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.
|@ 4 Ω||75 W RMS x 4|
|@ 2 Ω||100 W RMS x 4|
|Bridged @ 4Ω||200 W RMS x 2|
|@ 4 Ω||60 W RMS x 4|
|@ 2 Ω||90 W RMS x 4|
|Bridged @ 4Ω||180 W RMS x 2|
|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||Switchable from 200 mV - 2 V RMS (Low) to 800 mV - 8 V RMS (High)|
|Min.Copper Power / Ground Wire Gauge||4 AWG wire|
|Fuse Rating||40 A (AFS, AGU or MaxiFuse™)|
|Filter Mode(s)||Low-Pass or High-Pass|
|Filter Slope(s)||12 dB/octave|
|Filter Frequency Range||50 Hz - 500 Hz|
|Detented, Calibrated Filter Freq. Potentiometers||No|
|Filter Defeat Function||Yes|
|Remote Level Control||No|
|Remote Level Modes||N/A|
|Channel Input Mode Switch||Yes (2/4 ch.)|
|Pass-Through Preamp Output||Buffered|
|Source Channel Selection for PreOuts||No|
|Height (H)||2.13 in / 54 mm|
|Width (W)||9.78 in / 248 mm|
|Depth (D)||6.96 in / 177 mm|
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.
JL Audio’s Differential-Balanced Inputs are engineered to combat induced cable noise, which is a common problem in car and marine audio installations. This technology allows for the use of conventional RCA cables, while delivering many of the benefits of a true balanced connection and accepting a wide range of input signal levels.
Today’s vehicles are equipped with sophisticated electronics capable of generating noise and interference that can intrude into the audio path, ruining the listening experience.
Most audio equipment uses single-ended, ground-referenced RCA jacks to receive audio signals. This means that the RCA shield is connected directly to signal ground. This is a simple, cost effective input design that works well for short runs in noise free environments. In noisier environments, this method cannot reject the common mode noise that could be on both RCA conductors (shield and center conductor).
By having more than one chassis-grounded RCA shield on a device, single-ended input designs are also more susceptible to ground loops. If noise is present on both conductors while the shield is connected to ground, the input amplifier will amplify the noise relative to the grounded RCA shield. When there are multiple RCA connections or any other conductors subjected to a magnetic field, this will cause a difference in potential across the RCA loop to be amplified at the grounded RCA as noise (a classic ground loop).
JL Audio’s Differential-Balanced Input circuits measure the center pin of the RCA connection relative to the RCA shield, even when the shield is not connected to ground, and even when the voltages at both conductors are moving relative to ground. Because both the center conductor and the shield see high impedance to ground at the input, a ground loop cannot be formed, as there is no current flow to induce a voltage as noise. This works equally well with differential-balanced, or unbalanced signal sources, making this input architecture compatible with all standard car and marine audio equipment, using standard, unshielded, twisted-pair RCA cables. No special cables are required, unlike the fully balanced connections used in professional audio.
Another benefit of the Differential-Balanced Input design is that it easily accepts low-level and high-level signals from a variety of factory head unit outputs and amplifiers, including single ended “ground referenced” sources, as well as Balanced or Unbalanced “Bridged or BTL” sources. This eliminates the need for Line Output Converters (LOCs) in most installation scenarios.
The obvious question is: “Why don’t all car audio amplifiers use Differential-Balanced Inputs?” The answer is simple: it costs more. Executing a proper differential-balanced input section requires more components and better quality components than a basic single-ended design, so you generally won’t find them on less expensive amplifiers.
Find the answers to many common questions:
U.S.A. Warranty Information - Mobile Audio Amplifiers and Electronic Products
JL Audio Amplifiers and Electronics are warrantied against defects in materials and workmanship for Two (2) Years from purchase date. The Mobile Audio Amplifier warranty can be expanded to a total of Three (3) Years from the date of purchase with the accompanying purchase of a qualifying JL Audio Amplifier Power Connection System and with installation by a JL Audio Authorized Retailer. JL Audio will, at its discretion, repair or replace any products that exhibit defects in materials and/or workmanship during the warranty period.
Please hold on to your sales receipt! All warranty service requires original sales receipt documentation. The warranty only applies to the original purchaser from an authorized retailer.
Note: Products purchased from unauthorized dealers are not covered under warranty.
The following is not covered under JL Audio's warranty program:
1. Product with defaced, altered or removed serial numbers (no valid, legible serial number = no warranty).
2. Product owned by anyone other than the original purchaser from an authorized JL Audio dealer. (The warranty is not transferable and will not apply to products purchased from unauthorized dealers.)
3. Product that has been physically abused (run over by a car or beat with a hammer, for example).
4. Product that has not been installed according to the instructions in the owner's manual
5. Product in which repair and/or modification has been attempted by unauthorized parties
6. Product damaged cosmetically due to improper handling or normal wear and tear
7. Product damaged in an accident, due to criminal activity (attempted theft, gunshot damage, etc.) or by 'acts of God' (flooding, lightning, locusts, etc.)
8. Custom finishes or other cosmetic treatments applied to products. (JL Audio will not be responsible for restoring or maintaining any custom finishes)
9. Installation and shipping costs associated with removing, re-installing or shipping the product to JL Audio for warranty service
Ask your dealer for details on warranty limitations.
If you need Service on your JL Audio Product:
All warranty returns should be sent to JL AUDIO 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. Return only defective components. 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. Always include proof of purchase (sales receipt).
“JL Audio's technical innovation takes the 4-channel Class-D amplifier to the next level.”
“this amplifier is one of the best thought out products to come across my bench in a while. Thanks in no small part to the years of car audio experience and the ability to exploit today’s high speed device technology, the JL Audio RD400/4 is a solid audio performer wrapped up in a box of common sense.”
Read the complete RD400/4 Amplifier Review (PDF)
– Garry Springgay, Performance Auto & Sound, Tuning Essentials - 2017 Tech & Car Audio - 7th Ed.
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