Increase the level of a sound by increasing the amplitude of the frequency. A volume control essentially adjusts gain for an audio/video system. Equalizers use gain to adjust various frequency bands in order to achieve a flat (or reasonably flat) frequency response. Gain is simply the increase of a signal. Amplifiers measure gain in decibels (dB). An amplifier’s gain is derived by dividing the output created by the amplifier by the input given to the amplifier (output over input). The gain of an amplifier describes the amount by which it increases the output of an incoming signal. Typically, higher gain is better.