MAC Autoformers?

The autoformers restricts the ability to vary power with impedance / sensitivity and ergo compromises frequency linearity with the vast majority of loudspeakers.
There’s a good reason so many other amps don’t use them.

 I’ll hazard a guess that Mac chose to use autoformers way back when early transistors weren’t as reliable. They chose to use the autoformers to increase reliability (which way back was part of Mac’s separation from much of the competition) and because it fit in with design parameters that they were already comfortable with. Most speakers of that era were thought to be used with tubes by the end user, that might not have realized the compromises that the autoformers introduced. IMHO, there is no good reason to use autoformers with the rugged transistors that have been available for almost 5 decades since then.

….Because despite the never ending reports over the last 50 years of the amps not using autoformers  overheating, destroying speakers and causing fires, consumers keep buying them in such vast quantities as to provide a huge and continuing to grow sample size for such inspection?

^No, usually. Typical loudspeakers vary sensitivity with impedance.

Shadorne, I don’t know. Careful amplifier pairing might be prudent.