[sdiy] DC wallwart +/- on-board V Reg ?

[Andre Majorel]

On 2015-03-05 17:07 +0000, Tom Wiltshire wrote:
> On 5 Mar 2015, at 16:35, Justin Owen <juzowen at gmail.com> wrote:
> 
> > I was hoping to get some advice on the potential
> > advantages/disadvantages/benefits/costs of circuits that use
> > a DC wall wart adapter (e.g. 9V boss-style adapters) to
> > power a voltage regulator (e.g. LM317) which then powers the
> > circuit - versus designs where the circuit is powered
> > directly from the wall wart (e.g. guitar pedals)?
>
> Noise is the biggest issue in my view.
> 
> With a 9V-from-external-wallwart, you have no idea what the
> power looks like. If you've got a regulator in between, you
> can be reasonably sure you're getting clean voltage of the
> right level.

About 10 years ago, I read something to the effect that getting
rid of the noise of a switch-mode power supply by following it
with a linear voltage regulator does not work. Not as well as
people think it should, anyway.

Sorry for making unsubstantiated claims but I cannot find the
source now. I think it may have been some app note mentioned
here. Anyone remember which ?

-- 
André Majorel http://www.teaser.fr/~amajorel/