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

[media at mail1.nai.net]

At 1:02 PM +0100 02/01/02, Nils Pipenbrinck wrote:
>
>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).

(They also sound like ass, especially when powering a circuit that supplies
60dB of gain.)

>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.

That seems like much more work than building a supply that runs off the
mains.  It would also be very inefficient.

>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?

I can't say that I have, but there are some good audio op-amps that will
run off a single supply.  You can also build a split supply from a single
supply using another op-amp, even in the same package.  You might want to
look at the application notes for the Analog Devices SSM2135.  Of course,
like any other chip I've ever used from them, it's been discontinued, so in
case anyone is reading this...

I HAVE ABSOLUTELY NO INTEREST IN THE OP275 IN A DIP PACKAGE.