Hi, everybody
looking at the stereophile power against distortion graph, and james confirming that sst/sst2 amps were biased at about 5% in class a, i would conclude that the knee at about 35watts/ 8 ohms or 10 watts/4 ohms and 6watts /2ohms would represent where the amp would switch in class Ab.
I dont know if James would confirm that.
I could not find any graphs for the cubed version.

Dan