System User Guide / Owners Manual

11
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.