[sdiy] AC Adapter - Getting Negative Voltages?

[Ken Elhardt]

Since nobody seems to know of any really small power supplies, as per
my previous post, I have question about AC adapters.  How does one get
a negative voltage from one?  Is there some kind of negative voltage
regulator that works off a positive voltage?  Or do you use the
positive voltage as ground, and ground as a negative voltage somehow?
Thanks for any info.

-Elhardt