Solving Noise Problems - JBL GTS100X Owner's Manual

Solving Noise Problems

The power supply system of
26
every vehicle has some electrical
"noise" that is generated by the
ignition system, the alternator,
the accessories, and their wiring.
High-performance audio equip-
ment is more likely to pick up
such noise than conventional
equipment because it has wide-
frequency bandwidth and high-
gain (amplification) circuits. The
GTS100x has built-in power sup-
ply filters to help prevent noise
problems. If noise occurs, it is
probably the result of improper
installation. The following sug-
gestions will help you eliminate
most noise problems.
Source Noise – Often, noise in a
system is picked up by the signal
source. Before attempting to
eliminate noise from the "amp,"
be sure it is not being picked up
by the signal source and then
passed on to the amp. To do this,
connect the signal source output
to an external amplifier which has
no other connection to the vehicle
except for the audio signal leads.
A battery-powered portable with
line inputs works well for this.
Listen to see if the noise is pres-
ent in the signal from the source
unit. If so, consult the manufac-
turer of the source unit, or your
JBL dealer, for help in elimi-
nating this noise. If there is no
noise in this signal, it can be
eliminated as the source of the
noise in your system.
Ground Loops – The vast major-
ity of noise problems in car audio
systems are caused by inade-
quate or improper grounding.
The head unit, the amplifier and
any other components must be
grounded to a major metal mem-
ber of the vehicle's frame. Make
sure to choose a solid metal
ground point. In many new vehi-
cles, some structural elements
are made of plastic.
Although use of a common
ground point is not usually neces-
sary, practical experience shows
that often the noise level in the
system will be lower if the ampli-
fiers and signal processors are all
grounded to the same point on the
chassis. Usually the head unit
does not need to be grounded to
the same point as the rest of the
system, but in some instances
grounding the head unit to the
same point will also help. If this
does not adequately reduce the
noise level, try another ground
point on the car frame. Some
ground points may work better
than others. In some instances
with plastic-bodied vehicles,