McIntosh MC2505 User manual

MC2505
SOLID
STATE
PRICE$1.25
STEREO
POWERAMPLIFIER
MC25O5

TheMclntosh"willtoperfection"requiresthatweprobe
constantlyintotheunknowntobringtheperformanceofour
electronicequipmentclosertoperfectionthaneverbefore.
Thisrequiresa constantandrelentlesssearchforlownoise,
broadbandconservativedesignwithaneverlowerdistortion
factor.Thisisnotrequiredofordinaryequipmentofaverage
designs.Itis,forus,a costlybutworthwhilescientificand
engineeringeffort.Ourcontinuingresearchbenefitsourcus-
tomerswiththealmostcompletelackofobsolescenceand
themostreliableequipmentevermade.Italsomeansthe
lowestlong-rangecosttoyou.NearlyalloftheMclntosh
equipmentevermadeisstilluseable,orinuse,thoughit
mayhavebeenmadetwentyyearsago.
GENERALDESCRIPTION2
TECHNICALDESCRIPTION2,3
LOCKINGMETERS4
PERFORMANCECHARTS5,6
CHARTS8
SPECIFICATIONS9
INA HURRY10
INSTALLATION11
TYPICALHOOKUP12
CONNECTING13
BLOCKDIAGRAM14
OPERATING15
GUARANTEE16
MC2505
Yourpurchaseofa Mclntoshinstrument
showsthatyouarea carefuldiscriminat-
ingbuyer.Onewhoisinterestedinquality
performance,qualityengineering,quality
manufacturing,andlongtrouble-free
equipmentlife.Youcanprotectyourin-
vestmentbyspendinga fewminutesread-
ingthisowner'smanual.
Whenyouboughta Mclntosh,youbought
countlesshoursofmusicalpleasureand
superiorperformance.Enjoyit!
MC25O5
1
CONTENTS
STEREO
POWERAMPLIFIER
SOLID
STATE

GENERALDESCRIPTION
Thedramaticdifferenceinthequalityofmusicreproducedthrough
aMclntoshinstrumentisduetolowdistortion.Thedistortionofyour
MC2505isguaranteedtobelessthan0.25%atanyfrequencyfrom
20Hzto20kHzwithbothchannelsoperatingat50wattsRMS.
Distortionismeasuredatfullratedpoweroutputwithbothchannels
operating.Atlessthanratedpower,distortionbecomessosmallit
canbemeasuredonlybythemostsophisticatedlaboratoryinstru-
ments.OnlyMclntoshgivesyouthiskindofperformance.
YourMC2505passedmorethan75testsbeforeitwasreadyfor
you.Eachconnection,wire,resistor,capacitorischeckedandre-
checked.Allspecificationsarechecked.Mclntoshtestingtakestime.
Theextrainvestmentinthoroughtestingassuresyouofgreater
musicalenjoyment.
TheperformanceofyourMclntoshMC2505isbackedbya money
backguarantee.OnlyMclntoshgivesyoua moneybackguarantee
ofperformance.YourMC2505mustbecapableofmeetingitspub-
lishedspecificationsoryougeta refundofyourpurchaseprice.
Mclntoshpromisesperformance.Weeithermeetourpromiseoryou
getyourmoneyback.
YourMC2505canbeprotectedbya freethreeyearfactoryservice
contract.Takeadvantageofthisservice.Fillintheapplicationcard
foundintheowner'spacket.Thefreethreeyearfactoryservice
contractcoverspartsandlabor.Ifanythinggoeswrongjustbring
yourMC2505toa factoryservicestation,orreturnyourMC2505
toMclntosh.AllpartsandlabornecessarytorepairyourMC2505
willbesuppliedfreeofcharge.Fillintheservicecontractapplica-
tionfoundintheowner'spacketnow.
2
Atwostagepreamplifierwiththreetransistorsineachchannel
increasestheinputvoltage16dB.
Thereare13transistorsineachpoweramplifiersection.Thetwo
stagepreamplifierisfedtoa pairofmatchedtransistorsarranged
asanemittercoupledamplifierwithtwoinputsandoneoutput.
Thesignalfromthepreamplifiersectionconnectstooneofthese
inputs.BothACandDCnegativefeedbackareappliedtotheother
input.Thislargequantityoffeedbackisusedtoreducenoiseand
distortion.Thesignalisthenfedtoa voltageamplifier.Thevolt-
ageamplifierisfollowedbytwodrivertransistors.
Theoutputsectionisarrangedasa seriespush-pullamplifier.
ThepowertransistorsusedintheoutputsectionofyourMC2505
areselectedfortheirhighpowerdissipationcapability,wide
frequencyresponse,andlarge"safeoperatingarea."Inaddition,
eachpowertransistorisgivenfourseparatetestsbeforeitisput
inyourMC2505.ThisadditionaltestingmakessureyourMC2505
willdeliveritsratedpowerfrom20to20kHzwithlowdistortion
andcompletereliability.
Thepowertransistorsaremountedonoversizedanodizedheat
sinks.Theheatsinksassurethatundernormaloperationthe
transistorswilloperateata lowtemperature.Iftemperaturesin-
creaseduetoa shortedspeaker,orrestrictedventilation,anauto-
matictemperaturesensingdeviceturnsofftheMC2505.The
deviceoperatesautomaticallyata presettemperature.TheMC
2505willturnonagainwhenthetemperaturehasreturnedto
normallimits.ThisadditionalfeaturegivesyourMC2505com-
pletereliabilityunderthemostextremeoperatingconditions.
TECHNICALDESCRIPTION

TheoutputstagesarematchedtotheloadbytheMclntoshauto-
former.TheMclntoshautoformeriscarefullywoundusingMcln-
toshtrifilarwindingandinterleavingtechniques.Trifilarwinding
andinterleavinggivesthetransformersexceptionalbandwidth.
Theautoformersproperlymatchthepowertransistorsto4,8,and
16ohmloadsatallaudiofrequencies.
TheuseoftheMclntoshdesignedtrifilarautoformermakesthe
Mclntoshsolidstateamplifierstheonlyamplifiersthatdeliver
FULLPOWERATALLSPEAKERIMPEDANCES.Youhavenot
beenpowerpenalizedforyourchoiceofloudspeakerswhenusing
theMclntoshMC2505.
Anotheroftheadvantagesoftheautoformersisthe25voltoutput
fora constantvoltagedistributionsystem.WiththeMC2505sev-
eralsetsofspeakerscanbeoperatedindependentlythroughout
yourhome.
Tofurtherinsurereliabilitya specialpoweroutputSENTRYMONI-
TORINGCIRCUITpreventsfailureofthepoweroutputtransistors
duetoexcessivemismatchoftheoutput.WhenyourMC2505
operatesnormallytheSENTRYMONITORINGCIRCUIThasno
effectonsignalspassingthroughthepoweramplifier.Ifthe
powerdissipationshouldriseabovenormaloperation,theSEN-
TRYMONITORINGCIRCUITrestrictsthedrivetotheoutput
transistors.TheSENTRYMONITORINGCIRCUITactsinstantane-
ouslyforanyinputsignalorloadcombination.Thisarrangement
assurescompletecircuitreliability.OnlyMclntoshgivesyouthis
degreeofprotection.
POWERSUPPLYSECTION
Therearethreeseparatepowersupplysections.Onepositiveand
onenegativehighcurrentsupplyisusedfortheoutputstages.
Theotherpositivesupplyisusedforthedrivingamplifierstages.
Allsuppliesarefullwaveandusesiliconrectifiers.Adequatefilter-
ingisusedtoassureanabsoluteminimumofhum.Thepowerout-
putstagefiltercapacitorshaveveryhighcapacity,whichallows
fullpoweroutputbelow20Hz.Thepowertransformerisgenerous
insizeandrunscool,evenunderheavyuse.
3

Ordinarymeterslackthecapabilityofindicating
theshortintervalpowerina soundwave.The
massofthemetermovementistoogreattore-
spondtoinstantaneouschangesinmusicpro-
grammaterial.Mclntoshsuperiorengineering
hasdevelopednewcircuitrythatpermitsthe
metersontheMC2505torespondtotheshort
intervalpowerina soundwavetoanaccuracyof
98%ofthetruevalue.ThisisanotherMclntosh
developmentthatrepresentsa majorstepfor-
wardintheuseofpowerlevelmeters.
Therearetwocircuitsthatgivethesemeters
theindicatingcapabilityoftheshortinterval
powerina soundwave.Thefirstcircuitisan
acceleratingcircuitthatcompensatesforthe
inertiacharacteristicsofthemetermovement.
Becausetheshortintervalpowerfluctuationis
sorapid,theeyemightnotperceivetheinstan-
taneouspowerreading.Thiscausedthedevel-
opmentofthesecondcircuit,whichisa "time
stretching"circuit.Thetimestretchingcircuit
delaysthemovementofthemeterneedleat
peakreadingfora fewmilliseconds.
WiththeaidoftheCBStestrecordSTR100,the
frequencyresponseofyourphonocartridgecan
bemeasured.Thegraphonpage5 showsthe
idealRIAAcurveusingtheCBSrecordSTR100.
Followthesestepstoplottheperformanceof
yourphonographcartridge.
1.Setthe"METERRANGESWITCH"tothe
—20 position.
2.Playthe1000Hztesttonerecordedon
theCBSTestRecordSTR100 onyour
phonograph.
3.Turnthe"LEFTGAIN"controluntilthe
leftmeterindicates"0."
4.Turnthe"RIGHTGAIN"controluntilthe
rightmeterindicates"O."
5.Writedownthemeterindicationateach
frequencyastherecordplays.
6.Transferthereadingsbyfrequencyto
thegraph.
7.ThegraphshowstheidealRIAAre-
sponsecurveusingtheCBS#STR100test
record.Compareyourcurvewiththecurve
onthegraph.A deviationof3 dBfromthe
idealisacceptable.Bymakingthischeck
atregularintervals,(forinstance,every6
months)anydeteriorationinthecartridge
orsystemwillbequicklydetected.
DYNAMICPEAK
LOCKINGMETERS
Ataperecordercanbecheckedinthesame
fashion.
1.Usea standardfrequencyresponsetape
asthesignalsource.
2.Completeallstepsoutlinedforphono
cartridges.
3.Younowhavea graphoftheplayback
characteristicsofyourtaperecorder.
Tofindtherecordcharacteristicsofthetape
recorderfollowthisprocedure:
1.RecordtheCBSTestRecord#STR100
onyourtaperecorder.Adjusttherecord
volumeonlyonthe1000Hzsignalfor
properrecordinglevel.DONOTADJUST
THERECORDVOLUMECONTROLDUR-
INGTHERECORDING.
2.Playbackthetapejustrecorded.Com-
pleteallstepsoutlinedfortapeplayback
characteristics.
3.A comparisonofthetwocurveswillgive
therecordingcharacteristicsofyourtape
recorder.A deviationof3 dBisacceptable.
Similarcheckscanbemadeonallprogram
sourcesinyourstereosystem.Followthesame
generalprocedureforanyprogramsourcefor
whicha standardreferenceisavailable.
•1

RELATIVEOUTPUTLEVELINdB
RELATIVEOUTPUTLEVELINdB
20
100
IDEALRIAASYSTEM
RESPONSE
USING
CBSSTR100
TESTRECORD
FREQUENCY
INHz
1k
10k
20k
4
2
0
-2
-4
-6
-8
-10 -12
14
-16 -13
-20
IDEALRIAASYSTEMRESPONSEUSING
CBSSTR100
TESTRECORD
20
100
FREQUENCY
INHz
1k
10k
20k
4
2 0
-2
-4
-6
-8
-10
12
-14
-16
-18
-20
5

RELATIVEOUTPUTLEVELINdBRELATIVEOUTPUTLEVELINdB
4
2
0
-2
-4
-6
-8
-10 -12
-14
-16
-18
-20
4
2
0
-2
-4
-6
-8
-10
-12
-14
-16
-18
-20
20k
10k
1k
FREQUENCY
INHz
IDEALRIAASYSTEMRESPONSE
USING
CBSSTR100
TESTRECORD
20
IDEALRIAASYSTEMRESPONSEUSING
CBSSTR100
TESTRECORD
6
20
100
100
FREQUENCY
INHz
1k
100k
20k

7

TYPICALPERFORMANCEDATA
HARMONICDISTORTIONvsPOWEROUTPUT
FREQUENCYINHERTZ
1k
10k
100k
100
100
0
10
PERCENTAGEINTERMODULATIONDISTORTION
0.6
0.5
0.4
0.3
0.2
0.1
10
POWEROUTPUTINEQUIVALENTRMSWATTS
8
POWEROUTPUTINRMSWATTS
20Hz
2kHz20kHz
100
10
PERCENTAGEHARMONICDISTORTION
0.6
0.5
0.4
0.3
0.2
0.1
POWER
OUTPUT
RMS
WATTS
70
60
50
40
30
20
10
POWEROUTPUTvsFREQUENCY
INTERMODULATIONDISTORTIONvsPOWEROUTPUT

SPECIFICATIONS
POWEROUTPUT:
STEREO—50RMSwattscontinuousperchan-
nelinto4,8,or16ohmsbothchannelsoper-
ating.
HARMONICDISTORTION:
STEREO—Lessthan0.25%at50wattsoutput
from20Hzto20kHzbothchannelsoperating.
Typicalperformanceislessthan0.1%at
ratedpower.Distortiondecreasesasoutput
powerisreduced.
INTERMODULATIONDISTORTION:
STEREO—Lessthan0.25%ifinstantaneous
peakpoweroutputis100wattsorlessper
channelwithbothchannelsoperatingforany
combinationoffrequencies20Hzto20kHz.
FREQUENCYRANGE:
20Hzto29kHz+0,-0.1dBatratedpower.
15Hzto60kHz+0,-0.5dBatratedpower.
10Hzto100kHz+0,-3.0dBatone-halfof
ratedpower.
NOISEANDHUM:
90dBormorebelowratedoutput.
OUTPUTIMPEDANCE:
STEREO—4,8,and16ohms
OUTPUTVOLTAGES:
25voltsSTEREO
DAMPINGFACTOR:
14at4 ohmsoutput
27at8 ohmsoutput
13at16ohmsoutput
INPUTIMPEDANCE:
200,000ohms
INPUTSENSITIVITY:
0.5volt.Levelcontrolprovidedforhigherin-
putvoltage.
POWERREQUIREMENTS:
117voltsAC50/60Hz,75wattsatzerosignal
output.
250wattsatratedoutput.
SEMICONDUCTORCOMPLEMENT:
26silicontransistors.
27siliconrectifiersanddiodes.
MECHANICALSPECIFICATIONS:
SIZE:5-7/16incheshigh,16incheswide,13
inchesdeep.
CHASSIS:Chromeandblack.
WEIGHT:38poundsnet,53poundsinshipping
carton.
SPECIALFEATURES
Theamplifieriscompletelystablewhencon-
nectedtoanyloudspeakersystemorevento
anyreactiveloads.TheMC2505hasspecialcir-
cuitstopreventdamagebyshortcircuitoropen
circuitoftheoutputloads,orbyanyamountof
outputimpedancemismatch.
Thermalcutoutsaremountedontheoutput
transistorheatsinkstoprovideprotectioninthe
eventofinadequateventilation.
9
ELECTRICALSPECIFICATIONS:

IFYOU'REINA HURRYPOWER
OFFON
Turnstheamplifieron/off.
SPEAKER
OFFON
Turnsthespeakeron/off.
HEADPHONE
Toconnecta setoflowimpedancestereoheadphones.
METERRANGE
Adjustmeterreadingstopoweroutputlevel.
10

INSTALLATION
Adequateventilationextendsthetrouble-freelifeof
electronicinstruments.Itisgenerallyfoundthateach
10°centigrade(18°F)riseintemperaturereduces
thelifeofelectricalinsulationbyonehalf.Adequate
ventilationisaninexpensiveandeffectivemeansofpre-
ventinginsulationbreakdownthatresultsfromunnec-
essarliyhighoperatingtemperatures.Thedirectbenefit
ofadequateventilationislonger,trouble-freelife.
Thesuggestedminimumspaceformountingthe
MC2505is14incheslongx 16½incheswidex 6 inches
high.Alwaysallowforairflowbyeitherventilation
holesorspacenexttothebottomoftheamplifierand
ameansforthewarmairescapeatthetop.
ItisrecommendedthattheMC2505bemountedina
normalorhorizontalposition.However,withadequate
ventilationtheamplifiercanbemountedinanyposition.
TopreparetheMC2505forinstallationremovethe
plasticprotectivecovering.TurntheMC2505upside
downsothatitrestsonitstopontheshippingpallet.
Removethefourplasticfeetfastenedtothebottom
ofthechassis.
Nextplacethemountingbrackets,thepartsbagand
themountingtemplateforeasyaccessibility.
Theprofessionalmountingdesigneliminatestheneed
foranyshelforbrackettosupporttheMC2505.Itis
completelysupportedbyitsownmountingbrackets.
Ifthecutoutistobelocatedfromtherearofthepanel,
thefollowingstepswillhelpyou.
Onthebackofthecabinetpanel,scribea vertical
centerlinethroughtheexactcenteroftheareainwhich
thecutoutistobemade.
Placethetemplateagainstthebackofthepaneland
matchthetemplatecenterlinewiththecenterlineonthe
cabinetpanel.
Makesurethatthereisatleast¼ inchclearancebe-
tweenthebottomofthedashedlineofthecutoutarea
onthetemplateandanyshelforbracebelowthepro-
posedcutout.
Markthetwolocatingholes("C"holesonthemount-
ingtemplate).
Drillthetwolocatingholes.Becertainthedrillisper-
pendiculartothepanel.
Nowpositionthetemplateonthefrontofthepanelby
aligningthe"C"locatingholesonthetemplatewith
thedrillholes.
WiththesawontheINSIDEOFTHEPENCILLINES
carefullycutouttherectangularopening.
Positiontheplasticmountingtemplateoverthearea
Securethemountingstripstotherearofthecabinet
panelusingtwoscrewsfromthehardwarepackage.
Insertthescrewsinthecenterholesofthecabinet
panel("B"holesonthetemplate)andtighten.The
screwheadshouldpullintothewoodslightly.(Usetwo
¾inchlongscrewsforpanelsunder½ inch,ortwo1¼
inchlongscrewsforpanels½ inchthickandlarger.)
Attachthemountingbracketstothecabinetpanelus-
ingfourscrews.
Placethetemplateoverthemountingscrews.The
mountingscrewsshouldbecenteredinthe"A"and
'B"holesonthetemplate.Thesidesofthemounting
bracketsshouldmatchtheverticaldashlinesonthe
template.Ifnecessary,loosenthescrewsandpushthe
bracketsintoalignmentandretighten.
Insertthepowercordthroughtheopening.Carefully
slidetheMC2505intotheopeningsotherailson
thebottomoftheequipmentslideinthetrackofthe
mountingbrackets.Continuetoslidetheinstrumentin
untilthefrontpanelisagainstthecabinetpanel.
AtthebottomfrontcornersofthePANLOCinstruments
arethePANLOCbuttons.
DepressingthePANLOCbuttonswilllocktheinstru-
mentfirmlyintheinstallation.
DepressingthePANLOCbuttonsa secondtime(as
witha ball-pointpen)willreleasetheinstrument.You
canthenslidetheinstrumentforwardtotheinspection-
adjustmentposition.
Depressingtheinspection-adjustmentpositionlatches
willallowtheinstrumenttobeslidcompletelyoutof
theinstallation.
VERTICALINSTALLATION
Inthehardwarepacketaretwohelicalsprings.Fasten
thespringstothesmallflangesattherearofthe
PANLOCbrackets.Theflangehasa notchanda hole
tomountthespring.Thespringsassistintheremoval
ofverticallymountedPANLOCequipment.
DONOTUSETHESPRINGSONHORIZONTALLYMOUNTEDEQUIPMENT.
11
ofthecabinetpaneltobecutoutforinstallation.
Thedesignofthemountingtemplateallowsyouto
positionorlocatethecutoutfromthefrontorrearof
thepaneltowhichtheinstrumentistobemounted.
Withthetemplateinplaceagainstthecabinetpanel,
markthe"A"and"B"drillholesandthefoursmall
holesthatidentifycornersofthecutout.Jointhecorner
markswitha pencil.Theedgeofthetemplatecanbe
usedasa straightedge.
IMPORTANT:DRILLTHE6 HOLESBEFOREMAKING
THECUTOUT
Accuratelydrillthethreeholesoneachsideofthecut-
outareawitha3/16inchdrill.

TYPICALHOOKUP
TO117V
ACOUTLET
ALTERNATESPEAKER
LEADCONNECTION
TOBEUSEDWHEN
PHASESWITCHAND
PHONEJACKONC24
ARETOBEUSED.
12
TUNER
ROTATOR
DIRECTIONAL
FMANTENNA
PREAMPLIFIER
MC2505POWERAMPLIFIER
ACLINE
ACLINE

CONNECTINGTHEMC2505
INPUT-STEREO
TheshieldedcablefromtheleftoutputoftheMclntosh
preamplifierispluggedintotheleftjack.Theshielded
cablefromtherightoutputoftheMclntoshpreamplifier
ispluggedintotherightjack.
SPEAKERS
SpeakersareconnectedatthebarrierstripsmarkedOUT-
PUTonthebackpaneloftheamplifier.Uselampcord,
bellwire,orwirewithsimilartypeofinsulationtoconnect
thespeakerstotheamplifier.Forthenormallyshortdis-
tancesofunder50feetbetweentheamplifierandspeaker,
#18wireorlargercanbeused.Fordistancesover50feet
betweentheamplifierandspeakeruselargerwire.
Theloudspeakerimpedanceisusuallyidentifiedonthe
loudspeakeritself.Connectoneoftheleadsfromtheleft
loudspeakertothescrewmarkedCOMontheLEFTOUT-
PUTbarrierstrip.Connecttheotherleadfromtheleft
loudspeakertothescrewmarkedwiththenumbercor-
respondingtothespeakerimpedanceontheLEFTOUT-
PUTbarrierstrip.Connectoneoftheleadsfromtheright
loudspeakertothescrewmarkedCOMontheRIGHT
OUTPUTbarrierstrip.Connecttheotherleadfromthe
rightloudspeakertothescrewmarkedwiththenumber
correspondingtothespeakerimpedanceontheRIGHT
OUTPUTbarrierstrip.
Theonlyadverseeffectontheoperationofa Mclntosh
amplifierwhenitisimproperlymatchedisa reductionin
theamountofdistortion-freepoweravailabletotheloud-
speaker.Closeimpedancematchingisdesirableformaxi-
mumdistortion-freepower.
SPEAKERCONNECTIONS
Usethistabletodetermineproperspeakerconnection:
Connectthe
Ifthespeakerimpedancespeakerleads
isbetween:betweenCOMand:
3.2to6.5ohms4 ohms
6.5to13ohms8 ohms
13to26ohms16ohms
Connectasfollows:
Ifthespeaker
impedanceis:
4ohms
8ohms
16ohms
Connectoneleft
speakertoscrew
LEFT-COMand
otherto:
LEFT-4
LEFT-8
LEFT-16
Connectoneright
speakerleadto
thescrewmarked
RIGHT-COMand
theotherto:
RlGHT-4
RIGHT-8
RlGHT-16
AMONOPHONICLOUDSPEAKER
TOBOTHTERMINALS.
THELOUDSPEAKERCANBEDAMAGED.
For25voltlineoperationconnectoneoftheleftleadstothe
screwmarkedCOMontheLEFTOUTPUTbarrierstrip.The
otherleftleadisconnectedtothescrewmarked16onthe
LEFTOUTPUTbarrierstrip.Connecttherightleadsin the
samemannerontheRIGHTOUTPUTbarrierstrip.
ACPOWER:
TheMC2505operateson117to130volt,50/60Hz.The
amplifierwillbeturnedonandoffifitspowercordisplug-
gedinoneoftheauxiliaryACoutletsontheprogramsource.
13
DONOTCONNECT

BLOCKDIAGRAM
14

OPERATINGTHEMC2505STEREOAMPLIFIER
LEFTGAINUsetheleftgaincontroltoadjustthevolumein
theleftchanneltothedesiredlisteninglevel.
Turnthecontrolclockwisetoincreasethe
volume.
RIGHTGAINUsetherightgaincontroltoadjustthevolume
intherightchanneltothedesiredlisteninglevel.
Turnthecontrolclockwisetoincreasethe
volume.
METERRANGEThemeterswitchhasfourpositions.Thefirst
positionisoff.WiththeswitchintheOFFposi-
tionthereisnoindicationonthemeters.
-20:Inthispositionofthemeterrangeswitch,
theamplifierwilldeliver¼ watt(250milliwatts)
whenthemeterindicates"0."Witha meterindi-
cationor—3 dB,theamplifierdelivers% watt
(125milliwatts)anda —10dBmeterindication
theamplifierdelivers25milliwatts.
-10:Inthispositionofthemeterrangeswitch,
theamplifierwilldeliver2½wattsoutputwhen
themeterindicates"0."Witha meterindication
of— 3 dB,theamplifierdelivers1 ¼ wattsoutput
anda —10dBmeterindication,theamplifierde-
livers¼ watts.
—0:Inthispositionofthemeterrangeswitch,
theamplifierwilldeliver50wattswhenthemeter
indicates+3dB,withmeterindicationof"0,"
theamplifierdelivers25watts,witha meterindi-
cationof-3dB,theamplifierdelivers12½
watts;anda meterindicationof-10dB,the
amplifierdelivers2½watts.
HEADPHONEUsethejackforlowimpedancestereohead-
phones.Anyheadphoneswith4,8,16ohmsmay
beusedwiththisjack.Theheadphonejackison
atalltimes.
SPEAKERSOFF:Theloudspeakersareturnedoffwhenthe
SPEAKERswitchisintheOFFposition.Youcan
listentoheadphonesinprivate.
THISSWITCHMUSTBEINTHE"ON"POSI-
TIONTOHEARMUSICFROMTHELOUD-
SPEAKERS.
ON:Musicwillbeheardthroughtheloud-
speakers.Usethisasthenormallisteningposi-
tion.
POWERThepowerswitchturnstheMC2505onoroff.
Theswitchdoesnotcontrolthepoweroutleton
thebackpanel.Ifyouwishtocontroltheopera-
tionoftheon/offswitchfroma preamplifiercon-
trolcenterleavetheswitchintheONposition.
InthiscasebesuretoplugtheACcordofthe
MC2505intothecontrolledoutletsontherear
ofthepreamplifiercontrolcenter.
OFF:IntheOFFpositiontheamplifieristurned
off.
15

Anapplicationfora FREE3 YEARFACTORYSERVICECONTRACT
isincludedinthepackwiththismanual.TheFREE3 YEARFAC-
TORYSERVICECONTRACTwillbeissuedbyMclntoshLaboratory
uponreceiptofthecompletelyfilledoutapplicationform.Theterms
ofthecontractare:
1.Transportationchargesareexcluded.
2.Thisagreementisgiventotheoriginalpurchaseronlyandis
nottransferable.
3.Theapplicationforthecontractmustbefilledoutcompletely.
4.Iftheinstrumenthasbeenmodifiedordamagedbyunauthor-
izedrepairthecontractwillbecancelled.
5.Toreceivefreeservice,thecontractmustbepresentedtothe
factoryauthorizedserviceagency,whentheequipmentispre-
sentedforrepair.
IftheapplicationisnotreceivedatMclntoshLaboratory,onlythe
serviceofferedunderthestandard90dayguaranteewillapplyon
thisequipment.
YourMC2505stereopoweramplifierwillgiveyoumanyyearsofpleasant
andsatisfactoryperformance.Ifyouhaveanyquestionsconcerningopera-
tionormaintenancepleasecontactthedealerfromwhomyoupurchased
thisinstrumentor:—
16
TAKEADVANTAGEOF3 YEARSOFFREEFACTORY
SERVICEBYFILLINGINTHEAPPLICATIONNOW
MC25O5
CUSTOMERSERVICE
MclntoshLaboratoryInc.
2ChambersStreet
Binghamton,N.Y.13903
Ourtelephonenumberis
607-723-3512
GUARANTEE
3YEARFACTORYSERVICECONTRACT
MclntoshLaboratoryIncorporatedguaranteesthisequipmenttobe
capableofperformanceasadvertised.Wealsoguaranteetheme-
chanicalandelectricalworkmanshipandcomponentsofthisequip-
menttobefreeofdefectsfora periodof90daysfromdateof
purchase.Thisguaranteedoesnotextendtocomponentsdamaged
byimproperusenordoesitextendtotransportationtoandfrom
thefactory.

MclNTOSHLABORATORYINC.
2CHAMBERSST.,BINGHAMTON,N.Y.13903
607-723-3512
Designsubjecttochangewithoutnotice.
PrintedinU.S.A.
038-341
BE042003