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Limited Warranty – Amplifiers (USA)

JL Audio warrants this product to be free of defects in materials and 
workmanship for a period of two (2) years from the original date of purchase.
This warranty is not transferrable and applies only to the original purchaser 
from an authorized JL Audio dealer. Should service be necessary under this 
warranty for any reason due to manufacturing defect or malfunction, JL 
Audio will (at its discretion), repair or replace the defective product with new 
or remanufactured product at no charge. Damage caused by the following is 
not covered under warranty: accident, misuse, abuse, product modification or 
neglect, failure to follow installation instructions, unauthorized repair attempts, 
misrepresentations by the seller. This warranty does not cover incidental or 
consequential damages and does not cover the cost of removing or reinstalling 
the unit(s). Cosmetic damage due to accident or normal wear and tear is not 
covered under warranty.

Warranty is void if the product’s serial number has been removed or defaced.

Any applicable implied warranties are limited in duration to the period of the 
express warranty as provided herein beginning with the date of the original 
purchase at retail, and no warranties, whether express or implied, shall apply 
to this product thereafter. Some states do not allow limitations on implied 
warranties, therefore these exclusions may not apply to you. This warranty gives 
you specific legal rights, and you may also have other rights, which vary from 
state to state. 

If you need service on your JL AUDIO product:

All warranty returns should be sent to JL Audio ’s Amplifier Service Facility 
freight-prepaid through an authorized JL Audio dealer and must be 
accompanied by proof of purchase (a copy of the original sales receipt). Direct 
returns from consumers or non-authorized dealers will be refused unless 
specifically authorized by JL Audio with a valid return authorization number. 
Warranty expiration on products returned without proof of purchase will be 
determined from the manufacturing date code. Coverage may be invalidated 
as this date is previous to purchase date. Non-defective items received will 
be returned freight-collect. Customer is responsible for shipping charges and 
insurance in sending the product to JL Audio. Freight damage on returns is not 
covered under warranty. 

For Service Information in the U.S.A. please call

JL Audio Customer Service:

  

(954) 443-1100

9:00 AM – 5:30 PM (Eastern Time Zone)

JL Audio, Inc.

10369 North Commerce Pkwy.

Miramar, FL 33025

(Do not send product for repair to this address) 

International Warranties:

Products purchased outside the United States of America are covered only  

by that country’s distributor and not by JL Audio, Inc.

Appendix A:
Input Sensitivity Level Setting

Following the directions below will allow the installer to adjust the input 
sensitivity of each amplifier channel pair in just a few minutes using equipment 
commonly available in installation bays. 

Necessary Equipment

• Digital AC Voltmeter
• CD or file with a sine-wave test tone recorded at 0 dB reference level in the 
frequency range to be amplified for that set of channels (50 Hz for subwoofer 
channels, 1 kHz for a midrange application). Do not use attenuated test tones 
(-10 dB, -20 dB, etc.). 

The Nine-Step Procedure

1) 

Disconnect the speakers from the amplifier’s speaker output connec-
tors (you need only disconnect one speaker wire).

2) 

Turn off all processing (bass/treble, loudness, EQ, etc.) on the source 
unit, processors (if used) and amplifier. Set the source unit’s fader con-
trol to center position and its subwoofer level control to 3/4 of maxi-
mum.

3) 

Turn the 

“Input Sens.”

 control all the way down.

4) 

Set the source unit volume to 3/4 of full volume. This will allow for rea-
sonable gain overlap with moderate clipping at full volume.

5) 

Using the chart on this page, determine the target voltage for input 
sensitivity adjustment according to the nominal impedance of the 
speaker system connected to the amplifier outputs.

6) 

Verify that you have disconnected the speakers before proceeding. Play 
a track with an appropriate sine wave (within the frequency range to 
be amplified) at 3/4 source unit volume.

7) 

Connect the AC voltmeter to the speaker output connectors of the 
amplifier. Make sure you test the voltage at the correct connectors  
(+ and –).

8) 

Increase the 

“Input Sens.”

 control until the target voltage is observed 

with the voltmeter.

9) 

Once you have adjusted the amplifier to its maximum low-distortion 
output level, reconnect the speaker(s) and listen to the system. The 

“Input Sens.”

 controls can now be adjusted downward if the amplifier 

requires attenuation to achieve the desired system balance.

 

Specifications

MX300/1

Rated RMS Power @ 

14.4V, <1% THD+N

160W x 1 @ 4 Ω

220W x 1 @ 3 Ω

300W x 1 @ 2 Ω

Rated RMS Power @ 

12.5V, <1% THD+N

160W x 1 @ 4 Ω

200W x 1 @ 3 Ω

250W x 1 @ 2 Ω

Frequency Response

20 Hz - 12 kHz (+0, -1dB), 7 Hz - 14 kHz (+0, -3dB)

S/N Ratio, A-weighted,  

20 kHz noise bandwidth

85 dB (Referred to rated power), 64 dB (Referred to 1 W)

Damping Factor

>150 / 50 Hz @ 4 Ω, >75 / 50 Hz @ 2 Ω

Input Voltage Range

250 mV - 4 V (Low) or 750 mV - 15 V (High)

Filter Modes

Low-Pass, defeatable

Filter Freq. Range, Slope

40 - 400 Hz, 24 dB/Octave

Detented Filter Freq.  

Potentiometers

40, 80, 130, 300 Hz (Calibrated)

Infrasonic Filter

20 - 40 Hz, 12 dB/Octave

Bass Boost EQ

0 to +12 dB @ 43 Hz

Output Polarity

0 or 180 degrees

Remote Bass Controller

M-RBC-1 (sold separately)

Min Power/GND Wire

8 AWG

Fuse Rating

30 A

Dimensions

1.77 in x 8.66 in 3.09 in / 45 mm x 220 mm x 78.5 mm

Appendix B
Remote Level Control

With the optional RBC-1 or M-RBC-1 Remote Level Control (each sold separately), 
you can control the subwoofer volume from the front of the vehicle/vessel. 
The remote’s plug connects to the amplifier’s harness-mounted RJ11 input 
jack. When connected to the amplifier, the Remote Level Control operates as 
follows. At full counter-clockwise rotation, the audio will mute completely. At full 
clockwise rotation the level will be the same as if the remote was not connected 
at all. In other words, it operates strictly as a level attenuator. This control will 
not affect the “Bass Boost” feature of the amplifier. Care should be taken to 
securely mount this control in a manner that does not interfere with vehicle/
vessel operation. When setting the amplifier’s input sensitivity, the Remote Level 
Control should be unplugged or at full clockwise rotation (maximum level).

Problem

Possible Cause

Solution

How to properly set 
input sensitivity

 

Please refer to Appendix A to set the 
input sensitivity for maximum, low-
distortion output.

Amplifier doesn’t 
turn on

Faulty fuse

Remove fuse and check with continuity 
meter. Replace if necessary.

Poor connection 
integrity

Check “+12V”, “Ground”, and “Remote” 
leads for pinched wires; ensure tight 
connections.

Insufficient 
“Remote” input

Make sure there is a suff12V 
supply at the “Remote” connection; if 
not a relay may be required.

Intermittent output, 
fluctuates when I tap 
on it or hit a bump

Poor connection 
integrity

Make sure insulation has been properly 
stripped back at connection points for 
good contact area.

Make sure input connectors are making 
good contact with input jacks of the 
amplifier.

Distorted, attenuated, 
or popping sound

Faulty speaker 
connection (Short 
Circuit / Over 
Current Protection)

Inspect speaker wires for possible short-
circuit, either together or shorted to the 
vehicle’s chassis ground.

Check the nominal load impedance at 
the amplifier is equal to or greater than 
2 ohms.

Output shuts off after 
a while

Overheating 
condition (Thermal 
Protection)

Make sure amplifier mounting area has 
adequate space for ventilation and heat 
dissipation.

Troubleshooting

MX300/1

Nom. Impedance

Target AC Voltage

25.3 V

25.7 V

24.5 V

 

Important!
Do not increase any “Input Sens.” setting for any amplifier channel or 
channel pair in the system beyond the maximum level established during 
this procedure. Doing so will result in audible distortion and possible 
speaker damage.

It will be necessary to re-adjust the “Input Sens.” for the affected channels if any 
equalizer boost is activated after setting the “Input Sens.” with this procedure. This 
applies to any EQ boost circuit, including source unit tone controls or EQ circuits. EQ 
cuts will not require re-adjustment.

Status LED’s / Protection Circuitry

There are two status indicator lights on the wiring end panel of the amplifier.

1. 

POWER

” (Green): Lights to indicate that the amplifier is turned on and 

operating normally.

2. 

PROTECT

” (Red): Lights to indicate the amplifier’s protection circuitry 

has been activated to prevent product failure due to thermal overload, 
over current or short-circuit to the amplifier’s outputs. When this pro-
tection mode is activated, the amplifier will shut down to protect its 
circuitry. When the problem is corrected, the amplifier will return to 
normal operation and the “Protect” LED will shut off. Connecting the 
speaker outputs to impedances lower than 2 ohms will also cause this 
protection mode to activate. 

POWER 

(Green LED)

PROTECT 

(Red LED)

Status

Note

ON

OFF

Normal Operation

 

OFF

ON

Thermal Protection

Lasts until temp cools to normal

OFF/ON

ON/OFF

Over Current

Green/Red LEDs alternate for 1 second

OFF

ON

Short Circuit

Possible audible “popping” noise

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