System User Guide / Owners Manual

13
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.