Purpose
The Direct Input box takes a high impedance, unbalanced signal and converts it to a low impedance, balanced signal.
This allows the signal to be sent over long cable runs with significantly less signal loss (especially in high frequencies) due to the lowering of the impedance, and greater rejection of interference due to the benefit of common mode rejection in a balanced signal. Furthermore, the lower impedance (around 600 ohms is normal) allows an insignificant load to the input of a mixing console or preamp which is also designed to accept input from low impedance microphones.
Read more about this topic: DI Unit
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