There are two types of di boxes and like most electronics this boils down to active and passive and which to get is pretty important and depends on your bass circuitry.
Active di box for bass.
What is a di box.
An active di contains a pre amp which boosts your instruments gain a little before the signal is sent.
On top of all this this active di box can be powered with phantom power a separate adapter or a 9v battery.
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Although many modern dis are far more.
Born out of necessity in studios such as motown and united sound systems to accommodate the electric instruments emerging in the 1960s direct boxes also known as dis which stands for direct inject began as a way to resolve a basic impedance mismatch between electrodynamic guitar pickups and sensitive studio electronics.
So for the next bunch of years everything worked just ducky until one day some guy decided to put a 9 volt battery inside the bass and buffer the signal.