JL Audio M400/4: 4 Ch. Class D Full-Range Marine Amplifier, 400 W

Summary

4-Channel Class D Marine Full-Range Amplifier, 100 W x 4 @ 2 Ω / 75 W x 4 @ 4 Ω - 14.4V

This tiny amplifier packs a serious full-range punch, delivering a staggering 100 watts to each of its four channels into 2 Ω (14.4V, 1% THD). The breakthrough that makes this much power possible in such a small chassis is our NexD™ ultra-high-speed switching design, which allows for full bandwidth Class D operation with extremely low distortion and outstanding efficiency.

Use the M400/4 in combination with our M600/1 monoblock to build a 1000 W amplification system to power four satellites and a subwoofer... and fit the whole thing under a seat. Or, use the M400/4 by itself to power two satellites, plus a subwoofer. With M-Series amplifier, the possibilities are endless.

The M400/4 includes a 12 dB / octave filter for each channel bank, which can be configured as a low-pass or high-pass filter and offers continuously variable cutoff frequency selection from 50-500 Hz. With the addition of an HD-RLC remote level control (sold separately), the amplifier's Ch. 1 & 2 level or overall level can be directly controlled from a remote location.

This marine amplifier features white and gray powder-coat finishes, a gasketed cover for the controls and stainless steel hardware for durability in the marine environment.

Overview 

NexD™ Switching Technology

Summary:
NexD™ amplifier technologies produce exceptional audio quality, unsurpassed total efficiency and high power from very compact amplifier designs.

Detailed Information:
Beginning with the original 'Slash' subwoofer amplifiers, JL Audio has been at the forefront of Class D amplifier design. Today, our flagship Single-Cycle Control™ technology sets the ultimate standard for Class D amplifier performance. The NexD™ amplifiers may be a bit less complex, more compact and more affordable, but they flow from the same minds that have set the trend in mobile amplifier technology for over a decade.

Let's get a little nerdy... A traditional PWM switching amp design uses a fixed switching frequency and varies the pulse width based solely on the audio input signal to the pulse modulator. This basic approach assumes some ideal conditions, like a rock-steady power supply, that do not necessarily occur in a real, in-car installation. Power supply sag with signal causes distortion at all power levels with these designs, even well below clipping. The cure for this is feedback (a corrective signal sent back to the input side), but this becomes impractical as the audio frequency increases, making it a good solution for band-limited (subwoofer) amps, but not for full-range amplifiers.

Taking the above into account when designing the NexD™ subwoofer amplifiers, we have taken the simple fixed PWM approach and enhanced it with a very high switching frequency: 240 kHz, which is about 4x higher than most Class D subwoofer amplifiers. This pushes the amplifier's bandwidth to at least 500 Hz with minimal distortion and improves efficiency, while keeping typically bulky circuity more compact. Your subwoofers will reward you with tight, rock-solid bass performance.

For the full-range NexD™ amplifiers and channels we applied a variable, ultra-high speed version of the NexD™ technology (switching at well over 400 kHz). In these designs, a self-oscillating modulator with "feed-forward" sends information about the instantaneous power supply voltage to the modulator, combining this with the input signal to cancel out any distortion due to supply voltage fluctuation. This reduces distortion prior to applying feedback, simplifying the overall feedback loop design.

The bottom line is simply great audio: clean, powerful and reliable.

Advanced Rollback Protection

Summary:
JL Audio's exclusive Advanced Rollback Protection circuit monitors the amplifier's thermal condition and adjusts amplifier operation to eliminate annoying amplifier shut-down events.

Detailed Information:
Should a JL Audio amplifier equipped with Advanced Rollback Protection reach an unsafe operating temperature, a special circuit rolls back peak power output, without changing gain, until the amplifier cools down to a safe operating temperature. The red "Thermal" LED will light to indicate this condition has been reached. Once the amplifier cools down, the circuit restores full peak power output and the red "Thermal" indicator reverts to its normal state. The operation of Advanced Rollback Protection is inaudible in most cases, but it ensures that your music keeps on playing, even under the most demanding conditions.

Specifications

• @ 4 Ω 75 W RMS x 4
• @ 2 Ω 100 W RMS x 4
• Bridged @ 4Ω 200 W RMS x 2

Rated Continuous (RMS) Power @ 12.5 V

• @ 4 Ω 60 W RMS x 4
• @ 2 Ω 90 W RMS x 4
• Bridged @ 4Ω 180 W RMS x 2

General Specifications

• Frequency Response 12 Hz - 22 kHz (+0, -1dB)
• S/N Ratio, referred to highest rated power >104 dB below rated power (A-weighted, 20 Hz - 20 kHz noise bandwidth)
• S/N Ratio, referred to 1 W >84 dB (A-weighted, 20 Hz - 20 kHz noise bandwidth)
• Damping Factor @ 4 Ω >150 / 50 Hz
• Damping Factor @ 2 Ω >75 / 50 Hz
• THD+N @ Rated Power <1% @ 2 Ω per Ch.
• Input Voltage Range @ RCA Inputs 100 mV - 4 V RMS
• Min Copper Power / Ground Wire Gauge 4 AWG wire
• Fuse Rating 50 A (AFS, AGU or MaxiFuse™)

Signal Processing

• Filter Modes Low-Pass or High-Pass
• Filter Slope (dB/Octave) 12 dB
• Filter Frequency Range 50-500 Hz
• Detented, Calibrated Filter Freq. Potentiometers Yes
• Filter Defeatable? Yes
• Remote Level Control Optional (HD-RLC)
• Remote Level Modes 2 or All channels
• Channel Input Mode Switch Yes (2/4 ch.)
• Pass-Through Preamp Output Type Buffered
• Source Channel Selection for PreOuts Yes

Physical Specifications

• Height (H) 2.05 in / 52 mm
• Width (W) 8.52 in / 216 mm
• Depth (D) 7.09 in / 180 mm
• Net Weight 4.75 lb / 2.15 kg

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