McIntosh C4 - User manual

INSTRUCTIONMANUAL
MclNTOSHMODELC-4andC-4P
AUDIOCOMPENSATORS
McINTOSHLABORATORY,INC.
320WaterSt.Binghamton,N.Y.
U.S.A.

INSTRUCTIONMANUAL
McINTOSHMODELC-4andC-4P
AUDIOCOMPENSATORS
TheMcIntoshAudioCompensatorisa completecontrolunitforprofes-
sionalorhomeentertainmentsystems.TheModelC-4derivesitspowerfrom
anyMcIntoshpoweramplifier;theModelC-4Pisself-powered.
Fiveinputchannelsareprovided,threeofwhichproduceconstantampli-
ficationovertheaudiospectrumof20-20,000cycles,onewhichiscompensated
formagneticphonographcartridgesandonewhichiscompensatedforeither
magneticorconstantamplitudecartridges.Eachinputisequippedwitha level
control.A threeoutputsystemisemployed,twomainoutputswhereallcon-
trolsareeffectiveandonetapeoutputwhereonlythechannelselectorandcom-
pensationselectorareeffective.
THEAUDIOCOMPENSATORISA COMPLETEPRE-AMPLIFIERAND
RECORDCOMPENSATOR:THEREFORE,THEUSEOFANAUXILIARY
EQUALIZERORPRE-AMPLIFIERWITHTHISUNITISNOTRECOMMENDED.
INSTALLATIONOFMODELC-4andC-4P
AUDIOCOMPENSATORS
TheC-4andC-4PAudioCompensatormaybemountedinanytypeequip-
mentcabinet,relayrackpanel,door,wall,etc.,orinitsowncabinetfor
chairsideoperation.ItisnotnecessarytodisassembletheAudioCompensator
formounting.Usingthemountingtemplatesprovidedwiththismanual,cuta
rectangularholeinthepaneltobeusedformounting,inserttheAudioCompen-
satorandsecurewithwoodormachinescrews.
WheninstallingtheC-4P,thepowersupplysectionshouldbemountedat
leasttwofeetfromtheAudioCompensator.
Aftertheseunitshavebeensecured,proceedasfollows:
1.Connectspeakertooutputofpoweramplifier.
2.InsertpoweramplifierlinecordintooneoftheAuxiliaryA.C.re-
ceptaclesprovidedattherearchassisoftheAudioCompensator.
3.C-4:Connectinter-unitcabletosocketlabeled"PRE-AMPINPUT"
onMcIntoshPowerAmplifiers.CAUTION:THEINTER-UNITCABLE
MUSTNOTBEREMOVEDFROMTHEC-4.
C-4P:InsertcableofD-8powersupplyintosocketlabeled
"INTER-UNITCABLE"onC-4P.Connectaudiocableprovidedbetween
RETMApinjacklabeled"MAINOUTPUT"onC-4Pand2.5Vinputof
poweramplifier.(Socketlabeled"PRE-AMPINPUT"onMcIntosh
poweramplifiers.)
-1 -

-2 -
4.TheAudioCompensatordelivers2.5 voltsofaudiosignalatfullout-
put.Thegaincontrolofthepoweramplifiershouldbeadjustedasout-
linedintheamplifierinstructionmanualforthissensitivity.(McIntosh
AmplifierModelsA-116,MC-30,MC-60,setgaincontrolfullycounter
clockwise;50W-2and20W-2fullyclockwise.)
5.TurnthevolumecontrolontheAudioCompensatorto"OFF".
6.InsertpowercordoftheAudioCompensatorintoa 117V.,50/60
cyclepoweroutlet.
7.TurntheSelectorSwitchontheAudioCompensatorto"5"andBass
controlfullyclockwise.
8.TurnthevolumecontrolontheAudioCompensatorclockwiseuntil
thepowerswitchisactivated.Allowthirtysecondsforwarm-up,then
advancethevolumecontrolto"10".
9.C-4:Adjustthehumreducingpotentiometeronthepoweramplifier
forminimumhum.C-4P:Adjustthehumreducingpotentiometeron
thepowersupplyforminimumhum.
10.TurnthevolumecontrolontheAudioCompensatorto"OFF".
11.InsertinputsintotheirproperjacksatthebackoftheAudioCom-
pensator,andallA.C.powercordsintotheA.C.outletsprovided.
INPUTCONNECTINGPROCEDURE
TheinherenthumandnoisevoltagesappliedtotheinputoftheAudioCom-
pensatorare-110DBM,or lessthan3 microvolts.To avoidloweringthe
signaltohumratiooftheAudioCompensator,byaddinghumvoltagestothe
input,extremecaremustbetakeninitsinstallation.Weofferthefollowing
recommendationsasa guidetoinstallation:
1.ConnectinputsofAudioCompensatorasoutlinedonthetablebelow.
CHANNEL
TAPE
AND
TUNER
MIC
PHONO1
AND
PHONO2
FORUSEWITH
RadioorTVTuners
TapeRecorders
CrystalorCeramic
cartridges
CrystalMicrophones
LowImpedance
Microphone
PhonographCart-
ridges(magnetic
orconstant
amplitude)
INPUT
MIN.
60MV
3MV
3MV
MAX.
20V
1V
1V
GAIN
32db
52db
52db
REMARKS
Inputsinexcess
oftherecom-
mendedminimum
shouldbereduced
bythelevelad-
justmentslocated
onthebackpanel.
Seetextforcom-
pleteoperation.
2.TheAudioCompensatorandmagneticphonographcartridgesshouldbe
mountedatleasttwofeetfrompowertransformers.
3.Inter-unitcablesprovidea completegroundsystem.Alternateground
wiresshouldnotbeusedsincetheywillproducegroundloopsandincrease
thehumlevel.

4.Theheatersofthe12AX7tubesusedintheC-4arereturnedto
groundthrougha humreducingpotentiometerinthepoweramplifier.
HeatersoftubesusedintheC-4Parereturnedtogroundthrougha hum
reducingpotentiometerinthepowersupply.Thiscontrolrequiresan
initialadjustmentforminimumhum,andshouldbereadjustedeach
timeoneormoretubesarereplaced.
5.GroundingtheturntablemotorframetotheAudioCompensator
chassisneartheinputjacksmayreducethehumlevelonthephono-
graphchannels.
OUTPUTCONNECTIONS
Threeoutputsareprovided:onetapeandtwomainoutputs.
Thetapeoutputmaybeusedforrecordingtapefromanysourceconnected
totheAudioCompensator.TheSelectorSwitch,andCompensationSwitchare
effectiveatthisoutput.AdjustmentoftheBassandTrebletonecontrolsand
Volumecontrolmaybemadewithoutaffectingtherecordedsignal.Thetape
outputdeliversa signalofonevolt.
Allcontrolsareeffectiveatthemainoutputs,whichareavailableatthe
octalsocketlabeled"INTER-UNITCABLE"betweenpins#1and#2(pin#1is
ground),andattheRETMApinjacklabeled"MAINOUTPUT".Theinter-unit
cableconnectingtheC-4toanyMcIntoshpoweramplifierusestheoctalsocket
output.Thepinjackoutputmaybeusedfordrivinga secondpoweramplifier
ifsodesired.
Themainandtapeoutputsarefedfromcathodefollowers.Theinputim-
pedanceofdevicesconnectedtotheseoutputsshouldbe50,000ohmsor
greater,andthecapacitivereactanceofaudiocablesconnectingthesedevices
shouldnotbelessthan8,000ohmsat20,000cycles.Thisisthereactanceof
acapacityof1000mf.Audiocablehavinga capacityof25mmfperfootmay
be40feetlong.
TAPEandTUNERChannels:Thesechannelsareeachterminatedbya
potentiometermountedonthebackpanelwhichshouldbeusedtoreducesignal
inputifinexcessof. 1 volts.Highimpedancesources,suchascrystal
microphonesandthedetectoroutputoftuners,maybeconnecteddirectlyto
thesechannelssincetheyhaveaninputimpedanceof660,000ohms.
MICChannel:Thischannelisterminatedbya 100,000ohmpotentiometer
mountedonthebackpanelwhichshouldbeusedtoreducesignalinputifin
excessof10MV.Lowimpedancemicrophonesinconjunctionwithaninput
transformer,suchasMcIntoshM-107,maybeusedonthischannel.
TheTAPE,TUNERandMICchannelsprovideflatamplificationfrom20
to20,000cycles.TheBassandTrebletonecontrolsmaybeusedtoalterthe
responseasdesired.
•
-3 -

-4 -
TYPICALINSTALLATION
AUDIOCOMPENSATORC-4
TYPICALINSTALLATION
AUDIOCOMPENSATORC-4P

PHONO1 Channel:Thischannelisequalizedforusewithmagneticphono-
graphcartridges.A levelcontrolisprovidedattherearpaneltoallowuseof
cartridgeswithoutputvoltagerangingfrom3 MVto70MV.Theterminationof
thischannelis100Kwhichisrecommendedbyseveralcartridgemanufacturers.
Ifa lowerterminationisdesired,a resistormaybeplacedacrosstheinput.
PHONO2 Channel:Thischannelisthesameasphono1 channelexcept
thata variableloadcontrolhasbeenadded.Thecontroliscalibratedfrom6.8K
to52Kandanyterminationinthisrangemaybeselected.Inaddition,thisload
controlhasa switchattachedwhichoperatesinthecounter-clockwiseposition.
Thispositionislabeled"FM".Whentheloadcontrolisplacedinthisposition,
anyconstantamplitudetypecartridge(ceramic,crystal,FMtype)maybeused,
allowingfulluseoftheflexibleequalizationavailable.Thelevelcontrolisalso
effectiveonthesecartridges.
AllcontrolsareeffectiveonthePHONOchannels.
TheCompensationswitchmaybeusedtocompensaterecordingsasrecom-
mendedbythemanufacturerortoadjustthecompensationfora morepleasing
tonalbalanceforthelistener.TheBassandTrebletonecontrolsareindepen-
dentofthecompensationswitchandmaybeusedasfineadjustmentsinconjunc-
tionwiththisswitch.
ThefivepositionchannelSelectorswitchmaybeusedtoselectanyofthe
fiveinputchannelsavailable.
TheVolumecontrolselectsthedesiredlisteninglevelandsinceitis
locatedattheoutputoftheAudioCompensator,thehighsignaltonoiseratioof
theunitismaintainedatalllevels.Byproperlyadjustingtheinputpotentiom-
etersonallchannels,thevolumelevelcanbeheldequalforallchannels;the
signalwillremainata constantloudnesswhenswitchingfromonechannelto
another.Themasteroff-onswitchisattachedtothevolumecontrol.This
switchcontrolsthethreeauxiliaryA.C.outletsontherearpaneloftheAudio
Compensator,aswellasthethreeauxiliaryA.C.outletsonthepowersupply
oftheC-4P.
GUARANTEE
Weguaranteetheperformanceofthisequipmentandthemechanicaland
electricalworkmanshiptobefreeofseriousdefectsfora periodof90days.
Thisguaranteedoesnotextendtocomponentsdamagedbyimproperusenordoes
itextendtotransportationtoandfromthefactory.
McINTOSHLABORATORYINC.
320WaterStreet
Binghamton,N.Y.,U.S.A.
-5 -

FREQUENCYRESPONSECURVESFOR
AUDIOCOMPENSATOR,MODELC-4
MCINTOSHLABORATORY,INC
4-20-55
NOTE:ORTHOPHONIC,R.I.A.A.,NEWAES,
ANDNEWNART8AREIDENTICAL
CURVES.
FREQUENCY
RESPONSEBELOW20CYCLES
FREQUENCY
COMPENSATIONCONTROL
(PHONOCHANNELSONLY)
BASSTREBLE FREQUENCY
TONECONTROLS
-6 -

-7 -
C-250076
SERIALNO.6092AND
MCINTOSHLABORATORY ,INC
AUDIOCOMPENSATOR,MODELC-4
5-11-55