RD400/4

4 Ch. Class D Full-Range Amplifier, 400 W

RD400/4

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

Utilizing our exclusive NexD™ high-speed switching technologies, the ultra-compact RD400/4 amplifier is engineered to deliver loads of audio output power, with incredible efficiency and low distortion. Don’t let its modern styling and small size fool you though, this little powerhouse churns out 100 watts of crystal-clear audio from each of its four channels into 2 ohms (14.4V, 1% THD) and is fully bridgeable, so it can be used as a 3-channel amplifier, or as a 2-channel amplifier producing a whopping 200W x 2 into 4 ohms.

For your convenience, the RD400/4’s controls can be found on top of the amplifier, beneath a protective cover, with all connections located along one side of its chassis. Studio-grade signal processing features include high or low-pass 12 dB / octave filters (defeatable) for each channel pair, with continuously variable frequency selection from 50-500 Hz, and dual-range, differential-balanced inputs capable of accepting most input voltage levels. Automatic turn-on capability (via signal sensing or DC-offset sensing) is standard equipment, along with all-new input type switches for bridging of stereo output channels without needing to use Y-adaptors.

Onboard LED-clipping indicators are also included with your RD400/4. This all-new, innovative feature lets you easily set your amplifier’s input sensitivity settings, quickly and accurately, with no special equipment needed. You’ll also find a set of preamp outputs on-hand, so you can pass signals to another amplifier, almost effortlessly. The RD400/4 features a durable, black powder-coated finish and a top-mounted, dual-color LED light strip that reports the overall status and condition.

NexD™ Switching Technology

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

Beginning with the original 'Slash' subwoofer amplifiers, JL Audio has been at the forefront of Class D amplifier design. Our NexD™ switching technology stems from our Class D expertise to deliver outstanding fidelity and efficiency, leading to compact amplifiers that deliver high power and exceptional value.

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.