RADIAL J48
Owner's Manual

Using the J48� with batteries The Radial J48� comes set to be used with 48V phantom power, as all mixers, pre-amplifiers and most mixer-amplifiers are equipped with phantom power. Should you encounter a situation where phantom power is not available such as when interfacing with vintage equipment, the J48� may be outfitted with one or two standard 9volt batteries. The conversion may be custom ordered from the factory at a nominal charge or may be field-installed by a competent technician. Contact Radial Engineering for the �Radial J48 Battery Installation Note� should you wish to do this installation yourself. Please note that as Radial Engineering cannot control battery option installation, any damage due to improper soldering or damage to components is not covered under warranty.

Part 6 - FAQ�s or Frequently Asked Questions What is the difference between Active & Passive? This is somewhat similar to comparing dynamic mics to condensers. Active DI�s have a built-in pre-amp that requires power to run while passive DI�s use a transformer to convert the signal. Both �transform� or convert the instrument�s high-impedance output to a low impedance balanced microphone level. This allows long cable runs without adding unwanted noise and will improve the instrument�s sound quality. The J48 uses phantom power to derive its power source. What is phantom power and will it harm my other equipment ? Phantom power is a DC supply that comes from the mixing console on pins 1 and 2 of the XLR connector. It was originally designed to provide power to condenser microphones. It is usually 48 volts and about 5mA. All equipment used in pro-audio is designed to interface when phantom is on. As such, phantom will not harm your equipment. Why do people use active direct boxes? Active direct boxes tend to have more �reach� in that they can capture harmonics and dynamics that can be lost with cheap passive direct boxes with steel core transformers. They are also less prone to loading the instrument, which can change the instrument�s tone. Can you explain loading? Years ago, most bass guitars used regular output pick-ups such as those found on Fender basses. Musicians found that connecting the bass �thru� a direct box and then to their amplifier caused the sound to change. This was caused by the added load of the direct box driving the signal to the mixer (and cable) that could be as far as 200 feet away. This would reduce the level going to the amplifier. Why is loading no longer the main concern? Back in the 1970�s and 1980�s, acoustic guitars did not have the sophisticated pick-ups and built-in pre-amps that are standard today. Electric basses now incorporate high-output pick-ups or have active electronics built in. Keyboards inherently have high output levels. These high output levels are so powerful; loading is no longer the concern. This �fix� has in fact caused a new problem; input distortion or saturation. What makes the Radial J48 so special? Let�s begin by understanding how active DI�s work: Active direct boxes are in fact signal preamplifiers. They boost the instrument�s signal to a manageable level. This means that active direct boxes require power to run. As such, they must either get their power from batteries or phantom power from the console. When using batteries, for the direct box to work properly, the batteries must be fresh. As soon as the power is low, the direct box will distort. This is why engineers hate batteries, and prefer phantom power. But phantom has limitations�. Phantom power was originally developed to supply low-current condenser microphones. Back then, no one ever figured that we would have to manage the high dynamic levels of today�s active instruments. We recently tested a Takamine acoustic guitar with built-in pre-amp and found that when pushed to the max, the output peaked at 7 volts. Considering that most DI�s can barely manage 2 to 3 volts, its no wonder guitars often sound harsh in a PA system. Active basses push the DI�s further due to their powerful low frequency content and keyboards (especially digital pianos) are even more demanding. The Radial J48� was specifically designed to solve this problem by boosting the internal rail voltage so that these instruments would not be able to overload the input. The J48� can be hit with as much as 10 volts and still sound great! This is called headroom. How does Radial increase the rail voltage? We take the input voltage and drive it through a special custom made DC-to-DC transformer. The transformer is coupled to a timing chip that essentially drives the signal the same way as the newer �switch mode� or �digital� power amplifiers work. This brings the current up to a workable level and creates a higher internal rail voltage to handle the dynamics. This allows the signal to stay out of the �danger zone� where square wave distortion may be encountered. Why does the LED not stay on? We felt that every milliwatt of available power should be diverted to provide maximum sound quality since phantom power has very little available current, we felt that lighting up an LED that requires almost as much current as the whole J48� circuit would not be wise. For the most part, direct boxes tend to be placed under keyboard racks or behind amplifiers and you can�t see the light anyway. Why do people use passive direct boxes? Passive direct boxes are often chosen as they are �plug & play� easy to use. When equipped with a high quality transformer, they can handle exceptionally high signal levels without harmonic distortion. A good one like the Radial JDI� will process the signal without introducing artifacts such as phase distortion. This is achieved because the Jensen Transformer we use is extremely well made.

Radial J48 - CableTek Electronics Ltd. © 2002