Gain is a quantity in decibels (dB) that is added to the intrinsic decibel level of the audio signal--that is, the level of the signal before it is altered by the gain control. A positive gain amplifies (boosts) the signal's volume, and a negative gain attenuates(cuts)it. The gain setting defaults to a value of 0.0 dB, meaning the signal's loudness is unaffected. Note that gain measures dB, not amplitude. The relationship between a gain in decibels and the corresponding linear amplitude multiplier is:

linearScalar = pow(10.0, gainDB/20.0)

The FloatControl class has methods to impose a maximum and minimum allowable value for gain. However, because an audio signal might already be at a high amplitude, the maximum setting does not guarantee that the signal will be undistorted when the gain is applied to it (unless the maximum is zero or negative). To avoid numeric overflow from excessively large gain settings, a gain control can implement clipping, meaning that the signal's amplitude will be limited to the maximum value representable by its audio format, instead of wrapping around.

These comments apply to gain controls in general, not just master gain controls. A line can have more than one gain control. For example, a mixer (which is itself a line) might have a master gain control, an auxiliary return control, a reverb return control, and, on each of its source lines, an individual aux send and reverb send.