JL Audio M400/4 User Manual (English)

Questions and Answers:

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michaelhillAug 6, 2025
What to do if my JL Audio M400/4 Amplifier turns on but there is no output?
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  Jeffrey HortonAug 6, 2025
  If your JL Audio Amplifier turns on but produces no output, take these steps: 1. Check the input signal from the source unit using an AC voltmeter while playing a test tone. A steady voltage (0.1 to 4.0 volts) should be present. 2. Check the amplifier's output at the speaker outputs, ensuring you disconnect the speakers first. You should measure 5V AC or more with the volume at halfway. 3. Verify that the speaker wires are properly connected to the terminal block, ensuring sufficient bare wire is making contact inside the terminal.
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Paula ParsonsAug 14, 2025
How to fix a JL Audio Amplifier that doesn’t turn on?
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  Victoria SpencerAug 14, 2025
  If your JL Audio Amplifier isn’t turning on: * Check the fuse with a continuity meter, as visual inspection may not reveal internal connection issues. Remove the fuse from the holder for testing. Also, inspect the fuse-holder. * Check the connections to the “+12VDC”, “Ground”, and “Remote” terminals for integrity. Ensure no wire insulation is pinched and each connection is tight. * Verify +12V at the “Remote” connection. If the source unit's turn-on lead is insufficient, use a relay. Test by jumping the “+12VDC” wire to the “Remote” terminal to see if the amplifier turns on.
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Amy TaylorAug 21, 2025
Why does my JL Audio M400/4 Amplifier shut off at high volumes?
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  Zachary Davis Jr.Aug 21, 2025
  If your JL Audio Amplifier shuts off at higher volumes, it might be due to a drop in voltage. The power supply requires a minimum of 10V. Check your voltage source and grounding point. Momentary voltage drops below 10V can occur, which are hard to detect with a voltmeter. Inspect all wiring and termination points to ensure proper voltage. Consider upgrading the ground wire connecting the battery to the vessel’s electrical ground and the power wire connecting the alternator to the battery, especially if your system has a main fuse rating above 60A. Grounding issues are a common cause of amplifier problems.
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Joshua HumphreyAug 29, 2025
Why do I hear ticking or popping sounds from my JL Audio M400/4 Amplifier speaker?
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  Daniel SwansonAug 29, 2025
  If you hear repetitive ticking or popping sounds from your JL Audio Amplifier's speaker, it could be due to: * A short in the speaker wires, either between the positive and negative leads or between a speaker lead and the vessel’s electrical ground. Disconnecting the speaker wires and using a test speaker with different wires can help diagnose this. * An incorrect load impedance. Verify that each amplifier channel is driving a load equal to or greater than 2 ohms in stereo mode (4 ohms bridged).

JL Audio M400/4 Specifications

General

Amplifier Class	Class D
Number of Channels	4
THD+N at Rated Power	< 1%
Fuse Rating	30 A
Power Output (4 Ohms)	75W x 4
Power Output (2 Ohms)	100W x 4
Power Output (Bridged 4 Ohms)	200W x 2
Frequency Response	10 Hz - 20 kHz