[sdiy] Opionions on Switchmode PSUs for analog synths?

Mattias Rickardsson mr at analogue.org
Sat Nov 2 13:18:49 CET 2019

Den lör 2 nov. 2019 03:33 <mskala at ansuz.sooke.bc.ca> skrev:

> On Sat, 2 Nov 2019, Adam Inglis wrote:
> > > It's worth pointing out that when the SMPS breaks you don't repair it
> >
> > > You can always repair a linear mode PS.
> >
> > Exactly!
> > Not doing the planet much good is it?!!
> Both devices will be thrown out eventually.  The linear regulator,
> being less efficient, is burning a lot more energy every moment it's
> in operation, and requires the transformer and so on upstream of the
> regulator to be larger to supply that power.  Pretty hard to spin that
> as an environmental win.

True, in the parts of the world where houses need cooling or in older
buildings where the heat is thrown out with the ventilation. Excessive
power draw is - and should be - then considered a waste of energy.

In modern heated houses it's harder to tell, since the heat energy isn't
wasted but mostly recirculated via ventilation and/or tap water.

This direct electrical heat can often be the least efficient heat source,
returning less than electrically powered heat pumps, but if it's produced
locally by solar panels it might be more of a tie.

Even if a linear PS is wasting 3 times as much energy as a SMPS, the synth
(etc) draws 3 times more power than that bad old linear PS. All of this of
course ends up as heat, so the comparison should probably be made not
between linears & switchers wasting 30 or 10 % of their energy (a factor of
3), but between the whole systems using 70 or 90 % of their energy (not
even close to a factor of 2).
The building where the product is used also affects the equation, as
mentioned above.

Perhaps the design of the powered unit should be scrutinized more often.
Using TL06x instead of TL07x op-amps, or using +/- 9 V instead of +/- 15 V
supplies, can reduce more waste than going from linears to switchers.

I'm not saying that linears are better, just that it's becoming more
difficult to say that they are worse. The best supply would be an efficient
switcher with low noise and long lifespan. :-)

/mr - we've had frosty mornings this week, so heat is nice 8-)

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