I
"-'
Introduction
Ground Loops
Sometimes currents flowing through the
ground
line generate a signal seen
by
another
part
of the
circuit sharing the same ground.
In
other words,
if
there are
two
identical signal
paths
within
a
circuit, they can form a loop which can result
in
hum
and/
or noise.
If
you
are
using
equipment
that
has
3-prong
"grounded"
AC
power
cords,
you
may
suffer from a
ground
loop
resulting
from
the interconnection of this equipment. The following
diagram
shows
how
cascading or
"chaining" the
output
of one 3-prong
grounded
system into
the
input
of
another
3-prong
grounded
system
with
a
standard
unbalanced 2 conductor
cord
(like a
1/4"
guitar cable)
can
result
in
a
ground
loop.
Unbalanced Output
10
Unbalanced Input.
Single
conductor shielded cable
·::>!~~~!.'
·
~!!:!·IIII"
~~--~ r-~~~
FIG. 1
Unbalanced Output
10
Unbalanced Input.
Single
conductor shielded cable
..
?I·~~~~·~~T.I:!·IIII"
~~--~
r-~~~
FIG. 2
Fig. 1 depicts a system interconnection
where
a
ground
loop
can
exist. Fig. 2 depicts a
system
interconnection
where
a
ground
loop does NOT exist.
When
interconnecting 3-prong
grounded
systems,
you
can
use
signal isolation transformers to
prevent
ground
loops. This
coupling
transformer effectively isolates two interconnected system signal grounds, while allowing
the
signal to pass through.
AC Line Conditioning
As is the case
with
any
computer device, the DP
/4
is sensitive
to
sharp
peaks
and
drops
in
the
AC line voltage. Lightning strikes,
power
drops,
or
sudden
and
erratic surges
in
the
AC
line
voltage can scramble the internal memory,
and
in
some cases,
damage
the
unit's
hardware.
Here
are a few suggestions to help
guard
against such occurrences:
• A Surge/Spike Suppressor. The cheaper of the options, a
surge/
spike
suppressor
absorbs
surges
and
protects
your
gear from all
but
the
most
severe over-voltage conditions.
You
can
get multi-outlet
power
strips
with
built-in
surge/spike
suppressors
for little
more
than
the
cost of unprotected
power
strips, so using one is a good investment for all
your
electronic
equipment.
• A Line Conditioner. This is the best,
but
by
far the more expensive
way
to protect
your
gear.
In
addition to protecting against surges
and
spikes, a line conditioner
guards
the
equipment
against excessively
high
or low line voltages.
If
you
use
the
DP
/ 4
in
lots of different locations
with
varying
or
unknown
AC line conditions,
you
might consider investing
in
a line
conditioner.
ENSONIQ DP/4 Musician's Manual
iii
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