What is an amplifier "gain" control?

What is an amplifier "gain" control and what does it do?An amplifier gain control (input sensitivity) is simply an level-matching device allowing you to match an amplifier's input circuit to a source unit's (or signal processor) output. Ideally gains are set so an amplifier's output "clips" at the same time the source unit "clips".

Gain Controls Are Not Volume Knobs

Contrary to popular belief, the relative position of an amplifier's gain control has absolutely no affect on how much power the amplifier produces. Rather, a gain control determines how far you must turn-up the source unit for the amplifier to make full power.

For High Voltage Sources (2.5 volts or higher)

Higher gain settings allow an amplifier to reach full power at lower volume control settings. This allows the amplifier to be driven into clipping easily and will increase the noise floor of the system, effectively decreasing the dynamic range of the system. This is undesirable.

Lower gain settings require higher volume control settings for the amplifier to reach full power. This will minimize amplifier clipping and decrease the noise floor of the system which will increase the dynamic range of the system. This is an optimum scenario.

For Low Voltage Sources (less than 2.5 volts & typical OEM interfaces)

Higher gain settings will be necessary for the amplifier to reach full power even at higher settings on the volume knob. However, this can increase the noise floor of the system at the expense of dynamic range. This is the best setting, considering the scenario.

Lower gain settings will not allow the amplifier to reach full power and will limit the dynamic range of the system. This may allow the source unit to clip before the amplifier which will be amplified and passed on to the speakers. This is an undesirable scenario.