The Radial JDI (part R800 1010 00) is Radial's premium passive direct box, used for three decades on concert tours and in professional studios to connect instruments such as electric bass, acoustic guitar and keyboards to a mixing console or recording interface. At its heart is a Jensen JT-DB-EPC audio transformer, which gives a smooth, warm sound with virtually zero phase deviation and harmonic distortion, handles extreme signal levels without distortion, and - because it passes signal magnetically - blocks stray DC and eliminates hum and buzz from ground loops. Being passive it needs no power. Controls include an input pad, mono merge for stereo keyboards, 180-degree polarity reverse, ground lift and a speaker filter for taking a signal from an amplifier's speaker output. Radial specifies 20 Hz - 20 kHz (+/- 0.2 dB), 135 dB dynamic range and +21 dB maximum input. It uses a 14-gauge steel chassis and outer shell, measuring 127 x 84 x 45.5 mm and weighing 703 g.