The EQ-31 Equalizer can be used in a variety of setups including: mixing consoles, fixed installation, in the effects loop of an amplifier, and in the tape loop of a home receiver.

In other words, they can only be used for tape recording and playback rather than for a "loop" containing an equalizer (for tone control) or other circuit such as a surround sound processor.

This function works best with types of noises such as a constant occurrence of a ground loop, air conditioner, hum, tape hiss or feedback.