A method of adjusting a loudness of an audio signal may include receiving an electronic audio signal and using one or more processors to process at least one channel of the audio signal to determine a loudness of a portion of the audio signal. The power supply being in communication with the battery and the light emitting diodes such that a constant voltage or constant current is supplied to the light emitting diodes as the battery discharges and the battery voltage falls below the output voltage. An input control arm protrudes downwardly from and forward of the outer longitudinal linkage bar, and a connector arm protrudes laterally inwardly from an inner end of the front lateral linkage bar, inwardly of the inner longitudinal linkage bar; the inner lateral end of the connector arm is pivotably connected to a forward end of the micro-manipulator input member.