Funk Tonstudiotechnik PAS-8 User manual

MANUAL
DIGITAL AUDIO-ROUTER

2
CONTENTS
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PLEASE NOTEpage3
INTRODUCTIONpage4..5
OPERATIONpage6
AUDIO FORMATANDCONFIGURATIONpage7
INPUTCONFIGURATIONpage8
AUDIO SIGNAL QUALITY page9
POWER SUPPLYpage10
OPTIONAL VERSIONSANDACCESSORIES page10
CABLING ANDSIGNAL DISTRIBUTIONpage11..12
PIN ASSIGNMENT page9..10
BLOCKCIRCUIT DIAGRAMpage13
MEASUREMENT GRAPHS FORJITTER SPECTRUMpage14
TECHNICAL SPECIFICATIONSpage15
ELECTROMAGNETICINTERFERENCEpage16
MAINTENANCEANDREPAIRpage17
CEDECLARATIONOFCONFORMITY page18

3
PLEASE NOTE
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This user manualonlyapplies to the PAS-8 digitalrouter with 8digitalinputs.
CAUTION:
Always connectthis deviceto a230 VAC/50..60 Hz(115 VAC/50—60 Hz) earthedpower supply.
Never connectthedeviceto anyoutletwithout aprotectiveearth contact!
Never expose thedevicetorainor moisture,asthiscreatesahazardof fire andelectricalshock.Do
notconnectthedevicetoapower supplyifithasbeendamagedmechanically,or iffluidsor objects
haveenteredintoit.Immediatelydisconnectthepower supplyintheevent of mechanicaldamageor
contactwith fluids. Onlyqualifiedservicepersonnelfollowingall applicablerulesandregulations
may openthedeviceorperformrepairs.
ENVIRONMENTAL REQUIREMENTS:
Never placethedevicenearheatsourceslikeradiators or hot-airvents. Donotexpose thedeviceto
dust, vibration, or mechanicalshocks.
CONDENSATION:
Whenthedeviceisbrought fromacoldintoawarmenvironment,water may condenseinthe
interior,andthere isariskof malfunction.Donotturnonthedeviceforthirtyminutesafter sucha
temperature changeinorder to allowthePAS-8 to assumethetemperature of theenvironment.
CLEANING:
Useasoftcloth slightlymoistenedwith amildsoapsolutionforcleaningthecasing,thefront panel,
andthecontrols. Donotuseabrasivepadsor powdersor alcoholor petroleum-basedsolventsto
cleanthedevice, as this may damagethecasingsurfaceandthecontrols.
WARRANTY:
Thisdevicehasathree-yearwarranty.Anymanufacturingor materialdefectswill berepairedfree of
chargeduringthis period. Unauthorisedopeningwill voidthewarranty!

4
PAS -8INTRODUCTION
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DIGITAL MONITORROUTER
The PAS-8DIGITAL AUDIO SIGNAL SWITCH is aprofessional monitor router for AES/EBUsignals. Itis used to
playback,record, andmonitor digitalsignals inrecordingandvideostudios. The PAS-8 is idealfor connecting
digitalaudio devicestoAES/EBUinterfacesandvariousperipheraldevices. All inputsandoutputshaveXLRjacks
withgold-plated contacts.
ThePAS-8is notaformat converter. However, itacceptsthecommonlyusedSPDIFsignal levels. Thesignal output
is at theusual AES/EBUlevel of4Vss (peakto peak).
Thedeviceis controlledusingbuttonsonthefrontpanel. However, itcanalso beremote controlledvia AMS-2 or
MTX-MONITOR monitor systems.
Asaspecialfeature,thePAS-8offers aswitchable INSERT function.This permitsaprocessingunitconnectedto
therearXLRjackstobeloopedintothesignalchain.This functioncanbeselectedfor themonitor or therecording
channel. This for instanceallows(asshownintheexamplebelow)adigitalcompressor toberoutedintothe
monitor channelfor adjustment,thenswitchedtotherecordingchannelafteroptimisation.Afterwards themonitor
channel will befree for monitoring again.
At this configurationexampleitis possibletomakeacopyfromeverysourcetotheCD-Recorderor tothedigtal
workstation. At thesame time itis possibleto monitor another sourceindependentfromtherecording signal and to
measurethelevelofthis signal. Thedigitalcompressor is switchableintothecopysignalpathor tothemonitor
signal for testing.

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PAS -8INTRODUCTION
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CIRCUITRY:
Therouter'sactivecircuitryensureslowjitter, which makesthedevicesuitablefor usebeforeaD/A converterin
thesignalchain.Inordertoimprovetheoperationofasubsequentconverter, theoutputamplifiers ofthePAS-8
come withDUTYCYCLEcorrection.This ensuresaDC-free outputsignalirrespectiveofthesignallevelandduty
cycle(meantime ratio ofpositiveandnegativebits)oftheselectedsource,inadditiontoreducingpotentialjitter
caused bythelow-pass effectofaconnected line.
SYNCHRONISATION:
ThePAS-8doesnotrequireexternalsynchronisation.Iftherouteris operatedasasignalswitch inasynchronised
peripheryenvironment,thensignalswitch-overis noise-free for twoidenticallymodulatedsignal sources, as well as
for digital=0.Thesame is truefor switchoverbetweentwosignals derivedfromasinglesourcebysplitting
betweentwo matrix inputs.
Switchingbetweentwodifferentlymodulatedsignals howeverproducesacrackingnoiseduetotheleveldifference
at themomentofswitchover. This typeofswitchovernoiseis inherenttothedesignoffastswitching analogueand
digital matrices.
Thedelaybetweenswitchingoff thefirstsignalandswitchingonthenew signalis inthenanosecondrange
(10-8...10-9 s).
FRONTPANEL
MONITOR SELECT:
Twosymmetricalstereorouters (monitor andrecordingrouter)formthecoreofthe PAS-8.The MONITOR
ROUTER is used to selectthedesired monitor signal.
RECORDSELECT:
Selectingthe RECORDROUTER allowsasignaltobeselectedastherecordingsourceindependentofthesignal
source.
DIGITALINSERT:
This buttonis used to insertanexternal digital processing unitinto themonitor or recording channel.
BACKPANEL
INPUT1
INPUT2
INPUT3
INPUT4
INPUT5
INPUT6
INPUT7
INPUT8
MONITORA
INSERTRET.
MONITORBRECORD ARECORDB
FUSE50 mAt

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PAS -8OPERATION
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OPERATION:
DIGITALINPUTSWITCHOVER:
Thedigital monitor signal is selected bypushing thecorresponding INPUT1..8 button. Selecting anew inputturns
off thepreviouslyselectedchannel. Inadditiontothedigitalmonitor matrix, therouteralso featuresasecond
digitalmatrix for recording. This allowsausertoselectasignalfrominputs1..8anduseitasthesourcefor a
connecteddigitalrecorder. This is independentfromthesignalthat is currentlybeingmonitored. Pressing SHIFT
andsimultaneouslyselectingadigitalsource(1..8)activatesthedigital RECORDING MATRIX androutesthe
selected signal to the recording output.
DIGITALINSERT:
The INS.MON and INS.REC areused to patch thepointofinsertioneither into
the monitor or the recording signal channel. Themonitor and recording channels
areinterlocked inorder to preventtheinsertfunctionto berouted into both
channels simultaneously. This means that beforetheinsertcanbepatched into the
monitor channel, any activerecording insertneeds to beswitched off and vice
versa.
CLOCKDISPLAY:
Thesetwo LEDs indicate thepresenceofadigital signal withavalid inputlevel at
theselected PAS-8input. For instance, ifaninputwithavalid digital signal is
selected for themonitor matrix, therelevant MON.CLK LED(green)lights up. This
also happens for non-modulated signals (digital level =0), as long as thesample
rate is present.
The REC.CLK LED(red)works similarlyfor theselected recording signal.

7
PAS -8AUDIOFORMATand CONFIGURATIONS
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DIGITALFORMAT:
The8inputsoftherouter'stwoactivedigitalmatricesaredesignedfor AES/EBU and AES-3 formats. Theinputs
also acceptSPDIFsignals, aslongastheusuallevel(400...500 mV)is maintained. Aselectedsignalis patched
throughtotheoutput(e.g. for anexternalD/A converter)andprovided(buffered)toasecondoutput(e.g. for a
digital peakmeter). This applies bothto therecording matrix and themonitor matrix.
Theoutputformat is thesame astheinputformat;thedigitalsignalis notprocessedinany way.(Further
processingsteps likeformat conversion,signaldistributionor samplerate conversionin AES/EBU or SPDIF
format areavailableusing the DAS-SRC or the DDA-12).
ThePAS-8is fullytransparentfor all data intheserialdata stream.All usualsampleratescanbeprocessed
(including 96 kHz and 24 bitsignals).
INPUTIMPEDANCE:
All inputsandoutputsofthedigitalrouteraresymmetricalandequippedwithtransformers. Theinputimpedance
canalso beset later, separatelyfor each input,byusingjumpers. Inputimpedanceis >1 kWwiththejumperopen
and 110 Wwiththejumper closed. This makes iteasier to distribute thesignal to additional recipients.
INPUTSIGNALSPLITTING:
Inordertosendasignalnotonlytothedigitalswitch butalso toaseconddigitalrecipient,thejumperfor the
relevantinputis openedintherouter. Thesignallineis routedfromthesourcetothePAS-8first,thentothe
second recipient.
Therouteris deliveredwitha110 Ohminputterminator. For moreinformationonconfiguringthePAS-8'sinput
resistors, pleasesee the"INPUT IMPEDANCE"section.
BACKUP:
Intheeventofapowerfailureor whenthedeviceis turnedoff,thecurrentinputselectionis automaticallybacked
upinnon-volatilememory.Assoonasthepowersupplyis back online,therouterautomaticallyrestoresthestored
configuration. This also allows the PAS-8 to beoperated withatime switch.
INPUTSIGNALMONITORING:
Thedigitalrouterindicatesthepresenceofa clock for thecurrentlyselectedinputat thefrontpanel, which
facilitates quick signal tracking whenrequired. Thereareseparate indicators for themonitor and recording channel.
PAS-8combined withAMS-2orMTX-MONITOR:
IfthePAS-8is usedincombinationwithan AMS-2 or MTX-MONITOR
analoguemonitor system,thePAS-8should besuppliedwithpowervia
thesemonitor systems. Inthis configurationthePAS-8powerswitch
should leftoff inorder to ensureacentral reset bythemonitor system.
ThePAS-8hasaninternalswitchingfeaturetoadaptthestart-uptime
tothedifferentrequirementsofAMS-2andMTX-MONITOR.Start-up
time is controlledbyJumper16 inthecentreofthemainboard. This
jumperis normallyclosed(for standaloneoperationor operationwith
MTX-MONITOR). For usewiththeAMS-2, jumper 16 has to beopen.
Jumper 16

8
PAS-8 INPUTCONFIGURATION
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CHANGING THEINPUTIMPEDANCE:
Thejumpers for inputimpedanceselectioncanbereachedbyopeningthedevicecover. Ifthejumperis onboth
contacts, inputimpedanceis 110 .Ifthejumperis ononlyonecontact,theinputimpedanceis >1 k .ThePAS-8
has 8jumpers for its 8inputs and anadditional jumper for thedigital insertinput.
Jumper for Inputimpedance1..8Jumper for insert
SPDIF SIGNALS TOBALANCEDAES/EBU INPUTS:
IfanSPDIFsignal is fed inthroughtheXLRinputs, theimpedanceat theconnected XLR
plug should beadjusted bywiring a232 Wresistor inparallel betweenpins 2and 3. This
sets theinputto acharacteristicimpedanceof75 , which is commonfor SPDIFsignals.
The"hot"wireoftheincoming lineis connected to pin2, whiletheshielding is connected
to pins 3and 1oftheXLRplug.
Pin1ontheXLRplug is leftopenifthesending deviceand thePAS-8need to be
galvanicallyseparated. Theshielding is onlyconnected to pin3inthis case.
Thefigureshows thesolder sideoftheXLRplug.
Pre-assembled adapter cables for this purposeareavailableunder thename CASA.
The CASA-T cablehas similar functions, butworks using anintegrated fastpulse
transformer, which allows itto beused withnon-standard balanced inputs (withoutan
inputtransformer).

9
AUDIOSIGNAL QUALITY
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INPUTANDOUTPUTAMPLIFIERS
The PAS-8 is designednotonlyasarecordingsignalswitch,butprimarilyasahigh-quality monitor matrix for use
withanexternalD/A converter. Inordertoguarantee therequiredhighsignalquality,all theoutputsofthese
routers areequippedwithautomaticdutycyclepost-correction(positiveandnegativepulsewidthsarebalanced).
This keeps thebitwidth(dutycycle) moreor less constantevenfor highlydifferentinputlevels andvaryingrise
and fall times ofthesignal at theinput. Thesame applies to thePAS-8's insertchannel.
Theabovediagram illustratestheoperatingprincipleofthedutycyclecorrection.Theupper, redcurveshowsa
highlymisalignedinputsignalwithanadditionaloffset inthedutycycleof30/70 (uppermostlineofthereadings).
Thesignallevelis approx. 3.5Vss. Thelower, bluecurveshowsthePAS-8'scorrected, cleanoutputsignalwitha
symmetricaldutycycleoftypically50 %(lines2to5ofthereadings).Thediagram also showstheaccurately
defined, overshoot-free riseand fall times as well as thedelaybetweeninputand output.
All amplifierstagesareoptimisedfor minimumjitter. Thelatency betweeninputandoutputis approx. 60 ns
(nanoseconds)for themonitor channeland70 nsfor therecordingchannel. AnactiveinsertinthePAS-8adds 30
ns. Theseextremelyshortlatenciesallowthedevicetobeusedeveninhighlycomplex, synchronousstudio
systems.

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PAS-8 POWER SUPPLY OPTIONAL VERSIONS
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POWER SUPPLY
Protectiveearthandtechnicalearthareseparate inthe PAS-8.
This isolatestheaudio circuitsfromparasiticcurrentsinthe
19-inch rack or theprotectiveearthconductor.
Technicalearthandchassis areconnectedinternallyviaseveral
parallel0.047 µFcapacitors. This createsalow-resistance
connectionthat servesasaHFshield, whilesimultaneously
preventingtheformationofagroundloop for themains
frequency anditsharmonics. Thankstothesefeatures, the
matrix is suitablefor usewithvariousearthingstrategiesinthe
studio.
Therouterworksflawlesslyevenwhenexposedtomainsvoltagefluctuationsbetween180 and245 VAC. ThePAS-
8's stabilised supplyvoltages areshort-proofand canbemonitored bymeans ofanLEDinthefrontpanel.
Themainsfuseis inthepowercablesocket belowthecablegland. Theductcanbepulledoutusingasmall
screwdriver. Theductalso containsasparefuse.Ifanew fuseis required, onlyusesfusesofthetype5x20 mm,
50 mA/250 V, anti-surge.
OPTIONALVERSIONSand ACCESSORIES
The PAS-8 is availableintwoversionsfor differentsupplyvoltages:230 V/50 Hz, or 115 V/50..60 Hz. Onlythe
manufacturer mayconvertthedevicefor adifferentpower supply.
ACCESSORIES–INTERFACE
Inthepack panelofthedigitalaudio routerthereis a4-poleminiDINsocket labelled
PASREMOTE.Itis usedfor connectingaserialremote controller. Theremote
controller has feedback LEDs for all functions.
This remote jack also allowsfor thePAS-8inputs to beswitched viathe AMS-2audio
monitorsystem or the MTXmonitor.Inthis casethePAS-8is suppliedwithpower
viatheMTXmonitor or theAMS-2andcanbecontrolledsimultaneouslybothat the
PAS-8itselfandfromtheanaloguemonitor systems. ThePAS-8'spowersupplyshould
beturned off (power switch)inorder to ensureacentralised reset at start-up.
AES/EBU ÞSPDIF ADAPTER CABLE(UAS)
This cableis usedtoadaptthelevel, impedanceandbalanceofdigitalXLRoutputs,
allowingthePAS-8outputstobeconnectedtounbalancedcoaxialinputs. Levels,
balancingandimpedanceareconvertedtostandard SPDIFvalueswithoutany format
conversiontakingplace.Pleasenote that thereceivingdeviceneeds tobeableto
process thetransmittedformat.Thecableis usablefor sampleratesupto192 kHz.
Availablelengths:0.5m, 1.0m, 2.0mand 3.5m.
SPDIF ÞAES/EBU ADAPTER CABLE(CASA-T)
This cableis usedtoadapttheimpedanceandunbalanceofdigitalSPDIFoutputsto
balanced110 ΩAES/EBUInputs, allowingthePAS-8inputstobeconnectedto
unbalancedcoaxialinputs. Balancingandimpedanceareconvertedtostandard
AES/EBUvalueswithoutany format conversiontakingplace.Pleasenote that the
receivingdeviceneeds tobeabletoprocess thetransmittedformat.Thecableis
usablefor samplerates up to 192 kHz. Availablelengths:0.5, 1.0, 2.0and 3.5m.