An audio power amplifier comprising: a first and a second amplification unit (10, 12), each amplification unit comprising: a switching voltage amplifier having a command signal input and an amplified signal output, a four-quadrant power supply having a synchronous output rectifier, the power supply providing power to the first and second amplification units, and control electronics providing signal inputs to the first and second amplification units and controlling the first and second amplification units such that the first and second amplification units are operable in each of two modes, the two modes comprising: a first mode, wherein the first amplification unit amplifies a first signal, the second amplification unit amplifies the first signal, and the amplified signal outputs of the first and second amplification units in parallel drive a single terminal of a first common load; and a second mode, wherein the first amplification unit amplifies a first signal, the second amplification unit amplifies an inverse of the first signal, and the amplified signal outputs of the first and second amplification units drive opposite terminals of a common load in a bridge-tied-load configuration. a first and a second amplification unit (10, 12), each amplification unit comprising: a switching voltage amplifier having a command signal input and an amplified signal output, a four-quadrant power supply having a synchronous output rectifier, the power supply providing power to the first and second amplification units, and a switching voltage amplifier having a command signal input and an amplified signal output, a four-quadrant power supply having a synchronous output rectifier, the power supply providing power to the first and second amplification units, and control electronics providing signal inputs to the first and second amplification units and controlling the first and second amplification units such that the first and second amplification units are operable in each of two modes, the two modes comprising: a first mode, wherein the first amplification unit amplifies a first signal, the second amplification unit amplifies the first signal, and the amplified signal outputs of the first and second amplification units in parallel drive a single terminal of a first common load; and a second mode, wherein the first amplification unit amplifies a first signal, the second amplification unit amplifies an inverse of the first signal, and the amplified signal outputs of the first and second amplification units drive opposite terminals of a common load in a bridge-tied-load configuration. a first mode, wherein the first amplification unit amplifies a first signal, the second amplification unit amplifies the first signal, and the amplified signal outputs of the first and second amplification units in parallel drive a single terminal of a first common load; and the first amplification unit amplifies a first signal, the second amplification unit amplifies the first signal, and the amplified signal outputs of the first and second amplification units in parallel drive a single terminal of a first common load; and a second mode, wherein the first amplification unit amplifies a first signal, the second amplification unit amplifies an inverse of the first signal, and the amplified signal outputs of the first and second amplification units drive opposite terminals of a common load in a bridge-tied-load configuration. the first amplification unit amplifies a first signal, the second amplification unit amplifies an inverse of the first signal, and the amplified signal outputs of the first and second amplification units drive opposite terminals of a common load in a bridge-tied-load configuration.