The Radial ProD2 is a high-quality, passive stereo direct box with exceptional build-quality and ease of use. The ProD2 is great for active acoustic guitars, bass guitars, electric pianos, synthesizers, drum machines, samplers, DJ mixers, CD, DVD and Mp3 players. Raidal ProD2 at a Glance: Full range passive direct box Custom isolation transformer eliminates noise Really easy to use Built like a tank Passive vs. Active DI The Radial ProD2 and ProDI (mono version) are full range passive direct boxes. Active direct boxes employ electronic circuits to change the impedance from hi-Z to lo-Z and balance the signal. Passive DI's employ a simple passive transformer to do the work. Active DI's require batteries, 48V phantom-power or external power supplies to power their circuits. Passive transformer-equipped direct boxes do not require any power to perform their task. The advantage of a transformer over typical active circuits can be summarized as "a