Radio Systems DA-16 User manual

1
DA-8andDA-16
DistributionAmplifiers

2
CONTENTS
INSTALLATION....................................................................................3
Mounting: ................................................................................................3
Connections: ................................................................................................3
OPERATION........................................................................................4
CIRCUITDESCRIPTION......................................................................5
PowerSupply: ................................................................................................5
Input Stage: ................................................................................................5
Output Stages: ................................................................................................5
DA-8/DA-16 PARTS LIST......................................................................6
DA-8-PARTS LAYOUT........................................................................7
DA-8-SCHEMATIC.............................................................................8
DA-8/DA-16 SPECIFICATIONS............................................................9
USING ACTIVEBALANCEDCIRCUITRY...........................................10
WARRANTY........................................................................................11
Repair Policy ..............................................................................................11
ReturnInstructions..............................................................................................11

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INSTALLATION
TheRadioSystemsdistribution amplifiercombinessolidstateelectronicsandfunctionalflexibilityinonesmall
package.Two highqualityaudioopampsprovidebalancedoutputandindividualgainadjustmentsofeachchannel.
Excellentisolation isprovidedbetweenoutputs.Eachbalancedchannel,regardless oflevelsetandload,is
unaffectedbytheotherchannels.Audiosourcescanberoutedtomultiplelocationswithvariouslevelrequirements
andimpedanceswhilemaintainingtheintegrityofthesignalqualitythroughout.
Thedistribution amplifierisavailableinasinglechannel,8outputmono version,ordualchannel,16 output
version.
MOUNTING:
TheDA-8 andDA-16 eachoccupyonly1-3/4inchofheightina19 inchrack. Toallow foradequate
ventilation,avoidmountingtheunitdirectlyabove large heat producingequipmentsuchaspowerampsorpower
supplies.
Whenstackingunits,itisrecommendedthat onerack space,(1-3/4inch),remainopenbetweeneverythree
units.
CONNECTIONS:
Theunitsareprimarilydesignedforbalancedinputsandoutputs.Theinputgroundisconnectedtothechassis
andpowersupplyat asinglepoint.
If unbalancedlinesareused,tietheunusedinput terminaltoground.However,donottietheunused output
terminaltoground.Wiretheoutputbetweenoneoutputterminalandtheinputgroundterminal.
Althoughtheoutputsareshortcircuitprotected,operatingintoless thana600 ohmloadisnotrecommended.
Theinputisbridging(highimpedance)andwill notloaddown anysource.Forfurtherdetails,see thesection on using
active balancedcircuitryinthismanual.

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OPERATION
Controlsconsistofindividualchannelgainadjustments.Nominaloperatinglevelsare0dBminputand+10
dBmoutput.Higheroperatinglevelscancutdynamic range byoperatingtoo closetotheclippingpoint.Adjusteach
outputtothedesiredlevel,keepingclippinginmind.
Theinputstagehasabuilt-in6dBpad.Thisisusedtoincreaseinputoverloadcapabilities.Forlow levelsignals
whereadditionalgainisrequired,remove R7,whichismountedon terminalposts.See thePClayoutforexact
position.
Todisconnectcircuit(signal)groundfromchassisground,cutthejumper,markedJon thePClayout,located
nearthepowertransformer.

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CIRCUIT DESCRIPTION
POWERSUPPLY:
Alarge circuitboardmountedtransformerandtwo,three terminalregulatorsprovideDCpower.IntheDA-
16,onesupplyisusedtopowerbothcircuitboards.
INPUT STAGE:
Ahighspeedopamp, 5534,isusedasadifferentialpre-amp. Thisunitexhibitslow noiseandhighoutput
drive capabilities.
RFIfilteringisprovidedbyC8andC9.
R5,R6 andR7 comprisea6dBpadusedtoraiseinputoverloadlevels.
OUTPUT STAGES:
TheoutputofIC1feedsgaincontrolsforeachchannelthroughacommon buss.IC2,a5534 opamp, operates
at 28 dBgain.Thiscreatesonesideoftheoutputsignal.IC3,another5534,operatesasaunitygaininvertertocreate
theothersideofthebalancedoutput.Thisschemealmostdoublestheavailableoutputvoltagetocreatethehigh
clippinglevelnecessaryinadistribution amplifier.The5534 integratedcircuitisutilizedforitshighspeed,highoutput
andlowdistortion capabilities.

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DA-8/DA-16 PARTSLIST
Allresistorvaluesareinohmsandare 1/4Wcarbon film,unlessnoted.
T1 PC-34-700
C1 .1uFmylar Dl lN4004
C2 2X1000uF35V D2 lN4004
C3 2X1000uF35V D3 lN4004
C4 15 uF35Vlowleakage D4 lN4004
C5 15 uF35Vlowleakage D5 LED
C8 100pFdisc J1 Header,3PinMTA
C9 100pFdisc J2 Header,3PinMTA
C10 10 uFNP25V
C11 10 uFNP25V
C12 .1uFmylar
C13 .1uFmylar
C14 .1uFmylar
C15 .1uFmylar
C16 .001disc
C17 .001disc
C18 18 pFdisc
R5 4.75K1%MF
R6 4.75K1%MF
R7 1K5%CF
R8 10MEG5%CF
R9 4.75K1%MF
R10 4.75K1%MF
R11 20K1%MF
R12 20K1%MF
R13 10Kvariable
R14 4.7K5%CF
R15 4.7K5%CF
R16 39K5%CF
R17 10K5%CF
R18 10K5%CF
R19 10K5%CF
R20 1005%CF
R21 1005%CF
R22 2.2K 1/2W5%CF
R23 100K5%CF
VR1 7818
VR2 7918
IC1 NE5534N
IC2 NE5534N
IC3 NE5534N

7

8

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DA-8/DA-16 SPECIFICATIONS
INPUTIMPEDANCE •10Kohms,balancedbridging
GAIN •0to+12dB,0to+26 dBwithoutpad
OUTPUTLEVEL •+25dBmMax.into600 ohms
OUTPUTIMPEDANCE •200ohms,balanced
FREQUENCYRESPONSE •+.1dB20Hzto20kHz
THD@+18 dBm •.01%max.20 Hzto20 kHz
SMPTE IM@+18dBm •.01%max.
MAXIMUMINPUTLEVEL •+26dBm,+14dBmwithoutpad
COMMONMODEREJECTION •60 dB@60Hzmin.
NOISE •Min.90dBrelative OdBinput
SLEWRATE •13V/microsec.
OUTPUTCHANNELISOLATION •>90dB
DIMENSIONS • 19"rack mount13/4"high6"deep

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USINGACTIVE BALANCEDCIRCUITRY
Balancedlineshavebeenusedformanyyearsandareincontinuedusetodaybecauseoftheirimmunityto
straypickup. Inducedsignalsappearon bothsidesofthebalancedline.Thereceivingendofthebalancedline
respondsonlytothedifference voltagebetweenthelineswhichisthedesiredsignal.Inducedsignalsarecommon to
bothandarebalancedout.
Transformershavebeenthemainstayofbalancedcircuitryfordecades.Unfortunately,transformerscause
distortion andringing,andaresusceptibletomagneticfluxpickup. Further,goodqualityaudiotransformersarevery
expensive.
Theuseofop-ampbalancedcircuitryhastheadvantagesoftransformerswithoutthedisadvantages.Theonly
caveat isthat carefulwiringpracticesaremoreimportantwithactive balancedthanwithtransformers.
Active balancedoutputsandinputsusethree wires:+,-,andground.The+and-terminalsarebothdriven
andneithershouldeverbeconnectedtoground.Forbestperformance,athree-conductorshieldedwireshouldbe
used.Thethirdwirecompletesthegroundcircuit.Theshieldshouldbeconnectedtothegroundat oneendofthe
wireonly.If atwo-wireshieldedcableisused,itisimportantthat agroundconnection bemadebetweenthesending
andreceivingunits.Agroundcircuitthroughequipmentchassisorthroughthree-prongACcordgroundisalso
acceptable.
Single-endedaudiointerconnectionslacktheinterferenceimmunityofbalancedhookups.Forthat reason,
keepunbalancedconnectionsshort,direct,andwell separatedfromAC powerwires.Todrive asingle-endedloadfrom
anactive balancedsource,usecoaxialwire:+tocenterconductorandgroundtoshield,leavingthe-output
unconnected.Tofeedanactive balancedinputfromasingle-endedsource,usecoaxialwire,connectingthehotcenter
conductorto+.Connecttheshieldtogroundandputajumperfromgroundto-.
Whendrivinganactive balancedinputfromatransformerbalancedfloatingsource,usetwo conductor
shieldedwire.Groundtheshieldat thesourceend.Establishgoodgroundbetweenthechassiseitherdirectlyor
throughACpluggroundprongs.Attheload,connectthe+leadtothe+inputandthe-leadtothe-input.Puttwo
300 ohmresistorsinseriesbetweenthe+inputandthe-inputandconnecttheirmid-pointtotheloadground.This
correctlyterminatesthesourceoutputtransformerforoptimumfrequencyandtransientresponse(freedomfrom
ringing)andprovidesalow impedancereturnpathforleakageandinducedhum.If morethanoneactive balancedload
istobeplacedacross afloatingbalancedtransformersource,install thisresistive termination onceonly.Fromthat
location totheactive balancedloads,run three-conductorshieldedwire,shieldcontinuedfromthesourcechassis,+
from+,-from-,andgroundfromthemid-pointoftheterminatingresistors.
Todrive abalancedfloatingtransformerloadfromanactive balancedsource,useshieldedwire.Connectthe
shieldtosourcegroundandleavetheshieldopenat theloadend.Connect+to+and-to-,andestablishagood
sourcegroundtoloadchassisconnection,eitherthroughathirdwireintheinterconnectcableorthroughchassis
contactorACcordthirdwireground.
Interconnectionsbetweenpiecesofstereoequipmentrequiredoublingtheconnectionsdescribedabove without
duplicatingthegroundconnection.Betweenpiecesofactive balancedstereoequipment,then,5shieldedconductors
shouldberun.
Whentestingactive balancedequipmentwithsingleendedtestequipment,donotconnectthe-totest
equipmentground.Mostmoderntestequipmentprovidesbalancedinputs.Inmanydual-traceoscilloscopes,balanced
signalsmaybedisplayedbyrunningthetwo inputsinthe“add”modewithoneinputswitchedtoinvert.Toperforma
testwithsingle-endedequipment,+and-outputsmustbetestedindependentlyandtheirresultsadded.Testingonly
asingleoutputresultsina6dbloss inoutputlevel.
Theactive balancedequipmentinterconnection format makespossiblestateoftheartfidelity.Careful
attention todetailandconservative practicewill berewardedwithoutstandingflat frequencyresponse,low distortion,
andwidedynamic range.