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Radial JDI Passive Direct Box

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The Radial JDI is a passive direct box designed to handle extreme signal levels without distortion of any kind. Unlike an active DI that is limited by the buffering amplifier's rail voltage, the JDI employs a Jensen audio transformer as the engine. Jensen transformers are legendary in their ability to gracefully handle transients while delivering a smooth, warm sounding Bessel curve, reminiscent of the finest vintage gear. Ruler flat from 10Hz to 40kHz and with virtually zero phase deviation, the JDI delivers the natural, pure sound of the instrument without artifact.
The 100% passive circuitry inside the JDI is incredibly efficient. The transformer performs both high-to-low impedance conversion and signal balancing at the same time with minimal loading and does so without any power whatsoever. The transformer also introduces a magnetic bridge that passes signal while rejecting stray DC voltage. This makes the JDI particularly adept at eliminating hum and buzz caused by ground loops.

Features include input and throughput -+" connectors, -15dB input pad, ground lift, and 180 degree polarity reverse to help phase align the instrument with the PA. A secondary circuit is added for direct interfacing with high output devices such as guitar or bass amp loudspeakers. And a unique merge function allows stereo sources such as keyboards to be summed mono, saving valuable input channels.

Built tough to handle the abuse of live touring, the JDI features a 14-gauge welded steel I-beam inner frame and a unique book-end outer shell. The innovative design eliminates stress on the PCB, reducing opportunity for solder joints to go 'cold' while the outer shell creates a protective zone around the switches and connectors. The steel casing resists noise-causing electromagnetic pollution and the transformer's sensitive inner workings are further protected from magnetic fields with a mu-metal can. This ensures the signal transfer is quiet and free from hum.

These combined features have made the Radial JDI the most popular passive direct box in professional touring and an excellent choice for instrument interface in the studio!

  • Application 1 - typical DI stage/studio setup: The JDI is used primarily to get an instrument signal to a mixing desk or PA system without coloring the natural sound in any way.
  • In this setup:
  • - A 5-string active bass connects to the JDI's ¼" input jack
  • - The JDI's ¼" thru jack is connected to the amplifier input
  • - The JDI's XLR output connects to oe of the mixing console mic inputs
  • - The JDI's 180° polarity and ground lift switches are set as required
  • Application 2 - JDI with acoustic guitar: Here the JDI is used to provide the front-of-house PA system with an balanced unaltered clean guitar signal for final EQ and effects processing.
  • - An acoustic guitar pickup connects to the JDI's ¼" input jack
  • - The JDI's ¼" thru jack is connected to the guitar amplifier input
  • - The JDI's XLR output connects to one of the mixing console mic inputs
  • - Polarity and ground lift switches are set as required
  • Application 3 - JDI with a stereo keyboard:
  • With keyboards or other stereo instruments, the JDI's 'merge' function can be employed by sending one channel to to the 'thru' jack. With the 'merge' switch engaged, the two channels are summed to mono and sent to the XLR output.
  • - The left channel is sent to the JDI's ¼" input jack
  • - The right channel is sent to the JDI's ¼" thru jack
  • - The JDI's 'merge' button is engaged summing both channels to mono



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