Vocal and instrument processors

Radial J+4 - Active -10dB to +4dB stereo line driver with transformer isolated inputs

Product Code: RA-J+4

Radial Engineering
$589.00 inc GST
RRP $589.00
*Recommended Retail Price may not be a true representation of the market price
Limited Stock
Increase value Decrease value
Unit of Measure


3 Year
UPC 6 761010 3969 2 Radial Part No. R800 8015

Technical Specifications
Brands Radial Engineering
Product type Splitters
  • Details
  • Downloads

Balanced -10dB to +4dB Signal Driver

The J+4™ is a stereo interface designed to accept unbalanced low output devices such as instruments, computers or mobile devices and boost their signal to a balanced +4dB level for connection to professional audio recording and playback equipment.

  • Stereo preamp boost signals to +4dB balanced line level
  • Increases gain for low output instruments & music players
  • Transformer isolated to eliminate noise caused by ground loops
  • Multiple input connector options to interface with any device

Boost and balance any stereo signal

The J+4 allows you to boost nearly any stereo signal up to a +4dB balanced line level output, which can be sent over long distances without signal loss and connected directly to pro audio equipment such as mixers or recording interfaces. Multiple input connectors are available for integration with a variety of devices, including a stacked set of ¼" jacks for DJ mixers or keyboards, RCAs for CD players and a mini 3.5mm jack for smartphones and tablets. The J+4 delivers exceptional sonic performance, and is able to provide clean gain and eliminate noise by combining the advantages of active signal buffering with transformer isolation.

J+4 Applications

Using the J+4 to boost a stereo signal

Increasing the output from a CD player to a +4dB balanced signal is easy. Just plug into the RCA inputs, adjust the volume level and the J+4 does all the work. Transformer isolation eliminates ground loops for quiet performance every time.

Using the J+4 with your computer

Today, computers and laptops are being used in all types of audio-visual systems. The J+4 makes it easy to interface with a built-in 3.5mm (1/8") TRS jack. Plug in and the J+4 will boost and balance the signal and deliver a professional line level signal.

Using the J+4 with a keyboard

Many keyboards and synthesizers do not have enough output to effectively drive the line level input on a mixer. This is particularly troublesome on older keyboards such as a Rhodes piano. The J+4 makes it easy with built-in ¼" inputs and balanced XLR outs.


  • Peter Janis explains the J+4 Signal Driver


Jimmy Douglass

Justin Timberlake, Rolling Stones, Jay-Z, Led Zeppelin, Foreigner, AC/DC

"The Radial J+4 sounds great, is well built and practical. It seems like somebody actually thought about making a good product and then actually did... Great stuff!"

James Finnerty

City & Colour, Arkells, Lights

"I’ve been using Radial products for over ten years because they sound fantastic and the build quality is top notch. There are very few times during a recording/mix session or a live show when I don’t have a piece of Radial gear in the chain."

Product Documents

No documents available