McIntosh C32 User manual

THEMclNTOSHC32SOLIDSTATESTEREOPREAMPLIFIER
ReadingTime:44MinutesPrice$1.25

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Recordthatserialnumberhere
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toyouforanyfutureservice.

YourC 32StereoPreamplifierwill
giveyoumanyyearsofpleasantand
satisfactoryperformance.Ifyou
haveanyquestions,pleasecontact:
CUSTOMERSERVICE
MclntoshLaboratoryInc.
2ChambersStreet
Binghamton,NewYork13903
Phone:[phone]
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Contents
INTRODUCTION2
HOWTOINSTALL2
HOWTOCONNECT4
USINGTHEFRONTPANELCONTROLS8
USINGTHEPUSHBUTTONS11
BALANCINGYOURSTEREO12
LISTENINGTOYOURSTEREO12
PERFORMANCELIMITSANDRATINGS13
PERFORMANCECHARTS14,15
TECHNICALDESCRIPTION16
BLOCKDIAGRAM19
THREEYEARSERVICECONTRACT
Anapplicationfora FREETHREEYEARSERVICECONTRACTisincludedwiththismanual.
Thetermsofthecontractare:
1.Mclntoshwillprovideallparts,materialsand
laborneededtoreturnthemeasuredperfor-
manceoftheinstrumenttotheoriginalper-
formancelimitsfreeofanycharge.The
SERVICECONTRACTdoesnotcoverany
shippingcoststoandfromtheauthorized
serviceagencyorthefactory.
2.AnyMclntoshauthorizedserviceagency
willrepairMclntoshinstrumentsatnormal
servicerates.Toreceivethefreeservice
underthetermsoftheSERVICECONTRACT,
theSERVICECONTRACTCERTIFICATEmust
accompanytheinstrumentwhentakento
theserviceagency.
3-Alwayshaveservicedonebya Mclntosh
authorizedserviceagency.Iftheinstrument
ismodifiedordamaged,asa resultofun-
authorizedrepairtheSERVICECONTRACT
willbecancelled.Damagebyimproperuseor
mishandlingisnotcoveredbytheSERVICE
CONTRACT.
4.TheSERVICECONTRACTisissuedtoyouas
theoriginalpurchaser.Toprotectyoufrom
misrepresentationthiscontractcannotbe
transferredtoa secondowner.
5.ForyourprotectionMclntoshselectsonly
dealerswhohavetechnicalcompetenceto
guidepurchasersfairly,andprovideservice
whennecessary.ToreceivetheSERVICE
CONTRACTyourpurchasemustbemade
froma Mclntoshfranchiseddealer.
6.Yourcompletelyfilledinapplicationfora
SERVICECONTRACTmustbepostmarked
within30daysofthedateofpurchaseofthe
instrument.
7.ToreceivetheSERVICECONTRACTallin-
formationontheapplicationmustbefilled
in.TheSERVICECONTRACTwillbeissued
whenthecompletelyfilledinapplicationis
receivedatMclntoshLaboratoryIncorporated
inBinghamton,NewYork.
Copyright© 1977byMclntoshLaboratoryInc.
1

Introduction
TheMclntoshC 32preamplifierprovidesthemostcom-
prehensiverangeoffunctionsandcontroloptions.Many
ofthesearenewina preamplifier.TheC 32canonly
serveyoubestwhenyouunderstandwhatitsfunctions
areandwhatitisdesignedtodo.Spendsometimewith
thismanualandgettoknowhowthispreamplifierworks.
TheC 32isa "dual"stereopreamplifierwitha built-in
MONITORPOWERAMPLIFIER.Therearetwototallyinde-
pendentleftandrightstereoprogramlinesrunning
throughthepreamplifier.OneprogramlineistheLISTEN
programline,theotheristheRECORDprogramline.Each
programlinecanselectitsownprogramsourcefromany
connectedinputsignal—i.e.PHONO,TUNER,AUX,or
TAPES1,2 or3 withoutinterferencewiththeotherpro-
gramline.
TheoutputoftheLISTENprogramlineisaffectedby
allthefrontpanelcontrols(excepttheRECORDswitch)
andisfedtotheOUTPUTMAINand/orOUTPUT1 and2
jacksasselectedbyfrontpanelpushbuttons.Theoutput
oftheRECORDprogramlineisnotaffectedbyfrontpanel
controls(excepttheRECORDswitch)andisfedtoall
OUTPUTRECORDjacks.
TheMONITORAMPLIFIERprogrammaybeselected
fromeithertheLISTENorRECORDprogramlines.Sepa-
rateGAINcontrolsforLEFTANDRIGHTMONITORAM-
PLIFIERarelocatedonthetoppanel.Thesignalselected
fortheMONITORAMPLIFIERisfedtothefrontpanel
HEADPHONEjacksandtherearpanelOUTPUTLINEand
MONITOROUTPUTconnectors.
Howtoinstall
ThePANLOCsystemofinstallingequipmentconve-
nientlyandsecurelyisa directresultofMclntoshresearch.
BydepressingthetwoPANLOCbuttonsonthefrontpanel
oftheC 32,theinstrumenteithercanbelockedfirmlyin
placeorunlockedsothatthechassiscanbeslidforward,
givingyoueasyaccesstothetopandrearpanels.
Thetrouble-freelifeofanelectronicinstrumentis
greatlyextendedbyprovidingsufficientventilationto
preventthebuildupofhighinternaltemperaturesthat
causedeterioration.Allowenoughclearancesothatcool
aircanenteratthebottomofthecabinetandbevented
fromthetop.Withadequateventilationtheinstrument
canbemountedinanyposition.Therecommendedmini-
mumspaceforinstallationis15inches(38.1cm)deep,
17inches(43.2cm)wide,and6 inches(15.2cm)high.
Toinstalltheinstrumentina Mclntoshcabinet,follow
theinstructionsthatareenclosedwiththecabinet.For
anyothertypeofinstallation:
1.UnpackfromCarton
RemovetheinstrumentPANLOCbrackets,hardware
package,andmountingtemplatefromthecarton.Re-
movetheC 32fromitsplasticbagandplaceitupside
downontheshippingpallet;unscrewthefourplastic
feetfromthebottomofthechassis.
2.MarkforPosition
Placethemountingtemplateinpositiontocoverthe
areaofthecabinetpanelwheretheinstrumentistobe
installed,andtapeitinplace.Thebrokenlinesthat
representtheoutlineoftherectangularcutoutalso
representtheoutsidedimensionsofthechassis.Make
suretheselinesclearshelves,partitions,oranyequip-
ment.Withthetemplateinplace,firstmarkthesixA
andB holesandthefoursmallholesthatlocatethe
cornersofthecutout.Then,jointhefourcornermark-
ingswithpencillines,usingtheedgeofthetemplate
asa straightedge.
2

3.DrillHoles
Usinga drillwitha 3/16inchbitheldperpendicularto
thepanel,drillthesixA andB holes.Then,usinga drill
bitslightlywiderthanthetipofyoursawblade,drill
oneholeateachoftwodiagonallyoppositecorners.The
holesshouldbarelytouchtheinsideedgeofthepencilled
outline.Beforetakingthenextstep,makesurethat
thesixA andB holeshavebeendrilled.
4.SawPanelCutout
Sawingcarefullyontheinsideofthepencilledlines,
firstmakethetwolongcutsandthenthetwoshort.
Aftertherectangularopeninghasbeencutout,usea
filetosquarethecornersandsmoothanyirregularities
inthecutedges.
5.InstallMountingStrips
Inthehardwarepackageyouwillfindtwomounting
stripsandtwosetsofmachinescrews.Forpanelsthat
arelessthan½ inchthick,usethe¾ inchscrews;for
panelsthataremorethan½ inchthick,usethe1¼inch
screws.
Startingattheright-handsideofthepanel,inserta
screwoftheproperlengthintothecenterholeinthe
panel,markedB onthetemplate.Onthebackofthe
panel,aligna mountingstripwiththeholesinthepanel
andtightenthescrewuntilthescrewheadispulled
slightlyintothewood.
Repeatthisproceduretoattachthemountingstrip
totheleftsideofthepanel.
6.AttachPANLOCBrackets
UsingtwoscrewsoftheproperlengthintheA holeson
eachside,attachthePANLOCbracketstothecabinet
panel;theshortflangeismountedagainstthefront
(face)ofthecabinetpanel.Thescrewspassthroughthe
PANLOCbracketflange,thecabinetpanel,andthen
throughthemountingstripspreviouslymounted.
7.InstallInstrument
GuidetheACpowercordthroughthepanelopeningto
thebackofthecabinet;then,slidetheinstrumentinto
theopeningcarefullysothattherailsonthebottomof
eachsideofthechassisengagethetracksonthemount-
ingbrackets.Continuetoslidetheinstrumentintothe
cabinetuntilitisstoppedbytheadjustpositionlatches.
Pressthelatchesinward,thispermitstheinstrumentto
slideintothecabinetuntilitsfrontpanelisflushwith
thecabinetpanel.DepressthePANLOCbuttonsatthe
lowerleftandrightcornersoftheinstrumentpanelto
locktheunitfirmlyinthecabinet.Depressingthe
PANLOCbuttonsagainwillunlocktheinstrumentso
thatitcanbeslidforwardtotheadjustposition;
pressinginwardontheadjustpositionlatchespermits
removalfromthecabinet
3

HowtoConnect
CONNECTINGA TURNTABLETOPHONO1
Connect the cablefrom the "left" channel ofthe turn-
tableintotheINPUTL PHONO1 jack.
Connectthecablefromthe"right"channeloftheturn-
tableintotheINPUTR PHONO1 jack.
PHONO2 isprovidedfortheuseofa secondturntable.
Connectthecablefromthe"left"channeloftheturn-
tableintotheINPUTL PHONO2 jack.
Connectthecablefromthe"right"channeloftheturn-
tableintotheINPUTR PHONO2 jack.
OntherearpanelaretwogreenACpoweroutletsand
aslideswitchmarkedAUTO/MANUAL.PlugtheACpower
cablesfromtheturntableintothegreenTURNTABLE
POWERoutletson therearpanel.Whentheswitchis in
theAUTOposition,powertotheblackACpowerout-
lets,canbecontrolledbythefrontpanelPOWERswitch
orbythecurrentdrawnbya turntablepluggedinto
thegreenTURNTABLEPOWERoutlets.Thecurrentsens-
inggreenACpoweroutletswillcontroltheACpower
totheentiresystemfromtheACpoweron/offswitchon
theturntable.Whentheturntableisturnedoffwithits
ownACpowerswitch,nocurrentisdrawnwhichcauses
thecurrentsensingrelaysintheC 32toturnoftallAC
powertothesystem.WiththeAUTO/MANUALswitchinthe
MANUALposition,ACpowertothesystemwillbecontrolled
bythefrontpanelPOWERpushbuttononly.
Someturntableshaveelectroniccircuitsthatdrawcurrent
allthetime.TousetheseturntablestheAUTO/MANUAL
switchmustbeintheMANUALposition.
ThegreenACpoweroutletsareprotectedwitha one
amperefuse.Anyincreaseinthevalueofthisfusewill
affecttheoperationofthesensingcircuitandcancause
severedamage.
GROUNDCONNECTION
Asinglegroundpostisprovided.Groundsforturntables,
recordchangers,tapedecks,etc.shouldbeconnectedto
thispost.Theleftandrightprogramcablesandtheground
wirefromthatsourceshouldbewoundortwistedtogether.
Toavoidhum,makesurethegroundwiredoesnotmake
anyconnectionstotheshieldsoftheleftandrightprogram
cablesbetweentheprogramsourceandtheC 32.
CONNECTINGA STEREOTUNER
Connectthecablefromthe"left"channeltuneroutput
totheINPUTL TUNERjack.
Connectthecablefromthe"right"channeltuneroutput
totheINPUTR TUNERjack.
AUX—Anyhighlevelprogramsourcesuchasa tuner,
aTVsetora taperecordercanbeconnectedtotheINPUT
AUXjacks.
CONNECTINGTAPERECORDERS
ToRecord:
Connecta cablefromtheOUTPUTL TAPE1 jacktothe
lefthighlevelinputofthetaperecorder.
Connecta cablefromtheOUTPUTR TAPE1 jacktothe
righthighlevelinputofthetaperecorder
Connectsecondandthirdtaperecordersinthesame
fashiontotheTAPE2 andTAPE3 outputs.
ToPlayback/Monitor:
Connectthecablefromtheleftchanneloutputofa tape
recordertotheINPUTL TAPE1.
Connectthecablefromtherightchanneloutputofa tape
recordertotheINPUTR TAPE1.
Connectsecondandthirdtaperecordersinthesame
fashiontotheTAPE2 andTAPE3 INOUTjacks.
TAPERECORDERFRONTPANELCONNECTION
InputsandoutputsforTAPE3 areavailableattheTAPE3
IN-OUTjacksonthefrontpaneljustleftofthepushbuttons.
Thisallowsrapid,temporaryconnectionstoTAPE3 position
withoutgettingattherearpanel,A metalshieldedV
stereophoneplugisusedforbestshielding—similarto
theplugsusedonlowimpedanceheadphones.Connections
followtheindustrystandardsandaretip:leftsignal,ring:
rightsignal,and,sleeve:commonground
Connectinga TapeRecordertotheListenProgramLine
Connecta cablefromtheOUTPUT1 —LEFTjacktothe
lefthighlevelinputofthetaperecorder
Connecta cablefromtheOUTPUT1—RIGHTjacktothe
righthighlevelinputofthetaperecorder.
Outputsignalwillbetedtothetaperecorderwhenthe
frontpanelpushbuttonOUTPUT1 ispushedin.
CONNECTINGTHEC 32TOPOWERAMPLIFIERS
ConnecttheOUTPUTMAINjackstotheinputofa
stereopoweramplifier.TheLeftMAINjackisconnected
totheleftamplifierinputjack.TheRightMAINjackis
connectedtotherightamplifierinputjack.
Twoadditionalstereopoweramplifiersmaybecon-
nectedinthesamefashiontotheOUTPUT1 andOUTPUT2
jacks.Audiooutputsignalissuppliedtothesejacksonly
whenfrontpanelpushbuttonSPEAKER/OUTPUT1 and2
pushbuttonsarepressedIN.Theinputimpedanceofthe
amplifiersusedshouldbe5,000ohmsorgreater.
SPEAKERCONTROLRELAY
TocontrolloudspeakersbyuseofSPEAKER/OUTPUT1
and2 pushbuttonsonthefrontpanelanaccessoryMclntosh
SCR(SPEAKERCONTROLRELAY)isneeded.Plugthespecial
cablefromtheSCRcontrolintotheSPEAKERCONTROL
RELAYreceptacle.Thespeakersarethenconnectedtothe
SCRcontrol.
TheSCRhastwoACpoweroutletsthatprovideaddi-
tionalcapacityof2400watts.Usetheseoutletstosupply
ACpowertoamplifiersorothercomponentstobecon-
trolledbytheONOFFcycleoftheC 32.UsetheSCR
wheneverthetotalloadtobeswitchedbytheC 32exceeds
itsratingof600watts.
4

TAPERECORDER3
TUNER
FMANTENNA
ACPOWERTO
TAPERECORDERS.
TUNERS,POWER
AMPLIFIERS.
TOTALOF600WATTS.
FORMOREACPOWER
USETHESCRSPEAKER
CONTROLRELAY
ACPOWER
ACPOWER
TURNTABLE#2
TURNTABLE#1
5
TAPE
RECORDER
2
TAPE
RECORDER
1

USEOF
PUSHBUTTONS
SPEAKER/OUTPUT
REMOTE
SPEAKERS
SPEAKER
CONNECTIONS
TOAC
LINE
6

MAIN
SPEAKERS
MONITORAMPLIFIER
SPEAKERS
7

UsingtheFrontPanelControls
LISTENandRECORDInputSelectorSwitches
Thecontrolatthelefttopofthefrontpanelselectsthe
inputfortheLISTENprogramline.Theleftbottomcontrol
selectstheinputfortheRECORDprogramline.Bothop-
erateinthesamemanner.
MODESELECTOR
TheMODESELECTORfacilitatestheaccurateadjustment
ofa stereosystemfordifferencescausedbyroomacous-
tics,loudspeakerplacementandtheothercomponents
usedinthesystem.
TheMODESELECTORswitchaffectstheprogramon
theLISTENprogramlineonlyandconnectstheprogram
totheloudspeakerinsevenways:
LtoL andR:Connectstheleftinputtobothloudspeakers.
RtoL andR:Connectstherightinputtobothloud-
speakers.
STEREOREV:Connectstheleftinputtotherightloud-
speakerandtherightinputtotheleftloudspeaker.
STEREO:Connectstheleftinputtotheleftloudspeaker
andtherightinputtotherightloudspeaker.
MONO(L+ R):Addstheleftandrightinputstogetherand
connectstobothloudspeakers.
L+ R toL:Connectstheleftplusrightprogramtothe
leftloudspeakeronly.
L- R toR:Connectstheleftplusrightprogramtothe
rightloudspeakeronly.
EQUALIZERFREQUENCYControls
EachoffiveEQUALIZERFREQUENCYcontrolsraisesor
lowersa bandoffrequenciescenteredonthefrequency
markedabovethecontrol.Bothleftandrightchannelsof
theLISTENprogramlineareaffected.Thecenter,orflat,
positionofthecontrolhasa detentforeasyreference.
UsetheEQUALIZERFREQUENCYcontrolstomodifythe
soundandbalanceofmaterial.Herearesomesuggestions
fromwhichtostart:
Problem
Basstooweak
Malevocalistneedsreinforcing
Femalereinforcing
Humonprogram
Violins,trumpetsdull
Drum"brushes"notaudible
EqualizerCorrection
Raise30and/or150
Raise150
Raise500
Reduce30andLFFILTER
Raise1500
Raise10K
Topreventinterferencefromsubsonicandsupersonic
signals,theC 32includessubsonicandsupersonicfilters
thatattenuatesignalsbelow20Hzandabove20,000Hz.
TheyarebypassedwhentheEQOUTpushbuttonispressed
INwhichextendsthefrequencyresponseto10Hzto
100,000Hz.
BALANCEandLOUDNESS
TheBALANCEandLOUDNESScontrolsareconcentric.
TheBALANCEcontrol(largeouterknob)adjustsforequal
volumeofeithertheleftorrightchannels.Thevolumeof
thechannelscanbevariedrelativetoeachotherwithout
affectingtheircombinedvolume.
LEFT. . . turningthecontroltotheleftaccentstheleft
channelbyreducingtherightchanneloutput.
RIGHT. . . turningthecontroltotherightaccentsthe
rightchannelbyreducingtheleftchanneloutput.
LOUDNESS
TheLOUDNESScontrol(smallcenterknob)increases
bothbassandtreblefrequenciesofbothchannelsasitis
turnedclockwise.AdjustmentoftheLOUDNESScontrol
allowslife-likefrequencybalancewhenplayingmusic
softly.Itscontouristhesame,regardlessoftheposition
ofthevolumecontrol.Thiscontourisaccuratelymodelled
afterthefamilyof"EqualLoudness"curvesidentifiedby
FletcherandMunson.
8

EXPANDER
TheEXPANDERaffectsbothchannelsoftheLISTEN
programlineonly.Thecircuitenablesyoutocorrectfor
thecompressionthatisimposedonmostoftheprogram
materialavailable—records,tapesandFM.Compression
isusedformanypracticalreasonsbutlimitsthedynamic
range—and,therefore,therealism—ofthemusic.Programs
varyintheirneedforexpansion.Liverecordingsmaynot
needanyatall.RotationoftheEXPANDERcausesthe
loudnessoftheprogramtobeaffectedlogarithmically.
Thepointatwhichoperationoftheexpanderstartsis
selectedbytherotaryLEVELMATCHcontrolonthetop
panel.Theattackspeedoftheexpanderissetwiththe
SPEEDswitchonthetoppanel.SettingsofFAST,NORM
andSLOWchangetheattacktimeoftheexpander.
AstheEXPANDERcontrolisrotatedclockwisethecircuit
actsintwoways:
1.Loudnessisreducedforsignalsbelowa predetermined
setlevel.Thefartherbelowsetleveltheprogramis,the
moretheloudnessisreduced.
2.Loudnessisincreasedforsignalsabovesetlevel.The
greatertheprogramisabovesetlevel,themorethe
loudnessisincreased.
Theamountofloudnessexpansionimposedonincoming
signalsisdeterminedbythepositionoftheEXPANDER
control.Clockwiserotationincreasestheeffect.Asthe
EXPANDERknobisrotatedclockwise,undesirablenoises
suchashum,scratchandhissarereduced.Thecharts
showtheactionoftheEXPANDERCIRCUIT.Whenrotated
fullycounterclockwise,thefrontpanelEXPANDERknob
activatesa switchwhichcompletelyby-passesallEX-
PANDERcircuitry.
TheLEVELMATCHcontrolonthetoppaneloftheC 32
adjuststhesetlevel.Thisisthepointaboveandbelow
whichexpansionisintroducedwhentheEXPANDERknob
isturnedclockwise.SettheLEVELMATCHcontrolsforeach
channelwhilelisteningtoa program.SwitchtheEXPANDER
inandout.Theaveragesoundlevelofthesystemshouldbe
thesamewiththeEXPANDERknobinthedesiredposition
ofEXPANSIONasitisinthebypass(OFF)position.
9

A.Toreducenoise(hum,hissorscratch)
1.SelectthedesiredprogramsourcewithLISTENfront
panelselectorswitch.
2.SwitchtoppanelSPEEDcontroltoNORM.
3.IncreaseVOLUMEcontrolduringa quietpassageof
theprogramuntilnoiseisclearlyaudible.
4. Rotate EXPANDER controlclockwise until the noise
isacceptablyreduced.
5.AdjusttheLEVELMATCHcontrols.
B.Toimprovethe"live"soundofrecordedortransmitted
programmaterial:
1.SelectLISTENinput.
2.SwitchtoppanelSPEEDcontroltoNORM.
3.IncreaseVOLUMEtosatisfactorylevel.
4.RotatetheEXPANDERcontrolclockwiseuntilthe
dynamicrangeofthemusic,theratioofloudtosoft
iscorrectforyou.
5.AdjusttheLEVELMATCHcontrolsasdescribedpre-
viously.
ByusingtheEXPANDERcontrolsinconjunctionwiththe
EQUALIZERFREQUENCYcontrols,theC 32maybeused
tode-emphasizeanddecompressdiscandtapeprogram
material.
HEADPHONEJacks
ThestereoHEADPHONEjacksaredrivenbythebuilt-in
MONITORAMPLIFIER.EitherLISTENorRECORDprograms
canbehearddependingonthepositionoftheINPUT
switchontheMONITORAMPLIFIERlocatedonthetop
panel.TheLEFTandRIGHTGAINcontrolsregulatehead-
phonevolume:
A.InconjunctionwiththemainfrontpanelVOLUMEcon-
trolifthetoppanelINPUTswitchisinLISTENposition,
B.ExclusivelyiftheINPUTswitchisinRECORDposition.
TheupperHEADPHONEjackisusedtofeedelectrostatic
headphones.ItisfeddirectlybytheMONITORAMPLIFIER.
Electrostaticheadphonesrequiremorepowerthandynamic
typeheadphonesasa rule.Thelowerheadphonejackis
usedtofeedlowimpedancedynamicheadphones.Itis
fedbytheMONITORAMPLIFIERthrougha matchingnet-
work.
MONITORAMPLIFIER
Althoughitsprimarypurposeistodrivetheheadphone
jacks,theMONITORAMPLIFIERmayadditionallybeused:
1.Tolisten,onspeakers,toanyoftheinputsconnectedto
theC 32withouttheuseofa separatestereopower
amplifier.Stereoloudspeakerscanbeconnectedtothe
rearpanel8 ohmterminals.Theprogramsourceforthe
MONITORAMPLIFIERmaybeselectedfromeitherthe
LISTENprogramlineortheRECORDprogramlineby
meansofthetoppanelINPUTswitch.BesidetheINPUT
switchareLEFTGAINandRIGHTGAINcontrols.They
controlthevolumeoftherespectivechannelsofthe
MONITORAMPLIFIER.
2.Todrivea 600ohmunbalancedlineconnectedto
OUTPUTLINEjacks.
3.TheextensiveflexibilityoftheC 32permitsmanyother
possibleusesoftheMONITORAMPLIFIERsuchas
addinga reverberationdevice,timedelayor"ambience"
accessoryunit,discrete4-channel,etc.
10

UsingthePushbuttons
PHONO1-2
ThePHONO1-2pushbuttonselectsfromeitherPHONO1
orPHONO2 inputs.Whenthebuttonisout—theindicator
abovethe1 willlightandthePHONO1 signalswillbe
connectedtotheLISTENandRECORDswitches.Whenthe
pushbuttonisin,theindicatorabovethe2 willlightand
thePHONO2 inputswillbeconnectedtotheLISTENand
RECORDswitches.
RECORDMONITOR
WhenpressedIN,theRECORDMONITORpushbutton
switchestheLISTENinputtotheoutputoftheRECORD
programline.IntheINpositiontheprogramheardonthe
LISTENprogramlineistheprogramontheRECORDpro-
gramline.
EQOUT
TheEQOUTpushbuttonoperatestobypasstheprogram
equalizers,theLFandHFfiltersandthesubsonicand
supersonicfiltersontheLISTENprogramline.Withthe
EQOUTpushbuttonpressedIN,thetotalbandwidthof
theC 32is10to100,000Hz.Theindicatorlightabove
theEQOUTpushbuttonisilluminatedwhenthepushbutton
ispressedINindicatingthattheEQUALIZERFREQUENCY
andtheHFandLFFILTERSareremovedfromthecircuit.
LFFILTER
TheLFFILTERaffectsonlytheLISTENprogramline
whenpressedin.WiththeLFFILTERINallfrequencies
below50Hzareattenuatedattherateof12dBperoctave.
Useittoreduceundesirablelowfrequencynoisesuchas
rumbleoracousticfeedback.
HFFILTER
TheHFFILTERaffectsonlytheLISTENprogramline.
WiththeHFFILTERINallfrequenciesabove7,000Hzare
attenuatedattherateof12dBperoctave.Useittoreduce
undesirablehighfrequencynoisesuchasrecordsurface
noiseortapehiss.
SPEAKER/OUTPUT1 and2
TheSPEAKER/OUTPUT1 and2 pushbuttonsoperate
onlyontheLISTENprogramline.Eachservedualpurposes.
WhenpressedIN,they
A.ConnecttheLISTENprogramtotheOUTPUT1 and2
jacksontherearpanel.Soundcanthusbeswitchedon
andoffinareasservedbyadditionalamplifierscon-
nectedtothesejacks.Typicaluseswouldbetheswitch-
ingofmusictoselectedlivingareas,a swimmingpool
oranoutdoorrecreationarea.
B.Controltheoperationofa SCRrelaywhenitisplugged
intotherearpanelSPEAKERCONTROLRELAYsocket.
TheSCRcontrolstheaudiototwopairsofstereoloud-
speakers.TheACpowertotwoACreceptaclesontheSCR
iscontrolledbytheON-OFFcycleoftheC 32.Thetotal
ACpowercapacityofthereceptaclesis2400watts.
POWER
The POWER switch energizes theC 32 circuits and sup-
pliesACpowertotheblackrearpanelACpoweroutlets.
TheblackACpoweroutletsarenotfused.
11

BalancingYourStereo
Theperformanceandenjoymentofa stereosystemis
greatlyincreasedwhenthesoundisproperlybalanced.
Balanceisaffectedbymanythingsincludingroomacous-
tics,furnitureplacement,roomshape,smalldifferencesin
loudspeakers,etc.Theinputgaincontrolsonyourstereo
poweramplifiershouldbeusedtobalancethesystem.
TheBALANCEcontrolontheC 32shouldbeusedtoadjust
forimbalanceinprogrammaterial.
1.SettheMODEtoMONO.
2.Playa familiarrecording.
3.TurntheBALANCEcontroltothe12o'clockposition.
4.Whiletheprogramisplaying,standbetweenthetwo
loudspeakers.Listenfora differenceinloudnessbe-
tweenspeakers.Balancethesystembyadjustingthe
controlsonthepoweramplifiers.Next,settheMODE
selectortoSTEREO.Ifthereisthena differencein
loudnessturntheBALANCEcontroltowardthespeaker
thatisnotasloud.AdjusttheBALANCEcontroluntil
thesoundisequallyloudfrombothspeakers.
ListeningtoYourStereo
LISTENINGTOSTEREORECORDS
TurntheLISTENselectortoPHONO1,orPHONO2,
whicheverisconnectedtotheturntableyouwishtohear.
SettheMODESELECTORtoSTEREO.
AdjusttheVOLUMEcontroltothedesiredvolume.
LISTENINGTOMONOPHONICRECORDS
TurntheLISTENselectortoPHONO1 orPHONO2,
whicheverisconnectedtotheturntableyouwishtohear.
TurntheMODESELECTORtoMONO
AdjusttheVOLUMEcontroltothedesiredvolume,
LISTENINGTOA TUNER
TurntheLISTENselectortoTUNER
Adjustthevolumetoa comfortablelevel.
LISTENINGTOA TAPERECORDER
ThreetaperecorderscanbeusedwiththeC 32.
TurntheLISTENselectortoTAPE1,2 or3 whicheveris
connectedtothetaperecorderyouwishtohear.
TurntheMODESELECTORtoSTEREOorMONO,depend-
ingontheprogramonthetape
AdjusttheVOLUMEcontroltothedesiredvolume.
TAPEMONITORING
Aprogrambeingrecordedmaybemonitoredeitheras
itisfedtothetaperecorder,or,inthecaseoftaperecorders
havingseparateplaybackheadsandassociatedpreampli-
fiers,directlyoftthetape.Tomonitortheprogrambeing
tedtothetaperecorder,presstheRECORDMONITOR
pushbuttonIN,Tomonitorfromtheplaybackheadofthe
taperecorderastheprogramisbeingrecordedturnthe
LISTENswitchtoTAPE1.2 or3.
USINGTHELISTENCONTROLSFORTAPERECORDING
Tomodifya programbeforerecording,theOUTPUT1
or2 outputsontheprogramlinemaybefedtoa tapere-
corder.Forconnectioninstructions,seepage4 under"How
toConnect."
ThecontrolsintheLISTENprogramlineareallavailable
toalterthesignalbeforerecordingNotethatoncere-
cordinghasstarted,thecontrolswillchangetheprogram
tothetaperecorder.Sincetheavailablesignaloutput
fromtheOUTPUT1 orOUTPUT2 ismuchhigherthanthe
outputavailablefromtheOUTPUTTAPE1,TAPE2,or
TAPE3 jacks,besurethesignaldoesnotoverloadthetape
recorderinput,
HOWTOCOPYTAPE
ThetapetobecopiedistedtoINPUTTAPE1 Setthe
RECORDselectortoTAPE1.Thesignalavailableatthe
OUTPUTTAPE2 and3 jacksistheplaybackofTAPE1
Recordingisdoneoneitherrecorder2 or3,orbothand
canbemonitoredontheLISTENprogramlinebyselecting
theappropriateTAPEpositionoftheLISTENknob.
12

PerformanceLimitsandRatings
PerformanceLimitsdiethemaximumdeviationfrom
perfectionpermittedfora Mclntoshinstrument.Wepromise
youthatyourC 32mustbecapableofperformanceator
exceedingtheselimitsoryougetyourmoneyback.
FREQUENCYRESPONSE
+0-0.5dB20Hzto20,000Hz
(withequalizerout:+0-1dBfrom10Hzto100,000Hz)
DISTORTION
.05%maximum,atratedoutputlevel,20Hzto20,000Hz
INPUTSENSITIVITYANDIMPEDANCE
PHONO1 and2 2 millivoltsat47,000ohms65pF,
AUXiltary,TUNERTAPE1,2 and3:250millivoltsat
50,000ohms
HUMANDNOISE
AUXiliary,TUNER,TAPE1,2 and3.IHF100dBun-
weighted--90dB
PHONO1 and2 IHF90dB,unweighted80dBbelow10
millivoltinputorequivalenttolessthan1 microvoltatthe
inputterminals
OUTPUTLEVELANDIMPEDANCE
MAINOutput2.5voltswithratedinput,220ohmssource
impedance,tooperateinto5,000ohmorgreater
TAPE Output 250 millivolts with rated input to operate
into5,000ohmsorgreater
MONITOR,HEADPHONE,LINEOutput:12
wattsperchannel,continuous,into8 ohms
at0,1%harmonicdistortion20Hzto
20,000Hzor5 voltsRMSinto600ohm
line—levelcontrolsprovided
PROGRAMEQUALIZER
Five,2 octavefrequencybands,eachbandhas12dBof
boostorcutat30,150,500,1500and10,000Hz
LFFILTER
Flatorroll-oftat12dBperoctavebelow50Hz
HFFILTER
Flatorroll-offat12dBperoctaveabove7000Hz
VOLTAGEAMPLIFICATIONinDecibels
(allequalizersandfiltersflat)
Input
Auxiliary,Tuner
Tape1,2 or3
Phono1
Phono2
Main
20dB
62dB
Tape
1,2,3
0dB
42dB
Monitor
Amp
20dB
62dB
SEMICONDUCTORCOMPLEMENT
67Transistors
35IntegratedCircuits
62Diodes
2FieldEffectTransistors
1SiliconControlledRectifier(SCR)
ACPOWEROUTLETS
2automaticcurrentsensing(green)
4switched(black)
POWERREQUIREMENTS
120volts,50/60Hz,25to85watts
MECHANICALINFORMATION
SIZE:Frontpanelmeasures16incheswide(40,64cm)by
5-7/16 inches deep (13.81 cm). Chassis measures 15
incheswide(38.1cm)by5 incheshigh(12.7cm)by13
inchesdeep(33.02cm),includingPANLOCshelfandback
panelconnectorsKnobclearancerequiredis1-1/2inches
(3.81cm)infrontofthemountingpanel.
FINISH:Frontpanelisanodizedgoldandblackwith
specialgold/tealnomenclatureillumination.Chassisis
black
MOUNTING:ExclusiveMclntoshdevelopedprofessional
PANLOC
WEIGHT,26pounds(11.79kg)net,36pounds(16.33kg)
inshippingcarton
13

14
PerformanceCharts

15

TechnicalDescription
Thedualprogramlinecontrolbeginsattwostereo
selectorswitchesfeedingfroma commongroupofinput
sources(PHONOPREAMP,TUNER,AUX,TAPE1,2,or3)
totwoseparatestereohighlevelamplifiers.Oneofthese
istheLISTENamplifier,theotheristheRECORDamplifier.
TheLISTENamplifierprovidessignalprocessingbyhigh
andlowpassfilters,fiveequalizers,loudnesscompensation
anda logarithmicexpander.Theother,theRECORDam-
plifier,feedstheselectedsignaltothetaperecordoutput
connections.
AstereomonitoramplifierintheC 32feedsHEAD-
PHONE,MONITORandLINEOUTPUT.Theinputtothe
MONITORAMPLIFIERcanbeselectedfromeitherLISTEN
orRECORDprogramlines.
PhonoPreamplifier
Eachphonopreamplifiercircuitusesfourspeciallyse-
lectedlownoisetransistorsarrangedinverylowimpedance
configuration.Toachievelownoisea 68ohmfeedback
terminationisused.Asa consequence,thepreamplifier
mustbecapableofoperatingasa poweramplifiertodrive
thislowimpedancewithlowdistortion.Theactualpower
outputcapabilityofthisstageismorethan100milliwatts.
TheC 32isengineeredtofollowtheRIAAequalization
curveprecisely.Onepercentresistorsandfivepercent
capacitorsareusedtoensureexactequalizationofthe
playbacksignaltotheRIAAcurve.
InputSelectorSwitching
Allinputswitchingisdoneelectronically,usingField
EffectAnalogswitches(FET).ThemechanicalLISTENand
RECORDswitchesonthefrontpanelaresimple,singledeck
switchesthatareselfcleaningandextremelyreliable.They
switchsmallDCvoltageswhichturntheFETAnalog
switchesonoroff.Thedesigneliminatesdegradationof
frequencyresponseornoisepickup.
ModeSelection
TheLISTENsignal,asitleaveitsinputselectorswitch
isconnectedtotheMODESELECTORswitch.Theconfigura-
tionofthisswitchpermitscombiningtheL andR programs
andconnectingtoLEFTorRIGHToutputs.Thisprocedure
revealssystemimbalanceoflessthana decibel,thuspro-
vidingthemeansforveryprecisesystembalancing.LEFT
inputtobothL andR outputsandRIGHTinputtoboth
LandR outputsisalsoprovidedagainaffordingthesame
degreeofprecisioninbalancinginputsignals.Theswitch
alsoprovidesSTEREOREVERSEandMONOpositions.
PreciseTrackingVolumeControl
Thevolumecontrolisdesignedandmanufacturedfor
MclntoshLaboratory.Itisa stepattenuatorwhichhasleft
torighttrackingaccuracywithin1 dBthroughoutitsentire
range.Suchextremelyaccuratematchingisachieved
throughelectronicallycontrolledlasertrimmingofthe
resistancematerialdepositedonpairsofprintedcircuits.
Sincetheswitchcommutatortouchesonlycontactpads
andnottheactualresistanceelement,trackingaccuracy
isnotdegradedwithuseasinordinaryvolumecontrols.
LoudnessCompensation
Inthepast,loudnesscontrolshavetypicallyusedsimple
passivecircuitsconnectedtoa taponthevolumecontrol.
Asa consequence,compensationaccuracywasdependent
onmanyvariablessuchasspeakerefficiency,amplifier
16

gainanddifferencesininputlevel.
TheC 32usesactivecircuitry,electricallyindependent
ofthevolumecontrol.CloseconformitytoFletcherMunson
EqualLoudnessCurvesisattainedregardlessofvolume
controlposition.
ActiveFilterCircuitry
Loudness,equalizer,andbandpassfiltersoftheC 32
areallconstructedwithionimplantedjunctionfieldeffect
operationalamplifiers(popularlycalled"OpAmps").
Thesenewdevicesamplifywitha 6 dBbettersignalto
noiseratiothanbipolarinputopamps.
ProgramEqualizers
Toadjustforprogramlimitationsandpersonalprefer-
encestheC 32LISTENprogramlinehasa fivebandboost/
cutprogramEQUALIZERbasedonresonantcircuitopera-
tionalamplifier.ThepreamplifierisflatwhentheEQUAL-
IZERcontrolsareatthe12o'clockposition.EQUALIZER
centerfrequenciesof30,150,500,1500and10,000Hz
werechosentocovertheaudiospectruminapproximately
equaltwooctavebandwidths.Maximumboostandcutis
12dBatbandcenters.
HF andLF Filters
TheHFandLFfiltersareselectedbypushbuttonswitches
ina mannerelectricallysimilartotheprogramEQUALIZERS
andarepushbuttonswitchselected.TheHFfilterattenu-
atesallfrequenciesabove5 kHz,reachinga rateof12dB
peroctave,at7 kHz(atwhichpointattenuationis3 dB
belowthe5 kHzlevel).TheLFfilterattenuatesallfre-
quenciesbelow50Hz,ata rateof12dBperoctave.
AllprogramEQUALIZERSandHF/LFfiltersarebypassed
whentheEQOUTpushbuttonswitchisdepressed.The
EQOUTswitchalsoremovessubsonicandsupersonicfil-
tersbelow20Hzandabove20,000Hz,extendingtotal
frequencyresponseto10Hzto100,000Hz.
TheExpander
Toovercomethecompressionimposedinradiobroad-
castingandrecording,andtoreducehum,scratchandhiss,
theC 32hasa logarithmicprogramexpanderinthe
LISTENprogramline.Controlsareprovidedtoadjustthe
operatingpoint,attacktimeandexpansionratio.
Signalfromtheequalizercircuitisappliedtoa voltage
controlledamplifier(VCA)whichoperatesasa variable
gainblock.ControlvoltagesforthisVCAaredeveloped
froma sampletakenfromtheoutputoftheequalizer.The
electronicprocessingofthissampleisdetailed.Itincludes
bandshaping,logarithmicamplification,fullwaverectifi-
cation,levelsetting,expansionratioregulation,attack
timing,levelsettingandDCamplification.Theresulting
voltagecontrolsthegainoftheVCAtocauselogarithmic
gainreductionbelowsetlevelandlogarithmicexpansion
abovesetlevel.
Aswitchedbypasslinkprovidesa programpatharound
theexpander,tomaintaina constantsignallevelwiththe
expanderinoroutofthecircuit.Thegainoftheamplifier
blockincorporatedinthelinkapproximatesthegainof
theexpandercircuit.
TheRecordProgramLine
TheC 32isdesignedtopermitsimultaneousrecording
onuptothreetaperecordersofanyprograminputselected
ontheRECORDswitchregardlessofwhatisbeingheard
ontheLISTENprogramline.TheRECORDswitchselects
itsinputfromthesameinputs,butentirelyindependently
fromtheLISTENswitch.Asthisselectionisbymeansof
highimpedanceFETAnalogswitches,switchingtoorover
aninputinuseontheLISTENprogramlinedoesnotcause
anyaudiointerference.
OutputfromtheRECORDswitchisfedthroughtape
interlockswitchestothethreepairsoftaperecorderoutput
jacks.Intheeventthatoneofthetaperecordersischosen
asaninputsignaltotheRECORDprogramline,itsasso-
ciatedtapeinterlockisopenedtopreventfeedbackthrough
thattaperecorderbackintotheC 32input.
MonitorAmplifier/HeadphoneCircuits
TheC 32containsa stereopoweramplifierwhichpro-
videsadequatepowertodriveelectrostaticheadphones.
TheupperHEADPHONEoutputjackisconnecteddirectly
tothisMONITORAMPLIFIERoutput,makingthefull12
wattsperchannelpoweravailabletodrivethosehead-
phoneswhichrequireit.ThelowerHEADPHONEjackis
fedthrougha networkdesignedtomatchlowimpedance
dynamicheadphones.
Inaddition,theMONITORAMPLIFIERmaybeswitched
toeitherprogramline,controlledandconnectedwith
enoughflexibilitythatseveralotherusesforitarepossible.
Someoftheseare:
1.Asa preamplifier/poweramplifierina completely
separatestereosystem.
2.Topowerrearchannelspeakerswhenusedina 4-
channeldiscreetsystem.
3.Tooperatespeakersinanotherarea.
4.Tofeeda 600ohmline.
OntherearpanelaretwogreenACpoweroutletsand
aslideswitchmarkedAUTO/MANUAL.PlugtheACpower
cablesfromtheturntableintothegreenTURNTABLE
POWERoutletsontherearpanel.Whentheswitchisin
theAUTOposition,powertotheblackACpoweroutlets,
canbecontrolledbythefrontpanelPOWERswitchor
bythecurrentdrawnbya turntablepluggedintothe
greenTURNTABLEPOWERoutlets.Thecurrentsensing
greenACpoweroutletswillcontroltheACpowertothe
entiresystemfromtheACpoweron/offswitchonthe
turntable.Whentheturntableisturnedoffwithitsown
17

ACpowerswitch,nocurrentisdrawnwhichcausesthe
currentsensingrelaysintheC 32toturnoffallACpower
tothesystem.
SpecialOutputSwitching
InadditiontotheOUTPUTMAINjacks,twoadditional
pairsofoutputjacks,OUTPUT1 andOUTPUT2,arepro-
vided.Theseareindividuallyswitchedfromthefront
panelpushbuttonsSPEAKER/OUTPUT.TheC 32output
signalcanbefedtotwoadditionalstereopoweramplifiers
independentofthemainsystemstereoamplifier.Alter-
natively,theseoutputsmaybeusedtodrivereverberation
devices,delaylines,etc.TheSPEAKER/OUTPUTpushbutton
switchesprovidethevoltagetocontrola SCRspeakercon-
trolrelay.
PowerSupply
Tominimizehumpickup—andthusimprovesignalto
noiseratio—theC 32powertransformeristripleshielded.
Shieldingincludesa copperstrap,a siliconsteelstrapand
finally,a steeloutershell.Thetransformeroutputvoltage
isfedtoa fullwavebridgewith5,000microfaradfilter
capacitorstoprovidetheplusandminus24voltspowering
theMONITORAMPLIFIER.Theplusandminus18volts
neededforlowlevelandopampstagesisderivedfromthe
24voltsupplyandcontrolledwithintegratedcircuitvol-
tageregulators.
TurnonDelay
TheC 32hastransientfreeturnonandturnoffcharac-
teristics.A relay,timecontrolledbya transistorswitch,
connectstheoutputofthepreamplifiertotheoutputjacks.
Thecontroltothetransistorswitchisderivedfroma long
timeconstantcapacitorchargingnetworkthatturnsthe
relayonapproximatelytwosecondsaftertheC 32is
turnedon.Thesamecircuithasa shortturn-offtimecon-
stantwhichturnsofftherelaybeforethepreamplifier's
mainpowersupplyhashada chancetodischarge.
18