Q: What is a direct box anyway?
A: A direct box is an impedance matching and signal-balancing device. DI's convert hi-impedance instrument signals to mic-level balanced lines for interface with pro-audio equipment such as mixing consoles. A good direct box will ensure proper electrical signals are maintained throughout the signal chain and allow long cable runs without added noise. A good DI box is just as important as a good microphone.

Q: Is the Duplex like two Radial JDI's in one box?
A: Yes, and then some. The Duplex uses two of the same Jensen audio transformer found in the JDI. The Duplex adds some i/o options the standard JDI does not have, for each channel. The +4dB balanced XLR line-input is one, the RCA in and thru jacks are another. The only JDI feature missing from the Duplex is the speaker paralell.

Q: What is the difference between a passive and an active DI?
A: Passive direct boxes use a transformer to convert the electrical signals while active direct boxes use an amplifier circuit. Passive boxes have the advantage of providing isolation which can reduce ground hum in systems.

The difference can be thought in terms of dynamic (passive) and condenser (active) microphones. There are good dynamic mics and there are good condenser mics. A good passive direct box depends on the quality of the transformer that is being used. The Radial Duplex, like the award winning JDI, the JD6, JD7 and other fine Radial DI's and splitters use the world's finest audio transformers, Jensen. In fact, Radial is Jensen's biggest customer. There is no better audio transformer for a DI. They sound fabulous! In fact way better than most active direct boxes.

Q: Why do people use active direct boxes?
A: Because a good passive direct box requires a good transformer and these are expensive. The Duplex uses two expensive Jensen Transformers, which.are considered to be the best in the world. Active DI boxes can be made for much less money and will generally sound better than cheap passive boxes made with inferior transformers.

Q: So why not buy an inexpensive active direct box?
A: Active DI's can be good but they can have several disadvantages: First and foremost, active direct boxes require power. This means that they must either run off batteries, phantom power from the console or use a power source like a 'wall-wart' or AC/DC supply. When the power is low, they distort. This means that for the direct box to work well, you must keep the batteries at full charge which is impractical if not impossible. Radial's answer to this dillema is the J48, a phantom powered active DI that uses a unique digital switching power supply that increases the rail voltage so that it never distorts. However, the J48 is not cheap either.

Q: What makes the JDI Duplex better than the rest?
A: A good direct box needs to address several facets to be functional: The sound, the feature-set and construction are all essential parts that make up the whole.

Lets start with the construction. Radial DI's are in fact two boxes in one–a 14-gauge steel outer shell which overlaps and surrounds a 14-guage steel chassis. The the PC board, circuit, transformer and switches are attached with machine screws to the chassis. Feel the heft of a Radial DI and you know you are dealing with quality. The rigid design ensures that there will not be any stress on the mil-spec PC board's solder joints. The outer book-end design provides easy access to the connectors while creating a protective zone for the switches. In the real world of touring, DI boxes are stepped on & abused. Radial DI’s must be able to stand-up to this kind of treatment.

As for feature set, we know of no other DI box that offers as many features. This makes the JDI practical in pretty much any application. Finally, the sound. Check out the specifications and you will find that it is extremely linear from 20Hz to 20kHz, it exhibits almost no distortion in the most rigorous and demanding 20Hz region and with virtually zero-phase distortion throughout the audio bandwidth, what you put in - you get out. Nothing added, nothing changed.