[sdiy] most efficient way to get 5V from 12V?

[Danjel van Tijn]

If I want to run the digital parts of my module at 5V I am going to
need to convert the 12V source. On some Euro modules the 5V conversion
is done externally via a Doepfer 5V adapter (just has a regulator and
a heatsink on it and plugs into the bussboard)

Is there any reason that I can't do this on the module?  If I do it
there, what is the most efficient way (i.e. generates the least heat)
so that I don't need a large heat sink?

cheers,
Danjel