Krells class A plateau biasing network, is not as good as normal high biased or pure class A, to spell it out simply.
1: The network senses the transient and raises the class A automatically to keep the transient in class A.
2:It then keeps that class A level for a few seconds just in case there's another transient following or not, if not it dies back down to Class B
3: The trouble with this system of sensing and raising is that the initial transient that comes along has long gone through to the speakers before the network has had a chance to raised the Class A. So it or the first part of it still in class B
4: So your not hearing the initial transient in class A it's B, and that's why this system will never be as good as normal class A biasing but then you get the continuous heat problem with that, and much larger heat sinks,
I use to water cool my heatsinks jackets, it was the only way for me to get 150w pure class A without the size and weight.
Cheers George