GTO 4060 (serv.man8) - JBL Car Audio User Guide / Operation Manual. Page 6

Determine your system plans and set 
the crossover mode switch accordingly. 
If your system design does not include 
a subwoofer, set the crossover mode to
OFF and skip to “Setting Input Sensitivity.”

Initially set the crossover frequency 
control midway. While listening to music,
adjust the crossover for the least 
perceived distortion from the speakers,
allowing them to reproduce as much 
bass as possible. 

Systems using a separate subwoofer set
the crossover mode to HP (high pass) for
your full-range speakers. Adjust the
crossover frequency to limit bass and 
provide increased system volume with 
less distortion.

For subwoofers, choose the highest 
frequency that removes vocal information
from the sound of the subwoofer.

If using the GTO4060 or GTO2060 to drive
a subwoofer(s), set the crossover mode to
LP (low pass).

1. Initially turn the GAIN control(s) to 

minimum (counter clockwise).

2. Reconnect the (–) negative lead to the

vehicle’s battery. Apply power to the
audio system and play a dynamic music
track.

3. On the source unit, increase the volume

control to 3/4 volume. Slowly increase
the GAIN control(s) toward three
o’clock until you hear slight distortion in
the music. Then reduce the GAIN
slightly until distortion is no longer
heard. 

NOTE: After the source unit is on, a blue
LED will light, indicating the amplifier is
on. If not, check the wiring, especially the
remote connection from the source unit.
Also refer to “Troubleshooting” guide.

No audio 

No voltage at BATT+ 

Check voltages at

(POWER LEDs

or REM terminals, 

amplifier terminals

are off)

or bad or no ground 

with VOM

connection

No audio 

Amplifier is

Make sure amplifier

(POWER

overheated

cooling is not blocked

LEDs are on)

at mounting location;
verify speaker-system
impedance is within 
specified limits

Voltage more than 16V

Check vehicle

or less than 8.5V on

charging system

BATT+ connection

No audio

Voltage less than 9V on 

Check vehicle

BATT+ connection

charging system

DC voltage on 

Amplifier may need

amplifier output 

service; see enclosed
warranty card for
service information 

Distorted audio

Input sensitivity is 

Check GAIN

not set properly, or

level setting; or

amplifier or source 

check speaker wires

unit is defective

for shorts or grounds

Distorted audio

Short circuit in 

Remove speaker leads

speaker or wire

one at a time to locate
shorted speaker or 
wire, then repair 

Music lacks 

Speakers are not 

Check speaker

“punch”

connected properly

connections for
proper polarity