Proel D10A Active Direct Injection BoxDI Boxes perform several important functions: they are designed for impedance matching and balancing the signal of a guitar, a keyboard or any line level output source, and for injecting directly the signal with very long connections to the XLR microphone inputs of a mixing console. D10A is an active direct box with transformer and requires the phantom power to work. The advantage of a transformer is the possibility to avoid any electrical connection