It’s the first stereo direct box manufactured by Radial Engineering Ltd. President Peter Janis says, “Since the Radial J48’s release in 2001, it has become the world’s most popular active direct box for live touring. Today it can be found on stages as diverse as Paul McCartney, Linkin Park, The Who, Madonna and on live recordings by Tommy Emmanuel. What makes the J48 unique is the internal switching power supply. This at once elevates the internal rail voltage for greater headroom and less distortion while providing a method to lift the audio ground without losing phantom power. This produces a wider frequency response, a higher output level over a passive DI and eliminates having to deal with batteries going dead in the middle of a show."
Like all Radial products, the J48 Stereo begins with rugged 14 gauge steel construction and a book-end design that protects sensitive switches and connectors from damage. The internal I-beam ensures the fragile internal PC board will not torque, which could lead to premature ‘cold solder joints’ developing, causing joint failure.
All connectors are made from glass-filled nylon and are insulated from each other. Extra duty nickel-silver contacts are employed that will not tarnish over time.
Inside, a unique power supply converts the 48-volt phantom, increasing the headroom for improved signal handling and lower distortion. This results in a linear frequency response that spans from 10Hz to 40kHz, while being able to handle high-output instruments such as a digital piano or active bass without choking. An additional -15dB pad may be engaged should the need arise.
A built-in high-pass filter gently rolls off low frequencies below 80Hz to clean up mud and excessive resonance. This is augmented with a side access 180° polarity reverse that can be handy when using the J48 Stereo with dual element pickups to either phase align the sources or eliminate hot-spots on stage that can cause feedback.
The other benefit of this unique design is the way the J48 Stereo handles hum and buzz caused by ground loops. The traditional solution to eliminating a ground loop is to lift the audio ground by disconnecting pin-1 at the XLR output. When this is done, the 48-volt phantom DC power from the console is shut off. Other manufacturers solve the problem by introducing a battery into the equation. Unfortunately batteries are inconsistent, and when they begin to drop power, it can severely affect the available voltage and resulting headroom. Instead, the J48 Stereo employs a DC-to-DC converter with a high-frequency transformer that enables the audio ground to be lifted at the power supply. This does not shut off the phantom power and is invisible to the user.
The J48 Stereo is equally suited for stereo instruments or may be used with two different instruments at the same time.