An audio sound system has a printed circuit board disposed within a compact case. The PCB has a power conversion circuit for generating an operating potential, audio amplifier circuit coupled for receiving the operating potential to amplify an audio signal, and peak voltage and current limiting circuit coupled to the audio amplifier circuit to avoid hard clipping of the audio signal. The power conversion circuit has heat-generating components. A cooling tunnel is mounted over the printed circuit board. A cooling fan is mounted in the compact case adjacent a first opening of the cooling tunnel for directing air flow through a second opening of the cooling tunnel over the PCB. The cooling tunnel has a notch formed in a side of the cooling tunnel for directing air flow over the PCB. The audio amplifier circuit can generate greater than 500 watts into a 4-ohm load.