An electronic device utilizing a transformer or amplifier to change the electrical output of an electric instrument (for example, an electric guitar) to the impedance and level usually obtained from a microphone.

A converter that changes an unbalanced, high impedance signal into a balanced, low impedance signal. The most common use is so that a keyboard or tape deck can be plugged into a balanced microphone input. There are two different types of direct boxes--the active and the passive. An active direct box requires power to operate (battery, AC power supply, or phantom power), while a passive direct box does not.

a device that not only physically changes the audio connectors, but it also changes the audio signal from unbalanced to balanced

an impedance matching and signal-balancing device

a type of impedance matching transformer

Used in line to convert a high impedance signal into a low impedance signal.