Grimm Audio CC1 User manual

Please read this manual before operating the unit!

TPInLB

Table of Contents

Introduction 4

ImportantSafetyInstructions 5

1.Installing 7

2.SignalConnections 8

3.Operation 8

4.SettinguptheStudio 12

5.ProTools 16

6.JitterandPLL’sexplained 18

7.Specifications 23

8.GrimmAudioLimitedWaranty 25

Introduction

ThankyouforchoosingtheGrimmAudioCC1CentralClockdistributorforyour

productionenvironment.Thisproductfeaturesarichsetofdistributorfunctions,

baseduponanultralowjitterclockoscillator.Itembodiesourcompanyphilosophy

ofprovidingthemosttransparentsignalchainpossible,enablingyoutoachievethe

bestpossibleresultssonicallyandartistically.LargepartsoftheCC1circuitry,like

theoscillatoranditspowersupplies,useadiscretedesign.BecauseofthisaCC1

hasmorethan700components.Duringconstruction125seperateelementsare

tested.

TheCC1canbeusedinawidevarietyofapplicationssuchas:

•HouseSyncgenerationinaudioand/orvideostudios.Sixteenoutputspermitthe

useofthereliable“star”distributionscheme.TheextremelylowjitteroftheCC1

clockoutputsmaximisesthesoundqualitypotentialoftheattacheddevices.Incase

youneedtoslaveyoursystemtovideoclock,pleaseinsertaGrimmAudioVCC,

‘videotowordclockconverter’beforetheclockinput.

•Clockstabilityimprovement,andhenceimprovedsound,ofdigitallivedesksand

digitalsnakes.

•Clockdistributioninbroadcaststudios.

•Improvementofyourhomeaudiosystem.Forinstanceinconjunctionwithword

clockequipeddevicesorasreclockunitinbetweenatransportormediasystem

andaDAconverter.

Thismanualdescribeshowtosetuptheunitinyourstudio,liveorhomeenviron-

mentaswellasimportanttipsonhowtogetthebestperformancefromtheCC1.In

addition,somebackgroundinformationontheunit’soperationisprovided.

Wehopethisinvestmentwillbringyoumanyyearsofcreativeenjoymentandhelp

youachieveyourgoals.

Important Safety Instructions

Grimm Audio gaat er van uit dat u deze Engelstalige tekst volledig begrijpt. Als u hier moeite

mee heeft dient u contact op te nemen met Grimm Audio. Op verzoek sturen wij u een vertaling

toe.

Grimm Audio nimmt an, dass Sie diesen Englischen Text völlig verstehen. Wenn notwendig,

nehmen Sie bitte Kontakt auf mit Grimm Audio. Auf Wünsch wird Ihnen eine Übersetzung zu-

geschickt.

Grimm Audio suppose que le lecteur comprend parfaitement le texte en Anglais ci-dessous. En

cas de doute s.v.p. contacter Grimm Audio. Si necessaire, on pourra vous envoyer une traduc-

tion.

Grimm Audio da por supuesto que el texto en versión Inglesa no ofrece ninguna duda de in-

terpretación y se entiende integramente. Si este no fuese su caso rogamos contacte con Grimm

Audio quien, a petición, se encargaría de enviarle la correspondiente traducción.

Please follow these precautions when using this product:

1.Readtheseinstructions.

2.Keeptheseinstructions.

3.Heedallwarnings.

4.Followallinstructions.

5.Dangerousvoltageisinsidethisapparatus.Openingisonlyallowedbyqualified

servicepersonnel.

6.Verifylinevoltagebeforeuse.

7.Donotdefeatthesafetypurposeofthepolarizedorgrounding-typeplug.A

polarizedplughastwobladeswithonewiderthantheother.Agrounding-typeplug

hastwobladesandathirdgroundingprong.Thewidebladeorthethirdprongare

providedforyoursafety.Whentheprovidedplugdoesnotfitintoyouroutlet,con-

sultanelectricianforreplacementoftheobsoleteoutlet.

8.Protectthepowercordfrombeingwalkedonorpinched,particularlyatplugs,

conveniencereceptables,andthepointwheretheyexitfromtheapparatus.

9.Unplugthisapparatusduringlightningstormsorwhenunusedforlongperiods

oftime.

10.Donotusethisapparatusnearwater.

11.Donotusethisapparatusoutside.

12.Donotexposetheapparatustodrippingorsplashing.Donotplaceobjects

filledwithliquids(flowervases,drinkcans,coffeecups,etc)ontheapparatus.

13.Cleanonlywithadry,soft,non-fluffycloth.Donotsprayanyliquidcleaneronto

thecabinet,asthismayleadtodangerousshocks.Donotsprayanyliquidcleaner

ontothefaceplate,asthismaydamagethefrontpanel.

14.Installinaccordancewiththemanufacturer’sinstructions.

15.Donotinstallnearanyheatsourcessuchasradiators,heatregisters,stoves,or

otherapparatus(includingamplifiers)thatproduceheat.Avoidexposuretodirect

sunlight.

16.Useonlyattachmentsoraccessoriesspecifiedbythemanufacturer.

17.Useonlywithacart,stand,bracket,ortabledesignedforusewithprofessional

audioormusicequipment.Inanyinstallation,makesurethatinjuryordamagewill

notresultfromcablespullingontheapparatusanditsmounting.Ifacartisused,

useprecautionwhenmovingthecart/apparatuscombinationtoavoidinjuryfrom

tip-over.

18.Thisunitrunsslightlywarmwhenoperatednormally.Operateinanormalventi-

latedarea.Ifthisproductwillbeinstalledinarack,makecertainthereissufficient

airmovementwithintherack.

19.Referallservicingtoqualifiedservicepersonnel.Servicingisrequiredwhenthe

apparatushasbeendamagedinanyway,suchaswhenthepower-supplycordor

plugisdamaged,liquidhasbeenspilledorobjectshavefallenintotheapparatus,

theapparatushasbeenexposedtorainormoisture,doesnotoperatenormally,or

hasbeendropped.

20.WARNING: Toreducetheriskoffireorelectricshock,donotexposethisappa-

ratustorainormoisture.

1. Installing

Unpacking and Inspection

YourCC1wascarefullypackedatthefactoryandthecartonitcameinwasde-

signedtoprotectitfromthetrialsandtribulationsofshipping.Keeptheboxandall

packingmaterials,sothatintheunlikelyeventthatyouneedtoreturntheCC1for

servicing,youcandososafely.

Mounting the CC1

TheCC1canmountinanystandard19”rack.TheCC1doesnotproduceRFfields

norissusceptibletothem.Youcanpositionitnearotherdigitalgearsuchascom-

puteranddiskrecorderswithoutworry.Ingeneralitisagoodideatokeepsome

distancebetweenmonitors(LCDandCRT)andaudioandwordclockcablesbecause

ofriskofinducedlowlevelnoiseduetostraymagneticfields.

GrimmAudioproductshavearealwoodfaceplatethatprovidesabeautifuland

vividappearance.Tomaintaintheoutstandinglooks,oneisadvisedtotakesome

precautions:

-DonotplacetheCC1inhumidnorverydryenvironments.Thewoodmightcrack.

-Donotusechemicaloralcoholbasedcleaneronthewood.

AC Power Hookup

TheCC1hasalinearpowersupplythatneedstobefactorysetforyourlocalline

voltage.MakesuretocheckthenotedlinevoltageonthebackbelowtheIECcable

entrance(‘wiredfor...V’)andverifythatthiscomplieswithyourlocallysupplied

linevoltage.GrimmAudiocannotberesponsibleforproblemscausedbyusing

theCC1withimproperACwiringorvoltage.SincetheCC1doesnothaveapower

switchonthefrontpanel,aconvenientwaytopowerdowntheunitistousea

powerstripequippedwithaswitch.

2. Signal Connections

TogglesMaster44.1/48kHzandSlave

Togglesgroup1sampleratemultiplicationfactor

Togglesgroup2sampleratemultiplicationfactor

AES3-out

(follows

AES3-in when

available

and selected,

otherwise

group 2)

AES-in

lockstatus

Inputs

(AES3-in also

for reclocking

purpose)

AES-out

behavior

(thru or

mute) Impedance

group1

(75 Ohm

or Lo-Z)

Impedance

group2

(75 Ohm

or Lo-Z)

Phaseof

BNC11,

12,13,14

(normal or

180°)

Outputs

group1

Outputs

group2 Indication

offactory

setline

voltage

value

unlock

behavior

(hold or

mute)

3. Operation

Master mode

Theleftmostfrontpanelpushbuttonselectsbetweentwobaseclockrates:44.1kHz

or48kHz.Thetwootherpushbuttonsdeterminetheactualclockfrequencytrans-

mittedacrossthe16BNCoutputs.Theycontrolintwogroups.Group1arechan-

nels1-12.Thesecondpushbuttonsetsthemultiplicationfactorforthisgroupto

1x,2xor4x.Group2arechannels13-16,andtheirmultiplicationfactorissetby

thethirdpushbutton.Setting“48kHz”usingtheleftmostpushbutton,“1x”onthe

middleselectorand“2x”ontherightmostselectorwillsettheclockrateongroup1

BNC’sto48kHzandongroup2BNC’sto96kHz.

TheAES3outputhastwofunctions,dependingonthesettingofthedipswitch

marked“aes”ontherear.Itdetermineswhethertheaudiocontentfoundatthe

AES3inputispassedthroughtotheoutput(“thru”)ornot(“mute”).In“mute”mode

theAES3datawillbeblackandrunattherateselectedforgroup2.In“thru”mode,

theAES3outputwillobviouslyrunatthesamerateastheAES3input.Onlossof

inputsignal,theoutputwillremainatthesamesamplingrate.

TheexactbehaviouroftheAES3outputinmastermodedependsontheusecase:

1.NosignalconnectedtotheAES3input.TheAES3outputisablacksignal(no

audio)withthesamesamplingrateastheGroup2BNCoutputs.Thechannelstatus

bitsindicate“Grade1reference”iftheCC1hasgonethroughtheoptionalfrequen-

cycalibration,otherwise“Grade2reference”.TheAESlockindicatorontherearis

off.

2.AsignalisappliedtotheAES3inputthatisnotsynchronoustotheCC1.The

AES3outputisablacksignalwiththesamesamplingrateastheGroup2BNCout-

puts.TheAESlockindicatorontherearblinks.

3.AsignalisappliedtotheAES3inputthatissynchronoustotheCC1,butthe“aes”

dipswitchissetto“mute”.TheAES3outputwillstillbeblackandsynchronous.The

presenceoftheaessignalhasnoeffect.In“master”modewiththe“aes”dipswitch

setto“mute”,anysignalattheAES3inputisbasicallyignored,exceptthatthe“aes

lock”lightontherearwillbeontoindicatethepresenceofasynchronousinput.

4.AsignalisappliedtotheAES3inputthatissynchronoustotheCC1,andthe

“aes”dipswitchissetto“thru”.TheAES3outputfullycopiesaudioandsubcode

data(butnotthejitter!)fromtheAES3input.InthismodetheAES3outputwill

neverindicate“grade1”asAES11requiresablacksignal.The“aeslock”lightison.

5.Iftheinputsignalislostfromcase4,thesamplingfrequencysettingisretained,

assuddenlossofsignalismostlikelyaccidental.Thisisdifferentfromcase1

whereanAES3inputsignalwasneverpresent.IftheremovaloftheAES3inputwas

onpurpose,changingthegroup2multipleonthefrontwillreturntocase1,and

theAES3outputwillonceagainbesynchronoustotheselectedmultipleofgroup2.

Slave mode

Slavemodeisthethirdsettingontheleftmostselector.Inslavemode,theCC1will

lookatthewordsyncinputaswellastheAES3inputforavalidsignal.Slavemode

permitsthefollowingusecases:

1.Wordsynconly.Uponselectionofslavemode,theCC1selectsthewordsync

input.Themiddleandrightselectoronceagainsetgroups1and2toamultipleof

thebaserate.TheAES3outputwillbeblack,synchronisedtogroup2andthechan-

nelstatusmarked“noreference”.Uponlossoflock,theoutputfrequencywillbe

heldconstant,seecase4.

2.AES3only.Uponselectionofslavemode,theCC1selectstheAES3input.The

“aes”dipswitchattherearselectswhethertheaudiodataistransmitted(thru)or

not(mute).Inthrumode,theAES3outputwillobviouslyrunatthesamemultipleas

theAES3input.Inmutemodeitwillbesynchronoustogroup2,audioisblackand

marked“noreference”.Uponlossoflocktheoutputratewillbeheldconstant,see

case4.The“AESlock”lightontherearwillbeonaslongastheCC1PLLislocked.

3.BothAES3andwordsyncarepresent.Wordsyncwilltakeprecedenceoverthe

AES3input.In“thru”modetheAES3outputwillproduceajitter-freecopyofthe

AES3input,providedtheinputsignalissynchronous.In“mute”modetheAES3

inputwillbeignoredaltogether.UponlossoftheAES3inputtheAES3outputwill

reverttoblack.Uponlossofthewordsyncinputtheoutputfrequencywillbeheld

constant(within1ppmofthelastdetectedfrequency)andthefrontslavelightwill

blinktoindicateanerror.Thefaultconditionisclearedeitherbyreattachingthe

wordsyncorbycyclingthesourceselectorthroughthetwomastermodesbackto

slavemodetoforcetheCC1tolocktotheAES3signalinstead.TheCC1willnever

automaticallyswitchfromwordsynctoAES3topreventclockloops.

4.NovalidsignaloneitherwordsyncorAES3input.Theresponseisnowdeter-

minedbythedipswitchnamed“unlock”.Whensetto“thru”,theclockfrequencywill

beheldconstantwithin1ppmofthelastvalidmeasuredfrequency.Whensetto

“mute”,theoutputswillbemuted.Inbothcasestheslavelightwillblinktoindicate

anerror.The“mute”modeisadvantageousatforinstancepostproductionwhere

theclockusuallyisoutofsightinamachineroom.Uponlossoflock,allclocksdis-

appearandyoursoftwareautomaticallyprovidesawarning.The“thru”modehasan

advantageinforinstanceliverecordingorPublicAddress.Heresoundshouldnever

mute,whateverhappens.

Lock indication

TheCC1detectswhethertheinputsignalisamultipleof44.1kHzor48kHz,and

indicatesthisontheLEDsabovethesourcepushbutton.Thefrequencymultiple

settingsofgroups1and2remainassetbytheuser.WhiletheCC1acquireslock,

theslavelightwillblink.Thiscantakeupto20s,onaccountoftheCC1’sextremely

slowPLLdesign(seechapter6,“JitterandPLL’sexplained”).Oncefrequencylock

isachieved,theslaveLEDwillcomeoncontinuously.ThePLLwillthensettleto0º

phaselockwiththeinputinanevenslowermode.Thesmallestachievablephase

errordependsmostlyonthestabilityoftheincomingclock.Thestatic(average)

phaseerrorisfactory-alignedtowithin50ns.

The“lock”LEDontherearindicatestheAES3receiverstatus:

1.Off:NoAES3signalpresent.

2.On:AES3signalpresentandfoundtobesynchronouswiththeCC1.

3.Blinking:AnAES3signalispresentbutitisoutofsyncwiththeCC1.

Impedance

The“impedance”DIPswitchesontherearalloweachindividualoutputtobeset

tolow-impedance(25ohmstypical)orcharacteristic(75ohms)impedance.The

switchesarefactorysetto75ohms.Shouldthereceivingdevicehaveproblems

recognisingthewordsyncsignal,youmighttrythelowimpedancesetting.

Wordsyncconnectionsareusually5Vsquarewavestransmittedover75ohm(vid-

eo)coaxcables.Althoughthewordclockfrequencyitselfisrelativelylow,thetran-

sitionsaresteep.Takenasawhole,wordsyncisawidebandsignal,necessitating

characteristicterminationatleastatoneendofthecable.Single-terminatedlines

areusuallyterminatedonthesourceend.Betterstillisseriesterminationonthe

transmitendandparallelterminationonthereceivingend.Thisminimisesreflec-

tionsevenwhenthecableimpedanceisnotexact.Doubleterminationlikethispro-

ducesa6dBloss,resultingina2.5Vsignal.AllGrimmAudioproductsaredesigned

toworkinthismanner.

Thereisnostandarddefiningwordsyncconnections.Asaresult,impementations

varyacrossmakes.Outputsmaybeseriesterminatedorlowimpedance,DCorAC

coupled.Inputsmaybeparallelterminatedorhighimpedance.Thisyields8permu-

tations,allofthemencounteredinthewild.TheCC1inputwillcorrectlyinterpret

allvariantswithoutusermanipulation,buttheimpedanceoftheCC1’soutputs

mayneedtobesetlowinsomecases.Aparallel-terminatedinputexpectinga4V

inputsignalwillonlyworkwiththeCC1’soutputimpedancesetlow.Afairnumber

ofproductswerefoundtohaveparallelterminatedinputbutstopworkingaround

2.5VwhichiswhytheCC1putsoutaslightlyhigher-than-normalvoltageinorderto

allowcorrectoperationinthefactorypresetmode.Nevertheless,someequipment

willonlyrespondcorrectlywhentheoutputimpedanceDIPswitchissettolow.

Phase

Channels11to14canbepolarity-reversed(180ºphaseshift)tocaterforequip-

mentthatusesthefallingedgetosynchroniseoninsteadoftherisingedge.Should

youencounteroperationalproblemswithequipment,eventhoughitislocked,

checkthemanualforanymentionofclockphaseandtrythe180ºswitchsetting.

AES and unlock switches

The‘aes’and‘unlock’switchescanbesetto‘‘mute’or‘thru’.Thebehaviorofthe

CC1inthesemodesisdescribedinChapters‘Mastermode’and‘Slavemode’.

Key Lock mode

IfyourCC1isusedinonesettingmostofthetimeyoucanuse“KeyLock”modeto

preventclockingerrorsbyaccidentalpressingofcontrolbuttonsontheCC1’sfront

panel.InthismodetheCC1doesnotrespondtothepushofanybutton.“KeyLock”

modeisengagedbyholdingthe“44.1/48/Slave”buttonduringpowerup.Itwill

thenlockthemodethatwassetbeforethelastpowerdown.Toleave“KeyLock”

mode,holdthe“44.1/48/Slave”buttonduringpowerupagain.

4. Setting up the Studio

Inadigitalstudioallequipmentwillneedtobesynchronised.Ifallthereisaretwo

boxes,onesendingandonetransmitting,allthatisneededisadigitalsignaland

therecipientwilllocktothat.Whenmultiplesourcesarefeedingintoonerecipi-

ent(e.g.adigitaldeskconnectedtoseveraldigitalrecordersandconverters),all

sourceswillneedtobesynchronous.Thisiswhatahousesync(akamasterclock)is

for.Severalformatsareinuse.TheAESpromotesastandardcalledAES11thatuses

anAES3link,butmostequipmenttendstouseawordsyncsignalonaBNCconnec-

tor.TheAES11standardistobeamendedtoincludethispractice.Wethinkthisisa

goodmove,sincethepurityofaclockrecoveredfromanAES3linkisrathersuscep-

tibletoissueslikecablelengthandbandwidthlimitations.TheAES3outputonthe

CC1isprovidedtocaterforthefewequipmentthatneedsAES11overAES3.When

theoutputisnotusedforthispurpose,itdoublesasajitterremovalfunctionfor

anyAES3signal(provideditissynchronouswiththeCC1).

Moststudiosthathaveintroducedahousesynchavenoticedachangeintheoverall

soundqualityoftheirequipment.Usuallyforthebetter,sometimesfortheworse.

Atissueisjitter(akintowowandflutter,butthenappliedtothesamplingclock).

Chapter6“Jitterexplained”willgointomoredetails.Theimportantpointtoremem-

beristhatjitteraffectsaudioqualityonlyatpointsinthechainwhereanactual

time-basedconversionistakingplace,typicallyADandDAconvertersbutalso

increasinglyasynchronoussamplingrateconverters.

Connection

TheCC1willusuallybelocatedinthemachineroom.Eachdeviceconnectedtothe

CC1issetto“slavetowordsync”.Thebestconnectionschemeis“stardistribu-

tion”witheachoutputoftheCC1connectedtoonedevice.Thesixteenoutputswill

normallysuffice.Daisychainconnectionsarebestavoided,asareT-junctioncon-

nections.Thelatterwillmostlikelyfailanywaybecauseofthelackofstandardisa-

tionofterminationimpedanceandsignallevel,nottomentionmechanicalfailureof

T-junctionsthemselves.

Trytopreventcirculatinggroundcurrentsthroughthecoaxcables(groundloops).

Ascoaxcablesgo,theyareunbalancedandcurrentsflowingthroughthecable

shieldswillimposeanerrorvoltageonthesignal,causingjitteratthereceivingend

thatwasn’tthereatthetransmittingend.Onecommoncauseofcirculatingcurrents

isleakagecurrentthroughthepowersupplyofanungroundedproduct.Anotheris

voltagedropbetweentheearthgroundconnectionbetweendevicesthatarelo-

catedfarapart.Minimizingtheloopareaencircledbytheentireloop,comprising

thewordsynccableandthemainscordsisusuallyagoodidea.Byallmeans,never

defeatthesafetyearthconnectionofanydevicethatisdesignedtohaveanearth

connection.Liftinggroundsmayproducealethalshockhazard.

TheCC1itselfhasalow-impedancereferenceplaneattherear,insuringthatit

willneverbeaffectedbycirculatingcurrents.Notallequipmentisdesignedinthis

manner.Incaseyoursystemholdsinterfacingequipmentthatissensitivetoground

loops,GrimmAudiohasanisolationtransformeravailableondemand(CI1).Such

devicesdegradeclockqualitysomewhatsotheyshouldbeavoidedwhendriv-

ingequipmentofwhichtheAD/DAsectionisused.Whenacurrentloopinvolving

severalpiecesofgearneedstobebroken,itisbesttoinstalltheCI1inlinesfeed-

ingnon-performance-criticalequipmentsuchasdigitalI/Osoundcards,andtouse

normal,directconnectionsbetweentheCC1andanyAD/DAconvertingequipment.

AES3 reclocking

Apartfromthewordsyncinputandsixteenoutputs,theCC1alsosportsanAES3

inputandoutput.TheoutputcancarryanAES11DARSsignalbutitmayalsobe

usedtotransmitare-clocked(de-jittered)copyofthesignalattheAES3input.This

maybeusefulwhendrivingajittersensitivedevicelackingawordsyncinput,most

typicallyanoutboardDACinthemonitoringsystemoradigitalloudspeaker.

Thereclockingfunctionisavailableinallconfigurations,thatis,master,slavedto

wordsyncorslavedtotheAES3inputitself.Apartfromthelattertrivialcasethis

impliesthatthesourceoftheAES3signalshoulditselfbesomehowsynchronised

totheCC1.Settingthe“aes”switchto“thru”activatesthereclockingmode,pass-

ingmaximallyjitter-freesignaltoe.g.aDAC.Inmostcasesthiswillimprovereplay

qualitysignificantly.

Inconsumeruse,mostequipmentfeaturesRCAS/PDIFconnectorsinsteadofXLR

AES3connectors.TofacilitateHi-FiuseoftheCC1,allourconsumerunitsare

shippedwithanS/PDIF<->AES3conversioncableset.

Clock Loop

Aclockloopisarunawaysituationwheretwodevicesareslavedtoeachother,for

instancetheCC1slavedtoarecorderwhichinturnisslavedtotheCC1.Neitherde-

viceistheclockmasterandtheresultwillusuallybethattheclockfrequencyends

upatanextremeofthetuningrangeofoneofthedevices.BeforesettingtheCC1

toslave,insurethattheclockinputoriginatesfromamaster.

PLL setting in attached devices.

Audiodevicescapableoflockingtoanexternalclockuseaphase-lockedlooptodo

so.Detailsofthisarecoveredinourwhitepaper“PLLandclockbasics”thatcanbe

foundontheinfopageofourwebsite.AnimportantthingtoknowforaCC1useris

thatsomeproductshavetwomodes,usuallycalled“fast/wide”or“slow”.Theslow

settinghasthebestsuppressionofincomingjitter,andistheoptimumchoicewhen

theincomingclockispolluted.Thedownsideoftheslowsettingisthatthejitterin

therecoveredclockisfullydominatedbytheclockoscillatorthatformspartofits

PLL.Iftheincomingclockhappenstobemuchstablerthanthat,theslowmodewill

actuallyendupaddingjitter.Thelatterscenarioisalmostguaranteedtobethecase

withtheCC1,whichissignificantlycleanerthananyclockoscillatorwe’vefound

incommerciallyavailableaudioproductssofar.Asarule,inthiscaseitisusually

bettertoselectthe“fast”mode.Infastmode,thePLLwilltracktheincomingclock

morecloselyandiftheincomingclockisextremelyclean,thesamewillgoforthe

regeneratedclock.

ProductsthathaveafixedslowPLL,suchasthosefromApogee,dCS,LynxorPrism

Sound,willimprovecomparablylittlecomparedtoproductswithaswitchableor

relativelyfastPLLlikethosefromAvid,LavryEngineering,MOTU,Mytec,SSLor

RME.Digitalloudspeakersthatfeatureawordclockinput,likeDynaudioAir,will

alsobenefitfromslavingtotheCC1.

Syncing to Video

Beforecomplicateddigitalstudiosbecamepractical,videostudioshavebeenus-

inghousesyncsfordecades.Assoonasmorethanonecameraisused,allsources

needtobesynchronised.Apartfromatimebasereferencethereisalsoaneed

toknowtheactualtimingofaframe.Thisinformationisprovidedbytimecodes.

Althoughthetimecodesignalisofcoursesynchronouswiththevideosync,itis

usuallytransmittedseparately.Insomecasesthe“LTC”codeisusedasmainvideo

sync,butfortunatelyitisgoingoutoffashion.LTCisprobablytheleaststabletime

referencearound.

Enterdigitalaudio.Theaudiotracknowneedstobesynchronisedtothepicture.

Wordsynchasabettertimeresolutionthanvideosync,butstillthemostcommon

practiceislockingtheaudioclocktothevideoclock.Evenmoderndigitalvideopro-

ductionpracticetendstolockaudiotoananaloguevideosignal.Thisisunfortunate

becauselowjitterisnotexactlyadesignspecforavideosyncgenerator.

TheCC1cannotslavetovideosyncdirectly.Inordertoavoiddirectcrosstalkbe-

tweentheblack-burstgeneratororreceiverandtheaudioclock,wehaveomitted

videosyncfunctionality.OurbestadviseistousetheCC1astheaudiomaster

andslaveallvideototheaudiowordsync.Ifyouneverthelessdoneedtoslavethe

audiosystemtovideosyncyoucaneitherbuyourVCC‘VideotoWordClock’con-

verteroruseanyothergenericvideotowordclockconverter.Connecttheretreived

wordclocktotheCC1’swordclockinputandhavetheCC1cleanupthesyncand

distributeclocktotheaudiodevicesasusual.Theextraordinarystabilityofthe

CC1’sPLLwillmakesuretheresultcomesascloseaspossibletomakingtheaudio

chainmaster.

Hints

•Selectdecentquality75Ohmcoaxcablesandcertainlydonotskimponthequal-

ityoftheconnectors.

•Makecablesnolongerthannecessary.

•Cablesaddpropagationdelay.Itisexceedinglyrarefordifferencesinclockphase

toaffecttheinteroperabilityofconnectedaudioequipment,butifithappens,using

equallengthcablesthroughouthelps.

•Disconnectunusedgear.

•IdeallydonotleavethewordclockinputconnectedwhentheCC1ismaster.

Althoughunlikely(theCC1hasarelaytoactivelydisconnecttheinputwhennotin

use),thereisapossibilityofcross-talkfromtheinputclocktotheoutputs.Like-

wise,donotleaveanAES3cableattachedifnotneeded.

5. Pro Tools

AvidProToolsisbyfarthemostcommonDAW,warrantingaspecialsectionon

howtosetuptheCC1inaPTrig.Inourexperiencedescribedmethodistheset-up

thatleadstothebestsoundquality.Anydeviationfromthismethodmightgiveyou

stablesync,butwillprobablynotbesonicallyoptimal.

Pro Tools in music production, CC1 master

ProTools192interfacesfeaturea“LoopSync”functionwhereclockcablesarecon-

nectedinaring:every“LoopSyncin”isconnectedtothenextunit’s“LoopSync

out”,thelastunitconnectstothefirst.Likeinanycorrectclocksetup,oneunitis

masterandallothersslave.TheadvantageofLoopSyncisanyunitcanbedesig-

natedmasterandrunonitsinternalclock.Allothersslavetothatunit.TheLoop

Syncinputofthemasterunitisignoredandeffectivelyanordinarywordclockdaisy

chainresults.NowifProToolsistoslavetowordclock,theunitthatreceivesthe

wordclockalwaysbecomesloopmaster,theothersautomaticallyslavetoLoop

Sync.WecanmakeuseofthisfeaturebyfoolingthesystemintobelievethatLoop

Syncisinuse,whileactuallyastarclockdistributionisutilized.Starclockdistribu-

tionhastheadvantagethatitismorefailsafethandaisychainingandjittergainof

subsequentPLL’sisavoided.

•ConnectanoutputofCC1’sgroup2tothe“ExternalWordClock”inputofthefirst

unitinthechain(ifpresenttheSyncI/O,otherwisethefirst192).

•ConnecttheoutputsofCC1’sgroup1totheLoopSyncinputofeach“192”inter-

face.Every192getsitsownconnectiontotheCC1(stardistribution).Makesure

group1issetto‘x1’.

Incaseyouneedtorunhighersampleratesthan44.1or48kHz,onlysetgroup2

ontheCC1frontpanelto“x2”or“x4”andleavegroup1on“x1”.ThisbecausePro

Tools“ExternalWordClock”inputneedstoreceivetheactualsamplerate,butthe

LoopSyncinputsalwaysrunatthebaserate.

•Softwaresettings:

Setup – session setup

1.SetSyncsourceto“WordClock”.Thisconfiguresthefirstunittolocktoex-

ternalwordclockandtheotherstoloopsync(indicatorslightup).

Pro Tools in music production, CC1 slave

AnalternativesetupwhenusingaSyncI/Oasfirstunitinthechainistoassignthe

SyncI/OmasterandslavetheCC1toitsLoopSyncoutput.Theadvantageisthat

thewholesystemwillautomaticallytracktheproject’ssamplerate.Disadvantage

isthatintheoryjitterontheCC1’soutputswillbeslightlyhigher.TheCC1’sjitter

attenuationhoweverissolargewedonotexpectthistobeaproblem.

•ConnecttheLoopSyncoutputoftheSyncI/O(whichisfirstunitinthechain)to

thewordclockinputoftheCC1.PutCC1inslavemode.

•ConnecttheoutputsofCC1’sgroup1and/orgroup2totheLoopSyncinputof

each“192”interface.Every192getsitsownconnectiontotheCC1(stardistribu-

tion).Makesuregroup1and2aresetto‘x1’.

•Softwaresettings:

Setup – session setup

1.SetSyncsourceoftheSyncI/Oto“Master”.All192interfacewillautomati-

callyswitchtoLoopSync,whichistakencareofbytheCC1.

Pro Tools in post pro.

Hereyou’llneedtosynctovideoandtimecode.Asoutlinedabove,setthevideo

equipmenttolocktowordsyncoruseavideosyncgeneratorthatacceptsaword

syncinputfromtheCC1.NaturallytheProToolshardwareisreceivingwordclock

directlyfromtheCC1.AlsoconnectvideosynctotheSyncHD,itwillbeusedjust

fortimecodesynchronisation.

Thewordclockconnectionsareasdescribedintheformerparagraphs“ProTools

inmusicproduction”.Specialattentionisneededforthetimecodeconnection.Up

tillProTools8therewasnowayofcombiningtheSonyP2“MachineControl”time

codesignalwithanexternalwordsyncliketheCC1.SelectingSonyP2forcedthe

SyncI/Otoslavetovideosync.WithcurrentversionsofProToolsyoucanlock

towordclockwhileatthesametimeusingthevideorefinputontheSyncHDfor

frameedgealignmentofP2sync.However,thisonlyworksforPALandNTSC,not

forhidefrates.Itishopedthatafuturesoftwareupdatewilladdressthis.Inthe

meantime,forhidefproduction,pleaseusethefollowingworkaround.

SincethereisnosuchissuewithLTC,wegettousethreeconnectionstotheSync

HD:wordclock,LTCandSonyP2forpuremachinecontrol.Forclocking,havePro-

Toolsslavetowordclockasdescribedinthismanual.Inthiscasedonotconnect

videosynctotheSyncHD.Thisinsuresthat,ifyouhappentoaccidentallyswitchto

thevideosyncinput,yougetaclearerrormessagetoalertyoutotheproblem.For

timecodeandmachinecontrol,followthenextsteps:

•Softwaresettings(takecaretoexecutethefollowingstepsintheorderde-

scribed):

Setup – Peripherals

1.Onthe“Synchronisation”tab:selectdevice“SyncHD”andport“any”(theLTC

inputwillbeautomaticallyselected)

2.Onthe“MachineControl”tab:tick“9pinsserial”(SonyP2).Untick“useserial

timecodeforpositionalreference”.LeavingthisoptiontickedcausestheSync

HDtotrysyncingtovideosyncinsteadofwordsync.Anadditionaldisadvan-

tageofSonyP2isthatitdoesnotsporta“continuousresync”likeLTC,signal-

ingtimecodeonlytogetherwithtransportcommands.

Setup – Session setup

3.SetSyncSourceto“WordClock”(thepreviousstepwillhaveautomatically

selectedvideosyncinstead,hencetheneedforexecutingthestepsinorder).

TheLoopSyncindicatorswilllightup.

Controllingtheexternalmachinecanbedoneintwoways:

a.ThetransportbuttonsonProToolscontrolthemachineviatheSonyP2interface.

ThemachinegeneratesLTC.ProToolsisslavedthroughtheSyncI/O’sLTCinput

oranyotherLTCtoMTCconverterconnectedtoyourcomputer.Lockisachieved

withinonesecond.Thisisthepreferredmethod.

b.ProToolsiscontrolleddirectlybyitstransportbuttons.Theexternalmachine

locatesandgetsintoplaythroughSonyP2locatorcommands.Theuserselectsa

cuepointandhitsplay.Theexternalmachinewillrewindtothistimecodeminusa

pre-rollandstartsrolling.ProToolswaitsuntilitseesthecorrecttimecodecoming

back(ProToolsslavestotheLTCofthemachine).Apotentialproblemoccurswhen

theexternalmachinefailstoachievesyncduringthepre-rollperiod.Whenevery-

thingisslavedtowordsyncthereislittlechanceofsuchathinghappeningandone

secondofpre-rollshouldsuffice.Whileplaying,ProToolswillrunintriggersync

mode.Thatis,onceit’sstartedplayingitwillignorepositionalinformation,verify-

ingonlythattimecodeisstillrunning.Thismethodmayforinstancebeselected

whenusingharddiskvideoplayers.

6. Jitter and PLL’s explained

Jitterisaninstabilityinthetimingofaclocksignal.Ideallytherisingorfalling

edgesofaclocksignalareallseparatedbyexactlythesameamountoftime.In

reality,thetimingismoreuncertain.Thegraphbelowshowsthetime-domainview

oftheproblem.

Astableandajitteryclocksignal

Wecanalsolookattheproblemspectrally.Anidealclockhasonlyasinglefrequen-

cycomponents(andharmonics).Allenergyisconcentratedonaninfinitelynarrow

frequencyband,seethetoppicturebelow.Whenjitterispresent,sidebandsoccur.

Somespectralenergyislocatedawayfromtheclock.Thefasterthetimingchatters,

thefurtherawayfromthemainfrequencyyou’llfindenergy.

frequency

Amplitude Amplitude

Jittery clock

Jitter-free clock,

slightly off the

ideal frequency

Theredcurveinthebottomgraphshowsonlyrandomjitter.Sometimesjitter

isperiodicalandthenyouwouldn’tseeasmoothslopebutsharppeaks.Anim-

portantnoteisthatfrequencyaccuracyhasabsolutelynothingtodowithjitter

atall.Theredgraphshowsajitteryclockwithanexactlycorrectfrequency,say

44100.0000000Hz,theblueoneshowsaclockthat’ssomewhatoffbutotherwise

brilliantlystable.Afrequencyerrorcanbeannoyingfromapracticalperspective,

Spectraofclocksignals

butasfarassignalqualityisconcernedyou’rebetteroffwithastableclockatan

inexactfrequency.

Jitterisnotaprobleminfullydigitalprocesses.Aslongasitisn’tsolargethata

processorcan’tdistinguishthepreviousbitfromthenext,all-digitalprocessesare

completelyindifferentaboutjitter.Theproblemoccurswhenyougofromtheana-

loguedomainintothedigitaldomainorback.Digitalaudiopresumesuniformsam-

pling.Thatway,givenastringofnumbersandknowledgeofthesamplinginterval,

youcanperfectlyreconstructasampledsignal.Withjitterthattheoryfallsflatonits

back.

Imaginethesignalontop.TheADconvertersamplesitatneatlyuniformintervals.

TheDAconverterreconstructsthecorrectvaluesbutitgetsthetimingwrong.The

differencebetweentheredandbluecurveshowstheerror.Ortaketheconverse:

theDACisfinebuttheADCtooksamplesatthewrongtime.Theeffectismuchthe

same.What’sworseinthiscaseisthatthenumberswe’verecordedarenowwrong.

InthepreviouscasewecouldslapinabetterDAC,withajitteryADCthegameis

over.

PLL’s

Converterchipsneedahighfrequencyclocksignal,usuallysomethingaround

22MHz.Itisalwaysmadebyalocaloscillator(anythingfromasimpleRCoscillator

inareceiverchiptoacrystaloscillator)regardlessofwhethertheunitisoperating

inmasterorslavemode.Thislocaloscillatorisindispensible:externalsyncsig-

nalsmaybeAES/EBU,asampleratefrequency“wordclock”orevenavideosignal,

neitherofwhichareofanydirectusetotheAD/DA.Instead,thelocaloscillatoris

speduporsloweddowntomakeitruninstepwith(“lockedto”)thesyncsignal.A

systemthatusesalocaloscillator“pulled”insyncwithanexternalsignaliscalled

aPhaseLockedLoop(PLL).A“phasedetector”comparesthelocalclockwiththe

JitterinAD(top)andDA(bottom)converters

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