Audio Gurus and all,

Hello again, I made a new revision of my first schematic I have added BJT drivers and reconfigure the VAS CCS in order to feed more current to bias VBE but I'm kind of stuck here...would any of you be so kind in helping me straighten out those curves in the graph? (attached below) As I am a hobbyist perhaps my approach is leading me into circles and missing the right spot to where the error/fault lies.

Data taken from simulation software follows,

Amplitude 250mv

Freq. 20Khz

Harmonic Distortion = 9.5704%

DC offset 3.3mv

Output resistor IRFP240 = 3.64mv

IRFP9240 = 3.53mv

Gate voltage IRFP240 = 3.77v

IRFP9240 = 2.46v

Bias trimpot set at 50%

What I have done so far,

added small resistor at the bases of drivers, no effect

added small value cap between base/collector also, no effect

added small value lead cap connected to base of driver, THD rises

100pf at C12 minimal reduction on THD figure.

This is my first attempt working with MosFet based amplifier and I wanted to do it right the first time. Pointers, advise, recommendations is very much welcome and I will do my research.

Kind Regards!

Albert

@Valery, I did adapt your bias spreader scheme but it looks though that it works the same as with my schematic.(or my implementation could be wrong)