Ross ADA-7551 User manual

ADA-7551
Audio DistributionAmplifier
AM-7551-03

ADA-755
I Audio
Disribution
Amplifier
+ 15 Volts
-15 Voltt
+ 16 Volt3
- 16 Voltr
OUT I+
OUT 2+
OUT 3+
oUT a+
OUT 5+
oUT 6+
OUT 7+
OUT I-
OUT 2-
OUT 3-
OUT 4-
ouT 5-
ou? a-
ouT 7-
ADA 7551 BLOCKDIAGRAM
OUTPI'T STACIS
u4c
INPUT AYP GAIN STAGE
urc
UTB
UID
JPz UlA
U4D Ol O-r
ncl
INVERTER
U38
PO'ER REGUL.I,TORS
OIG---r
I
RG--_
OUT 6-
Ol O- I
RG-+
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ADA-755I Audio DishibutionAmplifier
Introduction
The RossADA-7551 Audio Disbibution Amplifier providesa meaxr of mplifing and distributing
program-level
audiowith virtually no lossof quality, Useof thelatest
tlpes of integrated
circuits vrhich
aredeveloped
specificallysuited
to professional audioap'plicationsassunx,avery low level of distortion
and
noise.
Installation
ThecardTRAY TYPEjumper (JPl) settingsmustbesetbeforeuse. All jumper plugsmustbe setin a
verticalrow correspondingwith thetraytypedesignationasfollows:
RossTrays GVG' Trays
CAUTION:
If JPI is not setcorrectlyfor aGVG tray, damageto theintegrated
circuits may occur.
Operation
Controls areprovided for settingthegain of the amplifier,
The GAIN jumper plug is to besetfor the desired
gainrange. In mostinstallationsit will besetto the
0 dB position to obtainunity gain.
TheGAIN potentiometer
providesafine control of thegainandhasarange
of +/- 6dB.
There is no needto setthe common mode BAL adjustmentas it hasbeenprecisely factory pre-set and
sealed. This amplifier incorporates
anadvancedtype of input stagethat does
not haveto be balancedfor
each
installation.
Circuit Descriotion
The input stagq U6, performs the firnction of converting the balancedinput signal into an unbalanced
(single ended)signalfor further processing.
This stageis unique becauseit functions exactly asif the amplifier hada floating transformer input. This
means that it responds only to the voltage difference between the two input lines and ignores any
imbalance to ground- This gives the distribution amplifier the very desirable ability to accept any
out-of-balance input signal and produce a perfectly balancedoutpul As a consequence,
it also has an
exceptionalability to reject commonmodehum andnoiseoverthewhole audioband.
The input circuit includesdiodes
to protectthe amplifier against
damaginginput noisespikes.
The amplifier gain is provided by circuit U3A. JP2 selectsthe desiredgain range and RVI provides
vernier gain adjustment-
l-3

ADA-755
I AudioDishibutionAmplifier
The positive line outputs
aredrivenby unlty-gain stagesUl. andU4. Thesecircuits aredesigned
to be
verystableandnotoscillate
atanynormal
lineload.
Thenegative
outputstagesU2 and U5aredrivenbyunrty-gain
inverterU3B.
Thepowerinputvoltageof approximately
+l- 16
volts isreduced
to +/- I5volts by transistors
Q2andQl .
_
This lower voltagepowersthe input andgain stages
while the outputstages
are fed directly from the
. powersupply.
--
Alignment
The only alignment controls provided are for balancing the common-moderejection of the input
amplifiers. To adjusttheBAL eontol, make
theindicated
connectionsto theterminalblock associated
withthe
particular
amplifier.
OTE: thiscontrolhasbeen
preciselycalibrated
atthefactory,it mustnotbeadjusted
U6 hasbeen
replaced.
Placetheamplifieron
theextenderboard.
Use
ashort
jumper
wiretoconnectthe
tray"input
*" and
"input
-" terminals
together.
Connectanaudio
generator
between
"input*" and
ground.Set thegeneratorfrequencyto I KFIz
andoutputlevelto+20 dBu.
Connectabalanced-input
sensitive
audio
levelmeteror distortionanalyser
to a balanced
pairof
amplifieroutputs.
With the outputlevel metersetto the mostsensitive
scale,
adjustthe INPUT BAL potentiometer
to obtainthelowest
possible
outputlevel. It should
bepossible
to obtainanoutputlevelof atleast
-80dBu.
(l00dB below
+20
dBu). Seal
the
pot.
Disconnectthetestsetup.
IA
I -.t
t.
2.
5-
4.
5.

ADA-755
I Audio
DisEibution
Amplifier
Specifications -
Input Iqimlmpedanoe >3SKohs,bahoced
MaxInptkvel +34dBu [+30
dBln]
CommonModeRejection >l00dB
@60I'4'
>80d8
@z0KIlz
Dutput Nrmberofotrputs E
MaxOutputlevel +2EdBu
[+24ffim]
OntputImpedance 48ohms, [ 600ohms]
Output
Isolation >70
dB
S/NRatio >100
dB(unitygain)relative
to
+t dBu
GainRange -lt to
+34
dB
[+6dBfineadjustment)
Frequency
Response +l-
0.V2dB20IIztozOKIlz
TotalHarmonicDistortion 4.AU)% f0.ffi7o/ol
Intermodulation <0.002yo
[0.006%
KSMPTE)
Crosstalk
between
Amplifi ers >100 dB
PowerConsumption
@+8 dBu
output l.6w [2.6w]
Alltestsperforrned
at
+18
dBuand
cover20Hzto 20
KHzunlessotherwise
specified.
All measurements
madewith anAudio hecision System
One
testset Performanceof
:he
600ohmversion
is similar, except where
indicatedI J.
l-5

t. I
L16
ADA-755
I Audio
Distribution
7551A-00t
Item QTY
ADA 755I
Bill ofMaterials
Part Dqscriptim
RET
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MPI
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JPI
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JPPLUGIDJPPLUGIC,
JPPLUGIBJPPLUGIA,
JPPLUG2
RV2
RVI
FCB
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R29
R30
R50
R49
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360-005
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403-{X}+16
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812-l9t
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8tt-332
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827-270
827470
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950.018
ADA 7551-600
7551A
-001A
(600
ohm
version)
Bill of materials
sameas
per
75514,above
withthe followingexceptions-
NOVALI'ERESISTToR
5%
NOVALUqRESTSTOnr%
CAPACIIO&
CERAMICr0oY
2%22p
CAPACIIO&
CERAMrcWOYT/o47
9
CAPACIIOR,CERAMIC4n7
CAPACIIO&CTRAMIC
lOn
CAPACIIOR,
GI-ASSl00n
CAPACIIOR,
TAIITALUM63v l00u
CAPACIIO&
TANTALTMl6V 47u
CAPACITOR,TAI.ITALI.TM
25V6ut
CONNECTOR,DO5P,PCBMNT,
90DEG
DIODE
STCNALGPIN4I48
PCB,EESTOR
HEADE&
12PIN,2ROW
MALq PL23
BLI LL.T
HEADE&16
PrN,2ROWMArB PL23BLI tl.l
INT4O|TTPENSATED,
DUAL
LGNOISEOBAMP
-6dB
DIFFERENNAL
LINERECETVER
,FET-TNruT,
HIGHOUTPOWE&
QUAD
OPAMP
JTMPER2-POSnON
LOWPROFILE
VARTABIJ,RESISTOR,
I/4 DIA I.TI.'RNIOOR
VARTABLE,
RESTSTO&20.,Tt
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ADA-755
I AudioDistibution
Amplifier
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Coeyright
Of995
byRossVideo Linito&
PrimedinCmada
A[Rigbs rcscrved
Atl spccificdiosare srbject
tochangowithortnotico.
Nopart ofthismanualmay
be
repoducedinmy form
without
priorunitenpemissi,on
fromRoss
Video
Limircd"
FgRr-r Rossil ac Trademalcs
of
RossVideoLimited
- EtohnS'trcet
Iroquois,Ontario
- KOBIKO
DISTRIBUTION
PRODUCTS
WARRANTY andREPAIRPOLICY
l. Roo VideoLimited (theCourpany)warana ia producatobefrecfrom defectsin worhanship andmaterial
under
normaluseandservicefor aperiodof FIVE years
fromtto datcof ship,me,nt
If, within thewarranf pedo4
thecustomernotifiestheCompmythataproductisdefective,
theCompany
will correct
thedefect,eithcrby
repairingtbcdefective
productorby $ipping areplaceme,nt
product
tothecustomer,
asdet€rmbedby the
Company.
2. li"bilitio rmder thiswarrantyis limited to therepairorreplaccment
of theproductasdetermined
by thc
Companyaridisin lieu of all other warrantiesexpressed
or implird.
3. thir *"r"-ty doesnotextendto anyproduct
whichhasbe€n
srbjectcd
tomlsnse,nejlect, accident,
improper
instatlation
or application,
na doesit orrcndto products
whichhavcbecnrcpaird c altcredoutside
thefactoryby
personnel
gtherthm thosc
of tbeComp,ay,rmlessexpressly
authsisedin writing by lbeCompmy.
4. W"rr"rrty repairswitt bemade atthcCompan/s plantrmlessofterwisespecificdin writing by theCompany.
All
packing shipping;andspecial
handling
costs
will bepaidfor by tte customer.
5. Noo-*"r"-ty repairserviccmadeatthefactorywill beatcustom€rexponsc.
Costof repain will bequoted
following examination
of theproduct
by Company
personnel.
6. h noeventshatlRossVideoLimited beliablefor direcr,indirect,special,
bcide,nta!or consequential
darnages
(includinglossof profits).