High-performance vehicular entertainment systems are employing ever-higher-power audio amplifiers, with attendant heat-dissipation requirements. One solution to this problem is the two-state switching amplifier, which reduces thermal loads by 60% in a 12-volt system. Heat and size considerations causing selection of this approach are discussed. A feedback-controlled modulation technique with high loop gain is employed. Power supply rejection and distortion requirements are met. RFI suppression techniques including shielding and spectrum spreading are required. Final performance achievement and limitations are reviewed.