Abstract: A single mechanically adjustable power-frequency control circuit is disclosed which is especially adaptable for use in controlling an audio electrical signal in an automotive entertainment device such as a radio or a tape player. The circuit comprises a parallel resistor and capacitor which are coupled between the wiper arm of a volume potentiometer and one end of the potentiometer by a power boost slide switch. Actuation of the switch couples the resistor and capacitor in parallel with a portion of the volume potentiometer resistance and thereby selectively emphasizes certain portions of the entire audio frequency spectrum of an audio output signal while simultaneously substantially changing the magnitude of the output signal throughout the entire audio frequency range.