A DI will match a high impedance output to a low impedance input or vice versa.
It also can do the folowing
* Reduce Hum, Buzz, electrostatic interference
* Helps output a stronger signal ( if your instrument wont
put out enoungh, you can Di to the mic preamps on your mixer
* An active DI can give you a cleaner low end and clearer highs
* combine a direct signal through the DI to mixer and a miked signal from the same di to miked amp to mixer.
You don't HAVE to use a DI but there are benefits.
[This message has been edited by Shailat (edited 02-02-2000).]