Radial produces a number of active DI boxes to address various requirements. Selecting some, such as the J33 for a turntable, is easy… while choosing between others can be confusing. This section aims to simplify the process by bringing various active DI boxes together for comparison.
For the most part, active DI boxes are employed on low-output, passive instruments. Like condenser microphones, active DIs tend to have more reach over passive, transformer-based counterparts due to the sensitivity of the input. But as with all amplifiers (an active DI box is in fact an amplifier of sorts) these can distort if the input exceeds the available headroom. More headroom can be achieved by increasing the size, or power generated, by the supply. For instance, a DI box like the JDV employs a 15 volt, 500 milliamp power supply that has incredible headroom, but it needs to be locally powered. This may not be convenient on a live stage. Thus the reason most live engineers prefer to use an active DI box that derives its power from the 48 volt phantom power generated by the mixing console. Phantom power typically generates 48 volts, but only offers 5 to 10 milliamps of current. Innovative powering schemes such as the one employed inside the Radial J48 elevate the headroom to an acceptable level. This enables most instruments to be connected without fear of distortion and is likely the reason the J48 is used on the biggest stages by the biggest acts around the globe.
The J48 and Pro48 are primarily designed for live stages. These employ similar audio signal paths and derive their power from 48V phantom. The Pro48 is basically a trimmed down version that eliminates the stereo to mono merge function, polarity flip, and high pass filter while reducing the size. This enables us to reduce the price to make it more affordable.
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