JBL GTH400-20107 - Manual (Page 18)

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•The GTH400 will draw as much as 60
amps from the vehicle’s electrical
system, enough to overload
conventional vehicle wiring. Therefore
the +12 volt power supply must be
taken directly from the positive side of
the battery.
Do not connect to the vehicle’s fuse
block or to a wire feeding other
accessories.
•To prevent electrical system damage
or fire, a fuse holder and fuse (not
included – maximum 60 Amp) must be
installed in the power supply wire as
close to the battery as possible, and
before the wire travels through the
firewall or other metal panel.
Ground Wire
•Proper grounding is extremely
important. Use a heat- and oil-
resistant stranded copper automotive
wire equivalent to the size used for the
+12V connection. Crimp or solder and
insulate any wire-to-wire connections.
Keep the ground wire as short as
possible. A ground wire must be
solidly connected to a major sheet
metal structure of the vehicle such as
a panel near the amp-mounting
location. Scrape all paint and primer
off the sheet metal at the grounding
point to ensure a good electrical
connection. Attach the wire to the
grounding point with a nut, bolt and
star washer. The high current
demanded by high-powered amplifiers
requires a more secure ground than
the typical sheet-metal screw will
provide.
The color code for the speaker-level
input harness is as follows:
Speaker-Level Input Harness
Color Codes
Group 1 Left (+): White
Group 1 Left (–): White with
Black Stripe
Group 1 Right (+): Gray
Group 1 Right (–): Gray with
Black Stripe
Group 2 Left (+): Green
Group 2 Left (–): Green with
Black Stripe
Group 2 Right (+): Purple
Group 2 Right (–): Purple with
Black Stripe
5. Adjusting the Gain
Before operating the GTH400, recheck
all wiring connections to make sure they
are correct and secure. Be sure that a
fuse (60 amps, not included) is installed
in the +12V line near the battery.
Reconnect the negative ground (–)
terminal of the battery. Make sure that
the mode switches, crossover switches,
Group 2 & 3 Input switches, and
crossover frequency modules, are
properly set.
•The setting of the gain controls on the
GTH400 is important to ensure proper
performance, low noise levels, and
maximum reliability in the system. As a
general rule, controls on components
at the front-end of the system (source,
equalizers, electronic crossovers, etc.)
should be set as high as possible, with
the amplifier gain control set as low as
possible while still providing adequate
volume levels. Using a high signal level
from the source and a low gain setting
on the amplifier will help keep
GTH400-20107 06/03/98 15:49 Side 17