Radial Engineering JDI

This is the first DI box I've been using.
I use 81/85 EMG's on guitar and also an active pickup on bass. The last one has an extremely high output, that no audio interface could handle (from those which I've been using: Avid FastTrack C400 and Focusrite Forte). The JDI handles both in excellent way. There is no any overload or distortion, just saturating when signal comes to it's highest levels. It all sound in a very musical way comparing to direct instrument input on audio interfaces.
I also tried the JDI before Axe FX II input and the bass sounded significantly better this way while the guitar sounded better without it.
The build quality seems to be very good.
'Ground' button is a very useful feature. It helps to cut off the noise while using tube amplifier and other devices like audio interface simultaneously.
I had not opportunity to compere the JDI with other DI boxes but nevertheless I'm very happy with it.

I didn't know I needed this until I bought it. Now I'm runnign through it on almost all my tracks. Radial is a solid company from Canada making some of the most useful gear out there. This JDI is a classic. It's passive, so no power needed, it's built to last years, the sound it produces is warm and smooth, and the features on it are super useful. I just ran it from the output of my pedal board to the guitar amp and it sounds better with it in the chain then without. Also great for recording. Just tried a drum machine through it directly into DAW. Sounds great. I like this DI.

The Radial Engineering JDI has become one of those rare pieces of gear I trust completely, no matter the situation. From studio sessions to live stages, it delivers exactly what you want from a professional DI: transparency, reliability, and zero drama.

The sound is where the JDI truly shines. Thanks to the legendary Jensen transformer, it captures the source with exceptional clarity, tight low end, and a smooth, natural top without any harshness. It handles everything I throw at it—bass, keys, acoustic instruments, even hot line-level signals—without distortion or loss of detail. The passive design also means no power worries and rock-solid consistency.

Build quality is top-tier. Like all Radial gear, it feels indestructible, with thoughtful features such as the ground lift and pad that actually do what they’re supposed to do. This is the kind of box you buy once and use for decades.

In short, the JDI isn’t flashy—it’s just perfect at its job. If you care about sound quality and want a DI you’ll never need to second-guess, this is an easy, lifelong recommendation.

I wouldn't be without this incredibly useful little box. Built like a tank, very transparent sound when used as intended. There is nothing to dislike. If I lost it, I'd replace it in a flash.

It also works well as a conventional DI placed before the amplifier, However, I normally use this in a slightly strange way. I plug the line output of my preamp into the guitar input which drives the tranformer much harder than my weedy passive pickups alone manage. This gets a great recorded sound with a little added "something"

The other feature it has is a *merge* function. This allows the input and the bypass sockets to both be used as inputs. I think it's meant for keyboards and things, however we use it slightly differently. My band shares a rehearsal room with another band. Sometimes we have a jam session with all the musicians who use the room. We plug both bass amps into the DI using the merge function and send the output to one of the inputs on the recording interface. That way whoever is playing the bass gets recorded on the same channel. That way we can both play our own rigs as we please, and both appear on the recording without having to swap cables about.

Incredibly useful, if you don't have one yet, buy one!