Assuming that a tube amplifier can be built with a balanced output (e.g. the
Zechendorff circuit), what are the pros and cons of using an autoformer to
match output impedance vs. a standard transformer?

It would seem offhand that an autoformer could have sonic advantages (e.g
lower losses, no coupling degradation, etc.). Would it cost less to
manufacture? And finally, would a toroid be a suitable implementation (I
am aware of toroid problems, especially with saturation, when used for
standard output coupling).

TIA,

Jon