Vertical Mosfet Amplifier with high THD distortion levels

Hi everyone,

I'm new at solid state amplifier design, I've made this designs based on Bob Cordell's book, but I don't know if they work because my last designs were based in Randy Slone's book and they suffer from quiescent bias instability.
These two class B amplifiers have very poor THD characteristics, the amplifier at the picture named "Amp1" has a THD1 performance of ~0.0027%, and a THD20 of ~0.05% at 60 W of continuous average power, the amplifier at picture named "Amp2" has a THD1 performance of ~0.0025%, and a THD20 of ~0.05%. From 1W to 80 W of continuous average power both amplifiers have 0.01% (THD1 max) and 0.2% (THD20 max) those are very poor characteristics, I don't know what I have made wrong but this values are really terrible, even my stereo HiFi is better with an STK4231II power IC which has got bootstraped VA, and 0.001% THD1 and less than 0.01% THD20. The short circuit protection circuit seems to work very well in simulations, but I don't know if that circuit works in the real world.

Could someone help me solving this problem?

Thank you very much for your attention,
Best regards,
Daniel Almeida

Attached Images

	Amp1.png (62.8 KB)
	Amp2.png (59.9 KB)