[sdiy] Re: [AH] synth-diy?

[Tim Parkhurst]

On 10/26/07, gregory zifcak <zifcak at hotmail.com> wrote:
>
> thanks for the responses. what about +/-15 from a 18VAC (non-center tapped), as that's what i have lying around?
> thanks,
> greg
>

Hey Greg,

Most of the bipolar supplies out there (including the Thomas Henry
example) use a center-tapped transformer. Correct me if I'm wrong List
Members, but I believe this means a 30V center tapped unit will have
two 15VAC outputs (180 degrees out of phase from each other), and the
center tap behaves as 0V. From what I've read, using a center tapped
xfmr reduces the ripple in the rectified DC output, so this would be
the best performing solution. However, with a little looking about, I
found a schemo for a bipolar supply that doesn't require a center
tapped transformer and may be just what you need (courtesy of the
General Guitar Gadgets site):
www.generalguitargadgets.com/pdf/ggg_bipolar_ps.pdf

Depending on how much current you need, you may want to add heat sinks
to the regulators. The warning for the Thomas Henry bipolar supply
(using the same 78xx and 79xx regulators) still applies: the heat
sinks for the two regulators are at different voltage levels, so make
sure they don't touch each other, or any conductive parts of the PCB
or the case!

Hopefully this gets you going. :-)


Tim (not bipolar, but not quite center tapped either) Servo
-- 
"Imagination is more important than knowledge." - Albert Einstein