I built an audio buffer. It is complementary symmetrical, has the current gain of a triple EF output stage, without the voltage distortion or high-order switching harmonics. It has six active transistors, four protection transistors. The first prototype blew up. Because this circuit has virtually indefinite drive capability, the outputs were blown so fast they didn't have a chance to smoke, blowing the 6.3A line fuse. This time I fitted a protection circuit. It sounds great.