JBL GTS 300 (serv.man2) User Manual / Operation Manual ▷ View online
either subwoofer or component
speakers in a bi-amplified system,
or conventional full-range speakers
in simpler systems.
The GTS300 and 600 also include
preamp-level outputs which can
provide either full-range, high-pass
or low-pass signal to drive
additional amplifiers. This lets you
build systems of virtually any
design without requiring a
separate electronic crossover.
speakers in a bi-amplified system,
or conventional full-range speakers
in simpler systems.
The GTS300 and 600 also include
preamp-level outputs which can
provide either full-range, high-pass
or low-pass signal to drive
additional amplifiers. This lets you
build systems of virtually any
design without requiring a
separate electronic crossover.
1.2 About Installation
Although the GTS300 and GTS600
are designed to make installation
as easy as possible, they are
sophisticated products that require
proper installation to realize their
full performance potential.
If you feel you do not have the
necessary knowledge and skills we
strongly recommend that the
installation be done by your
authorized JBL dealer.
If you choose to install the GTS300
or GTS600 yourself read
are designed to make installation
as easy as possible, they are
sophisticated products that require
proper installation to realize their
full performance potential.
If you feel you do not have the
necessary knowledge and skills we
strongly recommend that the
installation be done by your
authorized JBL dealer.
If you choose to install the GTS300
or GTS600 yourself read
all of the
information in this manual
before you start the installation.
Pay particular attention to the
safety precautions and notes.
before you start the installation.
Pay particular attention to the
safety precautions and notes.
2. Installation and Use
Refer to the “Crossover Frequency
Adjustments” and “Speaker Level
Input Impedance Adjustments”
sections of this manual to see if
you will need to make alterations
to their factory settings. If you are
not using the built-in crossover, or
the speaker level inputs, you may
skip this step.
Adjustments” and “Speaker Level
Input Impedance Adjustments”
sections of this manual to see if
you will need to make alterations
to their factory settings. If you are
not using the built-in crossover, or
the speaker level inputs, you may
skip this step.
1. Disconnect the negative cable
from the battery.
Note: If the
vehicle’s radio features a code
type security system, make
certain you know the code
type security system, make
certain you know the code
1
1. Introduction
Thanks for purchasing your new
GT series automotive amplifier.
The GT series amplifier you have
chosen includes many unique
features to enhance its perfor-
mance and utility. The power amp-
lifier circuitry is a fully discrete
design notable for its low dis-
tortion and unusually clean and
clear sound quality. Your GT series
amplifier will easily connect to
virtually any car audio system,
whether it is factory installed or
one purchased separately.
In addition to conventional
preamplevel inputs, this model
features JBL’s Universal Interface
design, which facilitates simple
connection to factory radios with
the low distortion that is usually
only associated with preamp level
connection. With Universal Inter-
face, a factory radio can be used
either as the main music source or
combined with a CD player or
changer, which includes volume
control capability, simultaneously
connected to the amplifier. By
providing this two-unit direct
connection, Universal Interface
circuitry eliminates the need for an
FM modulator to interface a CD
player to factory radios, improving
the fidelity of digital playback.
In addition, when using a high-
powered (BTL) radio through the
speaker-level inputs, Common
Sense turn-on circuitry senses the
common-mode voltage present on
the radio’s speaker wires, turning
the amplifier on without an
additional “remote” wire.
Also, the built-in active crossover
provides either full-range, high-
pass or low-pass operation. This
lets your GT series amplifier power
GT series automotive amplifier.
The GT series amplifier you have
chosen includes many unique
features to enhance its perfor-
mance and utility. The power amp-
lifier circuitry is a fully discrete
design notable for its low dis-
tortion and unusually clean and
clear sound quality. Your GT series
amplifier will easily connect to
virtually any car audio system,
whether it is factory installed or
one purchased separately.
In addition to conventional
preamplevel inputs, this model
features JBL’s Universal Interface
design, which facilitates simple
connection to factory radios with
the low distortion that is usually
only associated with preamp level
connection. With Universal Inter-
face, a factory radio can be used
either as the main music source or
combined with a CD player or
changer, which includes volume
control capability, simultaneously
connected to the amplifier. By
providing this two-unit direct
connection, Universal Interface
circuitry eliminates the need for an
FM modulator to interface a CD
player to factory radios, improving
the fidelity of digital playback.
In addition, when using a high-
powered (BTL) radio through the
speaker-level inputs, Common
Sense turn-on circuitry senses the
common-mode voltage present on
the radio’s speaker wires, turning
the amplifier on without an
additional “remote” wire.
Also, the built-in active crossover
provides either full-range, high-
pass or low-pass operation. This
lets your GT series amplifier power
2
before disconnecting the
battery!
battery!
2. Run a minimum AWG #8
power cable complete with a
40 amp fuse (not included) for
the GTS300 or an AWG #6 or
AWG #4 cable with an 80 amp
fuse for the GTS600 directly
from the positive + 12V battery
terminal to the disired
amplifier location. Keep the
fuse to within 6” of the battery
terminal, and before the wire
runs through any metal
partition.
40 amp fuse (not included) for
the GTS300 or an AWG #6 or
AWG #4 cable with an 80 amp
fuse for the GTS600 directly
from the positive + 12V battery
terminal to the disired
amplifier location. Keep the
fuse to within 6” of the battery
terminal, and before the wire
runs through any metal
partition.
Note: All wiring connections
should be made either by
soldering with heatshrink tubing
insulation or with high quality
crimp type insulated connectors
installed with a professional type,
articulated crimping tool.
Soldering crimptype terminals is
recommended for additional
security. Never use wire-nuts,
insulation-displacement
connectors (i.e. ScotchLok type),
or “twist and tape” connections.
Do not use electrical tape; it will
loosen with age and extreme
temperatures.
should be made either by
soldering with heatshrink tubing
insulation or with high quality
crimp type insulated connectors
installed with a professional type,
articulated crimping tool.
Soldering crimptype terminals is
recommended for additional
security. Never use wire-nuts,
insulation-displacement
connectors (i.e. ScotchLok type),
or “twist and tape” connections.
Do not use electrical tape; it will
loosen with age and extreme
temperatures.
3. Mount amplifier in the desired
location using four screws.
4. Connect power wiring as
shown i the Wiring Diagram.
5. Connect the outputs from the
head unit to the appropriate
inputs of the amplifier
according to the Wiring
Diagram with either high
quality low-level signal cables
with RCA plugs, with the
supplied speaker-level input
connector, or both.
inputs of the amplifier
according to the Wiring
Diagram with either high
quality low-level signal cables
with RCA plugs, with the
supplied speaker-level input
connector, or both.
6. Connect the speakers to the
amplifier according to the
wiring diagram.
wiring diagram.
7. Turn the input gain adjustment
to the 1/4 position.
8. Set the crossover switches as
desired.
9. Set the input mode switch to
stereo, left + right or right
input only operation.
input only operation.
10. Set the bass boost switch to
the desired position.
11. Reconnect the negative
battery cable.
12. Turn on the signal source at a
low volume level and check
for the correct output from
each speaker.
for the correct output from
each speaker.
13. Adjust the amplifier gain
control using the procedure
described in the “Adjusting
the Gain” section.
described in the “Adjusting
the Gain” section.
2.2 Controls and Connectors
1. Preamp-Level Input Connector –
Use these connectores for line
(preamp) level input to the
amplifier.
2. Preamp-Level Output Connector
– Use these outputs to send the
signal to additional amplifiers.
3. Speaker-Level Input Connector –
Use this connector for speaker
level input signals. A wire harness
is supplied for use with this
connector. This input also includes
JBL’s Common Sense input
circuitry which turns the amplifier
on as soon as the high powered
head unit connected to this input
is turned on.
4. Speaker Output Connector –
Connect speaker wiring to this
connector. See “Wiring” directions
for more information.
5., 6., 7., 8., Power Connector –
Connection for power wires #A.
See “Wiring” directions for
information on proper
connections.
Use these connectores for line
(preamp) level input to the
amplifier.
2. Preamp-Level Output Connector
– Use these outputs to send the
signal to additional amplifiers.
3. Speaker-Level Input Connector –
Use this connector for speaker
level input signals. A wire harness
is supplied for use with this
connector. This input also includes
JBL’s Common Sense input
circuitry which turns the amplifier
on as soon as the high powered
head unit connected to this input
is turned on.
4. Speaker Output Connector –
Connect speaker wiring to this
connector. See “Wiring” directions
for more information.
5., 6., 7., 8., Power Connector –
Connection for power wires #A.
See “Wiring” directions for
information on proper
connections.
9. Fuse – 40 Amp ATC type fuse for
the GTS300 and two 40 amp fuses
for the GTS600.
10. Gain Control – Use this control
to adjust the input sensitivity of
the amplifier. See the “Adjusting
the Gain” section for tips on
proper setup.
11. Preamp-Output Crossover
Switch – This switch controls the
built-in crossover that is directed
to the preamp-output connectors.
Set the switch to “Flat” for full
band operation. Set this switch to
“Low-Pass” to activate the low-
pass filter on the preamp output
(for subwoofer use). Set the switch
to “High-Pass” to activate the
high-pass filter for use with
satellite speakers.
12. Speaker Output Crossover
Switch – This switch controls the
built-in crossover that is connected
to the power amplifier circuitry.
Set the switch to “Flat” for full
band operation. Set this switch to
“Low Pass” to activate the low
the GTS300 and two 40 amp fuses
for the GTS600.
10. Gain Control – Use this control
to adjust the input sensitivity of
the amplifier. See the “Adjusting
the Gain” section for tips on
proper setup.
11. Preamp-Output Crossover
Switch – This switch controls the
built-in crossover that is directed
to the preamp-output connectors.
Set the switch to “Flat” for full
band operation. Set this switch to
“Low-Pass” to activate the low-
pass filter on the preamp output
(for subwoofer use). Set the switch
to “High-Pass” to activate the
high-pass filter for use with
satellite speakers.
12. Speaker Output Crossover
Switch – This switch controls the
built-in crossover that is connected
to the power amplifier circuitry.
Set the switch to “Flat” for full
band operation. Set this switch to
“Low Pass” to activate the low
pass filter on the amplifier (for
subwoofer use). Set the switch to
“High Pass” to activate the high
pass filter for use with satellite
speakers.
13. Input Mode Selector – This
switch is used to set the input
mode for both preamp and
speaker-level inputs.
Set this switch to Stereo for
normal operation using both left
and right inputs. Set this switch to
R to drive both the left and right
output channels with only a single
input on the right channel. Set this
switch to “L+R” to sum the left
and right inputs for a mono output
on both amplifier channels.
Power Indicator LED (on chassis
top) – LED steadily illuminates for
normal operation. LED blinks
when protection circuitry or
muting is engaged.
14. Bass Boost Switch – This
activates a built-in Bass Boost
circuit used to increase low-bass
output.
subwoofer use). Set the switch to
“High Pass” to activate the high
pass filter for use with satellite
speakers.
13. Input Mode Selector – This
switch is used to set the input
mode for both preamp and
speaker-level inputs.
Set this switch to Stereo for
normal operation using both left
and right inputs. Set this switch to
R to drive both the left and right
output channels with only a single
input on the right channel. Set this
switch to “L+R” to sum the left
and right inputs for a mono output
on both amplifier channels.
Power Indicator LED (on chassis
top) – LED steadily illuminates for
normal operation. LED blinks
when protection circuitry or
muting is engaged.
14. Bass Boost Switch – This
activates a built-in Bass Boost
circuit used to increase low-bass
output.
3
➀
Preamp Level RCA Inputs
➁
Preamp Level RCA Outputs
➂
High Level Speaker Inputs
➃
Speaker Outputs
➄
Remote Turn On Output
➅
Battery Ground
➆
Battery (+12v) In
➇
Remote Turn On Input
➈ Fuse
40A
LINE
INPUT
PREAMP
OUTPUT
OUTPUT
L
L
R
R
SPEAKER LEVEL
INPUT
SPEAKER
OUTPUT
POWER
FUSE
40A
BRIDGED
+
_
+
_
+
_
+
_
BATT(+)
REM OUT
REM IN
GND
Power
Connector
Connector
R
L
R
L
BASS BOOST
INPUT MODE
STEREO
ON
OFF
L+R
R
SPEAKER OUTPUT
CROSSOVER
LOW PASS
HIGH PASS
FLAT
PREAMP OUTPUT
CROSSOVER
HIGH PASS
FLAT
LOW PASS
NOM
GAIN
MIN
MAX
➉
Gain Control
Preamp Crossover Frequency Selector
Amplifier Crossover Frequency Selector
Input Mode Selector
Bass Boost
3. System Design Using the
GTS300 or GTS600:
GTS300 or GTS600:
3.1 Speaker Requirements
When used in the non-bridged
mode the GTS300 or GTS600 can
easily drive 2 ohm speaker loads.
When only one speaker is
connected to each channel,
virtually any conventional speaker
may be used.
When the GTS300 or GTS600 is in
bridged mode, the combined
impedance of the speaker (or
speakers) connected to the bridged
channel should be at least 4 ohms.
Sustained operation of the GTS300
or GTS600 in bridged mode with
less than 4 ohms will likely cause
overheating.
The GTS300 or GTS600 must not
be used with speakers that have
either one of their input terminals
wired to the frame of the speaker
or to the chassis of the vehicle.
mode the GTS300 or GTS600 can
easily drive 2 ohm speaker loads.
When only one speaker is
connected to each channel,
virtually any conventional speaker
may be used.
When the GTS300 or GTS600 is in
bridged mode, the combined
impedance of the speaker (or
speakers) connected to the bridged
channel should be at least 4 ohms.
Sustained operation of the GTS300
or GTS600 in bridged mode with
less than 4 ohms will likely cause
overheating.
The GTS300 or GTS600 must not
be used with speakers that have
either one of their input terminals
wired to the frame of the speaker
or to the chassis of the vehicle.
3.2 Signal Sources
The low level preamp outputs of
any radio/tape deck, CD player or
preamp/equalizer so equipped can
drive the GTS300 or GTS600. The
gain controls of the GTS300 or
GTS600 are used to match the
amplifier’s input sensitivity to the
output voltage of the source. This
matching is important to keep
noise low and is explained in the
“Adjusting the Gain” section of
this manual.
Thanks to Universal Interface
Circuitry, the GTS300 or GTS600
can also be connected to power
amplifiers, radios or equalizers
that are equipped with only
speaker outputs by connecting
them through the speaker level
input connector. Inside the GTS300
or GTS600, the speaker-level and
preamp-level inputs are connected
through a mixing circuit, which
allows them to be used
simultaneously. Therefore a low
level source, such as a CD player
equippe with a volume control
may be connected to the preamp-
level inputs at the same time as a
powered radio/tape unit is
connected to the speaker-level
inputs. This provides a higher
performance alternative to an FM
Modulator connection when you
wish to add CD capability to a
factory casette stereo. Switching
from one source to the other is as
simple as turning the desired
source on and turning the
undesired one off – no additional
switches or relay connections are
needed.
any radio/tape deck, CD player or
preamp/equalizer so equipped can
drive the GTS300 or GTS600. The
gain controls of the GTS300 or
GTS600 are used to match the
amplifier’s input sensitivity to the
output voltage of the source. This
matching is important to keep
noise low and is explained in the
“Adjusting the Gain” section of
this manual.
Thanks to Universal Interface
Circuitry, the GTS300 or GTS600
can also be connected to power
amplifiers, radios or equalizers
that are equipped with only
speaker outputs by connecting
them through the speaker level
input connector. Inside the GTS300
or GTS600, the speaker-level and
preamp-level inputs are connected
through a mixing circuit, which
allows them to be used
simultaneously. Therefore a low
level source, such as a CD player
equippe with a volume control
may be connected to the preamp-
level inputs at the same time as a
powered radio/tape unit is
connected to the speaker-level
inputs. This provides a higher
performance alternative to an FM
Modulator connection when you
wish to add CD capability to a
factory casette stereo. Switching
from one source to the other is as
simple as turning the desired
source on and turning the
undesired one off – no additional
switches or relay connections are
needed.
4. Wiring
Proper wiring of the GTS300 or
GTS600 and the associated
GTS600 and the associated
4
(+)
(–)
(+)
(–)
Parallel Wiring
Series Wiring
2 Ohms
Nominal
Impedance
Nominal
Impedance
8 Ohms
Nominal
Impedance
Nominal
Impedance
4
Ohms
4
Ohms
4
Ohms
4
Ohms
