McIntosh C108 - User manual

INSTRUCTIONMANUAL

MclNTOSHMODELC108

AUDIOCOMPENSATOR

-1 -

INSTRUCTIONMANUAL

McINTOSHMODELC-108

AUDIOCOMPENSATOR

TheMcIntoshAudioCompensatorisa completecontrolunitforprofessional

andhomeentertainmentsystems.Fiveinputchannelsareprovided;threewhich

produceconstantamplificationovertheaudiospectrumof20cyclesto20,000

cycles,andtwowhichareequalizedforusewithmagneticphonographcartridges.

TheC-108AudioCompensatorrequiresanexternalpowersource.A

McIntosh50W-2,20W-2,orA-116PowerAmplifier,orD-101powersupplymay

beusedforthispurpose.

PHYSICALSPECIFICATIONS

UNIT

C-108

C-108a

(C-108inwooden

enclosure)

C-108h

(C-108withcabinet

mountingpanel

11"x 4-1/4")

DIMENSIONS

10"x 3-1/2"x 7-1/2"

11-1/2"x 4-1/4"x 8"

10"x 3-1/2"x 7-1/2"

WEIGHT

6lbs.

7lbs.

6lbs.

INSTALLATIONWITHMcINTOSHAMPLIFIERS

1.Connectspeakertooutputofamplifier.

2.InsertPowerAmplifierlinecordintosocketlabeled

"PWRAMP"onC-108.

3.Insertinter-unitcableofC-108intosocketlabeled

"PRE-AMP"onpoweramplifier.

-2 -

4.Turnthepoweramplifiervolumecontrol(50W-2or

20W-2)tofullvolumesetting.Thevolumecontrolon

theA-116,30wattpoweramplifier,isinoperative

whenthepre-ampsocketisusedandthisstepmaybe

disregardedwhenusingthisamplifier.

5.TurnthevolumecontrolontheC-108to"OFF".

6.InsertthepowercordoftheC-108intoa 117V.A.C.

poweroutlet.

7.TurntheselectorswitchoftheC-108to"5"andbass

fullyclockwise.

8.TurnthevolumecontrolontheC-108clockwiseuntil

thepowerswitchisactivated.

9.Allowthirtysecondsforwarm-up,thenadvancethe

volumecontroltofullvolume.

10.Adjustthehumcenteringpotentiometeronthepower

amplifierforminimumhum.

11.TurnthevolumecontroloftheC-108toa minimum

andallothercontrolstothedesiredsettings.

12.Insertinputsintotheirproperjacksattherearof

theC-108.

INSTALLATIONWITHMcINTOSHD-101POWERSUPPLY

1.Connectspeakertopoweramplifier.

2.Insertpoweramplifierpowercordinsocketlabeled

"PWRAMP"onD-101.

3.InsertD-101powercordintosocketlabeled"PWR

AMP"oftheC-108.

4.Insertinter-unitcableofC-108intosocketlabeled

"PRE-AMP"oftheD-101.

5.Connect"OUTPUT"ofD-101totheinputofpower

amplifier(socketlabeled"PRE-AMP"onMcIntosh

PowerAmplifier).J-107seriescablesmaybeused

forthispurpose.

-3 -

6.Followsteps4 through9 above.

7.AdjustthehumcenteringpotentiometerontheD-101

forminimumhum.

8.Followsteps11and12above.

INPUTCONNECTINGPROCEDURE

TheinherenthumandnoisevoltagesappliedtotheinputoftheC-108is

-110DBM,orlessthan3 microvolts.Toavoidloweringthesignaltohumratio

oftheC-108byaddinghumvoltagestotheinput,extremecaremustbetakenin

itsinstallation.Weofferthefollowingrecommendationsasa guidetoinstalla-

tion:

1.ConnectinputtoC -108asoutlinedonthetable

below.

CHANNEL

1&2

FORUSEWITH

AM-FMTuner

WireReproducer

TapeReproducer

CrystalPickup

CrystalMicrophone

LowImpedance

Microphone

HighLevelMagnetic

cartridges.(Ter-

minatedfor

PickeringCartridge)

LowLevelmagnetic

cartridges.

(Terminatedfor

Audaxpolyphase

cartridgeand

WeathersFM

cartridge.)

INPUT

(For3 v.output)

Min.Max.

.1V20V.

12MV.60MV.

30MV..15 V.

12MV.60MV.

GAIN

30db

48db

40dbfrom

Turn-overto

20,000cps.

48dbfrom

Turn-overto

20,000cps.

FREQUENCY

RESPONSE

(20-20,000cps.)

+.25db

Risesatthe

rateof6 db

peroctavebe-

lowturn-over

frequencyto

20cps.

REMARKS

Inputlevelsinex-

cessof. 1Vshould

bereducedby

potentiometeron

backpanel.

Inputnottoexceed

60MV.

Cartridgeofother

manufacturersmay

beusedbutinput

mustbeterminated

asrecommendedby

manufacturer.Alter

R6&R7orR8.

-4 -

2.TheC-108andmagneticphonographcartridgesshould

bemountedatleasttwofeetfrompowertransformers.

3.Inter-unitcablesprovidea completegroundsystem.

Alternategroundwirescreategroundloopswhichwill

usuallyincreasehumlevel.

4.Theheatersofthe12AX7tubesusedintheC-108are

returnedtogroundthrougha humbalancingpotentiom-

eterinthepoweramplifier(orD-101powersupplyif

used).Thiscontrolrequiresaninitialadjustmentfor

minimumhum,andshouldbereadjustedeachtimeone

ormoretubesarereplaced.

5.GroundingtheturntablemotorframetotheC-108

chassisneartheinputjacksmayreducethehumlevel

onthephonographchannels.

TheoutputstageoftheC-108isa cathodefollower.Thegeneratorresis-

tanceofthistubeis600ohms,butshouldnotbeloadedwitha capacitivereactance

oflessthan10,000ohmsat20,000cycles.Thisisthereactancepresentedby

750micromicrofarads,andisequaltothatofa cable30feetlongandhavinga

capacityof25mmfperfoot.UnderspecialcircumstanceswheretheC-108must

beconnectedtothepoweramplifierbya longercable,eitherlowercapacity

mustbeemployed,ortheoutputmustbereduced.

OPERATION

REDUCETURNTABLERUMBLE,

ORLOWFREQUENCYDISTURB-

ANCESONALLCHANNELS.

SELECTDESIREDBASS

COMPENSATIONON

CHANNELS4 AND5.

SELECTDESIREDTREBLE

ROLL-OFFONALLCHANNELS.COMPENSATEFOREAR

CHARACTERISTICAT

REDUCEDVOLUMEON

ALLCHANNELS.

SELECTANYONEOFFIVE

INPUTCHANNELS.UNUSED

CHANNELSAREGROUNDED

TOPREVENTCROSSTALK.CONTROLBASSRESPONSE

ONALLCHANNELS.CONTROLTREBLERESPONSE

ONALLCHANNELS.

CONTROLVOLUMEON

ALLCHANNELS.ON-OFF

CONTROLFORC-108

ANDITSPOWERSUPPLY.

Channels1 and2:

Channels1 and2 areeachterminatedbya potentiometer.Thesepotentiom-

etersarescrewdriveradjustmentsonthebackpanelandshouldbeusedtoreduce

signalinputtothesechannelsifinexcessof. 1 volts.Correctadjustmentoccurs

whenthesoundlevelofchannels1 and2 isequivalenttothatofchannels4 or5.

Highimpedancesources,suchascrystalmicrophonesandthedetectoroutputof

tuners,maybeconnecteddirectlytothesechannelssincetheyhaveaninput

impedanceof660,000ohms.

Channel3:

Channel3 isa highgainmicrophonechannelhavinganinputimpedanceof

100,000ohms.Theinputtothischannelshouldnotexceed60MV.Lowimpedance

microphonesinconjunctionwithaninputtransformer,suchastheMcIntoshM-107

(ATI-1),maybeusedonthischannel.

Channels1,2 and3 provideflatamplificationfrom20cyclesto20,000

cycleswiththebassandtreblecontrolsintheircentralposition,andthetreble

compensationswitchesintheupposition.Thesecontrolsmaybeusedtoalterthe

responseofthesechannelsasshownonpage9.

Channels4 and5:

Channels4 and5 areequalizedforusewithmagneticphonographcartridges.

Thedegreeofequalizationmaybevariedwiththebassandtreblecompensation

switchesasshownonpages8 and9.Thebassandtrebletonecontrolsmaybe

usedto supplementthesecompensationswitches.

Theinputsofchannels4 and5 havebeenterminatedtogiveflatresponsefrom

thePickeringandAudaxPolyphasecartridgesrespectively.Ifcartridgesofother

manufacturersareused,theterminatingresistorsshouldbereplacedbyvalues

recommendedbythemanufacturer.Forexample,the47,000ohmterminating

resistanceofchannel5 shouldbereplacedby12,000ohmsiftheG.E.reluctance

cartridgeisused.IfitisdesirablenottoaltertheC-108an18,000ohmresistor

maybeconnectedacrosstheG.E.cartridgeinthelinetothecartridge.

- 5 -

TheAuralCompensatormaybeusedtocompensatefortheresponsecharac-

teristicoftheearasloudnessisadjusted.Theresponseofthiscontrolis

plottedonpage9.Thiscontrolshouldnotbeuseduntilallotheradjustments

havebeenmade.

TheRumbleFiltermaybeusedtoeliminateturntablerumbleandotherlow

frequencydisturbances.Theresponseofthiscontrolisplottedonpage9.

AnadditionaloutputjackhasbeenprovidedattherearoftheC-108.This

jackmaybeusedforrecordingtapewhilethesignalisbeingmonitoredbythe

poweramplifier.Theselectorswitch,rumblefilter,andbasscompensation

switchesareeffectiveattheauxiliaryoutput.

GUARANTEE

WeguaranteetheperformanceoftheC-108andthemechanicalandelec-

tricalworkmanshiptobefreeofseriousdefectsfora periodof90dayswiththe

exceptionthatwedonotguaranteethetubesandfiltercapacitorbeyondthatof

theirmanufacturers.

McINTOSHLABORATORY,INC

320WaterStreet

Binghamton,NewYork

—6—

-7 -

Forconvenienceofinstallation,wehavemadethefollowingconnectorsand

cablesavailablefromyourdealer.

J-100OutputPlug

J-101Inputplug

*J-102J-100Outputplugfittedwith6 footlengthoftwo

conductorcable,connectedfor4 ohmoutputof

McIntosh50W-2or20W-2.

*J-103SameasJ-102,butconnectedfor8 ohms.

*J-104SameasJ-102,butconnectedfor16ohms.

*J-105SameasJ-102,butconnectedfor32ohms.

*Forusewith20W-2or50W-2Amplifiersonly.

J-109J-100outputplugfittedwith6 footlengthoftwo

conductorcableconnectedfor4 ohmoutputof

McIntoshA-116.

J-110SameasJ-109,butconnectedfor8 ohms.

J-111SameasJ-109,butconnectedfor16ohms.

J-106SameasJ-102,butconnectedfor600ohms,for

usewith50W-2,20W-2orA-116.

J-107J-101inputplugfittedwith6 feetof25MMF

capacityperfootcableandphonopinjack.For

2.5Vinputof50W-2,20W-2,orA-116.

J-107aSameasJ-107,but12ft.long.

J-107bSameasJ-107,but18ft.long.

J-107cSameasJ-107,but24ft.long.

J-107dSameasJ-107,but30ft.long.

J-108Phonopinjackfittedwith6 feetof25MMFcapa-

cityperfootcable,withshieldandcenter

conductorstrippedandtinned.

J-112Inputplugfittedwith6 feetof25MMFcapacity

perfootcableandphonopinjack.For. 5Vinput

ofA-116.

J-101

J-103

J-104

J-105

J-106

J-107

J-107a

J-107b

J-107c

J-107d

J-108

J-101

J-100

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