McIntosh C26 User manual

READINGTIME:32Minutes
Price$1.25
THEMclNTOSHC 26SOLIDSTATESTEREOPREAMPLIFIER

YourC 26stereopreamplifierwill
giveyoumanyyearsofpleasant
andsatisfactoryperformance.
Ifyouhaveanyquestionsconcerning
thisinstrument,pleasecontact:
CUSTOMERSERVICE
MclntoshLaboratoryInc.
2ChambersStreet
Binghamton,NewYork13903
Phone:[phone]
WARNING:TOPREVENTFIREORSHOCK
HAZARD,DONOTEXPOSETHISUNITTO
RAINORMOISTURE.
TakeAdvantageof3 years
ofFREEService. . .
FillintheApplicationNOW.
CONTENTS
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©1970ByMclntoshLaboratoryInc.
HowtoConnect...4,5,6
WhattheControlsDo...7,8
UsingtheFrontPanelControls...8,9
UsingthePushbuttons...10
AdjustingtheTopPanelControls...11
ListeningtoYourStereoSystem...11
PerformanceLimits...12,13
PerformanceCharts...14
TechnicalDescription...15
BlockDiagram...16
ServiceContract...1
Installation...2,3
THREEYEARSERVICECONTRACT
1

Adequateventilationextendsthetrouble-free
lifeofelectronicinstruments.Itisgenerallyfound
thateach10°centigrade(18°F)riseintempera-
turereducesthelifeofelectricalinsulationbyone
half.Adequateventilationisaninexpensiveand
effectivemeansofpreventinginsulationbreak-
downthatresultsfromunnecessarilyhighoperat-
ingtemperatures.Thedirectbenefitofadequate
ventilationislonger,trouble-freelife.
Allowatleast15inchesdeepx 17½incheswide
x6 incheshighformountingtheC 26.Always
allowforairflowbyeitherventilationholesor
spacenexttothebottomofthepreamplifierand
ameansfora warmairtoescapeatthetop.
ItisrecommendedthattheC 26bemountedin
anormalorhorizontalposition.However,with
adequateventilationthepreamplifiercanbe
mountedinanyposition.
TopreparetheC 26forinstallationremovethe
plasticprotectivecovering.TurntheC 26upside
downsothatitrestsonitstopontheshipping
pallet.Removethefourplasticfeetfastenedto
thebottomofthechassis.
Next,placethemountingbrackets,theparts
bagandthemountingtemplateathand.
ThePANLOCprofessionalmountingdesignelimi-
natestheneedforanyshelforbrackettosupport
theC 26.Itiscompletelysupportedbyitsown
mountingbrackets.
Thedesignofthemountingtemplateallowsyou
topositionorlocatethecutoutfromthefrontor
rearofthepaneltowhichtheinstrumentistobe
mounted.Positiontheplasticmountingtemplate
overtheareaofthepaneltobecutoutforinstalla-
tion.
Ifthecutoutistobelocatedfromthefrontof
thepanel,beginatstep2.Ifthecutoutistobe
locatedfromtherearofthepanel,beginhere.
1.Onthebackofthecabinetpanel,scribea
verticalcenterlinethroughtheexactcenterof
theareainwhichthecutoutistobemade.
Placethetemplateagainstthebackofthe
panelandmatchthetemplatecenterlinewith
thecenterlineonthecabinetpanel.
Makesurethatthereisatleast¼ inchclear-
ancebetweenthebottomofthedashedline
ofthecutoutareaonthetemplateandany
shelforbracebelowtheproposedcutout.
Markthetwolocatingholes("C"holeson
themountingtemplate).
Drillthetwolocatingholes.Becertainthe
drillisperpendiculartothepanel.
Nowpositionthetemplateonthefrontofthe
panelbyaligningthe"C"locatingholeson
thetemplatewiththedrillholes.
2.Ifthecutoutistobelocatedfromthefrontof
thepanel:
Withthetemplateinplaceagainstthecabi-
netpanel,markthe"A"and"B"drillholesand
thefoursmallholesthatidentifythecornersof
thecutout.Jointhecornermarkswitha pencil.
Theedgeofthetemplatecanbeusedasa
straightedge.
IMPORTANT:DRILLTHE6 HOLESBEFORE
MAKINGTHECUTOUT.
Accuratelydrillthethreeholesoneachsideof
thecutoutareawith3/16inchdrill.
WiththesawontheINSIDEOFTHEPENCIL
LINEScarefullycutouttherectangularopening.
Securethemountingstripstotherearofthe
cabinetpanelusingtwoscrewsfromthehardware
package.
2

instrumentinuntilthefrontpanelisagainstthe
cabinetpanel.Atthebottomfrontcornersofthe
PANLOCinstrumentsarethePANLOCbuttons.
DepressingthePANLOCbuttonswilllockthein-
strumentfirmlyintheinstallation.Depressingthe
PANLOCbuttonsa secondtime(aswitha ball-
pointpen)willreleasetheinstrument.Youcan
thenslidetheinstrumentforwardtotheinspec-
tion-adjustmentposition.Depressingtheinspec-
tion-adjustmentpositionlatcheswillallowthein-
strumenttobeslidcompletelyoutoftheinstalla-
tion.
Insertthescrewsinthecenterholesofthecabi-
netpanel("B"holesonthetemplate)andtighten.
Thescrewheadshouldpullintothewoodslightly.
(Usetwo¾ inchlongscrewsforpanelsunder½
inch,ortwo1¼inchlongscrewsforpanels½ inch
thickandlarger.)
Attachthemountingbracketstothecabinet
usingfourscrews.
Placethetemplateoverthemountingscrews.
Themountingscrewsshouldbecenteredinthe
"A"and"B"holesonthetemplate.Thesidesof
themountingbracketsshouldmatchthevertical
dashlinesonthetemplate.Ifnecessary,loosen
thescrewsandpushthebracketsintoalignment
andretighten.
Insertthepowercordthroughtheopening.
CarefullyslidetheC 26intotheopeningsothe
railsonthebottomoftheequipmentslideinthe
trackofthemountingbrackets.Slidetheinstru-
mentinuntilitstopsattheadjustpositionlatches.
Pressthelatchesinandcontinuetoslidethe
3

HowtoConnect
CONNECTINGA RECORDPLAYERTOPHONO1
Connectthecablefromthe"left"channelofthe
recordplayerintothe"L"PHONO1 inputjack.
Connectthecablefromthe"right"channelof
therecordplayerintothe"R"PHONO1 jack.
PHONO2 isprovidedfortheuseofa second
recordplayer.
Connectthecablefromthe"left"channelofthe
recordplayerintothe"L"PHONO2 inputjack.
Connectthecablefromthe"right"channelof
therecordplayerintothe"R"PHONO2 inputjack.
CONNECTINGA STEREOTUNER
Connectthecablefromthe"left"channeltuner
outputtothe"L"tunerinputjack.
Connectthecablefromthe"right"channel
tuneroutputtothe"R"tunerjack.
AUX
Anyhighlevelprogramsourcesuchasanother
tunerora TVsetisconnectedtotheinputjacks
markedAUX.
CONNECTINGA TAPERECORDER
ToRecord:
Connecta cablefromtheL TAPEOUTPUTjack
markedTAPE1 tothelefthighlevelinputofa tape
recorder.
Connecta cablefromtheR TAPEOUTPUTjack
markedTAPE1 totherighthighlevelinputofthe
taperecorder.
Connecta secondtaperecorderinthesame
fashiontotheTAPE2 outputs.
ToPlayback/Monitor:
Connectthecablefromtheleftchanneloutput
ofa taperecordertothehighlevelinputs. . . L
TAPE1.
Connectthecablefromtherightchanneloutput
ofa taperecordertothehighlevelinput...R
TAPE.
Connecta secondtaperecorderinthesame
fashiontotheTAPE2 inputjacks.
CONNECTINGTHEC 26toPOWERAMPLIFIERS
ConnecttheMAINoutputjackstotheinputofa
stereopoweramplifier.TheL jackisconnected
totheleftamplifierinputjack.TheR jackiscon-
nectedtotherightamplifierinputjack.
TheoutputimpedanceattheMAINoutputis200
ohms.Longercablesthanaresuppliedcanbe
connectedbetweentheC 26andtheamplifiers.
Thelengthofthecableislimitedbythecapacity
ofthecable.Thetotalcapacitymustnotexceed
1,000pF.Forinstance:cableswitha capacityof
25pFperfootmaybe40feetlong.13.5pFper
footcablemaybe75feetlong.Theinputimped-
anceoftheamplifiersshouldbe47,000ohmsor
greater.
CTROUTPUT(L+ R)
UsetheCTRoutputtofeedleftplusrightsignal
toa separatepoweramplifierformonophonic
backgroundmusicorfora centerchannelspeaker.
ACPOWEROUTLETS
Thereare4 blackACpoweroutlets,andonered
ACoutlet.ThepowertotheblackACpowerout-
letsiscontrolledbythefrontpanelswitch.Use
theseoutletsfora tuner,taperecorder,etc.The
redreceptacleisonatalltimes.Usetheredoutlet
fora turntableorrecordchanger.Theturntableor
recordchangerisprotectedbythisarrangement.
Itisnecessarytoturnofftheturntableorrecord
changerwithitsownACpowerswitch.
GROUNDCONNECTION
Asinglegroundpostisprovided.Groundsfor
turntables,recordchangers,tapedecks,etc.
shouldbeconnectedtothispost.Theleftand
rightprogramcablesandthegroundwirefrom
thatsourceshouldbewoundortwistedtogether.
Toavoidhum,makesurethegroundwiredoes
notmakeanyconnectionstotheshieldsoftheleft
andrightprogramcablesbetweentheprogram
sourceandtheC 26.
4

TAPE
RECORDER
1
TAPE
RECORDER
2
TUNER
£
TAPE
MACH.
AC
LINE
TURNTABLE
AC
LINE
AC
LINE
5
FM
ANTENNATUNER
GROUND
LINE
TURNTABLE

AC
LINE
MONO
AMP
STEREO
AMP
AC
LINE
6
LEFT
REMOTESTEREO
LOUDSPEAKER
SYSTEM
RIGHT
LEFT
MAINSTEREOLOUDSPEAKERSYSTEM
CENTER
RIGHT
MONOLOUDSPEAKER
SYSTEM

Whatthe
ControlsDo
LOUDNESSCONTROL
FLATposition:(Maximumcounterclockwisero-
tation)Normalflatfrequencyresponse.Theloud-
nesscompensationistotallyinoperativeatthis
position.
Aloudnesscontrolprovideslow-frequencyboost
tocompensateforthebehaviorofthehumanear
atlowlisteninglevels.Theearislesssensitiveto
lowfrequenciesatlowlevels.Theloudnesscon-
trolfillsinlow-frequencytonesthattheearwould
normallyhearonlyathigherlisteninglevels.In-
creasedloudnesscompensationisthereforede-
sirableasthelisteninglevelisreduced.
TheC26LOUDNESSCONTROLautomatically
compensatesforthelackofsensitivityintheearas
thelisteninglevelisreduced.Thelowfrequencies
arethenheardincorrectproportiontothemid-
rangeandhighs.TurningclockwisetowardMAX
positionreducesthelisteningvolume,andauto-
maticallyincreasesthecompensationbyboosting
bass.Usetheloudnesscontrolforfullfrequency
rangelisteningateventhesoftestlisteninglevels.
TAPEMONITORSWITCH
TheC26TAPEMONITORswitchmakesitpos-
sibletoinstantaneouslycomparerecordedmaterial
withthesourcesignalfromeitheroftwotape
recordersusedwiththeC 26.Therecordersused
withtheC 26shouldhaveseparaterecordand
playbackheadsandseparaterecordandplay
amplifiers.
MONITOR
Withthebuttonpushedin,thesignalsourcebe-
comestheprogramasrecordedandisfedthrough
themainpreamplifieroutputstothepowerampli-
fiersandloudspeakers.
TheTAPEMONITORswitchesaremechanically
interlockedtopreventsimultaneousmonitoring
fromtwotaperecorders.IfonebuttonisattheIN
position,itmustbepushedagaintoreleaseitto
theOUTpositionbeforetheotherbuttoncanbe
pushed.
USINGONETAPERECORDER
Theoutputofa taperecordercanbeconnected
toeitherTAPE1 orTAPE2 input.Thecorrespond-
ingtapeoutputoftheC 26shouldthenbecon-
nectedtotheinputofthetaperecorder.Any
sourcecanberecordedwithoutbeingaffectedby
thetonecontrolorvolumecontrolsettings.The
playbackofthetaperecordingcanbemonitored
bypushingthecorrespondingtapemonitorbutton.
TWOTAPERECORDERS
TwotaperecorderscanbeusedwiththeC 26
preamplifier.Recordingscanbemadefromre-
corder1 torecorder2,orfromrecorder2 to
recorder1.
7

Example:Connecttheoutputofrecorder1 to
TAPE1 inputontheC 26.ConnecttheTAPE1
outputontheC 26totheinputofrecorder1.In
thesameway,connecttheoutputofrecorder2 to
TAPE2 inputontheC 26.ConnectTAPE2 output
oftheC 26totheinputofrecorder2.
BysettingtheC 26inputselectorswitchat
TAPE1,a recordingcanbemadeontaperecorder
2froma tapeplayingontaperecorder1.There-
cordingcanbemonitoredfromtheplaybackof
taperecorder2 bypushingtheTAPE2 monitor
button.
Thetaperecorderfunctionscanbereversedby
settingtheinputselectorswitchatTAPE2.A re-
cordingcanthenbemadeontaperecorder1,
froma tapeplayingontaperecorder2.There-
cordingontaperecorder1 canbemonitoredfrom
theplaybackoftaperecorder1 bypushingthe
TAPE1 monitorbutton.
TheC 26preamplifiercanalsobeusedwithone
recorderforrecordingotherprogramsourceswhile
playingtapesfroma secondrecorder.
Example:Connecttheoutputoftaperecorder1
totheTAPE1 inputsoftheC 26.Connecttheout-
putsoftaperecorder2 totheTAPE2 inputsofthe
C26.ConnecttheTAPE2 outputsoftheC 26to
theinputsoftaperecorder2.
ArecordingfromAUX,TUNER,PHONO1 or
PHONO2 canbemadeontaperecorder2 ifthe
selectorswitchissettothecorrespondingsource
position.Therecordingontaperecorder1 canbe
monitoredforplaybackbypushingtheTAPE2
monitorbutton.Atthesametime,theC 26canbe
usedtoplaya tapefromtaperecorder1 byreleas-
ingthemonitorbuttonforTAPE2 andpushingthe
monitorbuttonforTAPE1.Thesignaloftape
recorder1 willthengotothemainpreamplifier
outputswithoutaffectingtherecordingbeingmade
ontaperecorder2.
Taperecordingscanbemadesimultaneouslyon
twotaperecordersbyusingPHONO1,PHONO2,
AUXorTUNERasa programsource.Thetape
recordersshouldbeconnectedasdescribedin
example1.Settheinputselectorswitchtothe
desiredsource.Therecordingoneithertapere-
cordercanbemonitoredforplaybackbypushing
theappropriatetapemonitorbutton.
CAUTION:Whenrecordingwithtwotaperecorders
atthesametimefromthesameprogramsource,
mutualinterferenceoftherecorderbiasoscillators
canresult.Thiscanbeheardasa howlorsqueal
inthebackgroundwhentherecordingsareplayed
back.Thisnoiseiscausedbyinsufficientfiltering
ofthebiasoscillatorcircuitsinthetaperecorders.
Atestrunshouldbemadefortheparticularre-
cordersintendedforthisuse.
SPEAKERSWITCHES
Toswitchthemainandremotestereospeakers
usingthepushbuttonsonthefrontpanel,the
poweramplifieroutputleadsmustbeconnected
totheamplifieroutputterminalsontherearofthe
C26.Themainspeakersmustbeconnectedtothe
mainspeakerterminalsandtheremotespeakers
totheremotespeakerterminals.Ifeithermainor
remotespeakerbuttonispushedtoOFF,load
resistorsareautomaticallyconnectedtothepower
amplifiertocompensateforthespeaker.The
headphoneoutputisalwaysconnectedthrough
levelmatchingresistorstotheamplifierterminals
regardlessofthepositionofthemainorremote
switches.
8
Usingthe
FrontPanelControls
In theupperrightof thefrontpanelis theVOL-
UME-ON/OFFcontrol.
TurningtheVOLUMEtotallycounterclockwise
turnstheC 26OFF.TheVOLUMEcontrolregu-
latestheloudnessinbothchannels.TheVOLUME
controlhasbeenprecisiontrackedthroughoutthe
listeningrange(0to-65dB)foraccuratestereo
balance.
MODESELECTOR:Connectstheprogramtothe
loudspeakerinthefollowingsevenways:
LtoL & R:Connectsthe"left"inputtoboth
loudspeakers.
RtoL & R:Connectsthe"right"inputtoboth
loudspeakers.
STEREOREV:Connectsthe"left"inputtothe
"right"loudspeakerandthe"right"inputto
the"left"loudspeaker.
STEREO:Connectsthe"left"inputtothe"left"
loudspeakerandthe"right"inputtothe
"right"loudspeaker.
MONO(L+ R):addsthe"left"inputandthe
"right"inputandthenconnectstheL+R
programtobothamplifiersandloudspeakers.
L+ R toL:Connectsthe"leftplusright"pro-
gramtothe"left"loudspeakeronly.
L+ R toR:Connectsthe"leftplusright"pro-
gramtothe"right"loudspeakeronly.
INPUTSELECTOR:
Aux:Connectstheoutputfromanyhighlevelpro-
gramsourcerequiringflatamplificationtothehigh
levelinputstage.Sucha sourcecouldbea tele-

visionsetorothersourcethathasoutputof0.25
voltsormore.IntheAUXpositionthegainis20dB
totheMAINoutputs,0 dBtotheTAPEoutputs.
Theinputimpedanceis250,000ohms.
TAPE1:Connectstheoutputfroma completetape
recordertothehighlevelinputstageoftheC 26.
IntheTAPE1 positiontheC 26hasflatamplifica-
tion.Thereis20dBofgaintotheMAINoutputs,
0dBtotheTAPEOUTPUTS.
TAPE2:Connectstheoutputfroma completetape
recordertothehighlevelinputstageoftheC 26.
IntheTAPE2 positiontheC 26hasflatamplifica-
tion.Thereis20dBofgaintotheMAINoutputs,
0dBtotheTAPEOUTPUTS.
TUNER:ConnectstheoutputfromanyAM,FMor
FMSTEREOtunertothehighlevelinputstageof
theC 26.IntheTUNERpositiontheC 26hasflat
amplification.Thereis20dBofgaintotheMAIN
outputs,0 dBtotheTAPEoutputs.Theinputim-
pedanceis250,000ohms.
PHONO1:Connectstheoutputofanymagnetic
phonocartridgetothelowlevelinputstageofthe
C26.Theresponsehasbeenshapedtocompen-
sateforthecharacteristicsofthemagneticphono
cartridge.Thegainat1000Hzis62dBtotheMAIN
outputs,42dBtotheTAPEoutputs.Theinput
impedanceis47,000ohms.
PHONO2:SameasPHONO1.
LOUDNESS
TheC 26LOUDNESScontrolautomatically
booststhebassasitturnsdownthelisteningvol-
ume.Thebassisthenheardincorrectproportion
tothemid-range.
TurningclockwisetowardMAXpositionreduces
thelisteningvolume,whileautomaticallyboosting
thebassforfullfrequencylisteningateventhe
lowestvolumelevels.
TheC 26LOUDNESScontrolautomatically
booststhebassasitturnsdownthelisteningvol-
ume.Thebassisthenheardincorrectproportion
tothemid-range.
TurningclockwisetowardMAXpositionreduces
thelisteningvolume,whileautomaticallyboosting
thebassforfullfrequencylisteningateventhe
lowestvolumelevels.
BALANCE
TheBALANCEcontroladjustsforunequalloud-
nessineithertheleftorrightchannels.Theloud-
nessofthechannelscanbevariedrelativetoeach
otherwithoutaffectingtheircombinedloudness.
Left. . . turningthecontroltotheleftaccents
theleftchannelbyreducingtherightchannelout-
put.
Right.. . turningthecontroltotherightaccents
therightchannelbyreducingtheleftchannelout-
put.
BASS
TheC 26hasconcentric11positiontonecontrol
switchesforadjustingthebass.Theouterknob
adjuststheleftchannelbassresponse.Thecenter
knobadjuststherightchannelbassresponse.
Left:Adjuststhebassloudnessfromtheleft
loudspeaker.Clockwiserotationincreasesthe
bassloudnesswhilecounterclockwiserotationde-
creasesthebassloudness.Eachstepofthetone
controladjuststhebassloudness4 dB.
Right:Hasthesameeffectonthesoundfrom
therightloudspeaker.
TREBLE
TheC 26hasconcentric11positiontonecontrol
switchesforadjustingthetreble.Theouterknob
adjuststheleftchannelresponse.Thecenterknob
adjuststherightchanneltrebleresponse.
Left:Adjuststhetrebleloudnessfromtheleft
loudspeaker.Clockwiserotationincreasesthe
trebleloudnesswhilecounterclockwiserotation
decreasesthetrebleloudness.Eachstepofthe
tonecontroladjuststhetrebleloudnessabout
4dB.
Right:Hasthesameeffectonthesoundfrom
therightloudspeaker.
HEADPHONES
Lowimpedancedynamicheadphonesareplug-
gedintotheHEADPHONEjack.
Theoutputofthepoweramplifiersmustbeprop-
erlyconnectedtotheC 26backpanelforprogram
materialtobeavailableattheHEADPHONEjack.
9

UsingthePushbuttons
TheC 26isdesignedtobeusedwithtwocom-
pletetaperecorders.Thepushbuttonspermitnor-
malplaybackofeitherrecorder,ormonitorof
eitherrecorderasrecordingsarebeingmade.
TAPE1
PUSHBUTTONOUT. . . Theprogramsourceis
fedtothepoweramplifiersandheardthroughthe
loudspeakers.
IN...Theprogramsourcebecomesthere-
cordedtapeonthetaperecorderconnectedto
TAPEINPUT1.Therecordedprogramfromtape
recorder1 isfedtothepoweramplifiersandheard
fromtheloudspeakers.
TAPE2
Thesecondcompletetaperecordercanbe
operatedinthesamefashion.
LF (LOWFREQUENCYFILTER)
UsetheL F filterswitchtoreduceobjection-
ablelow-frequencynoisecreatedbya turntableor
recordchangeroracousticallycoupledfeedback.
OUT. . . filterdisconnected.
IN...low-frequencyrumbleandnoisebelow50
Hzarereducedwhentheswitchispushedtothe
INposition.
HF (HIGHFREQUENCYFILTER)
UsetheH F filterswitchtoreduceobjection-
ablehigh-frequencynoisesuchasrecordscratch.
OUT. . . filterdisconnect.
IN...rollsoffresponsesharplyat7000Hz.
SPEAKER
Whentheoutputofthepoweramplifierandthe
speakershavebeenconnectedtotheproperpush
connectersonthebackpanel,thepushbuttons
turnthespeakersONorOFF.(SeeDiagramPage
6).
Iftheprogramistobeheardfromthemain
speakersonly,theREMOTEpushbuttonispushed
IN.Thisturnsofftheremoteloudspeakers.
Iftheprogramistobeheardfromtheremote
speakersonlytheMAINpushbuttonispushedIN.
Thisturnsoffthemainspeakers.
Tohearprogramfrombothmainandremote
speakers,boththeMAINandREMOTEpushbut-
tonsmustbeintheOUTposition.
MAIN
PUSHBUTTONOUT...theprogrammaterial
isheardfromtheMAINspeakers.
IN...theMAINloudspeakersareturnedOFF.
REMOTE
PUSHBUTTONOUT...theprogrammaterial
isheardfromtheREMOTEloudspeakers.
IN...theREMOTEloudspeakersareturned
OFF.(Thesepushbuttonsdonotaffectthehead-
phonejack.)
PANLOC
MclntoshdevelopedPANLOCmountingbrings
professionalinstallationstechniquetostereo.
WhentheC 26hasbeeninstalledonPANLOC
brackets,pressingthePANLOCbuttonslocksthe
amplifierfirmlyinposition.Depressingthebuttons
(aswitha ballpointpen)willreleasetheinstru-
ment.Itcanthenbeslidforwardtothe"adjust-
ment"position.Inthe"adjust"positionthetop
panelcontrolsPHASEandCENTERCHANNEL
LEVELcanbeadjusted.ThePANLOCsystemgives
absoluteeaseofinstallation,operation,andmain-
tenance.
10

Adjustingthe
TopPanelControls
PHASE—ThePHASEisa two-positionswitch
thatreversesthephaseintheleftchannel.Im-
properlyphasedprogramsourcescanbecor-
rectedwiththisswitch.
1.SettheMODESELECTORswitchtoMONO.
2.Standabout10feetinfrontofandmid-way
betweenyourloudspeakers.Thesound
shouldappeartobedirectlyinfrontofyou.
Ifthesoundisnotdirectlyinfrontofyou
withthePHASEswitchinthe0°reversethe
leadsononeloudspeaker.Whenthesound
comesfromthemid-pointbetweenthe
speakerstheyareinPHASE.
CENTERCHANNELLEVEL— Leftandright
channelsareaddedtomakea centerchannelpro-
gramsource.Theprogramcanbefedtoa third
amplifierfora centerchannelspeakerorformono-
phonicremotespeakers.TheCENTERCHANNEL
LEVELcontroladjuststhevolumeonCTRCHAN-
NELoutputjackonly.Adjustmentisfrom—6dBto
+6dBwithrespecttotheMAINoutput.Clockwise
rotationincreasestheloudness.
ListeningtoYour
Stereosystem
LISTENINGTOA STEREORECORD
1.TurntheINPUTSELECTORtoPHONO1,or
PHONO2,whicheverisconnectedtothe
recordplayeryouwishtohear.
2.SettheMODESELECTORtoSTEREO.
3.AdjusttheVOLUMEcontroltothedesired
volume.
LISTENINGTOMONOPHONICRECORDS
1.TurntheINPUTSELECTORtoPHONO1,or
PHONO2,whicheverisconnectedtothe
recordplayeryouwishtohear.
2.TurntheMODESELECTORtoMONO.
3.AdjusttheVOLUMEcontroltothedesired
volume.
LISTENINGTOA TAPERECORDER
TheTAPEinputisused:
1.TurntheINPUTSELECTORtoTAPE.
2.TurntheMODESELECTORswitchto
STEREOorMONO,dependingonthepro-
gramonthetape.
3.AdjusttheVOLUMEcontroltothedesired
volume.
TwotaperecorderscanbeusedwiththeC 26.
Connecta threeheadtaperecordertoTAPE1
inputs.Connecta secondthreeheadtaperecorder
toTAPE2.Recordingandmonitoringcanbedone
withbothtaperecorders.
Tomonitorwhilerecordingyourtaperecorder
musthaveseparaterecordandplaybackheads
andseparateelectronics.Thepushbuttonswitch
letsyoumonitorthequalityoftaperecordings
madeduringtherecordingprocess.Whenthe
TAPEswitchisintheINpositionitwillplaythe
soundfromthetapeasitpassestheplayback
head,a momentafteritisrecorded.Therecording
processcontinuesasusual.Whentheswitchisin
theOUTpositionnormalprogramfromthesource
isheard.
HOWTOCOPYTAPE
1.Putthetapeontherecorderconnectedto
TAPE1 input.
2.TurntheinputselectortoTAPE1.
3.ThesignalavailableattheTAPEOUTPUT
jacksistheplaybackofTAPE1.
4.RecordontherecorderconnectedtoTAPE
2.Therecordingcanbemonitoredbypress-
ingintheTAPE2 pushbutton.Instantaneous
comparisonontherecordedprogramwith
theoriginalcanbeheard.
11

PerformanceLimits
POWERREQUIREMENT
120volts,50/60Hz,15watts
PerformanceLimitsarethemaximumdeviation
fromperfectionpermittedfora Mclntoshinstru-
ment.WepromiseyouthatyourC 26mustbe
capableofperformanceatorexceedingthese
limitsoryougetyourmoneyback.Mclntoshis
theonlymanufacturerthatmakesthisguarantee.
FREQUENCYRESPONSE
+0-0.5dB20Hzto20,000Hz
DISTORTION
Willnotexceed0.1%atratedoutputlevel,20
Hzto20,000Hz
INPUTSENSITIVITYANDIMPEDANCE
AUXILIARY,TUNER,TAPE1,TAPE2 0.25volts
at250,000ohms
HUMANDNOISE
AUXILIARY,TUNER,TAPE1,andTAPE2 85dB
belowratedoutput
PHONO1,PHONO2 74dBbelow10millivolts
input,equivalenttolessthan2 microvoltsat
theinputterminals
OUTPUTLEVELANDIMPEDANCE
MAINOUTPUT2.5voltswithratedinput,200
ohmssourceimpedance,tooperateinto47,-
000ohmsorgreater
TAPEOUTPUT0.25voltsfromlowlevelinputs,
200ohmssourceimpedance,tooperateinto
47,000ohmsorgreater
CENTERCHANNELOUTPUT(L+ R)2.5volts
withratedinputtobothchannels,1,200ohms
sourceimpedance,tooperateinto47,000
ohmsorgreater
AlevelcontroladjuststheCENTERCHANNEL
outputfrom-6dBto+6dBwithrespectto
MAINoutput
VOLTAGEAMPLIFICATIONINDECIBELS:
AUXILIARY,TUNER,TAPE1 andTAPE2
toMAINOUTPUT20dB
toTAPEOUTPUT0 dB
PHONO1 andPHONO2 (at1,000Hz)
toMAINOUTPUT62dB
toTAPEOUTPUT42dB
ACPOWEROUTLETS:
1unswitched(Red)
4switched
FACILITIESANDFEATURES
BASS
Separate11positionrotaryswitchesforeach
channel.-20dBto+16dBat20Hz
TREBLE
Separate11positionrotaryswitchesforeach
channel.-20dBto+20dBat20,000Hz
LOUDNESS
Flatresponse,orcontinuouslyvariableloudness
equalizationasvolumelevelisreduced
BALANCE
Naturalbalanceatcenterposition,attenuation
ofleftorrightchannelbyrotatingcontrol
VOLUME
Precision"tracked"atalllisteninglevels.(0to
-65dB).Doesnotchangestereobalanceasloud-
nessischanged.TheACpowerON/OFFswitchis
coupledwiththiscontrol
INPUT
Sixpositions—AUXILIARY,TAPE1,TAPE2,
TUNER,PHONO1,andPHONO2
MODE
Sevenpositions— Leftchannelonlytoboth
speakers.Rightchannelonlytobothspeakers,
StereoReverse,Stereo,Mono,L + R,L + R to
rightspeakeronly,andL + R toleftspeakeronly
TAPEMONITOR
Twopushbuttonswitches.Eitheroftwotape
recorderscanbemonitoredbyselectingtheTAPE
1pushbuttonorTAPE2 pushbutton.Theyareme-
chanicallyinterlockedtoacceptonlyonepush-
buttonattheINpositionatonetime
LFFILTER(RumbleFilter)
Flatorroll-off6 dBper
downto12dBat20Hz
HFFILTER(ScratchFilter)
octavebelow50Hz,
Flatorroll-off6 dBperoctaveabove6,000Hz,
down12dBat20,000Hz
12

SPEAKER
Main— SwitchtheMAINloudspeakersystem
ONorOFFwithoutaffectingtheperformance
ofREMOTEspeakers.
Remote— SwitchtheREMOTEloudspeaker
systemONorOFFwithoutaffectingtheper-
formanceofMAINspeakers.
HEADPHONEJACK
Theoutputofthepoweramplifiersmustbe
properlyconnectedtotheC 26backpanelfor
programmaterialtobeavailableattheHEAD-
PHONEjack.
SECONDARYCONTROLS
Thesecontrolsarelocatedbehindthefront
panelontopoftheC 26.Theyarereadilyaccessi-
blebydepressingthePANLOCbuttonsandsliding
theC 26forwardonthePANLOCbrackets.
CENTERCHANNELLEVEL
Topofchassiscontroltoadjusttheoutputlevel
oftheleftplusrightprogrammaterialattheCEN-
TERCHANNELoutputonthebackpanel.
PHASECONTROL
Electronicallyreversephaseintheleftchannel
tocorrect"outofphase"programsources.
TRANSISTORCOMPLEMENT
18silicon-planartransistors,and3 silicon
diodes.
SIZE:Frontpanelmeasures16incheswide(40.64
cm)by5-7/16incheshigh(13.81cm).Chassis
measures15incheswide(38.1cm)by5 inches
high(12.7cm)by13inchesdeep(33.02cm),
includingPANLOCshelfandbackpanelcon-
nectors.Knobclearancerequiredis1½inches
(3.81cm)infrontofthemountingpanel.
FINISH:Frontpanelisanodizedgoldandblack
withspecialMclntoshgold/tealpanelnomencla-
tureillumination.Chassisisblack.
MOUNTING:ExclusiveMclntoshdevelopedpro-
fessionalPANLOC.
WEIGHT:18pounds(8.16kg)net,33pounds
(14.97kg)inshippingcarton.
13
MECHANICALINFORMATION

Performance
Charts
LOWANDHIGHFREQUENCYFILTERCHARACTERISTICS
PHONOEQUALIZATIONCHARACTERISTIC(RIAA)
100
10001000020000
20
15
10
5
0
-5
-10
-15
-20
FREQUENCYINHERTZ
20
FREQUENCYINHERTZ
BASSANDTREBLETONECONTROLCHARACTERISTICS
LOUDNESSCONTROLCHARACTERISTICS
1000020000
14
100
FREQUENCYINHERTZ
1000020000
1000
20
RESPONSE
INdB
0
-5
-10
-15
-20
-25
20
100
FREQUENCYINHERTZ
1000
20
15
10
5
0
-5
-10
-15
-20
Response
indB
10001000020000 100
Response
indB
20
0
-5
-10
-15
-20
Response
indB

TheC 26preamplifierfunctionscanbedivided
into5 sections.Theyare:phonopreamplifier,
mainpreamplifier,powersupply,centerchannel
amplifier,andspeakercontrol.
PHONOPREAMPLIFIER
Therearethreetransistorsineachchannelof
thephonopreamplifier.Theinputtransistor,a
high-gainamplifier,divesanemitterfollower.The
emitterfollowerdrivesthethirdtransistorwhich
isanotherhigh-gainamplifier.Toreducenoise
anddistortiontheoutputofthethirdtransistoris
connectedbya negativefeedbacklooptothe
emitteroftheinputtransistor.Thefeedbacknet-
workalsoprovidesprecisionRIAAfrequency
compensationrequiredformagneticphonograph
cartridgesanda lowoutputimpedanceforthe
tapeoutput.Feedbackremainsineffectevenat
20Hz,wheregainishighest.
Thephonoinputsensitivityis2 millivolts.Inthe
C26,phonoinputoverloadisvirtuallyimpossible.
Forexample,at1,000Hz,thephonoinputcircuit
willaccept150millivoltsofsignalwithoutover-
load.
Tenmillivoltsofsignalatthephonoinputat
1,000Hzwillproduce1.2voltsatthetapeoutput.
MAINPREAMPLIFIER
Therearefivetransistorsineachchannelofthe
MAINPREAMPLIFIER.Theselectorswitchcon-
nectseithertheoutputofthephonoamplifieror
ahighlevelinputtothemainpreamplifier.
Thehighlevelinputimpedanceis250,000ohms.
Thehigh-levelinputfeedsthroughthevolumecon-
troltoa pairoftransistorsconnectedashigh-gain
amplifier.Intheleftchannelthesecondtransistor
isconnectedina balancedoutputarrangementto
provideequalamplitudesignalsforthephase
switch.Withthisarrangementtheoutputlevel
doesnotvarywhenthephaseswitchischanged.
Negativefeedbackisusedtoreducenoiseand
distortionandtoprovidethelowimpedance
neededtodrivethehighlyselectivefilternetworks
whichfollow.
Thefilternetworksareswitchcontrolled.The
high-frequencyfilternetworkreducestreblere-
sponseabove5,000Hz.Thelow-frequencyfilter
reducesbassresponsebelow50Hz.Theslopeof
thefiltersisselectedformaximumrejectionof
objectionablenoises.Carefuldesignhaskeptthe
lossofusableprogrammaterialtoa minimum.
Thesignalisthenfedintotheloudnessand
balancecontrols.Theloudnesscontroliscon-
tinuouslyvariable.Itmaybeusedinconjunction
withthevolumecontrol.Rotatingtheloudness
controlproducesanyloudnesscompensationfor
adesiredlisteninglevel.At50%rotation,theloud-
nesscontrolwillbeeffectivebelow150Hz,gradu-
allyincreasinglow-frequencyoutputtoa maximum
of6 dBat20Hz.Atfullrotation,theloudness
controlwillbeeffectivebelow1,000Hzgradually
increasinglow-frequencyoutputtoa maximumof
15dBat20Hz.
Theoutputofthebalancecontrolisconnected
toanemitterfollowerwhichisthefirststageof
thetonecontrolsection.Theemitterfollowerpro-
videsa high-inputimpedancerequiredforloud-
nessandbalancecircuitsanda low-outputimped-
anceforthetonecontrolcircuits.Theremaining
twotransistorsareconnectedasa high-gainampli-
fierstage.Againnegativefeedbackisusedto
assurelowdistortionand,inaddition,accurately
shapesthetone-controlresponsecurvesandpro-
videsa lowoutputimpedanceforthemainout-
puts.Negativefeedbackismaintainedatallfre-
quencies,evenwiththetonecontrolsturnedto
fullboost.
CENTERCHANNELAMPLIFIER(L+ R)
Thecenterchannelamplifierisa singletransis-
torconnectedasa voltageamplifier.Themainleft
andrightoutputsarefedthroughmixingresistors
totheinputofthevoltageamplifier.Thecenter
channellevelcontrolisconnectedina negative
feedbacklooparoundthevoltageamplifier.Itper-
mitsadjustingtheoutput±6dBcomparedtothe
mainoutputs.Feedbackalsoprovidesa lowout-
putimpedanceforcenterchannel.
POWERSUPPLY
Carefuldesignofthepowersupplysectionin-
surespropersupplyvoltagesforthepreamplifier
circuits.A widevariationoflinevoltagewillnot
affecttheD.C.voltageoutputofthepowersupply.
Aseriesregulatortransistoractsasa highlyeffec-
tivefilterforA.C.rippleaswell.Thevoltageregu-
latortransistorisstabilizedbya zenerreference
diodeforconstantvoltageoutput.
15

Block
Diagram
16

MclNTOSHLABORATORYINC.
2CHAMBERSST.,BINGHAMTON,N.Y.13903
607-723-3512
DesignandPricesubjecttochangewithoutnotice.PrintedinU.S.A.
038-867
BE032003