Page 1
ADA-7551
Audio Distribution Amplifier
AM-7551-03
Page 2
ADA-755
I Audio
Disribution
Amplifi er
+
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-+
t-2
Page 3
ADA-755
I Audio
Dishibution
Amplifier
Introduction
The
Ross
ADA-7551
Audio Disbibution
Amplifier
provides
a meaxr of mplifing
and distributing
program-level
audio
with
virtually no loss of
quality,
Use of
the
latest
tlpes
of integrated
circuits
vrhich
are
developed
specifically suited
to
professional
audio ap'plications assunx, avery
low level of
distortion
and
noise.
Installation
The
card TRAY
TYPE
jumper
(JPl)
settings must be set before use.
All
jumper
plugs
must
be set in
a
vertical
row corresponding with the tray
type
designation as follows:
Ross Trays GVG' Trays
CAUTION:
If JPI is not
set correctly
for a GVG
tray, damage to the integrated
circuits may
occur.
Operation
Controls
are
provided
for setting the
gain
of
the amplifier,
The
GAIN
jumper
plug
is to be set
for
the desired
gain
range. In most installations it will be
set to
the
0 dB position
to obtain unity gain.
The
GAIN potentiometer
provides
a fine control of the
gain
and has a
range
of
+/-
6dB.
There is
no need to set the
common
mode BAL adjustment as it has been precisely
factory
pre-set
and
sealed.
This amplifier incorporates
an
advanced type of
input
stage that does
not have to be balanced
for
each
installation.
Circuit
Descriotion
The
input
stagq U6,
performs
the firnction of converting
the balanced input
signal into
an unbalanced
(single
ended)
signal for further
processing.
This
stage is unique
because it
functions
exactly
as if the amplifier
had a 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
balanced outpul As
a consequence,
it
also has
an
exceptional
ability to reject
common
mode
hum
and noise over the whole audio
band.
The
input
circuit includes diodes
to
protect
the amplifier against
damaging input
noise
spikes.
The
amplifier gain
is
provided
by
circuit
U3A. JP2 selects the desired gain
range and
RVI
provides
vernier gain
adjustment-
l-3
Page 4
ADA-755
I Audio Dishibution Amplifier
The
positive
line outputs
are driven
by
unlty-gain
stages Ul.
and U4.
These circuits
are
designed
to be
very
stable and not
oscillate
at any
normal
line load.
The negative
output stages U2
and
U5
are driven
by unrty-gain
inverter U3B.
The
power
input voltage of approxim ately
+l-
16
volts
is reduced
to
+/-
I 5
volts by
transistors
Q2
and
Ql
.
_
This
lower
voltage
powers
the
input and
gain
stages
while
the
output
stages
are fed
directly from
the
.
power
supply.
--
Alignment
The
only alignment controls
provided are for balancing
the common-mode
rejection
of the input
amplifiers.
To adjust the BAL eontol,
make
the indicated
connections to the
terminal block
associated
with
the
particular
amplifier.
OTE:
this control has been
precisely calibrated
at
the
factory, it must
not be
adjusted
U6 has been
replaced.
Place the amplifier on
the extender board.
Use a short
jumper
wire to connect the
tray
"input
*"
and
"input
-"
terminals
together.
Connect an
audio
generator
between
"input
*"
and
ground.
Set
the
generator frequency to
I KFIz
and output level to
+20
dBu.
Connect a balanced-input
sensitive
audio
level
meter or
distortion analyser
to a balanced
pair
of
amplifier outputs.
With the output level meter set
to
the most
sensitive
scale,
adjust the INPUT
BAL
potentiometer
to obtain the lowest
possible
output
level.
It should
be
possible
to obtain
an output level
of
at
least
-80
dBu.
(l00dB
below
+20
dBu). Seal
the
pot.
Disconnect the test set up.
IA
I
-.t
t.
2.
5-
4.
5.
Page 5
ADA-755
I Audio
DisEibution
Amplifier
Specifications
-
Input
Iqimlmpedanoe
>3SKohs,bahoced
MaxInptkvel
+34dBu
[+30
dBln]
Common Mode Rejection
>l00dB
@60I'4'
>80d8
@z0KIlz
Dutput
Nrmberofotrputs
E
Max Outputlevel
+2EdBu
[+24ffim]
Ontput Impedance
48 ohms, [ 600 ohms]
Output
Isolation
>70
dB
S/N Ratio
>100
dB
(unity
gain)
relative
to
+t
dBu
Gain Range
-lt
to
+34
dB
[+6dBfineadjustment)
Frequency
Response
+l-
0.V2 dB 20IIz
to zOKIlz
Total
Harmonic Distortion
4.AU)%
f0.ffi7o/ol
Intermodulation
<0.002yo
[
0.006%
KSMPTE)
Crosstalk
between
Amplifi ers
>100
dB
Power Consumption
@
+8
dBu
output
l.6w
[2.6w ]
All tests perforrned
at
+18
dBu and
cover 20 Hzto 20
KHz unless otherwise
specified.
All
measurements
made with an Audio
hecision System
One
test set
Performance of
:he
600
ohm version
is similar,
except
where
indicated
I J.
l-5
Page 6
t.
I
L16
ADA-755
I Audio
Distribution
7551A-00t
Item
QTY
ADA 755I
Bill of
Materials
Part Dqscriptim
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950.018
ADA
7551-600
7551A
-001A
(600
ohm
version)
Bill
of materials
same as
per
75514, above
with
the
following exceptions-
NOVALI'ERESISTToR
5%
NOVALUqRESTSTOn r%
CAPACIIO&
CERAMIC r0oY
2% 22p
CAPACIIO&
CERAMrc WOY T/o 47
9
CAPACIIOR, CERAMIC 4n7
CAPACIIO&CTRAMIC
lOn
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GI-ASS l00n
CAPACIIOR,
TAIITALUM 63v
l00u
CAPACIIO&
TANTALTM l6V 47u
CAPACITOR,TAI.ITALI.TM
25V 6ut
CONNECTOR, DO5P, PCB MNT,
90 DEG
DIODE
STCNALGP IN4I48
PCB,EESTOR
HEADE&
12 PIN,2 ROW
MALq PL23
BLI LL.T
HEADE& 16
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INT4O|TTPENSATED,
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AMP
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DIFFERENNAL
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HIGHOUT POWE&
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t-6
Page 7
ADA-755
I Audio Distibution
Amplifi er
Nct
^
t-7
Page 8
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Page 10
Coeyright O f
995
by
Ross Video
Linito&
Primed inCmada
A[Rigbs
rcscrved
Atl
spccificdios are
srbject
to
chango withort
notico.
No
part
of this manual may
be
repoduced in my
form
without
prioruniten
pemissi,on
from Ross
Video
Limircd"
FgRr-r
Rossil ac Trademalcs
of
RossVideoLimited
-
EtohnS'trcet
Iroquois, Ontario
-
KOB IKO
DISTRIBUTION
PRODUCTS
WARRANTY
and REPAIR
POLICY
l. Roo
Video Limited
(the
Courpany) warana
ia
produca
to be frec
from defects in worhanship
and material
under
normal use and service for a
period
of FIVE
years
from
tto datc of ship,me,nt
If,
within
the warranf
pedo4
the
customer notifies the
Compmy
that
a
product
is defective,
the Company
will correct
the
defect, eithcr
by
repairing tbc defective
product
or
by $ipping a replaceme,nt
product
to
the
customer,
as det€rmbed by
the
Company.
2.
li"bilitio rmder
this
warranty is limited
to the repair or replaccment
of
the
product
as determined
by
thc
Company arid is
in lieu of
all
other
warranties expressed
or implird.
3. thir *"r"-ty
does not extend to
any
product
which has be€n
srbjectcd
to mlsnse, nejlect, accident,
improper
instatlation
or
application,
na
does it orrcnd
to
products
which havc becn rcpaird
c altcred outside
the
factory
by
personnel
gther
thm thosc
of
tbe
Comp,ay,
rmless expressly
authsised
in writing by
lbe
Compmy.
4. W"rr"rrty
repairs witt be made
at thc
Compan/s
plant
rmless ofterwise specificd
in writing by
the Company.
All
packing
shipping; and special
handling
costs
will
be
paid
for by tte
customer.
5. Noo-*"r"-ty
repair servicc made at
the factory
will be at
custom€r exponsc.
Cost
of repain
will
be
quoted
following examination
of
the
product
by
Company
personnel.
6.
h no event shatl Ross Video Limited be
liable for
direcr, indirect, special,
bcide,nta!
or consequential
darnages
(including
loss of
profits).
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