Solid state AB amp?

Thought that class A could be running alone
atmasphere would you explain what that means?

class A means that the output transistors never go into cutoff. In your case the output transistors cutoff at slight more than half of the output waveform.  This is to prevent any distortion at the critical point where the signal goes from positive to negative and vice versa. Class A makes significant heat since the transistors are on all the time; class AB makes a lot less heat and also more power.

The following excellent article by Nelson Pass may be of interest:

https://www.passlabs.com/press/leaving-class

Regards,

-- Al

Thanks guys

On the courious side...What type of amp do you have?

YBA Passion a650