What are the advantages of class-AB amplifiers?

Class-AB amplifiers give you the lower cost and cooler operation of class-B, with some of the finesse and fidelity of class-A.

You get the best of both worlds here, up to a point. Class-B amplifiers are no good for audio because of non-linearities around the crossover point, known as crossover distortion. They cost much less to make though and, offer more power and lower weight than an equivalent power class-A design. Class-A amplifiers have no crossover distortion but are heavy and run hot, for even modest power outputs.

Class-AB amplifiers operate in class-A up to a few Watts, and then revert to class-B to fill out the rest of the power envelope. At lower levels, you’ll have the sweet sound of class-A. For dynamic swings and higher volumes, you’ll have the punch of class-B. Obviously, the more class-A power on hand, the better the sound, other things being equal.

Almost all consumer-grade amplifiers are class-AB, because of the cost-effective nature inherent in this design topology. That being said, most consumer amplifiers run very little class-A power, sometimes only a couple of Watts, or less!