Radial J48 Active Direct Box Review

Radial J48 top
Radial J48 top

The Radial J48 48V Phantom Power Active Direct Box is a popular mid-priced DI that is useful both in the studio and onstage. In the studio it can be used to create a more faithful reproduction of your instrument’s tone. Onstage the box allows you to plug directly into the soundboard and retain the natural tone of your instrument. It also prevents input distortion from high output instruments. The DI can also be used to improve sonic results when used as part of a re-amping set-up. It can be used with acoustic, electric and bass guitars, as well as keyboards. For my purposes I bought it primarily for use in the studio on guitars and basses, and have been very pleased with the results.

The base of the Radial J48 is covered to provide electrical isolation.
The base of the Radial J48 is covered to provide electrical isolation.

Rock-solid build

The build quality of the Radial J48 is outstanding. The 14-gauge steel chassis is nigh indestructible and all the controls are fully recessed. Some of the functions are activated by plastic controls, but with the recessed design you’d have to give it a hard direct hit to do any damage. I would feel 100 per cent confident in taking it on the road. The base of the chassis has a covering which holds the box firmly in place. The covering also provides mechanical and electrical isolation.

The design is fairly simple but there are some useful functions packed in. The J48 has 1/4″ input and thru jacks along with an XLR output. The thru jack can be used to send the instrument’s signal to your amplifier. The unit requires phantom power to operate and there is an indicator which lights up briefly upon being powered up.

Useful features for stage and studio

Five switches are present on the DI: Pad, ground, low cut, 180º polarity reverse and merge. The -15dB input pad can be used to accommodate high output instruments while the ground lift reduces hum and buzz produced by ground loops. The 80Hz high-pass filter (low cut) can be engaged to tame instruments with an unwanted heavy bass response, such as some acoustic guitars. The 180º polarity reverse can be engaged to rein in onstage feedback. The merge function mixes left-right signals (via the input and thru) to mono (to the XLR output) without phase cancellation.

The Radial J48 has 1/4" input and thru jacks.
The Radial J48 has 1/4″ input and thru jacks.

Performance in the studio

Running my Fender acoustic directly through my audio interface, the guitar tone left much to be desired. It sounded thin, buzzy and artificial. Running the same guitar through the Radial J48 first produced a much more satisfactory sound. It sounded like a guitar should sound, rather than a poor imitation of one. The overall tone was fuller, the bass was thicker and unwanted buzzing sounds were removed. Whether I was playing open chords, single note melodies or power chords, the guitar sounded better when run through the J48.

Clean electric guitars produced similar results through the J48, with a fuller, more authentic tone being produced. When paired with amp-simulation software for creating distorted electric guitar, the J48 did a great job too. Without the DI, my distorted tones sounded thin and scratchy, despite a fair bit of tinkering within the software. The J48 instantly improved my results, producing a tighter and more focused low end. It also helped remove unwanted artefacts.

The Radial J48 viewed from another angle.
The Radial J48 viewed from another angle.

Run directly through my interface, my bass sounded somewhat thin and hollow. The bass frequencies were not very pronounced. Through the Radial J48, the low end was thicker and more authentic. The overall tone was closer to the tone of the bass when played through an amp. Playing in different places across the neck sounded consistently better. Certain types of playing made the bass sound quacky without the use of the J48, while using the J48 helped alleviate the issue.

The only negative I can think of is that the box doesn’t have an option for 9V battery power. However the battery-free design means that the J48 has a higher headroom than DI boxes that are compromised by allowing battery power. This means that the J48 can be used on guitars with active pick-ups. So whether the lack of battery power is a negative is up to personal preference. It’s not an issue for me personally and I’d much rather have the greater headroom. The unit can be modded to allow battery-powered operation if that is a sticking point though.

Thumbs up for the Radial J48

I’m going to be recording an EP soon and I intend to use the J48 extensively throughout the recording process. Every instrument I ran through it sounded significantly better. Dollar-for-dollar it’s probably one of the best acquisitions I’ve made for my studio set-up. The build quality and included features make it perfect for a stage set-up too. Radial have a variety of different DI models at different price points with the Radial JDI being the most popular passive DI. For me, the J48 hits a very good mix of high quality and relative affordability. I wouldn’t hesitate to recommend it to friends in the market for a DI box.

United States: Amazon, Musicansfriend, bhphotovideo
United Kingdom: Gearsformusic
International: Ebay, Thomann, Guitarcenter

When you need a road-worthy, dependable, clean, interference resistant direct box, the Radial J48 hits the mark in every way.
Excellent DI for both recording and live.
Very easy to use and set up. First time I gigged with it, I received many compliments on the tone.
It makes the signal sound like what you thought it should sound like. Clean, open and lush.

    Tech Specs

  • Type Active DI
  • Channels 1
  • Inputs 1 x 1/4″
  • Outputs 1 x XLR, 1 x 1/4″ thru
  • Height 2″
  • Depth 5″
  • Width 3.3″
  • Weight 1.55 lbs.
  • Manufacturer Part Number R800 3001

Radial listing
Radial YouTube introduction

The Radial J48 offers excellent value for money and produces great results both on stage and in the studio. The design is straightforward and the built quality is top-notch.
Sound quality97
Worth it?98
Reader Rating5 Votes92
Outstanding build quality
Several useful features included
Produces great results in the studio
Convenient and sounds good live
Easy to set up and use
No option for battery power
More Stories
Vivo x5 Max, a phone built for audiophiles