"Ed Engelken" ) writes:
An ordinary filament transformer with a 120 volt primary and 12.6 volt
secondary will work well. The turns ratio is about 10 to 1 and that
yields an impedance ratio of 100 to 1. That will match a 600-ohm
output to a 6-ohm load and will provide a decent match to an 8-ohm or
4-ohm speaker. A small 1 amp. transformer is sufficient. --Ed

And in the days of when boatanchors roamed the earth, one guy suggested
in a magazine article that this was a good way to use up all thos
400Hz transformers that most ended up with a stock of via surplus,
but which weren't too useful for power applications, since few
had a source of 400Hz power.

I guess the trick today is to find a piece of consumer electronics
in the garbage (so long as it doesn't use a switching supply) and
use the power transformer from that. Filament transformers are
as likely hard to come by as audio transformers these days. (Not
that either is really that hard to get, but if one doesn't have a
handy audio output transformer, they are likely to not have any
filament transformers handy.)

Michael