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

[Philip Olsson]

> 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

Can´t you drive the circut whit +9v? 
If its just the opamp that are going to be powerd check the datasheet for the opamp...
Its probly just a matter of changing resistors.
Could you show us the circut?
/ Olsson