A question for the cognoscenti autoformersI am not familiar with the "Zechendorff" circuit, but I am quite familiar with autotransformers.

The basic selling point of the autotransformer is that not all of the energy that passes through the transformer need pass through the magnetic circuit. Theoretically, this could result in a smaller magnetic circuit, less weight, etc. However, these advantages are only realized if the transformation ratio is small. An autotransformer wound to achieve a 10:1 impedance transformation will only save about 1/3 of the needed magnetic circuit as compared to a two-winding transformer. Then, of course you also give up the isolation achieved with a two-winding transformer.

An autotransformer would be good to match, for example, a 6 ohm amplifier to an 8 or 4 ohm speaker, and, as a point of fact, McIntosh used to do this with their "better" line of SS power amps. I don't think you would get a great advantage at the transformation ratios typically used in tube circuits, however.
"Jon Yaeger" wrote in message ...
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