An active di box includes a preamplifier to provide a stronger signal and higher input impedance.
Active di box.
This means that it can handle lower level signals and still sound good.
A di unit direct input is an electronic device typically used in recording studios and in sound reinforcement systems to connect a high output impedance line level unbalanced output signal to a low impedance microphone level balanced input usually via an xlr connector and xlr cable.
These days there are excellent passive and active di boxes.
This type of di was originally designed to provide an extra gain to boost the weak output of some passive single coil pickups but the extra gain is great for driving long cable runs and many modern active dis include advanced signal routing capabilities and higher headroom than their passive counterparts making them an excellent choice for keyboards and instruments with active pickups.
Di boxes which require a power source batteries or phantom power are called active di boxes.
And active dis can be designed to be extremely quiet hi fi and transparent tonally.
Active di boxes active direct boxes are in fact preamplifiers whose primary function is to provide higher input impedance than that of a transformer to drive instruments with low level signals.