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When we set out to develop the Radial J48, the single most important goal was increasing the headroom without compromising sound quality. To this end, every possible effort was made to deploy the limited energy resources of phantom power and apply them to the audio signal path.

To begin, phantom power is converted using a super-efficient digital switch-mode power supply that steps up the internal rail voltage to an impressive 9 Volts. This allows you to hit the J48 with plenty of level without choking! To further increase headroom, all non-essential devices such a power-hungry LEDs are turned off when the J48 is in use. Open up the Radial J48 and you will see over-sized capacitors that provide ample current storage to assure clean, unobstructed power for the signal. With added headroom comes improved performance in all areas: Less than half the phase distortion of competing DIs, significantly lower harmonic distortion and single-digit inter-modulation distortion are all realized. Paying attention to these basic details has the net result of better sound.

But great sound is not the only innovation: The Radial J48 introduces several new functions that improve functionality and open the doors for greater creativity. The input panel features the usual ¼” instrument input and thru-put connections. An innovative Merge function converts the thru-put into a second input to sum stereo sources to mono such as stereo keyboards or CD players when mixer input channels may be of short supply. A -15dB pad may also be inserted when confronted with abnormally high signals.

To reduce low-end rumble and run away acoustic resonance, a low-cut 80Hz high-pass filter is provided. As with any power system, whether it is acoustic or electrical in nature, bass always contains significantly more ‘RMS power’ than high frequencies. This is why low-frequency drivers require anywhere from 10 to 20 times more power in PA system designs than high-frequency tweeters. By gently removing unnecessary lows, the J48’s dynamic handling is increased by a full 3dB or twice the power handling. This innovative feature both reduces mud and increases headroom at the same time! The filter switch also performs a second function. Depressing the switch will momentarily illuminate the front panel LED to advise if 48V phantom power is present. The LED does not stay illuminated as it would draw energy away from the audio circuit and reduce headroom.

The output panel contains the balanced 3-pin XLR male, wired ‘pin-2 hot’ following the AES standard along with a 180º polarity reverse switch that toggles pin-2 to pin-3 ‘hot’. This allows the engineer to match older equipment and adds a dimension of creative freedom. Reversing the polarity (inverting the phase) can also be helpful on stages with acoustic instruments. The interaction between the wedge monitor, PA system and instrument amplifier can create hotspots as low-frequency modes amplify each other. By inverting the phase the hotspot can often be eliminated, resulting in less resonant feedback. The pin-1 ground lift switch disconnects the XLR at the output, thus grounding the J48 to the input side and eliminating ground loops.

As with all Radial direct boxes, the Radial J48 is designed for use in abusive environments such as on fast-paced stages of concert touring. An innovative book-end design provides a protective zone around the switches and connectors that makes it practically impossible to damage these components. The heavy steel construction is particularly adept at shielding the internal electronics from outside noise. The inner skeletal frame features a unique 14-gauge welded I-beam construction that makes it impossible to torque the PC board. Stress on the printed circuit board can introduce intermittent solder joints, which by all accounts is the primary cause of direct box failure.

An innovative full-bottom no-slip rubberized pad works double duty by assuring the J48 won’t slip and slide around when placed on an amplifier. The protective pad also ads an element of electrical mechanical shock resistance by providing a physical shield from guitar amp handles that are often directly coupled to the amp chassis.