Fleetwood Mac Live

Yes Live

J48 Stereo™ Development

Like the original J48, the J48 Stereo has been designed from the ground up to deliver the most natural tone. As a direct box manufacturer, we do not believe it is our task to alter the sound of your prized '1962 Fender Jazz Bass'. Instead, we prefer to retain and transfer the true character of the instrument to the mixing console without adding distortion or artifact of any kind. This enables the engineer to make the decisions. Radial's design philosophy has gained a tremendous following from many of the world's most demanding artists, engineers and producers.

Using only 48V phantom power, the J48 Stereo is an active direct box that produces an exceptionally linear response that extends from 10Hz up to well above 40kHz. Low distortion of all types is achieved via a unique internal switching power supply that raises the internal operating rail voltage for added headroom and improved signal handling. The results are truly amazing. The J48 Stereo delivers an ideal even-order harmonic cascade and a sonic performance that outperforms other DIs costing several hundreds more.

Going Stereo

For years, folks have asked us to make a stereo version of the J48. But each time they asked, we - in return - asked why do you need it? It seemed to us that for the most part, stereo sources such as keyboards or computer laptops are active, and a passive direct box like the Radial Duplex is perfectly suited for these. But as we delved further into the subject, we discovered that there are several good reasons for a high performance active stereo direct box. These concepts came from in-depth discussion with the stage technicians that manage the equipment for Yes, Fleetwood Mac and The Doobie Brothers who spend their days trouble-shooting.

We discovered that in certain circumstances, passive direct boxes do not deliver enough gain for some of the older vintage synthesizers or electric pianos. Pressure also came from multi-instrumentalists that need several active channels in as small of a package as possible. Techs often found themselves taping two or more J48s together in order to keep 'stereo signal paths' organized. With the cost of airline baggage skyrocketing, delivering a compact stereo solution has tremendous appeal. So we finally succumbed to the pressure and launched the J48 Stereo.

The Feature Set

Establishing the feature set was easy. We already had the circuit from the J48. It was really a matter of trying to pack everything into the same size enclosure. With two inputs, two thru-puts were required. We then incorporated the same high-pass filter as the J48 which both reduces low frequency rumble and feedback, while also cleaning up the mud by eliminating sub-sonics from the mix. This is particularly important with acoustic instruments as they are often turned down due to the problems they can introduce if not kept in check.

Staying on the subject of feedback, we also felt compelled to add a 180º polarity reverse switch on one channel. In the early days, a 'phase reverse' was primarily used to compensate for pre-AES standard gear where pins 2 and 3 would be inconsistent. Reversing these pins brought old gear into phase with newer gear – assuring proper phase coherence throughout. However, in recent years, engineers have come to appreciate the benefit of reversing the phase of a signal when fighting feedback on stage. When two signals combine – say from a wedge monitor and the PA system – these can cause frequency bumps which can accentuate feedback depending on where the artist is standing on stage. Reversing the polarity can actually move the feedback problem out of the way, without having to revert to dramatic EQ'ing in order to carve out problem frequencies.

Reversing the polarity on one side of a stereo source can also lead to interesting effects such as a wider stereo field. This trick is often used when combining a mic with a direct source.

Power Management

We then added a prerequisite ground lift switch. A ground lift switch is used to disconnect the audio ground between the send and receive pieces of equipment. This helps eliminate buzz and hum caused by so-called ground loops that are created when the electrical ground and audio ground are at odds. With a passive direct box, lifting the ground is easy: you merely lift pin-1 at the XLR. But with an active direct box, when you lift pin-1, you also disconnect the 48V phantom power.

As a workaround, most direct box manufacturers employ a 9V battery as a substitute for the 48 volts. Although this does work, it introduces a host of other concerns. First, when the battery power runs low, distortion increases ten-fold. Second, if the battery goes dead half-way through a performance, the artist looks like an idiot on stage and the stage tech is now looking for a new job. One should also consider the environmental side of using batteries and throwing them out. Not really a great option.

The J48 Stereo employs the same powering system as the original J48. This features an internal switching supply that converts the 48 volt phantom DC current to AC and back, passing the supply current through a transformer, which essentially isolates the input from the output. This eliminates a direct power connection and enables us to lift the ground inside the power supply using a clever circuit– effectively disconnecting the audio ground. You get the benefit of an active circuit without the hum, buzz or dead battery!

Today, the Radial J48 holds the position of the most specified direct box in professional touring. There is no doubt that the J48 Stereo will be a welcome addition in years to come.