[sdiy] +15 -15 volts from 9volt dc power supply?

[Tom Arnold]

On Wed, Sep 07, 2005 at 06:36:57PM +0100, Milo Barrowclough wrote:
>    im trying to get+15 -15 volts for cheap to power my diy synth modules.
>    Is it possibe to convert 9 volts dc (from a regular plug-in power
>    supply) to a dual voltage +15 -15 volts? Surely it must be possible
>    because the roland sh-101 uses a 9v dc power supply (or 9v dc
>    from batteries). this must be converted to +15-15 volts somehow for
>    powering the cem3340.

Pretty easy actually.  Well actually, not with the 9vdc wallwart, but you
should easily be able to find a cheap 12vac one.

Have a look at the power supply on this EFM schematic :
http://www.ele4music.com/pdfs/seq2a.pdf

Basically two half-wave rectifiers.  Feeds the top half of the AC voltage
swing to the positive regulator and the bottom half of the swing to the
negative.  You can do +-15 with a slightly higher voltage transformer and
different regulators.  Not good for much current but really cheap.

If you are going to power several modules, see if you cant pick up a
pre-made supply of some kind.  I use Power One brand units.  The +-15volt
unit is good for an amp or so which is enough for several modules, they are
well made and cheap on ebay.  I dont see any on your side of the pond right
now, but there are other manufacturers also and I'm sure you can find one
fairly cheap.  They're a little pricey to buy new but maybe someone else
will have a suggestion on that.

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