JL Audio MX280/4 Owner's Manual
280W Full-Range 4-Channel Class D Amplifier
IPX7 Water Resistant
Introduction
Thank you for purchasing a JL Audio amplifier for your sound system. Your amplifier has been designed and manufactured to exacting standards to ensure years of musical enjoyment. For maximum performance, we highly recommend installation by an authorized JL Audio dealer. If installing yourself, please read this manual thoroughly. For questions, contact your authorized dealer or call JL Audio Technical Support at technical@jlaudio.com or (954) 443-1100.
What's Included
- Amplifier
- Stainless steel mounting screws
- Spare 35A fuse
- User manual
Product Description
This is a four-channel, full-range audio amplifier utilizing Class D technology for all channels.
Installation Applications
This amplifier is designed for 12 volt, negative-ground electrical systems. Using it in systems with positive ground or voltages other than 12V may result in damage and void the warranty. This product is not certified or approved for use in aircraft.
Safety Considerations
- Mount in a dry, well-ventilated location away from other electronic devices. If a dry environment is not available, use a location not exposed to heavy splashing.
- While water-resistant, it should never be submerged or subjected to high-pressure water spray. Do not install where directly exposed to the elements.
- Do not mount in the engine compartment or areas of extreme heat.
- Securely mount the amplifier to prevent it from coming loose due to collision, sudden jolt, or vibration.
- Before drilling, check to ensure you will not drill into an exterior panel/hull, fuel tank, gas/brake line, wiring harness, or other vital system.
- Do not run system wiring outside or underneath the vehicle/vessel, as this is dangerous and can cause severe damage/injury.
- Protect all system wires from sharp edges (metal, fiberglass, etc.) by routing them carefully, tying them down, and using grommets and loom where appropriate.
- Secure all wiring as needed using cable ties or wire clamps to protect them from moving parts and sharp edges.
IPX7 Water Resistance Rating
This product has been tested to withstand immersion in water, up to 1 meter (3.28 ft.) deep, for up to 30 minutes (with control panel cover properly installed). Note: While designed to be water resistant, this product should never be submerged under water for prolonged periods or subjected to activity that creates pressure on it exceeding its depth rating.
Installation Procedure/Connections
Essential Safety Precaution: Disconnect the NEGATIVE battery post connection and secure the cable to prevent accidental reconnection during installation.
- Connect the RED power lead to the positive (+12V) battery post. Use 8 AWG minimum power wire.
- Install an appropriate fuse (35A recommended for this amplifier) within 18 inches (45 cm) of the positive battery post connection. Do not install the fuse until the power wire is securely connected to the amplifier.
- Connect the BLACK negative ground lead to a clean, solid metal grounding point near the amplifier (e.g., metal chassis ground). If no chassis ground is available, connect to the NEGATIVE battery post. Use 8 AWG minimum ground wire. Ensure all ground connections (source unit and amplifiers) are made at the same location.
- Connect the BLUE remote turn-on lead to the source unit's positive (+12V) remote turn-on output. If your source unit lacks a dedicated remote turn-on output, connect the lead to +12V via a switch powered by an ignition-switched circuit.
- Signal Input (Low-Level): Connect the amplifier's RCA input jacks to the source unit's preamp level output jacks.
- Signal Input (Hi-Level): If your source unit does not offer preamp level outputs, splice the speaker output wires of the source unit onto RCA plugs for each input pair or use a JL Audio ECS Speaker Wire to RCA adaptor (XD-CLRAIC2-SW). Observe correct polarity for Hi-Level Input connections to avoid signal loss.
- Connect the speaker output leads to the corresponding speaker wires.
- Make necessary adjustments to the filter controls and input sensitivity.
WARNING! Failure to make safe, tight, high-integrity power connections can result in fire and extensive damage!
Illustrates connections from the Battery (+12V, GND) and Remote Turn-On ([REM]) to the amplifier's power terminals ([+12V], [GND], [REM]). A 35A fuse is shown inline with the positive battery connection.
Shows RCA input jacks labeled [FRONT IN] and [REAR IN] for connecting to the source unit's audio outputs.
Depicts speaker output terminals labeled FL+, FL-, FR+, FR-, RL+, RL-, RR+, RR- for connecting to speakers. Notes indicate connections for bridged operation.
Control Panel Settings and Adjustments
Controls are located on the bottom panel beneath a gasketed, protective cover. Remove the four Phillips head screws from the center panel to access and adjust controls. Replace the cover when finished.
| Control | Setting | Mode / Function |
|---|---|---|
| Channel Mode | 2CH | #1) 4 Stereo Outputs (non-fading) #2) 2 Bridged Mono Outputs |
| 3CH | #1) 2 Stereo Front + 2 Mono Rear Outputs #2) 2 Stereo Front + 1 Bridged Mono Rear Output | |
| Input | Use Front Inputs Only | Applies to 2CH and 3CH modes. |
| Use Front and Rear Inputs | Applies to 4CH mode. | |
| Input Voltage | Low (250 mV - 4 V) | RCA/Preamp Level Range |
| High (750 mV - 15 V) | RCA/Preamp or Speaker Level Range | |
| Filter Mode | Off | Full-Range Operation of Input Signals |
| HP (High-Pass) | Configures Filter to Attenuate Frequencies BELOW the Selected Filter Frequency | |
| LP (Low-Pass) | Configures Filter to Attenuate Frequencies ABOVE the Selected Filter Frequency | |
| Filter Freq. | Variable (35-300 Hz, 12 dB/Octave) | Adjusts the filter cutoff frequency. |
| Input Sens. | Variable | Adjusts the input stage for maximum clean output. |
Note on Channel Mode and Input Settings: The table details how Channel Mode and Input selections affect the amplifier's configuration, including stereo, bridged mono outputs, and input signal routing.
Connections
| Label | Wire Color | Description |
|---|---|---|
| +12V | Red | Positive (+12V) Power Connection |
| GND | Black | Negative (GND) Ground Connection |
| REM | Blue | Positive (+12V) Remote Turn-On Input |
| FL+ | White | Ch. 1 (+) Positive Front Left Speaker |
| FL- | White/Black | Ch. 1 (-) Negative Front Left Speaker |
| FR+ | Gray | Ch. 2 (+) Positive Front Right Speaker |
| FR- | Gray/Black | Ch. 2 (-) Negative Front Right Speaker |
| RL+ | Green | Ch. 3 (+) Positive Rear Left Speaker |
| RL- | Green/Black | Ch. 3 (-) Negative Rear Left Speaker |
| RR+ | Purple | Ch. 4 (+) Positive Rear Right Speaker |
| RR- | Purple/Black | Ch. 4 (-) Negative Rear Right Speaker |
| Label | Plug | Description |
|---|---|---|
| FRONT IN | White RCA | Ch. 1 / Front Left Channel Signal Input |
| Red RCA | Ch. 2 / Front Right Channel Signal Input | |
| REAR IN | White RCA | Ch. 3 / Rear Left Channel Signal Input |
| Red RCA | Ch. 4 / Rear Right Channel Signal Input |
Note on Bridged Connections: The diagrams illustrate how to connect speakers for bridged operation, combining two channels into one for higher power output.
Specifications
| MX280/4 | |
|---|---|
| Rated RMS Power @ 14.4V | 50W x 4 @ 4Ω 64W x 4 @ 3Ω 70W x 4 @ 2Ω 140W x 2 @ 4Ω Bridged |
| Rated RMS Power @ 12.5V | 36W x 4 @ 4Ω 47W x 4 @ 3Ω 52W x 4 @ 2Ω 100W x 2 @ 4Ω Bridged |
| Frequency Response | 20 Hz - 20 kHz (+0, -1dB), 6.3 Hz - 30 kHz (+0, -3dB) |
| S/N Ratio, A-weighted, 20 kHz noise bandwidth | 89.5 dB (Referred to rated power), 70.5 dB (Referred to 1 W) |
| Damping Factor | >60 / 50 Hz @ 4Ω, >30 / 50 Hz @ 2Ω |
| Input Voltage Range | 250 mV - 4V (Low) or 750 mV - 15 V (High) |
| Filter Modes | Low-Pass or High-Pass, defeatable |
| Filter Freq. Range, Slope | 35 - 300 Hz, 12 dB/Octave |
| Detented Filter Frequency Potentiometers | 35, 80, 135, 300 Hz (Calibrated) |
| Input Mode Switch | 2 / 3 / 4 Channel |
| Min Power/GND Wire | 8 AWG |
| Fuse Rating | 35A |
| Dimensions | 1.77 in x 8.66 in x 3.09 in / 45 mm x 220 mm x 78.5 mm |
Status LED's / Protection Circuitry
Two status indicator lights on the wiring end panel:
| Status | POWER (Green LED) | PROTECT (Red LED) | Note |
|---|---|---|---|
| Normal Operation | ON | OFF | |
| Thermal Protection | ON | ON | Lasts until temp cools to normal |
| Over Current | OFF/ON | ON/OFF | Green/Red LEDs alternate for 1 second |
| Short Circuit | ON | ON | Possible audible "popping" noise |
Wiring Configuration Diagrams
The manual includes diagrams illustrating various wiring configurations:
- 4 Stereo Outputs (non-fading): Channel Mode: 2CH, Inputs: Use Front Inputs Only. RMS Power: 50W x 4 @ 4Ω.
- 4 Stereo Outputs (fading): Channel Mode: 4CH, Inputs: Use Front and Rear Inputs. RMS Power: 50W x 4 @ 4Ω.
- 2 Bridged Mono Outputs: Channel Mode: 2CH, Inputs: Use Front Inputs Only. RMS Power: 140W x 2 @ 4Ω.
- 2 Bridged Stereo Outputs: Channel Mode: 4CH, Inputs: Left Signal to Both Front Inputs / Right Signal to Both Rear Inputs. RMS Power: 140W x 2 @ 4Ω.
- 2 Stereo Front + 2 Mono Rear Outputs: Channel Mode: 3CH, Inputs: Use Front Inputs Only. RMS Power: 50W x 4 @ 4Ω.
- 2 Stereo Front + 1 Bridged Mono Rear Output: Channel Mode: 3CH, Inputs: Use Front Inputs Only. RMS Power: 50W x 2 @ 4Ω + 140W x 1 @ 4Ω.
Each configuration shows the amplifier inputs ([FRONT IN], [REAR IN]), source connection, and speaker outputs (FL+, FL-, FR+, FR-, RL+, RL-, RR+, RR-) with corresponding wire colors and labels.
Appendix A: Input Sensitivity Level Setting
This section provides a procedure for adjusting input sensitivity for optimal performance.
Necessary Equipment
- Digital AC Voltmeter
- CD or file with a sine-wave test tone (0 dB reference level) at the frequency range to be amplified (e.g., 50 Hz for subwoofers, 1 kHz for midrange). Do not use attenuated test tones (-10 dB, -20 dB, etc.).
The Nine-Step Procedure
- Disconnect the speakers from the amplifier's speaker output connectors.
- Turn off all processing (bass, treble, loudness, EQ, etc.) on the source unit, processors, and amplifier. Set the source unit's fader control to center position and its subwoofer level control to 3/4 of maximum.
- Turn the "Input Sens." control all the way down.
- Set the source unit volume to 3/4 of full volume. This allows for reasonable gain overlap with moderate clipping at full volume.
- Using the chart below, determine the target voltage for input sensitivity adjustment according to the nominal impedance of the speaker system connected to the amplifier outputs.
- 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.
- Connect the AC voltmeter to the speaker output connectors of the amplifier. Make sure you test the voltage at the correct connectors (+ and -).
- Increase the "Input Sens." control until the target voltage is observed with the voltmeter.
- Once the amplifier is adjusted to its maximum low-distortion output level, reconnect the speaker(s) and listen to the system. The "Input Sens." controls can be adjusted downward if the amplifier requires attenuation to achieve the desired system balance.
Important Note: Do not increase any "Input Sens." setting 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." if any equalizer boost is activated after setting it. EQ cuts will not require re-adjustment.
| Nom. Impedance | Target AC Voltage |
|---|---|
| 4Ω | 14.1 V |
| 2Ω | 11.8 V |
| Bridged to 4Ω | 23.7 V |
Troubleshooting
| Problem | Possible Cause | Solution |
|---|---|---|
| Amplifier doesn't turn on | Faulty fuse | Remove fuse and check with continuity meter. Replace if necessary. |
| Poor connection integrity (+12V, Ground, Remote) | Check "+12V", "Ground", and "Remote" leads for pinched wires; ensure tight connections. | |
| Insufficient "Remote" input | Make sure there is a sufficient +12V 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 | Ensure 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 stereo (4 ohms bridged). |
| Output shuts off after a while | Overheating condition (Thermal Protection) | Make sure amplifier mounting area has adequate space for ventilation and heat dissipation. |
Note on Input Sensitivity: Refer to Appendix A for proper input sensitivity setting to achieve maximum, low-distortion output.
Limited Warranty (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.
Service Information
For warranty returns, send the product 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.
