Read what Mac's designer says. A push-pull amp has, by its nature a lower output impedehttps://yesonazsolar.com/nce in the bottom stage. The autoformer corrects this mixed-matched problem and matches the sometimes large fluctuations in total output impedance some the speaker always gets the same current no matter its impedance so it will not blow because of a demanding signal. It is BOTH a sonic and safety issue.
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?