DOWNLOAD JBL GTQ 190 (serv.man2) Service Manual ↓ Size: 188.31 KB | Pages: 15 in PDF or view online for FREE

09

Owner’

s Manual

• Simultaneous Stereo + Mono Connection–
Each of the two groups of the GTQ amplifier
may be used to drive a stereo pair of
speakers with a mono speaker at the same
time. This is sometimes used for center-
speaker applications or for inexpensive
subwoofer addition with two-output
amplifiers. Unlike a true bi-amplified
subwoofer connection, however, this type of
system configuration does not provide fine
control of subwoofer-satellite balance. It
requires the use of a passive subwoofer
crossover instead of the superior active
circuitry already built into GTQ amplifiers,
and it does not separate the power amps
driving the satellites from the amps driving
the subwoofer. With the 4 speaker outputs
already available on the GTQ amplifier, a
stereo + mono connection for subwoofers
should not be necessary. If you wish to add
a center speaker, connect the main pair of
stereo speakers as in the stereo mode;
connect the mono speaker as indicated on
page 9 for bridge-mode connection. A high-
power L-Pad or power fader can be used to
attenuate the center channel for proper level
matching. Each speaker should have an
impedance that is equal to or greater than 4
ohms. The input-mode switch for the
channel pair being used in Simultaneous
Stereo + Mono should be set to STEREO.

• Proper wiring between the signal
source, any other components in the
system, and the GTQ amplifier will help
keep noise levels in the system low. Use
high-quality, twisted-pair cable or low-
capacitance shielded wire. 

Keep the wire as short as possible. Do
not splice together shielded wires. Do
not run audio signal wires alongside
power wires for an extended length
either for the amp or the vehicle’s
standard power wires. When wires are
run for long distances, separate the
audio signal wires from power supply
wires or vehicle wiring harnesses as
much as possible. When signal wires and
power wires must cross, try to keep them
perpendicular. Avoid routing any wires
near accessories such as ignition control
modules, tachometers, fuel pumps or fan
motors.
• The line-level inputs of GTQ amplifiers
accept standard phono plugs (also called
RCA plugs). The outputs of most head
units, equalizers, or crossovers also accept
phono plugs. If another type of connector
is used, adapters or special cables may be
needed. Proper wire and connectors can
be obtained from any JBL authorized
installation specialist.
• 

GTQ amplifiers have 2 built-in

frequency-selectable low-pass crossovers
and also 2 frequency-selectable high-
pass crossovers. Be sure the crossover
switches for each group and the preamp
outputs are properly set for the chosen
system configuration (see “Typical
Applications” and “Add-On and Upgrade
Steps” sections for suggestions). If you
have any questions about how to set the
crossover switches, contact your local
JBL dealer.

(+)

(–) 

(+) 

(–)

C

C

L

(+)

(–)

(–)

(+)

(+)

(–)

30A

GR1

R        GR1        L

LINE LEVEL

INPUT

SPEAKER LEVEL INPUTS

GR2

GR1

GR2

FUSE

30A

L

+ –

– +

+ –

– +

R

PREAMP

OUTPUTS

R        GR2        L

30A

GR1

R        GR1        L

LINE LEVEL

INPUT

SPEAKER LEVEL INPUTS

GR2

GR1

GR2

FUSE

30A

L

+ –

– +

+ –

– +

R

PREAMP

OUTPUTS

R        GR2        L

GR2

GR1

SPEAKER OUTPUTS

POWER

BATT(+)

BRIDGE

BRIDGE

+

+

R

L

–

–

+

+

R

L

–

–

REMOTE 

GND

GR2

GR1

SPEAKER OUTPUTS

POWER

BATT(+)

BRIDGE

BRIDGE

+

+

R

L

–

–

+

+

R

L

–

–

REMOTE 

GND

Simultaneous Stereo-Mono Connection Diagrams

GTQ 190 - English  06/03/98 11:49  Side 9

10

When speaker-level signal is used to
drive the GTQ amplifier, the signal goes
into the amp through a special eight-wire
harness/connector (see the “Controls and
Connectors” section). If extension wires
are needed between the head unit output
and the amplifier unit, use conventional 
speaker wire or twisted-pair wiring. Keep
the wiring inside the passenger and trunk
compartments, and make the wires as
short as possible. All connections should
be securely crimped or soldered and
insulated with heatshrink tubing.
• Use the color code of the input harness
wires and the identification on the
radio/tape deck output wires to be sure
that left and right channels are correctly
connected and the positive/negative
polarity of each channel is connected
correctly. For example, the left positive
output of the head unit must be
connected to the left positive input of the
GTQ amplifier.
• The Universal Interface Speaker-Level
Input may also be used to accept the
signal from a preamp-level balanced-line
driver capable of at least 4V output. To
utilize this option, terminate the signal
leads from the balanced line driver to a
Molex Mini-Fit Jr series 8P connector.
The color code for the speaker-level input
harness is as follows:

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

In some systems it may be desirable to
use both the speaker-level inputs and
line-level inputs simultaneously. For
instance, if you have a stock head unit in
your car you may connect the speaker-
level inputs of the head unit to the GTQ
amplifier. You may simultaneously
connect a CD player equipped with a
volume control to the preamp-level
inputs of the GTQ amplifier. Note: Front &
rear channels of the radio/tape and the
CD player must be driven into the group
1 and group 2 inputs of the amp (use Y
cables if necessary). The group 2 input
switch must also be set to the group 2
position. The Universal Interface circuitry
of the GTQ amplifier will isolate the inputs
from each other while mixing both

signals. Therefore switching from one
source to the other is as simple as
turning the unused source off, and
turning the desired source on. No other
switches or relay boxes are needed.
When using this setup it is also possible,
using the wiring setup shown below, to
allow either of the two sources to
remotely turn on the amplifier. This is not
necessary if the factory radio is of the
high-power BTL type. The Common
Sense turn-on circuit will activate the
GTQ amplifier when using the powered
source, and the conventional remote
connection of the preamp-level source
will activate the amp when it is used.

These switches are set according to the
number of inputs connected to the amplifier
group and the desired mode of operation.
See the diagrams on pages 4 and 5, and the
descriptions below for options.
• Conventional Stereo Operation – Set the
appropriate group mode switch to ST for
stereo. Connect the preamp-level head unit
outputs either to the two gold line input
connectors or connect the head unit speaker
outputs to the speaker-level inputs. When
using two head units, both the speaker and
preamp-level inputs may be used
simultaneously. Be sure to maintain left and
right channel consistency.
• Bridged Mode Operation – To select bridge
mode operation, set the mode switch for the
appropriate group in either the L only or L

+

R

position. In the L position, signal from the left
input is fed to both left and right amplifier
outputs for that group. In the L

+

R position,

the signal from both the left and right inputs
is summed internally. When using a group of
the GTQ amplifier for mono mode fed with a
stereo signal it is best to use the L

+

R mode.

When feeding a single GTQ amplifier
channel group with a mono signal from an
outboard crossover, use the L mode and
connect your source input to the left input of
the desired group to be used in bridged
mono.
• Simultaneous Stereo 

Mono – Set the

Mode switch for the appropriate group to the
stereo position. Main speakers are connected
normally to the left and right stereo outputs
of the group, and a center speaker or
subwoofer speaker is connected to the same
group as in bridged mode. Refer to the
diagram on page 9 for connection details.

GTQ 190 - English  06/03/98 11:49  Side 10

11

Owner’

s Manual

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.

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.

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

12

GR 1

GR 2

,,

,

,

C

C

GR 1

GR 2

L

L

GR 1-L

GR 1-R

GR 2-R

GR 2-L

GR 2-R

GR 1
GR 2

,

,

GR 1-L

GR 1-R

GR 2-L

c

GTQ 190 - English  06/03/98 11:50  Side 12