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https://www.enjoythemusic.com/superioraudio/equipment/0826/Esoteric_S_05XE_Class_A_Stereo_Monoblock_Amplifier_Review.htm

The Esoteric S-05XE is a power amplifier rated at 30 Watts per channel into 8 Ohms. Its most noteworthy feature is its Class A circuit design. For those not familiar with solid-state Class A power amplifiers, the main difference between them and more conventional Class AB or D amps is that a Class A amplifier’s transistors are biased to always remain fully “on”. In most other amplifier types, they turn on and off in response to the musical signal. Class A power amps offer sonic benefits because their transistors operate continuously. This eliminates crossover distortion and helps reproduce sound without the harsh frequency peaks, unnatural edginess, or listening fatigue sometimes associated with more customary Class AB or Class D amplifiers. But as some say, there is no such thing as a free lunch. Because fully active Class A devices are always in the “on” state, these power amps operate at only 20% to 25% efficiency. As a result, they typically run very hot because unused energy is dissipated as heat.