Name: JL Audio RD400/4 (Open Box, Great)
Brand: JL Audio
SKU: ls-rd4004-u8
Price: 265.99 USD
Availability: Discontinued

by JL Audio

About
FAQ
Specs & Details
Product Videos
Reviews
Add-ons
Recently Viewed
Related Searches

JL Audio RD400/4 (Open Box, Great) Image 1 — JL Audio RD400/4 (Open Box, Great)

JL Audio RD400/4 (Open Box, Great) Image 2 — JL Audio RD400/4 (Open Box, Great)

JL Audio RD400/4 (Open Box, Great) Image 3 — JL Audio RD400/4 (Open Box, Great)

JL Audio RD400/4 (Open Box, Great) Image 4 — JL Audio RD400/4 (Open Box, Great)

JL Audio RD400/4 (Open Box, Great) Image 5 — JL Audio RD400/4 (Open Box, Great)

JL Audio RD400/4 (Open Box, Great)-video

Product videos

Product highlights

• 75 watts x 4 channel @ 4 ohm
• 100 watts x 4 channel @ 2 ohm
• Bridged: 200 watts x 2 channel @ 4 ohm
• Total RMS Power: 400 watts
• Class D 2 ohm Stable 4-Channel Amplifier

Learn more about the ls-rd4004-u8

Product Highlights

• 75 watts x 4 channel @ 4 ohm
• 100 watts x 4 channel @ 2 ohm
• Bridged: 200 watts x 2 channel @ 4 ohm
• Total RMS Power: 400 watts
• Class D 2 ohm Stable 4-Channel Amplifier

Description

Authorized dealer

Item Condition - Open Box, Great:

This product works like new, is well-cared-for and in great condition. May show limited signs of wear or use and may be missing non-essential parts, accessories or original packaging.

4-Channel Class D Full-Range Amplifier

The JL Audio RD400/4 is a sleek, modern 4-channel amplifier from the RD series, designed for "do-it-yourself" audiophiles who want high performance with an easy setup. Using NexD high-speed switching technology, it delivers 400 Watts of total RMS power in a compact, efficient design. The RD400/4 is known for its "all-on-one-side" connection layout and top-mounted controls, making it very installer-friendly.

It features integrated LED clipping indicators for every channel pair. These lights allow you to set the gain (input sensitivity) to the exact point of maximum clean power without needing an oscilloscope. It also includes a durable black powder-coated finish and a top-mounted LED light strip that indicates the amplifier's overall status.

Product Details:

RD Series Class D 2 ohm Stable 4-Channel Amplifier
RMS Power Rating:

4 ohm: 75 watts x 4 channel
2 ohm: 100 watts x 4 channel
Bridged: 200 watts x 2 channel @ 4 ohm

Total power output: 400 watts
Onboard LED clipping indicator rings
1 pair of preamp output
Speaker-level (high-level) inputs (Requires adapter like the JL Audio XD-CLRAIC2-SW)
Signal sensing remote turn-on
NextD switching amplifier technology
Differential-balanced inputs help eliminate noise
Advanced Rollback Protection System prevents thermal shut-down
Input sensitivity:

Low level: 200mV - 2 volts
High level: 800mV - 8 volts

Frequency Response: 12 - 22000 Hz
Total Harmonic Distortion (THD): <1%
Signal to Noise Ratio: >104 dB
Variable high-pass filter: 50 - 500 Hz
Variable low-pass filter: 50 - 500 Hz
Fuse Rating: 40A (AFS, AGU or MaxiFuse)
4 AWG gauge amplifier wiring kit is recommended for installation
Dimensions: 9.78" L x 6.96" W x 2.13" H
Authorized Internet Dealer
2 Year Manufacturer's Warranty
MFR #: RD400/4

Product history:

	JL Audio RD400/4 (Open Box, Great) (newest, current model)
	JL Audio JX400/4D (previous model, replaced by JL Audio RD400/4 (Open Box, Great))
	JL Audio JX360/4 (previous model, replaced by JL Audio JX400/4D)

Frequently Asked Questions (FAQ)

My amplifier won't turn on and the status LED is completely dark. What should I check first?

Check your battery voltage and remote turn-on lead. The RD400/4 requires at least 10V to power up. If the voltage is lower, the amp will stay off. Also, verify that the 40A main fuse near the battery hasn't blown.

How do I use the built-in LED clipping indicators to set my gain without special tools?

Play a 1kHz test tone at 3/4 volume. Turn the "Input Sens." up until the LED turns red, then back it off slightly until it turns off. This ensures maximum clean power without risking speaker damage or distortion.

The status LED is alternating between Red and Blue. What does this mean?

This indicates a continuous "Over Current" condition, often caused by a short circuit in the speaker wiring or a speaker impedance that is too low. Check for loose wire strands touching the vehicle chassis or other terminals.

My factory radio doesn't have a remote turn-on wire. Can I still use this amplifier?

Yes. Set the "Turn-On Mode" switch to "DC" or "Signal." This allows the amp to sense the audio signal from your factory wires and turn on automatically, eliminating the need for a separate 12V remote lead.

Can I bridge this 4-channel amp to power two subwoofers?

Yes. Connect the positive (+) of the sub to the Left+ terminal and the negative (-) to the Right- terminal of each channel pair. Ensure each subwoofer has a minimum impedance of 4 ohms to prevent the amp from entering protection mode.

The amplifier keeps shutting off during high-volume playback. Is it overheating?

If the LED is solid Red, it is in thermal protection. Ensure there is at least 1 inch of clearance above the amp for airflow. Avoid mounting it upside down or in small, unventilated spaces where heat can build up.

I’m hearing a constant ticking or thumping sound from my speakers. How do I fix it?

This usually signals a recurring over-current fault. Inspect your speaker wires for any "pinched" areas where the insulation might be worn, or use a multimeter to ensure your speakers aren't dropping below 2 ohms per channel.

Should I use 8 AWG or 4 AWG wire for this specific 400W model?

For the RD400/4, 4 AWG 100% pure copper wire is highly recommended to prevent voltage drops. While 8 AWG may work for very short runs (under 10ft), 4 AWG ensures the amp gets the current it needs to perform at its full 400W rating.

Specifications & Details

Key Features

Amplifier Key Features

Speaker Level Inputs

Power Specifications - Full Range Channels

RMS Power @ 4 ohms

75 watts x 4 channel

RMS Power @ 2 ohms

100 watts x 4 channel

Bridged RMS Power

200 watts x 2 channel

Amplifier Specifications

Series

RD Series

Amplifier Class

Number of Channels

4-Channel

Total RMS Power Output

400 watts

Maximum Input Gauge Size

4 AWG

Minimum Impedance Unbridged

2 ohm

Minimum Impedance Bridged

4 ohms

Frequency Response

12 - 22000 Hz

THD at Rated RMS Power

<1%

Speaker Level Inputs

Optional (Requires Accessory Adapter)

Preamp Outputs

1 pair

Built-in Crossover

Low-Pass (LP)
High-Pass (HP)

High-Pass Crossover Frequency

50 - 500 Hz

Low-Pass Crossover Frequency

50 - 500 Hz

Signal-to-Noise Ratio

>104 dB

Remote bass/level controller

Fuse Rating

40A x 1

Total Fuse Rating

Strappable

Sonic Certified Amplifier

Yes

Amp Bluetooth Connectivity

Hi-Res Certified

Low-Level Input Sensitivity

200mV - 2 volts

High-Level Input Sensitivity

800mV - 8 volts

What is in the box?

Paperwork

User manual
Warranty/Registration card

WITB: Amplifiers

Amplifier
Adhesive brand badge
Allen wrench

Warranty and Return Policy

Parts Warranty Duration

2 years

Labor Warranty Duration

2 years

Warranty Provider

Manufacturer

Customer Ratings & Reviews

JL Audio RD400/4 (Open Box, Great) thumbnail image

Overall rating distribution

5 star		0%
4 star		0%
3 star		0%
2 star		0%
1 star		0%

Filter by Star Rating

Show only Verified Purchases

By feature average rating

Durability		0
Value		0
Features		0
Design		0
Usability		0

Customer Reviews

Sort by:

Sorry, no reviews found

Add-ons

Belva Nine Function Digital Multimeter

Perfect for any installation and troubleshooting

(7)

$9.99

List price $29.99

Add to cart

Steve Meade Designs IM-SG

Impedance Meter / Signal Generator

(4)

$451.99

List price $461.99

Add to cart

SMD DD-1 Distortion Detector

Set your gains like a Pro, accurately and quickly

(104)

$199.98

List price $209.98

Add to cart

High Quality Element Resistant AGU Fuse Holder

Belva BAGUH2 AGU Fuse Holder

(2)

$4.99

List price $9.99

Add to cart

Modular Linkable ANL Fuse Block

(4)

$14.99

List price $59.99

Add to cart

4 Pack of 80 Amp Nickel-Plated MANL Fuse

Mini-ANL (MANL/AFS) 80A Nickel Plated Fuses

(19)

$3.99

List price $8.99

Add to cart

4 Pack of 100 Amp Nickel-Plated MANL Fuse

Mini-ANL (MANL/AFS) 100A Nickel Plated Fuses

(17)

$3.99

List price $8.99

Add to cart

4 Pack of 150 Amp Nickel-Plated MANL Fuse

Mini-ANL (MANL/AFS) 150A Nickel Plated Fuses

(11)

$3.99

List price $8.99

Add to cart

2 Pack of 100 Amp Nickel-Plated ANL Fuse

ANL 100A Nickel plated for better power transfer

(8)

$3.99

List price $7.99

Add to cart

2 Pack of 200 Amp Nickel-Plated ANL Fuse

Two fuses per order. High quality 200 Amp ANL Fuses

(22)

$3.99

List price $7.99

Add to cart

2 Pack of 300 Amp Nickel-Plated ANL Fuse

Two fuses per order. High quality 300 Amp ANL Fuses

(19)

$3.99

List price $7.99

Add to cart

XIX2025 Strapping RCA

0.25 Meter (0.86 ft) Hyper-Flex RCA cable w/ Serpentine-Cut Nickel Plated Connectors

(21)

$14.99

List price $19.99

Add to cart

RCA Ground Loop Noise Isolator

RCA noise filter

(37)

$11.99

List price $19.00

Add to cart

Your Browsing History

AutoPage XT-90LCD Factory Refurbished

(Factory Refurbished) Replacement/Additional Remote for RS-900LCD (XT-90-LCD)

$59.99

List price $149.99

Welcome to the Team!

JL Audio RD400/4 (Open Box, Great)

We apologize

This item has been discontinued

Product Highlights

Description

4-Channel Class D Full-Range Amplifier

Product Details:

Product history:

Frequently Asked Questions (FAQ)

Specifications & Details

Item Details

Product and How-to Videos

Customer Ratings & Reviews

Customer Reviews

Related Searches

Are you sure you want to clear your garage?

This page was not designed for products.

Account

Shopping help

Company

Everyday heroes

Brand stores

Useful links

Subscribe

Welcome to the Team!

JL Audio RD400/4 (Open Box, Great)

We apologize

This item has been discontinued

Product Highlights

Description

4-Channel Class D Full-Range Amplifier

Product Details:

Product history:

Frequently Asked Questions (FAQ)

Specifications & Details

Item Details

Product and How-to Videos

Customer Ratings & Reviews

Customer Reviews

Related Searches

Are you sure you want to clear your garage?

This page was not designed for products.

Didn't find your car?

Account

Shopping help

Company

Everyday heroes

Brand stores

Useful links