CFA Diamond Buffer IPS: Does it Operate in Class B or class A?

There is a persistent assertion by small group of amplifier design practitioners that the diamond buffer input stage of CFA audio amplifier operates in class B (or AB) mode wherein there is a hard ‘handover’ between each half of the diamond buffer input stage as the input signal passes through 0V.  The most recent claim of this kind is in the June 2017 issue of AudioXpress by M. Kiwanuka .

The short article below explores this subject and finds that the claim is wholly incorrect: the front end of a CFA diamond buffer input stage operates well within the class A region for all known audio signals

You can download the article here:-  CFA Front End

Note that this article discusses discrete audio power amplifiers and not IC CFA operational amplifiers which are severely power constrained by design.