The PLINIUS SA-250 Mk IV uses fully balanced, Class-A operation to minimize even order distortions, and reduce crossover distortion and low-level non-linearities. PLINIUS points out that Class-A operation keeps the total current flowing, regardless of demand, while Class-AB varies the current flow with demand, as well as the rail voltage, and this can modulate the power supply. While this is true technically, the best Class-A and Class-AB amplifiers I have heard have been competitive in sound quality; the execution of a given design seems to matter more than the class of operation.