McIntosh MCP 1 User manual

YourMCP1 HeadAmplifierisdesignedtooper-
atetoitsperformancelimitsformanyyears.If
youhaveanyquestions,pleasecontact:
CUSTOMERSERVICE
McintoshLaboratoryInc.
2ChambersStreet
Binghamton,NewYork13903-2699
Phone:[phone]
TakeAdvantageof3 yearsof
ContractService...
FillintheApplicationNOW.
CONTENT S
SERVICECONTRACTINFORMATION1
INTRODUCTION2
HOWTOCONNECT2,3
PERFORMANCELIMITS3
HOWTODESIGNA HEADAMP4
MCP-1SCHEMATICDIAGRAM5
Copyright1983© byMcintoshLaboratoryInc.
1
McINTOSHTHREEYEARSERVICECONTRACT
AnapplicationforA THREEYEARSERVICECONTRACTisincludedwiththismanual.
Thetermsofthecontractare:
1.Mcintoshwillprovideallparts,materialsandlaborneeded
toreturnthemeasuredperformanceoftheinstrumentto
theoriginalperformancelimits.TheSERVICECONTRACT
doesnotcoveranyshippingcoststoandfromtheauthoriz-
edserviceagencyorthefactory.
2.AnyMcintoshauthorizedserviceagencywillrepair
Mcintoshinstrumentsatnormalservicerates.Toreceive
serviceunderthetermsoftheSERVICECONTRACT,the
SERVICECONTRACTCERTIFICATEmustbepresented
whentheinstrumentistakentotheserviceagency.
3.Alwayshaveservicedonebya Mcintoshauthorizedservice
agency.Iftheinstrumentismodifiedordamagedasa
resultofunauthorizedrepair,theSERVICECONTRACTwill
becancelled.Damagebyimproperuseormishandlingis
notcoveredbytheSERVICECONTRACT.
4.TheSERVICECONTRACTisissuedtoyouastheoriginal
purchaser.Toprotectyoufrommisrepresentation,thiscon-
tractcannotbetransferredtoa secondowner.
5.ToreceivetheSERVICECONTRACT,yourpurchasemust
bemadefroma Mcintoshfranchiseddealer.
6.YourcompletelyfilledinapplicationfortheSERVICECON-
TRACTmustbepostmarkedwithin30daysofthedateof
purchaseoftheinstrument.
7.ToreceivetheSERVICECONTRACT,allinformationonthe
applicationmustbefilledin.TheSERVICECONTRACTwill
beissuedwhenthecompletelyfilledinapplicationis
receivedbyMcintoshLaboratoryIncorporatedinBingham-
ton.NewYork.
8.UnitsinoperationoutsidetheUnitedStatesandCanada
arenotcoveredbytheMcintoshFactoryServiceContract,
irrespectiveoftheplaceofpurchase.Norareunitsac-
quiredoutsidetheU.S.A.andCanada,thepurchasersof
whichshouldconsultwiththeirdealertoascertainwhat,if
any,servicecontractorwarrantymaybeavailablelocally.

Introduction
WHYA HEADAMP?
Itisintheverynatureofa movingcoilcartridge,
thewayinwhichitmustbemadewiththelimita-
tionsimposedbytoday'smaterials,thatitrequiresa
headamp.A movingcoilcartridgeisreallyanelec-
tricalgenerator.Justlikethegeneratorsatanelec-
tricalgeneratingplantthatconverttheenergyfrom
fallingwater,themovingcoilcartridgemusthavea
sourceofmechanicalenergywhichitcanconvertto
electricalenergy.Forthemovingcoilcartridgethe
mechanicalenergyissuppliedbythemotionofthe
stylusasitfollowsthemusicsignalimpressedon
therecordgroovewalls.Themovementofthestylus
correspondingtothemusicalinformationisvery
small,beingmeasuredinonlythousandthsofan
inchortensofmicrons.Sucha smallmechanical
motionconvertsintoa correspondinglysmallelec-
tricalenergy.Theoutputofa movingcoilcartridgeis
measuredinonlymillionthsofa volt.A typicalmov-
ingcoilcartridgewilldeliveronlytwoorthreehun-
dredmillionthsofa voltwhichisequivalenttoan
energyoutputofonlya billionthofa watt.Thehead
ampmustamplifythisenergyandincreaseitsvolt-
ageleveltoa fewthousandthsofa voltinorderto
protectthemusicalcontentfromlossofinformation
andcontaminationbyinterferingelectricalfields
whichsurroundeverythingandeveryoneofus.Such
contaminatingfieldswouldaddnoiseandhumto
themusicalsignalanddecreaseitsmeaningforus.
ANALTERNATIVEDESIGN
Thereisanotherpossiblemeansofincreasingthe
voltageleveloftheheadampandthatisbyusingan
inputtransformer.Whilethetransformercanin-
creasethevoltageoutputofthemovingcoilcar-
tridgeitcannotamplifytheenergycontentofthe
musicalsignalfromthemovingcoil.Henceasthe
voltageofthemovingcoilisincreaseditscor-
respondingcurrentisdecreased.Thesourceim-
pedance,theratioofthemovingcoilvoltagetoits
currentisincreasedbythesquareofthevoltage
gain.Thusa voltagegainofsayonehundredtimes
isaccompaniedbyanimpedanceincreaseoften
thousand.Thehighertheimpedanceoftheoutput
circuitthemoresusceptibleitistointerferinghum
andnoisefields.Theheadampcansolvethispro-
blembybeingdesignedtohaveanoutputim-
pedanceofonlya fewohms.. .
Butthereisanotherproblemwithtransformers
operatingatextremelylowvoltagelevels.Theease
withwhichthemagneticcoreconcentrateslinesof
magneticforcevarieswithvoltagelevelatextremely
smalllevels.Thisvariationaddsdistortiontothe
musicsignalatlowfrequencies.TheMCP1 head
ampsolvesthisproblemtoo.Themusicaldefinition
oftheMCP1 isfarsuperiortoinputtransformers
thataremanytimestheweightandsizeoftheMCP1.
Forthehighestqualitymusicrecoveryfromyour
recordingsitisbesttolocatetheheadampcloseto
thebaseoftheturntablearm.Theextremelylow
energylevelsdevelopedbymovingcoilcartridges
mustbeprotectedfromexposuretolossofquality
fromlongcablestothepreamplifier.Whenthelow
voltagesignalsofthecartridgeareamplifiedbythe
headamp,theycanthenleaveforthepreamplifierin
robustform,abletosurvivethepassagewithout
lossofcontentandbeuncontaminatedbyadded
noiseordistortioncomponents.
TheMCP1 ispowereddirectlyfromyour117volt
line.Butaningeniousnewdevelopmentfromthe
Mcintoshengineeringgroupcompletelyisolatesthe
MCP1 fromanynoisecomponentsinthepowerline.
Itisimperativethattherebenogroundloops
(multiplegroundingpaths)ontheinputandoutput
cablesconnectingtheMCP1.Eachchannelofthe
MCP1 hasindependentgroundcircuits.Theinput
cablesfromthetonearmmusthaveseparate
groundsforeachchannelandthesegroundsmust
notconnecttotheturntableframeground.Theout-
putcablesfromtheMCP1 shouldhaveindependent
groundpathstothepreamplifier.Ifyouwouldliketo,
youcantestthegroundingsystemusinganohm
meter.WhentestingtheMCP1 withoutanyconnec-
tionstootherequipment,theohmmetershould
measure200 ohmsbetweentheleftandrightchan-
nelgroundsand100ohmsfromeachchannel
groundtotheMCP1 groundterminal.
2
Connecttheleadsfromyourturn-
tabletotheproperimpedanceforyour
cartridgeontheMCP1 input.
ConnecttheoutputoftheMCP1
headamplifiertothemovingmagnet
phonoinputonthepreamplifier.
Connecttheturntablegroundtothe
MCP1 groundterminal.
Then,connecta groundwirebetween
theMCP1 groundterminalandthe
groundterminalonthepreamplifier.
HowToConnect

PerformanceLimits
AndRatings
PerformanceLimits
Performancelimitsarethemaximumdeviation
fromperfectionpermittedfora Mcintoshinstru-
ment.Wepromiseyouthatwhenyoupurchasea
newMCP1 froma Mcintoshfranchiseddealer,itwill
becapableoforcanbemadecapableofperfor-
manceatorexceedingtheselimitsoryoucanreturn
theunitandgetyourmoneyback.Mcintoshisthe
onlymanufacturerthatmakesthisstatement.
INPUTIMPEDANCES—10,20,40and90ohms
GAIN—10W- 31dB,20W- 26dB,400- 20dB,90W- 13
dB
FREQUENCYRESPONSE—+ 0,-0.5dB,20Hzto
70kHz
TOTALHARMONICDISTORTION—Lessthan.01%
SIGNALTONOISERATIO—83dBA(re:500µVinput
at1 kHz,10Winput,withRIAA equalization)
(equivalentto- 149dBVatinputat1 kHz).
PHASESHIFT—Noninverting
CHANNELSEPARATION—Morethan90dB,20Hz
to20kHz GENERALINFORMATION
SEMICONDUCTORCOMPLEMENT—
22BipolarTransistors
2IntegratedCircuits
11Diodes
POWERREQUIREMENT—85-135V,50/60Hz,2 watts
MECHANICALINFORMATION
Size—7incheswide(17.8cm)by33/16incheshigh(8.1
cm)by5 inchesdeep(12.7cm)
FINISH—Cabinetisrosewoodfinishonsolid
macassarebony.Frontpanelisblackwithgold
nomenclature.Chassisisblack.
WEIGHT—3pounds(1.4kg)net,5.5pounds(2.5kg)
inshippingcarton
3

Thesignificanceofthisequationisthatittellsus
thenoiseina MCpreamplifierislargelydetermined
byen,transistornoisevoltageandnotin,transistor
noisecurrent,sinceRgenissmall.Thisdictatesthe
transistordesign.Fora transistortohavelowenit
musthavelowbasediffusionresistance,rbb.This
requiresthatthetransistormusthavea largebase
diffusionareawitha longcaseperimeterandusea
lowresistivitysiliconmaterial.Also,surface
leakagemustbeabsolutelyminimum.
Thecomplementaryinputstagetransistorsinthe
MCP1 havethesecharacteristics.Theequivalent
rbbcanbeloweredfurtherbyparallellinga number
oftransistors.Eighttransistorsareparallelledinthe
MCP1 whichgivesa reductionof9 dBinnoiselevel
overusingjustonetransistor.Thisdesignap-
proachescloselythetheoreticaloptimum.To
guaranteeperformanceeachinputtransistorisin-
dividuallytestedfornoisevoltageandnoisecurrent
at100Hz,1 kHz,and10kHzbeforeitismountedin
theMCP1.Thistestingistimeconsumingbut
assuresnoisefreeoperation.
EachchannelofamplificationintheMCP1 uses
twostagesofamplification.Thefirststagehaseight
lownoisebipolartransistorsina parallelcom-
plementarypush-pullconfiguration.Thisstage
amplifiesthesignalbetween2.5and20times(8to
26dB)dependingonwhichinputimpedanceisused.
Thesecondstageusesa pairofcomplementary
bipolartransistorswitha gainof1.8times(5dB).
Theoverallamplifierisdescribedasa noninverting
parallelcascadedcomplementarylownoisebipolar
transistoramplifiercircuit.
Thetwocascadedstagesofamplificationinthe
MCP1 preservethephaseoftheinputsignalandin-
creasethesignalhandlingabilityordynamicrange.
Theinputstageinvertsthesignalandthesecond
stagerestoresthephasetozero.Theinvertinginput
stagehasanimportantadditionalnoiseadvantage.
Iftheinputisopencircuitedthenoiseoutput
reducesinsteadofincreasingasinsomeother
designs.
Thepowersupplycircuitrequireda newapproach
withverycarefuldesign.ManyMCamplifiersuse
batteriestoavoidhumandnoiseproblems.These
amplifiers,ofcourse,requirebatteryreplacement
andusuallythenoiseanddistortionperformanceis
compromisedtoallowbetterbatterylife.TheMCP1
usesa linevoltagepowersourcetoeliminatethe
needtocompromiseitsnoiseperformance.Butthe
usualproblemofa powertransformerhadtobesolv-
edfirst.Powertransformerswhichuse50/60Hzhave
externalmagneticfieldswhichcanmodulatethe
minutesignalinthemovingcoilcartridge,addhum
andnoisetothecartridge,tothecartridgeconnec-
tingcableandeventothemainpreamplifier.The
designoftheMCP1 eliminatesallofthesepro-
blems.Knowingthata 50/60Hzhumfieldsimply
couldnotbetoleratedtheMcintoshdesigngroup
chosea totallynewapproach.A highfrequency,
completelyshielded,solidstateswitchmodepower
supplywasused.
TheACpowerlinefeedsa reactivevoltagedivider
anda fullwavebridgerectifier.Therectifierpro-
duces24voltsDCwhichisfilteredandsuppliedtoa
15voltseriesvoltageregulator.Thisregulatorhas70
dBripplerejectionandreducesthepowerlinehum
toa negligiblelevel.The15voltsDCpowersa stable
multivibrator/frequencydividerwithanoutputfre-
quencyof200kHz.The200kHzdrivesa push-pull
powerswitchingamplifierfollowedbya ferritecore
toroidaltransformer.Thistransformerhastwo
secondarywindingsbifilarlywound.Eachwinding
feedsa separaterectifierandfiltersystem.Thetwo
outputsarecompletelyindependent.Onefeedsthe
leftamplifierchannelandtheotherfeedstheright.
Filtersandshieldingareusedtocontainthe200 kHz
switchingwithinthepowersupplyitselfandthereis
nounwantedinterferenceradiationorconduction.
TheMCP1 hasthreeindependentgrounding
systemstopreventgroundloopswhenconnecting
inputandoutputcables.Thesteelmetalenclosure
connectstoa groundpostforgroundingtotheturn-
tableframeandassociatedamplifyingequipment.
Theleftandrightchannelshaveseparategrounds.
Thereisnohumornoiseintroducedasa resultof
theroutingofinputandoutputcables.
HowToDesignA
HeadAmp
Theinputtransistors,inputcircuitconfiguration,
andthepowersupplyrequiredcriticaldesigncon-
siderationsincenoiseandhummustbeheldtoan
absoluteminimum.
Transistornoiseischaracterizedbytwonoise
components;en,EquivalentShort-circuitRMSNoise
Voltage,andin,EquivalentOpen-circuitRMSNoise
Current.TheresistanceorimpedanceoftheMCcar-
tridgeandresistanceintheinputcircuitofthe
amplifieralsocontributeThermalNoiseVoltage,er,
asa resultofrandomelectronmovementwithin
theseresistances.Thecombinednoisevoltage,en,
appearingattheinputoftheamplifiercanbe
calculatedas:
4