"A class A amplifier has by definition 0 db of headroom."
I'm not so sure of that. Class A is often designed with bias current in order of 150% o max output current to guarantee that transistors won't become nonlinear - hence some headroom might be possible.
I'm not so sure of that. Class A is often designed with bias current in order of 150% o max output current to guarantee that transistors won't become nonlinear - hence some headroom might be possible.