And now for something completely different,

This is an alternative way of arranging a power amplifier, which makes driving the output transistors easy, as they referenced to ground. They drive a separate HT supply which is connected to the speaker. This particular circuit when using mosfet output devices has the interesting characteristic of a high output impedance, and fairly high distortion, or soft clipping, This circuit is to be used in a guitar amplifier, with the aim of getting that kind of sogginess of soft valve HT, and high pentode output impedance, interacting with the variable impedance of the speaker, to give lots of progressive levels of distortion, from none to square wave!

I used MOSFETs for increased ruggedness and distortion, it is biased at about 150mA, and generally seems quite well behaved. If however you remove the feedback from the top driver trany, it all gets very interesting, with a bizarre frequency response with a big resonance....

I intend to try and make a fast conventional amp based on this circuit, using over all feedback to turn it into a voltage output. It has the advantage compared to a conventional amp that the only real voltage swings are in the output devices.