Cyrus 6 DAC User manual

ENGINEERED TO ENTERTAIN
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v
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Cyrus6DAC,Cyrus8DAC,
Cyrus8QxDAC
Digitalamplifiers
-27
CD
Sample rate 44.1kHz
MUTE PHONES SETUPZONE 2INPUT

SERVICECAUTIONS
©CyrusAudioLtdJune2014Cyrus6DAC,Cyrus8DACservicemanualIssue1
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Thesetwosymbolsshownaredisplayedprominentlyonthebasecover.They
indicatethatthefollowingcautionsmustbeobservedbyallpersonnel‐
CAUTION:TOREDUCETHERISKOFELECTRICALSHOCK,DONOTREMOVECOVERORBACK.
THEREARENOUSERSERVICEABLEPARTSINSIDETHEPRODUCT.
ALWAYSREFERSERVICINGTOQUALIFIEDSERVICEPERSONNEL.
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STATICPRECAUTIONS
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WhenservicinganyCyrusproduct,adequatecaremustbetakenduringanyservice
worktoobservestaticprecautions,particularlywhenstoring,handlingorfitting
replacementcomponents.Thefollowingguidelinesmustbeobserved–
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Checkthatallcomponentpurchasesaredeliveredinstatic‐safepackaging.
Storeallcomponentsinastatic‐safeenvironment.
Alwayswearagroundingstrapandworkonagroundedbenchwhenhandling
componentsorservicingaproduct.Staticdamagemaynotbeimmediatelyobvious
andmayresultinadelayedactioncomponent/productfailure.
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LEAD‐FREECOMPLIANCE
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Thisproductwasmanufacturedusingcomponentsandprocessesthatdonotcontain
lead.Allcomponentsusedintherepairshouldthereforebesimilarlyspecified(lead‐
free)andobtainedfromthesparesdepartmentattheCyrusfactory.Inaddition,any
solderorsolder‐pasteusedintherepairprocessmustnotcontainlead.Ifinanydoubt
aboutthecorrectprocedures,contacttheCyrusServicedepartmentforadvice.
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SOUNDQUALITY
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Preservationofthe‘factory’soundisaprioritywhenservicingaproductforaCyrus
owner.Forthisreason,pleaseensurethatonlyoriginalspecificationcomponentsare
used,sourcedwherenecessaryfromtheServiceDepartmentattheCyrusfactory.Use
ofinferiorsubstitutecomponentsmaysignificantlydegradethesoundquality.
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SERVICEMANUALINDEX
©CyrusAudioLtdJune20141Cyrus6DAC,Cyrus8DACservicemanualIssue1
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INDEX
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Modeldifferences........................................................................2
Technicalspecifications...............................................................3
Typeidentification.......................................................................4
SMDcomponentreplacement.....................................................5
Blockdiagram..............................................................................7
Technicaldescription...................................................................8
FrontpanelcontrolPCB.............................................................11
Faultfinding...............................................................................12
UsewithPSX‐R...........................................................................16
Quiescentcurrentsetting..........................................................17
DCoffsetadjustment.................................................................18
MC‐BUSoperation.....................................................................19
Flashsoftware............................................................................20
Chassispartslist.........................................................................21
Frontpanelpartslist..................................................................23
MainPCBpartlist.......................................................................24
SubPCBpartlist.........................................................................35
Circuitdiagrams.........................................................................39

MODELDIFFERENCES
©CyrusAudioLtdJun20142Cyrus6DAC,Cyrus8DACservicemanualIssue1
Digitalamplifiermodels
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Thedigitalamplifierssharethesameconstruction,featuring6stereoanalogueinputsand5
digitalinputs.Thecircuitboardsarecommontoallmodels,withdifferencesinthecapacityof
thepowersupplytransformertodeliverdifferentpoweroutputs:
Cyrus6DACdelivers40Wcontinuouspowerinto8.
Cyrus8DACdelivers70Wcontinuouspowerinto8.
TheQxhighperformancedigitalvariant,theCyrus8QxDAC,addsanupgradedD/Aconverter
moduletothedigitalstageoftheCyrus8DAC.
TheCyrus8DACandCyrus8QxDACincludeconnectionforaPSX‐Rupgradepowersupply.
ThepowerfeedfromtheregulatedPSX‐Risfedtothepreamplifierstages.
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Modelupgrades
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TheCyrusfactoryoffersownerstheopportunitytoupgradetoahigherspecificationmodel.
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SomeoftheseupgradesmaybeavailableaskitstoenableaCyrusauthorisedserviceagentto
performtheupgrade.Inthesecasesdetailedinstructionsandkitsoforiginalpartswillbe
availablefromtheCyrusservicedepartment.
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Undernocircumstancesshouldanupgradebeattemptedonanownersamplifierwithout
thesedetailedinstructionsandanoriginalpartskit.

TECHNICALSPECIFICATIONS
©CyrusAudioLtdJun20143Cyrus6DAC,Cyrus8DACservicemanualIssue1
Cyrus6DACanaloguespecification
ContinuousPower...............................40W/CH(bothdriveninto8)
50W/CH(bothdriveninto4)
BurstPower.........................................190W(IHF,onechanneldriveninto1)
Distortion.............................................0.003%,1kHz(into8)
FrequencyResponse............................‐ 3dBat0.1Hzand100kHz
DampingFactor...................................150
Sensitivity.............................................Line:179mVfor40W
Inputimpedance..................................40k(RCA).
Outputvoltage.....................................179mV(Tapeout),360mV(Preout)
S/NRatio..............................................104dBA(ref.40W)
ChannelBalance..................................±0.2dB(0dBto‐63dB)
Volumecontrolaccuracy.....................±0.1dB(0dBto‐63dB)
Dimensions(HxWxD)...........................73x215x360(mm),2.8x8.4x14.1(inches)
Weight.................................................4.0kg
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Cyrus8DACanaloguespecification
ContinuousPower...............................70W/CH(bothdriveninto8)
115W/CH(bothdriveninto4)
BurstPower.........................................320W(IHF,onechanneldriveninto1)
Distortion.............................................0.002%,1kHz(into8)
FrequencyResponse............................‐ 3dBat0.1Hzand100kHz
DampingFactor...................................150
Sensitivity.............................................Line:237mVfor70W
Inputimpedance..................................40k(RCA).
Outputvoltage.....................................237mV(Tapeout),480mV(Preout)
S/NRatio..............................................105dBA(ref.40W)
ChannelBalance..................................±0.2dB(0dBto‐63dB)
Volumecontrolaccuracy.....................±0.1dB(0dBto‐63dB)
Dimensions(HxWxD)...........................73x215x360(mm),2.8x8.4x14.1(inches)
Weight.................................................5.9kg
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Cyrus6DAC,Cyrus8DACdigitalspecification
Inputvoltage........................................500mV
Inputimpedance..................................75
Sampleraterange................................32k‐96k
Audioformats......................................PCMstereoonly
S/NRatio..............................................>100dBA
THD+N(preout0dBFS).......................<0.004%,1kHz(into8)
Cyrus8QxDACdigitalspecification
Inputvoltage........................................500mV
Inputimpedance..................................75
Sampleraterange................................32k‐192k
Audioformats......................................PCMstereoonly
S/NRatio..............................................>100dBA
THD+N(preout0dBFS).......................<0.002%,1kHz(into8)
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TYPEIDENTIFICATION
©CyrusAudioLtdJun20144Cyrus6DAC,Cyrus8DACservicemanualIssue1
Ratinglabel
Eachamplifiercarriesaratinglabelontherearpanelwhichincludesdetailsofthefollowing:
Modelnumber
Thefullmodelnumberoftheamplifierisshown.
Nominalpowervoltage
Thiswillbeeither230VForuseonnominal220V‐240VACmainssupply.
115VForuseonnominal110V‐120VACmainssupply.
Powerconsumption
Themaximumpowerconsumptionfigureisindicated.
Changingthesupplyvoltagerating
Itispossibletochangethesupplyvoltageratingofanamplifierbetween115Vand230V
settings.ThefollowingadditionalpartswillberequiredfromtheCyruspartsdepartment–
Mainpowertransformerofthecorrectrating.
Mainsfuseofthecorrectrating.
Ratinglabelthatindicatesthenewsupplyvoltage.
Powercordwiththecorrecttermination.
Replacementspeakersockets(4mmfor115Voperation,BFAfor230Voperation).
Inaddition,theprimarywiringlinks(R410,R411,R412)thatsetthesupplyvoltageforthe
controlsystempowertransformerwillrequirerewiring(detailsinthePCBpartslists).
Modelnumberdisplay
Themodelnumberoftheamplifier(forexample–Cyrus8DAC)isdisplayedwhenthe
amplifierisconnectedtothemainsandalsoeachtimetheamplifierisswitchedonfrom
Standby.
Serialnumber
Eachamplifiercarriesaserialnumbercode,whichidentifiesthefollowing‐
Typeofproduct
Buildnumber
Paintfinish(colour)
Theserialnumberisonthebaseplate.Itisthereforeimportanttoensurethatabaseplate
removedfromaproductisre‐fittedtothesameproduct.InanycommunicationswithCyrus
ServiceorQualitydepartmentsitisessentialthatthefullserialnumberisquotedsothat
originalspecificationpartsandserviceinformationmaybesupplied.
PCBIdentification
EachPCBismarkedwithadesignrevisionnumberandthisnumbershouldbequotedinall
correspondencetotheservicedepartmentwhenrequestingtechnicaladviceorrequesting
spareparts.ThetablebelowshowsatypicalmainPCBnumber,whichcanbefoundoneach
revisionofPCB.
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RevisionnumberPCBmarking
Mainboardrevision2JG1012J2

SMDCOMPONENTREPLACEMENT
©CyrusAudioLtdJun20145Cyrus6DAC,Cyrus8DACservicemanualIssue1
Handling
SMDresistorsandcapacitorsarewidelyusedintheCyrusrangeofproducts.Whenhandling
SMDcomponents,certainprecautionsshouldbeobserved‐
HandlingSMDresistorsandcapacitors
AlwaysstoreSMDcomponentsintheiroriginalpackagingorinacooldryenvironment.
AlwayshandleSMDresistorsandcapacitorswithtweezersoravacuumpencil.
NeverhandleSMDresistorsandcapacitorswithfingers.
HoldtheSMDcomponentbythebody,notbytheends.
DonotuseSMDresistorsorcapacitorsiftheendsaredirtyordiscoloured.
DonotuseSMDresistorsorcapacitorsiftheyhavebeendroppedonthefloor‐ theymay
beinternallydamaged.
Alwaysusereplacementcomponentsofthecorrectsizeandshape.SMDcomponentsare
availableinmanydifferentpackages.Wherepossible,orderoriginalpartsfromCyrus.
HandlingSMDICs
Alwaysstorethesecomponentsintheiroriginalpackagingorinacooldryenvironment.
AlwayshandleSMDtransistorsandICswithtweezersoravacuumpencil.
NeverhandleSMDtransistorsandICswithfingers.
Ensurethattheconnectionpinsoflargermulti‐pinICsarenotdeformedordamaged
beforefitting.
MeasuringcircuitswithSMDcapacitorsandresistors
Avoidusingsharp,pointedprobesdirectlyonthecomponentendcaps.
MeasurevoltagesfromthePCBpadnexttothecomponent.
Staticprecautions
SMDcomponents,particularlyICs,maybedamagedbythestaticlevelspresentinthe
workshop.Damagecausedbystaticmaynotimmediatelycausecomponentfailurebutcould
causepartialdamageandapossiblefailureinthefuture.ObservingthesesimpleSMD
precautionswillavoidproductfailuresrelatedtostaticdamage‐
Alwayswearagroundedwristbandwhenreplacinganyelectroniccomponents.
Alwaysstorecomponentsintheiroriginalpackagingorconductiveplasticbags.
Neverstorecomponentsinplastictraysorbagswithoutprotection.
Soldering/desolderingSMDcomponents
Neverre‐useoldSMDcomponentsafterde‐soldering!
Alwaysapplysolderheatdirectlytothecontactarea.Avoidover‐heatingadjacent
components.
AlwaysrepairSMDPCBswiththecorrecttools.SMDcomponentscanonlybereplacedwith
ahotairpencilorsolderingirondesignedforSMDcomponents,preferablywith
temperaturecontrol.
Keepthesolderingtemperatureaslowaspossible.370ºCisrecommendedforSMDrework
onPCBsthatuselead‐freesolder.MostSMDcomponentswillwithstand370ºCfor5to10
seconds

SMDCOMPONENTREPLACEMENT
©CyrusAudioLtdJun20146Cyrus6DAC,Cyrus8DACservicemanualIssue1
Usetin/silversolderwhichhasalowermeltingpoint.Tin/silversolderpasteorsmallgauge
solder(26SWG)isrecommended.Donotusesoldercontainingleadwhenservicingthese
products.
Whenusingsolderpasteapressuredispensershouldbeusedtoensurethecorrectamount
ofsolderisappliedtoeachpad.
Solderpasteshouldnotbeusedwithdirectheatingmethodsasthesolderbetween
componentpinsmaynotbemelted.
Ifnecessary,removeexcesssolderpastewithsolderbraid.
RemovingSMDresistorsandcapacitorsfromthePCBwithasolderingiron
1.Fitthesolderingironwithatiplargeenoughtobridgebothendsofthecomponent.
2.Placethesolderingironsothatitsflattipwillheatbothendsofthecomponentatonce.
3.Whenthesoldermelts,removethecomponentwithtweezers.
4.AllowthePCBtocoolforafewminutes,removinganyexcesssolderwithdesoldering
braid.
FittingreplacementSMDresistorsandcapacitorstothePCBwithasolderingiron
1.Applyalittlefluxtotheconnections.
2.Placethecomponentinposition.
3.Tinthesolderingiron,bringthetipintocontactwiththePCBpadandflowsoldertothe
joint.Avoidbringingthesolderingirontipdirectlyintocontactwiththecomponent.
RemovingSMDICsfromthePCB
1.Usingfinetippedsidecuttersortweezercutters,snipalltheleadsofthedeviceand
removetheICbody.
2.DesoldertheleadsfromthePCBpads.
3.CleanupthePCBwithsolderbraid.
RemovingSMDICswithahotairSMDtool
1.FitasuitablesizetipfortheICbeingremoved.
2.HeattheICevenlyuntilthesoldermelts.
3.RemovetheICwithtweezers.
FittingreplacementICstothePCBwithasolderingiron
1.CheckthatthepinsoftheICarenotdistorted.
2.Usingtweezers,positiontheICoverthefootprint.
3.CheckthatalltheICpinsarecorrectlyalignedwiththepads.
4.Withaveryfinetipsolderingiron,solderinthepinsatthecornersoftheIC.
5.Re‐checkthealignmentandcorrectifnecessary.
6.WhenthealignmentisOK,soldertheremainingpinsoftheICtothePCB.


BLOCKDIAGRAM
©CyrusAudioLtdJun20147Cyrus6DAC,Cyrus8DACservicemanualIssue1
_ +
_ +
QxDACconnector
LPF LPF
DAC
IC801
PCM17 91A
+
‐
+
‐
I2 S
PCM2707
IC 60 1
SPDIF AK 411 8
IC701
QxConnector
DIGITALIN PUTANDDA CSTA GE
IN‐7(Optical)
IN‐11 (USB)
Digi talin pu ts
IN‐8(Optical)
IN‐9(Wired)
IN‐10(Wired)
CO N90 5
CON100 To RHC ha nne l
PRE‐OUT
OUT
‐30V‐42V
+30V+42V
POWERAMP
PGA2310/11/20
IC100
DATA
CS
CLK
VOLUMECONTROL
TAP E OUT
HE AD P HO N ES
LC78211
IN‐1 IN‐2 IN‐3 IN‐4 IN‐5 IN‐6
INPUT SELECTION
DIG
TAP E /ZO N E2 OU T P UT
PREAMP (LHCHANNEL)
IN‐1 IN‐2 IN‐3 IN‐4 IN‐5
IC101
LC78211
IC102
InternalDACconnectorpa rk
whenQxmo du leisin sta ll ed
InternalDACconnector
Connectthe internalDAC
orQxDAC(Cyrus8QxDAC)to
mainPC BconnectorCO N1 00
QxDAC
(Cyrus8QxDACon ly)
DIG


TECHNICALDESCRIPTION
©CyrusAudioLtdJun20148Cyrus6DAC,Cyrus8DACservicemanualIssue1
NOTE:‐Referencenumbersinthetextarefortheleftchannel.
AnalogueinputselectionandTapeMonitor
Theinputandtapemonitorselectionisviaanelectronicaudioselectorswitch(IC101).The
switchisa7way2poleswitchfollowedbyabuffer(IC103)whichthenfeedsaudiotothe
volumecontrolsectionofthecircuit.
TheZone2/Tapeoutputisseparatelyselectedviaasecondelectronicswitch(IC102).The
signalfromtheZone2/TapeselectoristhensenttotheZone2/Tapeoutputviathebuffer
IC104.
Digitalinputs
Inadditiontothesixanalogueinputsdescribedabove,theamplifiersincludeadigitalinput
switcherandatwochannelD/AConvertertoenableconnectionofanadditionalfivedigital
inputs,fourofwhicharestereoSPDIFformatandoneUSB.
Digitalinputselectionisperformedbyan8:1inputmultiplexerinaDigitalInputReceiver
(IC701).TheDIRisclockedbya24.576MHzreferenceclock.Theinputsamplerateis
determinedbycomparingtheincomingfrequencytothereferenceclock.Thefrequencyis
thenreadbythesystemmicrocontrolleronthefrontpanelPCB,anddisplayedonthefront
panelLCDdisplay.
TheoutputfromthemultiplexedSPDIFinputsignalisthensynchronisedbyaninternalPLLand
decodedtoI2S(a3‐wiredigitalaudioformat)byIC701.
TheUSBinputisdecodedbyIC601.ThisenablestheamplifiertoplaymusicfromaPCor
similar,butisnotsuitableforconnectingFlashdrivesorthelike.WhenaUSBdeviceis
connected,thepowersupplyforIC601ispoweredviaT601.WhenthereisnoUSBmaster
deviceconnectedtotheUSBtypesocket,thepowersupplyforIC601ispowereddown,
stoppingtheclockforIC601.Whenenabled,andwithaUSBaudiosignalconnected,IC601will
re‐formattheaudiosignaltoIEC958/SPDIFformatwhichisroutedtoIC701,thedigitalinput
switch.
TheI2SaudiodatafromtheinputswitchIC701isfedtoIC801,astereoD/AConverter.TheD/A
Converterconvertsthedigitalaudiointoananalogueoutput.Thisisamplifiedandfilteredby
IC802beforebeingpassedtotheDIGinputofIC101(theinputswitchonthemainanalogue
amplifierPCB)viaCON100.
ThedigitalaudiosignalsfromIC801arealsofedtotheQxDACupgradeconnectorCON902.Ifa
QxupgradeDACisfittedtoaCyrus8DAC,aflexfoilcableisfittedbetweenCON902andtheQx
DACPCBtoconnectdigitalaudioandpoweretctotheQxDAC.TheaudiooutputoftheQx
DACisconnectedtoCON100onthemainPCB.Inthisconfiguration,theaudiooutputcableof
theDigitalInputmoduleisconnectedtoaspareconnectorCON905.
ThepowerforthedigitalinputPCBissuppliedfromaseparatelowvoltagewindingofthemain
powertransformer.Thisisthenrectifiedandsubregulatedtoanumberofindividualsupplies,
one3.3Vandtwo5.0V.Therectifiedandunregulatedsupplyisalsopasseddirectlytothemain
analogueamplifierPCBtoprovidepowerfortheLCDbacklight.The15Vpowersuppliesfor
theanaloguepostDACfilterareprovidedfromthemainanalogueamplifierPCB.
WhentheamplifierissettostandbythepowertothewholedigitalinputPCBisremoved.
IfadigitalinputisnotselectedforlisteningonthemainamplifierorinZone2,thedigitalPCB
willbeheldinresettoeliminatedigitalnoiseinterferencecouplingtothemainanalogue
inputs.

TECHNICALDESCRIPTION
©CyrusAudioLtdJun20149Cyrus6DAC,Cyrus8DACservicemanualIssue1
Volumecontrol
Theoutputsignalfromtheinputselectorbuffer(IC103)iscoupledtotheinputofthedigitally
controlledvolumeIC(IC100).TheoutputofthevolumecontrolICisthenfedtothe
preamplifieroutputandthepoweramplifiers.
Poweramplifierstage
Thepoweramplifierisadiscretevoltagefeedbackdesign.RV201allowsadjustmentofthe
outputtransistorbiascurrent.T208andT210arethedrivertransistors.T206,T208andT210
areboltedtogethertoensuregoodthermalcoupling.T209andT211aretheoutput
transistors.
DCoffsetattheoutputoftheamplifiermaybesetunderconditionsofnosignalbyadjusting
RV203.Onceset,DCworkingconditionsarestabilisedwithinthepoweramplifierbyaDCservo
(IC200),measuringtheDCoffsetattheamplifieroutputandadjustingthebiasvoltageapplied
toT202Btocompensate.
PoweramplifierstandbycontrolisachievedviatheCCSpoint.Withthisline,the
microcontrollercanswitchthepoweramplifiersonoroffviathelevelshiftingandbuffer
circuitonthe‘ChargePump’schematicsheet.
Headphones
ThedrivefortheheadphonescomesfromadedicatedpoweramplifierIC901.Theheadphone
amplifierismutedbythemicrocontrollerwhenthepoweramplifiersareonandactivated
whenthepoweramplifiersareoff.ThePHONES_INsignalenablesthemicrocontrollerto
detectwhena3.5mmjackplugisinsertedintheheadphonesocket.
Powersupply
Thefrontpanelcontrolcircuit(withtheexceptionofthedisplaybacklight)ispoweredfroma
smallpowertransformermountedonthemainPCB.Whenexitingstandby,thecontrolsystem
switchesrelayRL401,applyingmainspowertothemainpowertransformer.Thisenablesthe
controlsystem,includingmicrocontroller,toconsumeverylittlepower,particularlywhenset
toStandby.
PowerforthedisplaybacklightandthedigitalinputPCBisprovidedseparatelyfromalow
voltagewindingofthemainpowertransformer.
Thepowersuppliesforthemainamplifier(VCC)are42V(Cyrus8DAC)or39V(Cyrus6
DAC).TheseareprotectedbyfastblowfusesFS401andFS402onthemainPCB.Inadditiona
regulated42Visderivedfromachargepumpcircuitandsuppliesthelowcurrentsectionof
thepoweramplifiers.Aregulatedpowersupplyof15Visderivedfromthepowersupplyfor
themainamplifierviaregulatorsVR402andVR403.The15Vsuppliesareusedfortheinput
selector,buffersandpartsoftheprotectioncircuits.5Visderivedfromthe15Vsuppliesfor
thevolumecontrolIC100.

TECHNICALDESCRIPTION
©CyrusAudioLtdJun201410Cyrus6DAC,Cyrus8DACservicemanualIssue1
Theprotectioncircuits
Over‐currentprotectionisachievedbydetectingthevoltageacrossthedualemitterresistor
R219.WhenahighlevelofcurrentisdetectedT304willturnon,switchingT307onetc.The
outputsignalfromthisdetectoristhensenttothemicrocontroller.
IftheDCconditionsoftheamplifierdriftbeyondacceptablelimits,thisisdetectedbyIC200
andassociatedcircuitryandprotectionwillbeactivated.
Thermalprotectionisachievedbythemicrocontrollerdetectingahightemperaturereading
fromthethermalsensor.
PowersupplyfailureisdetectedbyIC402arrangedasawindowcomparator.Thewindow
rangeissetbetween19Vand60V,astheamplifierwillworkbetweenthesevoltages.Ifthe
supplyvoltageisoutsidethatrangeapowersupplyerrorsignalissenttothecontrol
microprocessor.
Mainsdisconnectionisdetectedbythecontrolmicroprocessortopreventswitchoffnoise.
Thecontrolsystem
ThesystemmicrocontrollerandthedisplayarehousedonaPCBattachedtothebackofthe
frontpanelassembly.Theinputstothemicrocontrollerreadwhenthekeysarepressed,a
remotecontrolorMC‐BUScommandisreceivedandalsomonitortheworkingstatusofthe
amplifierviafaultdetectionlines.Themicrocontrolleristhenconfiguredtoupdatethedisplay
andsetthevolume,inputandothersectionswithintheamplifier.
ThefrontpanelcontrolsystemPCBisconnectedtothemainPCBviaasingle25wayflexible
cable.Asecond13wayflexiblecableconnectsdirectlyfromthefrontpanelPCBtothedigital
PCB.Notethatthisflexiblecableisinvertedcomparedtothe25waycable.Whencorrectly
installed,thewritingwillbevisibleonthe13waycable,andnotvisibleonthe25waycable.
ThefrontpanelcontrolPCBchangedduringthecourseofmanufacturingtheseamplifiers.The
second‐generationPCBincludesapushfunctionontherotaryencoder,whereasthefirst‐
generationPCBdoesnot.Moreinformationaboutthedifferencesbetweenthetwoversionsis
shownonthenextpage.

FRONTPANELCONTROLPCB
©CyrusAudioLtdJun201411Cyrus6DAC,Cyrus8DACservicemanualIssue1
ThefrontpanelcontrolPCBchangedduringthelifeoftheamplifiers.
ThetwoPCBversionsareeasytoidentifywithoutdismantlingtheamplifier.Therotarycontrol
ofthelaterversiondisplayPCBincludesapushfunction,theearliercontrolPCBdoesnot.
Operationoftheamplifierchangedslightlywiththeintroductionofthepushfunction.
IntheeventthatafrontpanelcontrolPCBrequiresreplacement,thereplacementPCB
suppliedwillbethesametypeastheoriginal.WhenorderingareplacementPCB,alwaysquote
theserialnumberoftheamplifierandstatewhethertherotarycontrolhasapushfunction.
NOTE:ThetwotypesofcontrolPCBarenotdirectlyinterchangeable.Toreplaceanoriginal
'non‐push'typePCBwiththelatertype'push'PCBwouldrequirechangesinothercircuitareas
andalsoupdateduserinstructions.
TheamplifieroperationalsoftwareislocatedonthefrontpanelcontrolPCB.
FrontpanelcontrolPCBswithoutpushcontrol
ReplacementPCBsaresupplied'clean'ofsoftwaresowhenreplacingthistypeitwillalwaysbe
necessarytoprogramthePCBviatheamplifierprogrammingconnector.
FrontpanelcontrolPCBswithpushcontrol
ReplacementPCBsaresuppliedpre‐programmedsocanbefittedwithoutre‐programmingvia
theamplifier.
Refertopage20formoreinformationaboutprogrammingtheamplifiers.




FAULTFINDING
©CyrusAudioLtdJun201412Cyrus6DAC,Cyrus8DACservicemanualIssue1
Theamplifiersarecomplex,microcontrolledproductsusingsmall‐scaleSMDtechnology.Do
notattemptanyfault‐findingorrepairononeoftheseproductsunlessyouareacompetent
audioengineerwiththecorrectSMDrepairtoolsandtrainedtofault‐findonthisequipment.
Thisfault‐findingguideisnotexhaustive,butshouldhelpacompetentengineertracefaults
withintheamplifier.Ifyourequiremoretechnicalhelpthanthisguide,contacttheCyrus
ServiceDepartment.
CAUTION
Thehigh‐efficiencyheat‐transferinsulationpadsfittedbetweenthepoweramplifieroutput
transistorsandthechassisoftheamplifiersaredesignedtosoften,meltandbondtothe
transistorandheatsinkwhentheamplifierfirstheatsup.Thisistoenablethepadstofillany
pitsinthesurfaceoftheheatsinkandprovideanexcellentthermalbondbetweenthe
transistorandheatsink.ForthisreasonanypadmaterialmustALWAYSbecompletelyscraped
fromtheheatsinkandthepadsreplacedifthesealisbrokenbetweenthetransistorand
heatsink,astheywillnotre‐bond.Conventionalpadsandgreasearemuchlessefficientheat
conductorsandarenotanacceptablesubstituteforthecorrectpads.Useofalternativepads
willriskfuturefailureoftheamplifier.AlwaysobtainoriginalpadsfromtheCyrusService
Department.
Layoutoftheamplifier
Theamplifierisconstructedwiththeanaloguepre‐amplifier,poweramplifierandpower
supplylayingonthemainPCBfixedinthebaseofthechassis,andasmallersubPCBlocated
overthisthatincludestheheadphoneamplifier,thepowersupplyforthedisplaybacklight,the
circuitryforthedigitalinputsandtheD/Aconverter.Theanalogueaudiooutputfromthe
digitalaudiosectionofthesubPCBconnectstothepreamplifieronthemainPCBthrougha
cable.
ThecircuitrythatcontrolstheamplifierislocatedonthefrontpanelPCBwiththeLCDdisplay.
Dismantlingtheamplifier
Basictests,alignmentandfusereplacementarepossiblewithoutremovingthesubPCB.All
alignmenttestpointsonthemainPCBandtherightchanneladjustmentpresetsareaccessible
aroundtheborderofthesubPCB.Theleftchanneladjustmentpresetscanbereachedthrough
anaccessholeinthesubPCB.
Foraccesstotestorrepairthepreamplifierorpoweramplifierstages,thesubPCBmustfirst
beremoved.WiththesubPCBremoved,theamplifierwillcontinuetofunctionasnormalfor
testandrepair,butwithoutthedisplaybacklightordigitalinputs.
ThesubPCBcannotsimplybeunpluggedfromitsmainPCBconnectorwithoutdamage.To
removethesubPCBleavingthemainPCBinthechassis,removethescrewssecuringtherear
paneltothesubPCBandthetwoalongthetopedgefixingittothechassis.Removethenut
securingtheheadphonesocket(specialtoolrequired).Oncethescrewsareremoved,therear
panelcanbetiltedbackslightlytoallowclearancetoremovethesubPCBfromitsconnector.
CAUTION:Whenre‐fittingthesub‐PCB,takeparticularcaretoensurethattheconnectorpins
arecorrectlyaligned.Misalignmentofthepinswillcauseconsiderabledamagetothesub‐PCB.
Initialprecautionsandfirsttests
Beforeconnectingpowertoanamplifierthatissuspectedtobefaulty,ensurethat
loudspeakersandloadsaredisconnectedfromthespeakersocketstoavoiddamagingthem.

FAULTFINDING
©CyrusAudioLtdJun201413Cyrus6DAC,Cyrus8DACservicemanualIssue1
Afirsttestistochecktheresistancebetweenthespeakerterminals.Thisshouldbe
approximately14.2kΩ.Ifthevalueissignificantlydifferent,theremaybeanoutputstagefault
ofthatchannel.Acompletecheckoftheoutputstagetransistorsisrecommended.Checkalso
theDCfuses.Iftheseareblownfollowthesamecourseofaction.
Iftheoutputtransistorsaresuspect,measuretheresistancebetweenbaseandemitter(the
outsidepins).Thisshouldbeapproximately68Ω ‐ 70Ω.Ifthemeasurementislow,the
transistormaybeblownandbothtransistorsshouldbereplacedinthatchannel.
Withtheloudspeakersdisconnected,connectthemainspower.Theamplifiershouldswitchon
andsettostandby(frontpanelLEDisred).IftheLEDdoesnotlightthemainsfusemayhave
blownortheremaybeafaultinthecontrolsystempowersupply.Disconnecttheamplifier
andcheckthemainsfuse.IfthemainsfuseisOK,re‐connectthemainsandcheckthe+5V
powersupplyforthefrontpanelcontrolPCBattheregulatorVR401output.Ifthisisabsent,
tracethecontrolcircuitpowersupplybackthroughtheregulator,D448bridgerectifierand
R421fusibleresistortothePCB‐mountedpowertransformerthatsuppliesthepowertothe
regulator.
Iftheamplifierhassettostandby,switchitonnow.ThemainsrelayRL401shouldclickand
poweristhenappliedtothemainpowertransformer.Thedisplaybacklightwilllightand
powerwillbeappliedtothecircuitsintheamplifier.Ifthedisplaydoesnotlight,checkFS901
onthesub‐PCB.IftherelaydoesnotoperatetheremaybeafaultwithinthedrivecircuitT400
etc,ortherelayitself.Therelaycanbetestedbyapplying12VtoSK401whenthepoweris
disconnected(a6LR619Vbatterycanbeusedforthistest).
Iftheamplifierswitcheson,checktheDCoffsetvoltageatthespeakerterminals.TheDCoffset
measuredshouldreadwithin±50mV.Ifthevoltageisgreaterthanthisthenfirsttrytosetthe
DCoffsetvoltage(seepage18).Ifthevoltagewillnotsetwithinthebandspecified,thepower
amplifiermaywellbefaulty.
IftheDCoffsetiswithinlimits,thenitissafetoconnectadummyloadorloudspeakers.Atthis
pointitisadvisabletomeasurethepoweroutputandTHDfromtheamplifiertoestablishifit
willmeetspecification(frontpageofthisservicemanual)anddetermineifthereisafault.
Poweramplifierfaults
DCrailfuses.IftheDCoffsetcannotbeadjustedtospecorifapoweramplifierstageisnot
functioningcorrectly,thendisconnectthepowerandchecktheDCrailfusesonthemainPCB.
Replacetheseifnecessary.Iftheyblowagain,thereisprobablyasemiconductorfaultinthe
poweramplifierorpowersupply.NOTE:‐Ifthestandbylightflashesredwhentheamplifieris
switchedonthisindicatesthataDCfusemaybeblown.
Powersupplyvoltagecheck.IftheDCfusesareOK,thencheckinitiallyallthevoltagesinthe
powersupplyoftheamplifier,includingtheregulatedpowersupply±42V.Iftheregulated
supplyneedsrepair,thencheckagainsttheschematictofindfailedcomponentsandreplace
them.IfthevoltagescheckOKthenthereisprobablyasemiconductorfaultintheleftorright
poweramplifier.
Semiconductorfaults.Thereisnoexactfault‐findingprocedureforthepoweramplifiercircuits,
howeveritisrecommendedthataDVMsetto‘diodetest’shouldbeusedtothoroughlycheck
eachsemiconductorinthepoweramplifierstage,alsosettheDVMtoohmsandcheckalllow
valueresistorssuchasR214‐219(leftchannel).Removeanysuspecttransistorsandre‐check
themoutofcircuit.Replaceasnecessarywiththecorrectoriginalcomponentssuppliedbythe
CyrusServiceDepartment.

FAULTFINDING
©CyrusAudioLtdJun201414Cyrus6DAC,Cyrus8DACservicemanualIssue1
Re‐testingtheamplifierafterrepair.Afterrepairingtheamplifier,connectaDVMtomonitor
thequiescentcurrentintherepairedchannel.AsyouswitchonfromStandby,watchtheDVM
readingwhichshouldreadjustafewmVmaximum.Ahighorrapidlyclimbingquiescent
readingwillprobablyindicatethatafaultstillexistswithinthepoweramplifierstage.Inthis
casetheamplifiershouldbeswitchedoffimmediatelytoavoidfurtherdamage.Ifthe
quiescentremainslow,thenproceedtosetthequiescentcurrentaccurately,referringtothe
correctsectioninthisservicemanual.
Ifthequiescentcurrentsetscorrectly,continuetocheckandsettheDCoffsetvoltageatthe
speakerterminals.
IfbothquiescentcurrentandDCoffsetsettingsarestableatthecorrectvalues,proceedto
connectspeakersordummyloadsandcheckthefunctionoftheamplifierwithasignal.
Preamplifierfaults
Powersupplies.Beforecommencinganyfaulttracingitisadvisabletorefertothepreamplifier
schematicsheetandcheckthepowersuppliestoeachofthepreamplifierICs.Intheeventofa
powersupplyfailure,tracethepowersuppliestothepreamplifierusingtheschematics.Note
thatpowertothepreamplifierregulatorsisroutedviathePSX‐Rswitchingcircuit
T401/T402/T405/T406whenaPSX‐Risnotconnected.
Nosignal.IfthepowersuppliescheckoutOK,thenpre‐amplifiersignalfaultsarebestfoundby
supplyingasine‐wavesignaltotheamplifierinputsandtracingthisthroughthepre‐amplifier
stageinputselectorandvolumeICstothepoweramplifier,andreplacinganycomponents
wherethesignalmaybelost.TheZone2outputcanhelptracesignalfaults.Ifthetestsignal
canbeseenattheZone2output,butnotatthePre‐ampoutput,thenthevolumecontrol
IC100orinputselector!C101maybefaulty.IfthereisnosignalattheZone2output,thenthe
Zone2selectorIC102maybefaulty.
Controlsystemfaults
Ifthefrontpaneldoesnotpowerupandsettostandbywhenpowerisapplied,thentestthe
controlsystempowersupplyasdescribedinthe‘Initialprecautionsandfirsttests’section.If
thefrontpanelinitialisesandsetstostandby,butthereareproblemswithanyelementofthe
controlsystemthefrontpanelcontrolPCBwillrequirereplacement.
Ifoneofthecontrolkeysisnotoperatingcorrectly,thencheckthattheswitchoperates
mechanicallyandthatitisnotstickinginthetechnicalmoulding.
Digitalaudiofaults
IfafaultissuspectedwithadigitalinputsubPCB,someinitialdiagnosticworkisworthwhile
beforeremovingthePCBasthiscannotbepoweredfortestsonceitisremovedfromthe
amplifier.
Connectadigitalinputtooneoftheelectricaloropticalinputsoftheamplifier.Selectthis
inputandcheckifthesamplerateiscorrectlyindicatedonthedisplay.Ifthesampleratereads
OK,thissuggeststhatthedigitalinputIC(IC701)isworkingcorrectly.
Checktheotherdigitalinputsinthesameway.TheUSBinputmaybecheckedbyconnectinga
computerasasourcewithanaudiosignalplaying.Ifalldigitalinputsareworking,butUSBis
not,thentheUSBdecoderIC601oroneoftheassociatedcomponentsmaybefaulty.
IftheinputselectorICisworkingforallinputs,thencheckbothleftandrightchannelsatthe
audiooutputoftheamplifierusingoneofthedigitalinputsasasource.Ifoneorbothofthe

FAULTFINDING
©CyrusAudioLtdJun201415Cyrus6DAC,Cyrus8DACservicemanualIssue1
audiochannelsisnotworking,theremaybeafaultwiththeDAC(IC801),filterIC(IC802)or
oneofthecomponentsassociatedwiththese.
Ifafaultisfoundfromthesetests,thenextsteprecommendedistocheckthepowersupplies
totheplug‐indaughterPCB.RemovethePCBforthesetests,thenswitchontheamplifierand
checkthatthecorrectvoltagesaresuppliedatthePCBconnectorfromthemainPCB.
Ifthevoltagesmeasurecorrectly,thenthefaultmustbeonthesubPCB.

USEWITHAPSX‐R
©CyrusAudioLtdJun201416Cyrus6DAC,Cyrus8DACservicemanualIssue1
UsewithaPSX‐R
WhenaPSX‐RpowersupplyisconnectedtoaCyrus8DAC,thepresenceofpowerasthePSX‐R
isswitchedfromstandbyautomaticallydisconnectsthefeedfromtheinternalpowersupplyto
thepreamplifierregulators(viaswitchtransistorsT406/T402).ThepowerfromthePSX‐Ris
thenfedtothepreamplifierregulatorsviaD451/D454.
NomodificationisnecessarytotheamplifierforusewithaPSX‐R,itmaybeconnectedwithout
anychangestotheamplifier.
TheconnectionsbetweentheamplifierandPSX‐Rfunctionasfollows‐
Pin1(Standby)
Thisisanoutputfromtheamplifiertosendastandbycontrolmessage(logic1,+5V)tothe
PSX‐R,enablingtheregulatedpowersuppliesofthePSX‐R.Notethatthispinwillnotchange
stateiftheamplifierdetectsafault(Seepin5).
Pin2(Positivesupply)
InCyrus8DACamplifiers,thispindelivers+18VfromthePSX‐Rtotheamplifier,switchedby
theStandbycontrolsystem.
Pin3(GND)
ThispinisthesystemgroundreturnbetweentheamplifierandPSX‐R.
Pin4(Negativesupply)
InCyrus8DACamplifiers,thispindelivers‐18VfromthePSX‐Rtotheamplifier,switchedby
theStandbycontrolsystem.
Pin5(PSX‐Rdetect)
ThispinisaninputtotheamplifiertodetectthepresenceofaworkingPSX‐R.Thepinalsosets
theworkingmodeofthePSX‐R.T408andassociatedcomponentsactonthelinetoseta
referencevoltagethatswitchesthePSX‐Rtovariablemode,setfor18Vsupply.

Thisdiagramshowsthepinnumbersofthe
powersupplyinputconnectoronthe
amplifier.Viewisoftheconnectorpinsfrom
therearoftheamplifier


QUIESCENTCURRENTSETTING
©CyrusAudioLtdJun201417Cyrus6DAC,Cyrus8DACservicemanualIssue1
Quiescentcurrentsetting(nosignalcondition)
Quiescentcurrentsettingshouldalwaysbesetcorrectlyafterrepairofthepoweramplifier.If
incorrectlyset,theamplifiersonicandtechnicalperformancewilldeteriorate,andifsettoo
high,thereisapossibleriskoftheamplifieroverheating.
Thefollowingprocedureshouldbefollowedexactlytosetthequiescentcurrenttothecorrect
value.Ifthequiescentcurrentwillnotsetcorrectly,thismayindicateapoweramplifierfault.
Switchoffthepowertotheamplifier.
Disconnectallloudspeakersordummyloads.
ConnectaDVMsettoreadmVtoSK205.
Switchonthepowertotheamplifier,andbringitoutofstandby.Ifamainsvoltage
adjuster(variac)isavailable,useittosetthemainsvoltageprecisely.
AdjustthequiescentsettingpresetRV201sothatthemeterreads8mV
ProceedtoconnecttheDVMtoSK206.AdjustthequiescentsettingpresetRV202sothat
themeterreads8mV.
Leavetheamplifiertostabiliseforfifteenminutesandrepeattheadjustmentsforboth
channels,takingthesettingto3.2mV0.25mV.
Checkperiodicallyandadjustifnecessaryto3.2mV0.25mVuntilsettled.Alsoensurethat
thenominalmainsvoltagehasnotdrifted.
SK206
3.2mV
RV202
SK205
RV201

DCOFFSETADJUSTMENT
©CyrusAudioLtdJun201418Cyrus6DAC,Cyrus8DACservicemanualIssue1
DCoffsetadjustment(nosignalcondition)
TheDCoffsetadjustmentsetstheDCvoltageatthespeakeroutputterminals.DCoffsetshould
alwaysbecheckedasamatterofroutinewhenanamplifierisreturnedforrepair,whetherthe
poweramplifiersectionhasrequiredrepairornot.
ThefollowingprocedureshouldbefollowedexactlytosettheDCoffsetvoltagetothecorrect
value.IftheDCoffsetvoltagewillnotsetcorrectly,thismayindicateapoweramplifierfault.
Switchoffthepowertotheamplifier.
Disconnectallloudspeakersordummyloads.
ConnectaDVMsettoreadmVtotheleftloudspeakerterminals(ashortcableterminated
withCyrusspeakerconnectorsisrecommendedtomakecertaincontactwiththe
terminals).
Switchonthepowertotheamplifier,andbringitoutofstandby.Setthevolumelevelto‐
15dB.
Leavetheamplifiertosettlefor5minutes.
CheckthevoltagereadingontheDVM.Avoltagewithintherange0V50mVisacceptable
andwillnotrequireanyadjustment.Ifthevoltageisoutsideoftheselimits,adjustRV203
tosettheleftchanneloffsetwithintherange0V50mV.
ConnecttheDVMtotherightchannel.
RepeatthevoltagechecktothesamelimitsandadjustRV204tocorrecttherightchannel
offsetifnecessary.
Leavetheamplifiertosettlefor15minutesandre‐checktheDCoffsetvoltages.

0.0mV
RV204
RV203