If you read Ken Kessler's book, there's significant disagreement about Autoformers between the various designers. I think it might've had marginally better relevance in the very early days of Solid State. Now there are even CAR stereo amps that can run .5 ohms all day at negligible distortion. It has to be a cakewalk for well isolated AC.
MAC Autoformers?
Someone is selling a MAC MA6500 Integrated claiming its superiority over the Ma6600 due to the fact that "it does not have the degrading autoformer design found in the MA6600". That is the first time I've heard a claim that the autoformer was a hindrance to better performance; I thought quite the opposite. What do you MAC Maves think?