[sdiy] DC/DC converters

[Steve Lenham]

> Hi all!
>
> I need a +5/+12/-12 supply for my new digital/analog project with one DC
> adapter input.
>
> I was planning to use a 7805 for the digital and a DC/DC converter for
> the +/-12V. I found this one from TRACO:
> http://www.elfa.se/pdf/69/06958912.pdf
>
> It has 50mVpp ripple/noise and 400kHz switching frequency. This should
> be no problem for analog audio right? Most linear regulators has more
> noise and ripple than that, I expect.
>
> Does anyone have experience with TRACO or DC/DC converters in analog
> audio?

Hi Fredrik,

I worked for a company making professional Outside Broadcast audio equipment 
and we used the Traco DC-DC converters regularly with no problems. We would 
always add an extra L-C filter stage on each output, mounted close to the 
converter - for example a cheap 1mH drum inductor and a 47u electrolytic 
plus a 100n poly - and that reduced the ripple to an even lower level.

That should be good enough for most analogue audio apps - as per the recent 
thread, anything more critical should probably have a local reference or 
locally decoupled supply anyway and not rely on the global PSU performance.

Hope that helps,

Steve L.