An amplifier level-setting apparatus is provided for obtaining the maximum power output and highest efficiency allowable for a predetermined level of distortion. According to the invention, a training signal is applied to the input of the amplifier prior to the desired signal. The training signal level is increased while the output distortion is measured. When the output distortion level reaches a predetermined limit, the corresponding training signal input level is saved. The input signal level is then adjusted to this saved level value, thereby resulting in the maximum amplifier output level possible that is still within the distortion limit.