[sdiy] getting +/- 12V from a 9V source

[Nils Pipenbrinck]

Hi list,

Just wondering. I'm still puzzeling about a preamp thing I want to built for
a friend (RIAA, maybe someone remembers my last post).

Now there is a problem with the power supply. I want to drive a +/- 12V
circuit from a 9V wallpart (because they are so cheap and common). I don't
feel like building a full blown +/- 12V supply just for a preamp.

Can't I just up-transform the 9V again? It shouldn't be a big deal to throw
together a wien-bridge sine oscillator, a fat tranny as a driver and the
output through two little transformers. Then add a rectifier, some caps and
a 7912/7812 pair.

My idea would be to use these 1:3 audio-transformers, which where used to
match the impendance of amplifier stages in early (tube and germanium)
amplifier designs. These are cheap and small. I have little experience with
them. Will they stand the current? I only need some mA to drive the 7812 and
a dual opamp.

Also a different option would be to use a diode+cap step-up circuit. I've
seen these as ready to use chips, but never dealed with them. Anyone used
them for audio?


Enlight me with your wisdom  :)

	  Nils Pipenbrinck