An old App note for audio enthusiast from Analog Devices about Current-Feedback approach in audio power amps its designs and history by Mark Alexander. Link here (PDF)
The subject of power amplifier design is one of those controversial areas of audio engineering that continues to receive intense debate, despite the fact that there are literally dozens of papers available to guide the designer. Many different topologies have evolved from the relatively modest beginnings of solid state power amplifier design in the late 1950s and early 1960s, and this has lead to a few very unique and original designs. A substantial number of transistorized amplifiers that were built during these early years were little more than redesigns of vacuum tube circuits with lower voltage supply rails, and often had performance levels that left a great deal to be desired. Quite a few of them sounded significantly worse than their thermionic predecessors. The “real revolution” in audio power amplifier design actually occured during the 1970s and introduced such new innovations as direct coupling, fully complementary design, pseudo Class A biasing, and current dumping.