Dean Jensen, 1974

Deane Jensen, 1974

Solved: transformer isolation eliminates DC noise

Transformer isolation

Inside the JDI-Duplex

Inside the JDI-Duplex

Chick Corea

Chick Corea

JDI Duplex™ Development

The Radial JDI Duplex™ is a fourth generation direct box that closely follows the original signal path set out by Deane Jensen, one of the true pioneers of audio transformers and the man responsible for advancing the science. Deane's original direct box design has been improved upon by adding an RF suppression network to eliminate noise and provide significantly greater connectivity.

The advantages of transformer isolation still remain: transformers have a truly unique advantage in electrical circuit design whereby they 'transform' an electrical signal into a magnetic field and then back again. This creates a magnetic bridge that allows the audio signal to pass while blocking stray DC noise. Even though this invention is over 100 years old, transformers continue to provide the very best form of isolation short of a fiber-optic strand. What Deane Jensen did was develop a method of constructing transformers that would pass audio with less distortion and phase shift at all frequencies and at all signal levels.

Radial continues this tradition with a commitment to employing the very highest quality transformers possible. This includes batch testing core materials for permeability, hand-stacking the laminates for optimal signal flow, the use of numerically controlled digital winders that precisely wind and scatter the ultra-fine coated strands, the use of internal Faraday shields to reduce noise, advanced potting techniques to secure the transformer against damage, and the use of a MuMETAL® outer can to prevent stray electro-magnetic fields from polluting the sensitive signal path. The Radial Duplex employs two 'made in the USA' transformers to provide impedance matching and perform the task of balancing the signal. This new generation stereo DI breaks tradition by incorporating greater connectivity for today's ever changing multi-media world.

Designed for quiet connectivity

Today, concerts are no longer limited to music. Computer generated video synchronized to lights and music with click tracks present the system designer with unlimited options and the AV technician with constant challenges to meet the demands. This new generation Duplex is true to its 'Swiss Army moniker' as it delivers greater connectivity to ease the installation process while eliminating hum & buzz caused by ground loops and troublesome noise from less than ideal consumer electronic sources.

In addition to the usual ¼" instrument inputs and outputs, the Duplex adds RCA connectors for consumer electronics such as CD or video players, a 3.5mm mini stereo jack for tablets and laptop computers, and a balanced +4dB XLR input on each channel to interface professional studio and live touring gear. To simplify setups, stereo sources can be mixed to mono by introducing a resistive summing mixer into the signal path. This opens the door to greater connectivity options while reducing the channel count. The Duplex is truly a 'one box does it all' solution that is sure to be an audio tech's dream come true!

Hitting hard without fear of overload

For the studio, the Duplex brings more than improved connectivity to bear: the natural Bessel curve with even-order cascading harmonics warms up the sound of even the most stark and rigid digital source. It also has the uncanny ability of handling extreme signals without the harsh odd-order harmonic distortion that is typical when active circuits are driven to overload. This is because transformers do not so much distort, they saturate. In other words, the Duplex will transition from clean to distortion in a gradual fashion. The sonic result is a natural compression that is often referred to as 'vintage' sounding. This makes the Duplex a perfect partner for digital pianos, samplers and ultra-dynamic sources that often overload the front end of most digital recording systems.

Treading softly with utmost attention to detail

Just because the Duplex is able to withstand extreme dynamics, this does not mean it is incapable of capturing the subtleties. Careful attention at every stage of construction ensures the Duplex will deliver the sound of the instrument without artifact or coloration. And with a high 130,000 ohm input impedance, the Duplex will not load the pickup and cause the signal to degrade when split between the stage amp and the audio system.

The Duplex has become a favorite for many acclaimed artists including Chick Corea, Tony Levin, Chuck Leavell, and engineers like Robert Scovill.