ATI Technologies DA208 Operating instructions

AudioTechnologiesInc. |154 CooperRoad#902|WestBerlin,NJ08091|Voice856-719-9900 |Fax[phone] |www. audio.com
©Copyright1997-2005, AudioTechnologiesIncorporated-PrintedinUSA
DA208 AND DA
416
DISTRIBUTION AMPLIFIERS
OPERATINGAND MAINTENANCEMANUAL

AudioTechnologiesInc. |154 CooperRoad#902|WestBerlin,NJ08091|Voice856-719-9900 |Fax[phone] |www. audio.com
DESCRIPTION
YourDA208/416 providestwo(DA208)orfour(DA416)independentone inby
fouroutcircuitgroups.Afourwayfeed issufficientformanyapplications,
however, if you need moreoutputs, you can parallelchannelsbybridgingseveral
inputsacrossthe sameline for1x8,2x8or1x16 operation.Sinceeachinput
circuithas30kohmbalanced inputimpedance,youcansimplyterminateyour
sourceline withasingle620-ohmresistor(ifnecessary)and thenparallelas
manyinputsasnecessaryacross it.
Eachinputcan bridge line levelsup to+24dBmwithoutclipping.Commonmode
humsignalsareattenuated by70dBandthe inputresistornetworkissplitand
heavilybypassed forgood protection fromRFsignalsriding on the inputlines.
The inputdifferentialamplifieroperatesatslightlylessthanunitygaintooptimize
input headroomand toprevent anysignalclipping fromoccurring priortothe gain
controls.
Eachoutputconsistsofan adjustablegainstage driving the HIoutputterminal
along withaunitygaininverterstage.The inverterdrivesthe LOoutputin
oppositephasetoprovide an activebalanced output. The adjustablegainstage
utilizesaunique circuitarrangementthatallowsustoprovide asmooth,full
range logarithmicgaincontrolforeachoutputusing alinearcermet
potentiometer. Thiscircuit provides20dBgainat full clockwiserotation, unitygain
inthe 12 o'clock position and taperssmoothlytofulloff atthe full CCWposition.
Sinceweactuallyvarythe gainofthe outputstage ratherthan taking the more
conventionalapproachofadjusting the inputleveltoafixed gainstage,wecan
usethe DAatlowoutputlevelswithverylittlenoisepenalty.You can easily
matchtheDAoutputstoconsolemediumlevelinputs(-20dBm)ortodrivesemi
proRCAinputs(singleended at. 10Vrms)withoutrequiring outboardattenuator
pads.
Eachbalanced outputstage isisolated fromthe outputterminalsbyDC blocking
capacitorsand 400 ohmsofbuildoutresistance.The buildoutresistorsaresplit
and bypassedtopreventanyRFsignalsthatmightbe picked upon aoutputline
fromfeeding back intothe DA.
YourDAhasclipping indicatorstowarnyou ofoverdriven and overloaded
outputs.Theseindicatorsindividuallysensenonlinearoperation ofanyoutput
channelbymeasuringthe errorvoltage atthe feedbackterminaloftheHIside
outputamplifier.Aslong asthe outputstage operateslinearly,the errorvoltage
atit'snegativeinput(forexampleWApin9)will remainverysmall.The onsetof
clipping,currentlimiting oreven slewratelimiting immediatelycausesalarge
increaseinthiserrorsignal,whichisthen fed throughR25 tothe erroramplifier
U5Aatpin13.U5A,inturn,drivesthe clipping LEDthrough Q1.Feedback
voltagesalsofeed the erroramplifierfromthree otheroutputchannels.

AudioTechnologiesInc. |154 CooperRoad#902|WestBerlin,NJ08091|Voice856-719-9900 |Fax[phone] |www. audio.com
Toavoidanycrosstalkthrough the summing network,CR3across R13 prevents
nonlinearclipping ofU5Aand thereforemaintainsan extremelysmall common
pointvoltage atU5Apin13.Ifanysingleoutputoranycombinationsofoutputs
aredriven too high,theywilllightthe clippingLED.Eachclipping indicator
monitorsonlyfouroutputs,making it easytolocatethe "hot"output.
YourDAoperatesfromabipolar15VDC regulated supply.The powersupplyis
designed forminimumsusceptibilitytopowerline transientsand conducted RFI
using ferritebeads,doublecapacitivebypassesand anon-concentricwound
semi-toroidalpowertransformer.
INSTALLATION
MOUNTING
YourENCORESERIES DAisdesignedforrackmountingon standardE.I.A.1
3/4-inchcenters.Eachunitdissipatesapproximately10 wattsand isventilated
through slotsinthe rearpanel.
WIRING
Therearethree wiregrounded plugs.The powerline ground couldcausealoop
withyourstudioground.Ifyou aresureyourstudiogroundwillprovide adequate
protectiontopersonnelincaseofanAClineshorttochassis,a3to2AC
adaptercan beusedtoisolatethe powerlineground.Werecommend thatthe
adapterbe removed and the powerline ground reconnected priortoanyservice
workrequiring removalof the studioground fromthe chassis.
Toallowmaximumflexibilityingrounding inhigh RFenvironments, the DAcircuit
groundsareisolated fromcaseground.Fornormaloperation,add aground
jumperfromthe barrierstripground terminaltothe chassisground screw.
The fourinchsilverbearing lowinductancecopperstrap whichyou are,of
course,using foryourstudioground isnotgoingtofitaround the #6 chassis
ground screwon the amplifierrearpanel.Run the strap towithinafewinchesof
the chassisand jumptothechassisground screwwithshieldbraid.
Wehavetaken measurestokeep RFoutofyourDA.Thisincludessplitand
bypassed inputand outputresistornetworks,beaded,bypassed andisolated
powerinputs,non-concentricwound powertransformers,anddoubleground
plane PCboards.However,inadifficultbroadcast application,anyRFshielding
and suppression systemisgoing tobe no betterthan the ground systeminto
whichitistrying todumptheunwantedRF.Foroptimalproductperformance,be
suretohaveagood grounding system.

AudioTechnologiesInc. |154 CooperRoad#902|WestBerlin,NJ08091|Voice856-719-9900 |Fax[phone] |www. audio.com
Audioinputsand outputsshouldbe connected using the rearpanellabelsasa
guide. HIoutputsareallinphasewitheachotherand inphasewiththeHIinputs.
CAUTION
YourDistribution AmplifierhasactivedriversforbothHIand LOoutput terminals.
DONOTGROUND eitherHIorLOterminals.Ifyou aredriving asingleended
(unbalanced-oneside grounded)highimpedanceor600ohmload,itshouldbe
connected between eitherHItoGND orLOtoGND.If you aredriving abalanced
load,connectitbetweenHIand LOoutputterminals.Itisgenerallyunnecessary
toterminatethe DAwitha600ohmload ifitisdriving ahigh impedanceinput
although placing aterminating resistoracrossaHI-Zinputatthe receiving end
will occasionallyreduceRFpickup.
ADJUSTMENTS
Itissometimesdifficulttomaintaingood noiseperformancewhen using aDAto
drivemediumlevelconsole(-20dBm)orIHF(.1V)equipmentinputs.You may
havefound itnecessaryinthe pasttoinsertattenuatornetworks between aDA
and mediumlevelconsoleinputstoallowthe DAtooperateatahigh enough
outputleveltomaintainagood signaltonoiseratio.YourDAwill reduceits
alreadylowoutputnoisestillfurtherasyou turndownits'gain.Inthe absenceof
high RFfields,you can distributeinputsignalsaslowas-20dBmtomultiple
loadsat0to-20dBmlevels.
MAINTENANCE
Powersupplyvoltagesare+and-15VDC nominal.
ICoutputDC Voltagesunderno signal;shorted inputconditionsshouldremain
within.1Vof ground. Greaterdeviation isanindication of ICorcircuit problems.
MODIFICATIONS
230 VACOPERATIONS
YourDAiswired for115 VAC,50/60Hzoperation unless otherwiserequested at
the timeordering.Itcan bemodified for230 VACoperationsbyremoving the
powertransformerprimaryjumpersJ3and J5and inserting ajumperinJ4.
Different typesof attachment plug orline cordsmaybe required forconnection to
alternatesupplyvoltages.

AudioTechnologiesInc. |154 CooperRoad#902|WestBerlin,NJ08091|Voice856-719-9900 |Fax[phone] |www. audio.com
SPECIFICATIONS
OUTPUTLEVEL:+24dBminto600 ohmbalanced loads.
THD:.001%typical, 20–20KHz.
IMD:.05%maximum, SMPTEmeasurement.
SLEWRATE:13 Voltspermicrosecond.
RESPONSE:+/-. 25dB, 30 to20,000Hz
NOISE:-100dBmEIN20Hz-20KHz
GAIN:20dBmaximum,eachoutputhas40dBsmooth
adjustment range going tofulloff.
CROSSTALK:70dBminimumat1KHz.
OUTPUTIMPEDANCE:400 ohmsbalanced,200ohmsingleended,splitand
RFbypassed, ACcoupled.
INPUTS:30Kohmactivebalanced,splitand RIFbypassed.
+22dBmmaximuminput level.
HUMREJECTION:70dBCMRat 60Hz
POWER:115/230 VAC+10%, 47-63Hz, 12 VA.
SIZE:19"Wx1-3/4"Hx7-1/2"D, 10 lbs.
TERMINALS:Eurostylemodularconnectors