Review: Radial JDI Stereo

It’s been nearly two decades since the release of the original JDI, and now Radial has introduced a Stereo version to its offering. Alistair McGhee quite literally lifts the lid on the new addition to see what it has in store for users.

I liked the transformers so much, I bought the company” – what Victor Kiam might have said had he been in pro-audio instead of personal grooming. And if, of course, he had bought Jensen transformers instead of Remington shavers, Jensen transformers being just about the biggest name in audio iron.

Of course, Victor was a man who loved the bright lights and probably didn’t care much for the nitty gritty of winding pro-audio gold, but he always, always looked fine in that suit on camera. Though I must confess I’ve always been a Philishave kind of guy myself. But in any case if you were thinking of doing a Victor on Jensen then I’m afraid you’ve missed the boat, because Radial Engineering, one of Jensen’s major customers, liked the transformers so much, they have bought the California-based company to ?cement what has already been a very successful partnership.

And to celebrate I’ve got the new Radial JDI Stereo passive DI to review. A significant clue to the purchase of Jensen can be found in the promotional material for the JDI – “The magic comes from the amazing Jensen transformers inside”. And we’d all agree that without first-class transformers your DI is going to struggle for magic. But does the stereo JDI have twice as much magic as the well-established JDI mono? Or does is lose 6dB of magic when mono summed?

I began by taking the lid off the JDI Stereo to compare innards with my standard JDI and true enough both Radials feature exactly the same Jensen JT-DB-EPC transformers, the only difference being the stereo model has two of them. Last time I looked at DIs I got some fantastic feedback from Bill Whitlock of Jensen and there’s no doubt that the Jensen product is carefully designed and engineered to be at the top of the transformer tree.

So you might think ‘an open and shut case I should buy the stereo model and get two JDIs in one box, cheaper than buying separate and saving on space and weight.’ However, there are some trivial and none trivial differences between the stereo model and the older mono JDI. A trivial but interesting difference is that an internal case redesign means my old JDI single channel is heavier than the new JDI Stereo – the internal case of the JDI Stereo being trimmed back slightly. Having said that, in a pro-audio bar room brawl I still reckon a JDI and an SM58 will be all you need to fight your way out. The “book” format of Radial’s products offers superb mechanical strength and protection for your connectors and switches.

Old versus new

Which brings me to some of the non-trivial differences between the old and the new. On the Stereo you get a ground lift that applies to both channels and -15dB pads on each individual channel. The sharp-eyed will have noticed that on the single-channel version of the JDI you get a bit more switchery.

First, a phase reverse – now of course you have one of those on the desk but it’s still handy to have the option right to hand. Secondly, the JDI classic has a Merge function, which is pretty cool. Using Merge turns the JDI’s “Thru” connector into another input and the DI then merges the two inputs into a mono output at the XLR. Tidy, as we say. And finally a “Speaker” option that allows you to take a feed to the DI from a speaker cabinet. Careful with that one!

A final consideration is that the JDI Stereo, unlike the JDI Duplex, has both circuits mounted on a common PCB. Sharing earths in this context means you will not get quite the isolation from crosstalk that is achievable with completely separate circuitry. I can’t see any info on the Radial site but shoving a bit of 1k tone into the left input and using the back of a fag packet, I reckon you see a smidgen of 1k on the right output, about 72dB down. The phase performance of Radial DIs has always been notable but it never hurts to be reminded of that. Using Visual Analyzer I measured just over two degrees of shift at 20Hz. Outstanding phase linearity.

The engineering quality is borne out in the listening. I’ve seen it said that the Radials ‘warm up’ the sound – I’ve always found accuracy to be their strongest suit. The frequency response is ruler flat and as we’ve seen the phase performance exemplary. And you can hear that side by side with lesser products. In these days of higher outputs on active instruments the huge headroom of transformers in passive DIs is also a plus. I’ve been using Radial DIs for quite a few years now and never have I ever thought I was getting anything less than the best from a Radial DI. And it is with some satisfaction that I’ve seen not a few of my former BBC colleagues become fans of the Canadian company’s gear.

Quite simply, Radial DIs and Jensen transformers are DIs done right.

Alistair McGhee began audio life in Hi-Fi before joining the BBC as an audio engineer. After 10 years in radio and TV, he moved to production. When BBC Choice started, he pioneered personal digital production in television. Most recently, Alistair was assistant editor, BBC Radio Wales and has been helping the UN with broadcast operations in Juba.