Arcam rDac - Page 4

InputStagesandswitchingCircuitpages2and3
TheinputsaresplitintotwogroupswiththeWolfsonSPDIFreceiveratlocationIC201dealing
withOpticalandCoaxialselectionwhilsttheMUXatlocationsIC202AIC202BandIC205A
switchbetweenSPDIF(optorcoax)andUSBorKLEERundercontrolfrommainmicro.
SPDIFinput
TheWolfsonWM8805SPDIFreceiversuppliesdatainaformatofData,LRCLK,BCLKandMLCK,
theoutputofIC201runsdirectlytotheDACviatheMUXatlocationIC202Awithexceptionof
theMCLKthistakeapaththruIC203aspartoftheMCLKMUXbetweenUSB/KLEERandSPDIF
MCLK’s.
USBinput
TheUSBdataarrivesatCON100beforetravelingtotheUSBstreamingcontrolchipatlocation
IC103viatheESDprotectionChipatlocationIC101thechipisloadedwiththeDCS
asynchronous/isochronousinputsystemfromIC100atbootup.
IC103hasitownMCLKsourceatlocationIC204anotherWM8805thistimeusedasanadaptive
clocksourcetheoutputisbufferedbyIC203C
TheData,LRCLK,BCLKareswitchedtotheDACviaIC202BwiththeMCLKcomingviaIC203.
DACandAudioStagescircuitpage4
TheWolfson8741DACcanbefoundatlocationIC301andtakesitssuppliesfrom3V3Dand
5VDAC,dataentersthechiponpins1–5andshouldbeseenasbelow.
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AnalogueaudioleavestheDACasbalancedpairsonpins16/17(left)and12/13(right)audio
thentravelsthruandfilternetworkenterstheOp‐ampatlocationIC300a/b(L/R)andthen
ontoIC302a/b(L/R)outputmutingistwofoldwithbothDACmute(transistormute)andfull
mute(relay)theDACmuteisprovidedbytransistorsTR302andTR305switchingtheaudio
downto0vthisunderthecontroloftheDACMUTElinefromIC107,therelaymuteisprovided
byRLY300andtriggeredfrom2linesonebeingthepowerdetectsourcedfromD400atpower
In–underlowpowertherelaywillcloseat5.3vD.CandisflippedbyIC105incombinationwith
IC104theoutputofIC104islowtomutetherelayisswitchedbyTR300.
Pinloc Signaltype
Pin1 LRCK
Pin2 SDATA
Pin3 BCK
Pin5 MCLK