Ask Jonah: Answering Reader Questions About Direct (DI) Boxes

ProSoundWeb: Passive DIs provide complete signal isolation due to their transformer and can operate without a power source. Active DIs need power (generally either phantom or batteries), can supply gain to the signal, and can have an extremely high input impedance, which is a must for certain sources such as piezos. Both types can handle the important tasks of balancing a signal and better matching (technically “bridging”) the impedance between the source and the mic preamp.