dbx 165A Instruction Manual - Page 8

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dbx 165A Instruction Manual
s
0
OPTIONAL
(FOR
FEED
T
O
AUXI
L
IARY
I
NPUT
MU
L
T
S
I
G
NA
L PROCESSOR>
NO
TE:
Straps
ha ve
been removed
.
SIGNA
L
INPUT
V
•
DETECTOR
INPUT
V
•
.
1
,
ICNAL
UTPUT
V
.
I
I
•
'
-
'
\
-
~
I~
(?;
•
DETECTOR
INPUT
.
I
~ ~
0
.
DETECTOR
INPUT
SIGNAL
I
OUTPUT
I
.
..1.
.
-
e;
r"b
(2
~__./
Fig. 6
-
Signal Input
&
Output Jacks With A Normalling
Jack For
T
he
Detector
Input
Dotted lines
i
ndicate location
of
opt
ion
al
mult
jack (parallel
wired) for feeding input of auxiliary
device
with
same
program as 165 Signal Input.
Output Connection
The output of the dbx 165 is designed to feed balanced
or unbalanced 600 ohm or greater
loads.
The output
stage
is
single
ended,
so that
in
normal operation, the
(-
) signal output terminal is
interna
lly
connected
to
the
( 7) terminal. When the system bypass switch is engaged,
the signal
inpu
ts
are directly connected to
the
signal
outputs (so
a
balanced
input
would produce a balanced
output).
Grounding
For maximum hum rejection, avoid common ground-
ing at the
inpu
t
and output (i.e., double grounding). One
method that usually works
is
to ground the shield at the
165's output Ground (~)
terminal and also ground
it
at
the
input
of the following device. Do not connect the
shield at the 165's
input
Ground terminal; leave the
input
shield connected only to
the
output of the device
feeding
the 165.
Stereo Coupler Cable
When you wish to link two Model
165's
for processing
a
stereo
program, a cable must be constructed to join
the Stereo
Coupler connectors on the
two
units. Use the
mating connectors supplied with
each
Model
165, and
wire the cable according to Figure 7. Use connectors
supplied
with units, or equivalent (Cinch-Jones
P-312-CCT).
Th
e
cable should be 6-pair, twisted 24 ga.
wire with shield (Belden 9506).
Once the cable
is
connected to the two 165's,
it
may
be
left
in
place at all times. When both units' Stereo
Coupler
switches are placed
in
"master" mode (button
OUT), the 165's operate complete ly
independe
ntly;
stereo
operation
is
achieved simply by switching one of
the two units to "slave" mode (button IN, Slave LED
ON).
Input Impedance & Terminations
There
is
sometimes a misunderstanding regarding the
nature of matching and bridging
inputs, the use
of
terminating
resistors,
and the relationship between
actual
inp
ut
impedance
and nominal source
impedance.
Most electronic outputs work well when "terminated"
165
STEREO
COUPLER
CABLE
1
BLK
-
'
(
'
RED
1
2
RED
BLK
2
3
BLK
WH
3
4
WH
BLK
4
BLK
5
GN
5
GN
6
BLK
6
7
BLK
BLU
7
8
BLU
BLK
8
9
BLK
BRN
9
10
RRN
BLK
10
1
1
BLK
BLK
11
12
YEL
YEL
12
SHIELD
Fig.
7
-
Stereo Coupler Cable
NOTE: The
cable for
the dbx Model
16
2 is
not
compatible
with
the Mode
l
165.
by an input (connected to an input)
having
the same or
a
higher
actual
impedance.
Outputs are usually over-
loade
d
when terminated by an
impedance
that
is lower
than the source
impedance.
When the input
impedance
is nearly the same
impedance
as
the
source,
it
is
known
as a "matching"
input.
When an
input
is 10
times the
source
imp
edance,
or more, the
input
is
considered
to
be a
"bridging"
input.
The dbx Model
165
signal
inp
ut
has an actual
impedance
of 22,000 ohms in
balanced
configuration
or
11,000 ohms
in
unbalanced
(it
has a high-Z* input).
This makes the
165
signal input
suitable
for use
w ith
virtually any nominal
source impedance, low
or high.
The dbx signal
input
will bridge 150-ohm or 600 -ohm
(low-Z)
lines.
The
dbx
165 detector
input
has
an
actual
impedance
of 600,000 ohms
in
balanced configuration
or 300,000
ohms unbalanced. This very high
impedance
means
the
level
detector will bridge virtually
any
nominal
source impedance.
It also means
that
when the jumper
connectors
l
in
k
the detector and
signal
inp
uts,
the
detector has a negligible effect on
th
e
165's
input
impedance as "seen"
by
the
source
device. The very high
impedance
of
the
detector does suggest,
however,
that
cables from an external processor to the detector
inp
ut
be kept as short as practical to
reduce susceptibil ity to
hum and RFI.
Terminating
resistors are
not
needed
for the dbx 165
signal or detector
input
s to operate
correctly,
but
may
be
requi
red
at these
inputs
when they are fed from
devices (such as passive
equalize rs) designed for a
specified load impedance.
The
dbx
165 output
is
capable
of dr
ivi
ng loads of
600 ohms or
greater.
While
it
may be
term
in
ated by a
low im
pedance,
such termination is
not
requir ed.
*
"Z" is an abbreviation
fo
r
"impedance."
7