11
Owner’
s Manual
Adjusting the Gain
Before operating the GTQ amplifier,
recheck all wiring connections to make
sure they are correct and secure. Be sure
that a fuse (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
Input switches, and crossover frequency
modules are properly set.
• The setting of the gain controls on the
GTQ amplifier 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 background
noise levels in the system low.
• To adjust a system using a single GTQ
amplifier, start with both of the amplifier
gain controls fully counterclockwise.
Some head units have additional output
level controls or switches. Set those to
their maximum position.
• Set the level controls on any associated
equipment such as equalizers and
electronic crossovers as recommended by
their manufacturers. Set all bass/treble or
equalizer controls to their centered or
bypassed positions. While listening care-
fully to the system output, adjust the
volume control of the radio/tape deck to
the point where you first begin to hear
audible distortion. Use caution: excessive
distortion can damage loudspeakers.
Reduce the level just to the point where
the distortion goes away. This is the
maximum undistorted output level of
your head unit and signal processors,
and should not be exceeded during use.
If audible distortion does not occur,
continue to increase the level until the
head unit is turned all the way up. If this
setting does not provide adequate
volume levels, gradually increase (turn
clockwise) the gain control for the main
(usually front) speaker groups on the
GTQ amplifier until the system plays as
loud as necessary or when the first signs
of distortion are heard.
• After adjusting the main speaker’s gain
control, you may then turn down the
head unit’s volume control to a
comfortable level, and adjust the
remaining channels for the desired
system balance. You will find this easiest
to do by adjusting the channels in the
following order: 1) front speaker group, 2)
rear speaker or subwoofer group.
Elaborate systems incorporating tri- or
quad-amplification can be complex to
adjust. Your local authorized JBL
installation specialist is the best person to
help with such adjustment.
Other Important
Characteristics
Power Consumption – Operating the GTQ
amplifier when the vehicle is not running
may discharge the battery. At high
volumes, the amplifier can draw as much
as 60 amps for brief bursts. After even a
short period of time, this current drain can
discharge the battery to the point that it will
not start the vehicle. Although power
consumption under no signal conditions is
less than a few amperes, even this small
power usage can discharge a battery over
several hours. When GTQ amplifiers are
turned off, there is no current drawn from
the battery despite the direct-to-battery
power connection.
Overload Protection – GTQ amplifiers
incorporate elaborate protection circuitry
to prevent damage to the amplifier
circuitry and ensure reliable operation.
This circuitry will turn the amplifier off in
the event of overheating, a short circuit on
the speaker output wiring, or improper
power supply connections. If the amplifier
cycles on and off, or does not work at all,
a problem in installation or an abnormal
electrical condition is indicated. Check
speaker wiring for short circuits or
impedance loads significantly below 2
ohms (4 ohms in bridged mode). Check
the power supply voltage at the input of
the amplifier to be sure that it is normal
(between 11 and 16 volts). Check that the
power wires are not reversed.
If the GTQ amplifier is operated at very
high power levels in a high ambient
temperature situation, the unit may not
be able to radiate all the heat generated
by such operation. If the temperature of
the amplifier reaches a level that could
cause damage, the thermal overload
protection circuit will turn the amplifier
off. It will turn the amp back on again
when it cools off. Repeated activation of
the protection circuits indicates that the
system is being improperly operated or
that the amplifier should be relocated to
an area that either has a lower ambient
temperature or one which allows more
air circulation around the unit.
Fuse Replacement – If the fuses on the
GTQ amplifier must be replaced, DO NOT
use a fuse rated for higher current levels.
Exceeding the standard fuse size or
bypassing the fuse holder will void the
warranty and may cause serious damage.
It is extremely rare for this fuse to blow. If
it blows repeatedly, it is most likely that
the amplifier has an internal problem that
will need to be repaired by an authorized
service center. The only external cause
for this fuse to blow is reversed polarity
of the power wire connections.
Add-On and Upgrade
Steps
The flexibility of GTQ amplifiers lets you
design and build systems of high
sophistication with only 1 or 2 amplifier
chassis. It is impossible to cover all of the
possibilities in this manual. Shown here
are three examples of system
configurations using GTQ amplifiers. Use
these examples and your imagination to
build systems of advanced design and
performance.
GTQ 190 - English 06/03/98 11:50 Side 11
