MC352 into varying-load speaker?

Better off with the autoformer than not. The 352 will be much more powerful than the 6500. Arthur

The autoformer doesn't work like Sean thinks it does.. Mcintosh output transformers are bifilar wound which is a complex technique used to nearly eliminate the inductance associated with the wire. We use it in the lab for special EMI filters (different core setup though). The coupling is just about perfect with a larger bandwidth than the output transistors. Just like tube amps - only better because not all manufactuers have the ability to bifilar wind their trannies.

Yes, all autoformer McIntoshes use bifilar winding (trifilar on some amps). McIntosh patented it in 1947 for their "unity-coupled" circuit, originally for tube amps of course but then they applied it to solid state in the early 60s and have ever since. I have performance data for a MC2255 and the bandwidth is nearly as wide as today's models.

I have tried Mc amps with autoformers and without, concluding that there is actually little sonic difference between them (when comparing appropriate models). The autoformer mainly acts as a stabilizer, as you said. I currently use a direct-coupled McIntosh amp myself. I like them either way. Arthur

Thanks Ron for the explanations! Cool hearing about the details involved. Arthur