelsunder½-inchthickor
1¼-inchscrewsforpanels½-inchthickorover.Place
amountingstriponthebackofthecabinetpanel.
Alignitwiththethreeholesinthepanelandtighten
thescrew.Thescrewheadshouldpullslightlyintothe
woodpanel.Attachtheothermountingstripbyrepeat-
ingtheprocedure.
5.MOUNTTHEPANLOCBRACKETS
AttachthePANLOCbracketstothecabinetpanel
usingfourscrewsoftheproperlength.Placethetem-
plateoverthemountingscrews.Thescrewsshould
becenteredonthe"A"and"B"holesinthetemplate.
Ifnecessary,loosenthescrewsandpushthemounting
bracketsintoalignmentthenretighten.
6.INSTALLTHEUNIT
Threadthepowercordthroughtheopeninginthe
cabinetpanel.Carefullyslidetheinstrumentintothe
openingsotherailsonthebottomoftheinstrument
engagethetrackonthemountingbrackets.Slidethe
instrumentinuntilitstopsatthead|ustposition
latches.Pressthelatchesinandcontinuetoslidethe
instrumentuntilitsfrontpanelisflushwiththecabi-
netpanel.AtthebottomfrontcornersarethePANLOC
buttons.DepressingthePANLOCbuttonswilllockthe
instrumentfirmlyinthecabinetpanel.Pressingthe
PANLOCbuttonsa secondtimewillreleasetheinstru-
mentYoucanthenslidetheinstrumentforwardtothe
adjustposition.Pressingtheadjustpositionlatches
willallowtheinstrumenttoberemovedfromthe
cabinet.
Howtoconnect
TheMPI4 maybeconnectedtoa stereoreceiver(Fig.
1)ortoa componentsystemwitha separatepreampli-
fierandpoweramplifier(Fig.2).Choosewhichmost
closelyresemblesyoursystem.
AUDIOINPUTS
LowLevelAudioInput
Useoneofthe6-footshieldedcablessupplied,tocon-
necttheleftchanneloutputonyourpreamplifiertothe
LEFTAUDIOINPUTontheMPI4 backpanel.Similarly,
connecttherightchannelpreamplifieroutputtothe
RIGHTAUDIOINPUT.
SPEAKERINPUT
Therearefourcolor-codedpushconnectorsontheback
paneloftheMPI4.Connectthesewithtwopairsofspeaker
cablestotheleftandrightoutputonthepowerampli-
fier.
BlackLeftspeakercommonterminal
GreenLeftspeakerhighterminal
WhiteRightspeakercommonterminal
RedRightspeakerhighterminal
SettheSPEAKERIMPEDANCEswitchontheMPI4 back
paneltoagreewiththespeakersystemimpedance:4W,
8W,or 16W.
TUNERINPUTS
SignalStrengthInput
Mclntoshtunersandreceiversprovidesignalforthe
SIGNALSTRENGTHINPUTata connectormarkedTP1
onthebackofeachtuner.Usingthe3-footlow-capacity
shieldedcablesupplied,connecttheTP1 outputtothe
SIGNALSTRENGTHINPUT.
TOPREVENTHIGHFREQUENCYLOSSES,THESPECIAL
3-FOOTCABLESSUPPLIEDMUSTBEUSED.DONOT
SUBSTITUTEORDINARYAUDIOCABLE.
Forothertunersorreceiverswhichdonotprovidea
signalstrengthoutput,consultthemanufacturerortheir
authorizedserviceagency.
DeviationInput
Mclntoshtunersandreceiversprovidesignalforthe
DEVIATIONINPUTata connectormarkedTP2 ontheback
ofeachtuner.Usingthe3-footlow-capacityshielded
cablesupplied,connecttheTP2 outputtotheDEVIA-
TIONINPUT.
TOPREVENTHIGHFREQUENCYLOSSES,THESPECIAL
3-FOOTCABLESSUPPLIEDMUSTBEUSED.DONOT
SUBSTITUTEORDINARYAUDIOCABLE.
Fortunersorreceiverswhichdonotprovidea devia-
tionoutput,consultthemanufactureortheirauthorized
serviceagency.
3

HOWtoConnect
FIG.1 CONNECTINGTHEMPI4 TOSTEREORECEIVER
(TYPICALCONNECTIONS)
STEREORECEIVER
ACCORD
ENVIRONMENTAL
EQUALIZER.IF
USED
BLACK
GREEN
RED
WHITE
4

FIG.2.CONNECTINGMPI4 TOCOMPONENTSYSTEM
(TYPICALCONNECTIONS)
STEREOFMTUNER
LEFT
SPEAKER
5
RIGHT
SPEAKER
ENVIRON-
MENTAL
EQUALIZER
(OPTIONAL)

FrontPanelinformation
FIG.3 FRONTPANEL
MODESELECTOR
TheMODESELECTORpushbuttonsselectthetypeof
displayseenonthescreenoftheMPI4.Eachofthefive
pushbuttonsselectsa trace—aglowinglineofgreenlight—
whichshowsa varietyofinformationaboutsignalsfrom
thetuner,preamplifierorpoweramplifier.Toassistthe
evaluationofeachdisplay,thereticleinfrontofthe
screenismarkedwithcalibrationpointswhichareusedto
measuresignalcharacteristics.AsMODESELECTOR
buttonsarepressed,thescreenreticleisilluminatedin
thesecolors:
ModeColor
MultipathBlue
StereoRed
LevelAmber
SweepGreen
MULTIPATH
WhenproperlyconnectedtoanFMtunertheMPI4
willdetectanddisplaymultipartreception.Multipart
receptionistheresultofa reflectedsignalarrivingatthe
tunerantennaslightlylaterthanthedirectsignal.By
rotatingor repositioningtheFM antennait is possibleto
reducemultipathreception.TheMPI4 makesiteasyto
knowwhentheFMantennaisorientedforthebestrecep-
tionofanystation.
ToshowmultipartreceptiontheMPI4 displaysin-
stantaneoussignalstrengthversusfrequencydeviation.
Signalstrengthisshownasverticaldeflectionofthein-
dicatordisplaybeam.Frequencydeviationisshownas
horizontaldeflection.Multipathreceptionappearsasa
peakorvalleyinthedisplay.
MultipathreceptiondegradesFMtunerperformancein
severalways:
1.Usuallythereisanincreaseinbackgroundnoise
level.
2.Distortionisoftenheardintheprogramsignal
3.Stereoseparationmaybereduced.
4.Thestereoeffectmaybecompletelylost.
5.Stereoindicatorsmayfailtofunction,orfunction
erratically.
Toovercomemultipartreceptionitisusuallynecessary
toturntheantennatoreceivetheFMsignalbyonepre-
dominantpath.Rotatinga directionalantennaiseffective
atcorrectingmultipathreception.Inareaswherea simple
antennasuchasa dipoleisusedrepositioningtheantenna
canachievesimilarresults.
IntheMULTIPATHmodetheMPI4 isa veryeffective
tuningindicator:
1.Signalstrengthisshownbytheverticalpositionof
thedisplaytrace.Thehigherthepositionofthe
tracethegreaterthesignalstrength.
2.Correcttuningoccurswhenthedisplaytraceis
centeredhorizontallyonthescreen.Sincethedis-
playtraceeffectivelyfollowsthetunerIFresponse
curve,centeringthetracetunesthedetectorto
thecenteroftheIFcurve.
Thedisplayofthesignal,whenthereisnomultipath
receptionaffectingtheprogram,appearsasa smooth
curvingline,(Fig.4).Thecalibrationpointsarethetwo
100%marksatthebottomofthescreen.Astheprogram
materialgrowslouderorsofter,thetraceexpandsand
contracts.The100%pointsindicatethehighestmodula-
tionpercentagenormallytransmittedbyanFMstation.
(Amoredetaileddescriptionappearsinthe"HowtoUse
Section.")
STEREO
Astereoprogramcausesa complexdisplaywhich
variesbetweena circularshapeandanellipticalshape.
Amonoprogramcausesthedisplaytobea slantedline.
Withanin-phasemonoprogram,thesignalfallsbetween
theL + R boundaries;inout-of-phasemonoprogramthe
tracefallsalongtheL — R boundaries.
6

FIG.4 MULTIPATHDISPLAY
LEVEL
TheaudioLEVELofstereosignalsisdisplayedastwo
verticalcolumnsonthescreen( Fig.5).Theheightof
eachcolumnisdeterminedbythepoweroramplitudeof
theinputsignal.Thecalibrationscalebetweenthetwo
columnsandthepositionofthePOWERLEVELknob
indicatetheactualpowerofthesignal.Thenomenclature
ontherecticleisshownindecibels(dB).
FIG.5 LEVELDISPLAYOFL & R CHANNEL
DUALTRACE
WhentheDUALTRACEbuttonsarepressed,theL
(Left)programandtheR (Right)programsareseenas
separatetracesonthescreen.Theleftchannelisthe
uppertrace;therightchannelisthelower.
IfonlyonebuttonunderDUALTRACEispressed(L
orR),thescreendisplaysonlythesignalselected.
SWEEPandSWEEPFREQUENCY
Musicalprogrammaterialhasmanyfrequenciesandit
maybedisplayedasa complexjumbleofwavesthatare
difficulttoview.Bychangingthetiming,orsweep,ofthe
trace,theMPI4 canlockontoanyportionoftheaudio
spectrum.Theresultisa clear,easy-to-viewwavethat
remainsstableonthescreen.UsetheSWEEPFREQUENCY
pushbuttonstoprovidea choiceoflowrangefrequencies
(20-200Hz),mid-rangefrequencies(200-2000Hz)and
high-rangefrequencies(2000-20,000Hz).UsetheSWEEP
controlforfinetuningofthesweepwithinanyrange.
GAIN
TheGAINcontroloperatesonlywhenpreamplifier
signalsarebeingdisplayed.TheGAINcontrolvariesthe
verticalsizeoftheimageinallaudiomodesofoperation.
Whena signalofunknownstrengthistobeviewed,start
withtheGAINfullycounterclockwise,thenturnthecon-
troluntilthedisplayreachescomfortableviewingsize.
WhentheGAINcontrolissettoOFF,ACpowerisremoved
fromtheMPI4.
POWERLEVEL
ThePOWERLEVELswitchdeterminesthefull-scale
calibrationinwattsofsignalsdisplayedonthescreen.
Whentheswitchisturned,a redindicatorilluminates
theselectedpowerrangeoftheWATTScolumnalong
therightsideofthescreen( Fig.6).Theserangesmeas-
uretheactualpowerlevelofthepoweramplifier.(How
tousetheserangeswillbedescribedinthenextsection.)
Whentheredindicatorisoppositethetopmostmarking,
PREAMP,thescreendisplaystheamplitudeofthepre-
amplifiersignal.
FIG. 6
INTENSITY
TheINTENSITYcontroladjustsbrightnessofthetrace
onthescreen.Forlongestscreenlife,usetheminimum,
comfortableviewinglevel.
Thetracewilldisappearwhenthereisnoinputsignal
present.Forextendedcathoderaytubelifea built-inauto-
maticintensitycontrolextinguishesthetraceduring
non-signalperiodstopreventa stationaryspotfrom
burninga permanentmarkinthescreensurface.
VERTICAL
TheVERTICALcontroladjuststheupanddownlocation
ofthetraceonthescreen.
HORIZONTAL
TheHORIZONTALcontroladjuststhelefttorightloca-
tionofthetraceonthescreen.
7

INPUTAUDIO
Amicrophone,taperecorder,FMtunerorotherequip-
mentnotnormallyconnectedtotherearpanelconnec-
tionoftheMPI4 maybepluggedintotheINPUTAUDIO
jackonthefrontpanel.Signalsaredisplayedonthescreen
forobservationortesting.Duringthistime,thePOWER
LEVELselectormustbesettothePREAMPposition.The
sizeofthedisplayisadjustedbytheGAINcontroland
TRIMcontrols.
Somemicrophonesmaynotgenerateenoughsignalto
drivethedisplaytocomfortableviewinglevels.This
canbecorrectedbyaddinga microphonepreamplifier
betweenthemicrophoneandAUDIOINPUTjack.
LevelsetPanel
information
AUDIOTRIMLEFT
Adjuststraceheightfora leftchannelpreamplifieraudio
signal.
AUDIOTRIMRIGHT
Adjuststracewidthforstereodisplayortraceheight
forsweeporleveldisplayfroma rightchannelpreampli-
fieraudiosignal.
SIGNALSTRENGTH
Adjuststraceheightabovethebottomorbaselineof
themultipathdisplay.
DEVIATION
Adjuststracewidthofthemultipathdisplay.
MULTIPATHPOLARITY
TheMULITPATHPOLARITYswitchcontrolspolarityof
thesignal-strengthsignal.Theminuspositionisusedwith
mosttuners.
TRACESEPARATION
TheTRACESEPARATIONcontroladjuststhedistance
betweenthetwotracesintheDUALTRACEmodeof
operation.
SWEEPEXPANSION
TheSWEEPEXPANSIONcontroladjustsmaximumwidth
ofthetracedisplay.SWEEPEXPANSIONoperatesonly
whenoneorbothoftheDUALTRACEpushbuttonsare
pressed.
TRIGGERSOURCE
TheTRIGGERSOURCEswitchselectsthesignalused
totriggerthedisplaysweep.IntheDUALTRACEmode
thesweepmaybetriggeredfromtheleftorrightchannel,
orfromthe60hertzlinefrequency.
FOCUS
TheFOCUScontroladjustssharpnessofthetrace.
LOWPASSFILTER
TheLOWPASSFILTERswitchinsertsorremovesa filter
thateliminates19,000and38,000Hzstereoreference
signals.Theseunwantedsignalsproducefuzzyandin-
distincttracesonthescreen.Themostusefulpositionis
theINposition.Onlyinspecialtestproceduresisitneces-
sarytoswitchthefilterOUT,
RETICLEILLUMINATION
TheRETICLEILLUMINATIONswitchturnsillumination
ofthescreenscalesonoroff.
LEVELMODE
IntheNORMALpositionthetwocolumnsriseandfall
likeVUmeters.InthePEAKpositionthecolumnsindicate
the"average"peaklevelforsignalsthatchangecon-
tinuouslyinamplitude.TheResetpositionresetsthe
Peakcircuitryandfreezesthehighestlevelachievedby
theaudio.
FIG.7 LEVELSETPANEL
8