SOT: Switching Vs Linear Power Supply

[gurutzeta]

What is the difference between a linear and a switching power supplies and which would be best to use for stompboxes and other audio related electronics designs?

[Mark Hammer]

Some people have suggested that switching power supplies may pose some problems.  All I can say is that I bought a terrific little 2.5Amp 12v switching adaptor a few years ago that powers my computer speakers quietly, effectively, and cool-ley, while taking up much less space than you'd expect for that much current.  So, my experience has been positive.

[Peter Snowberg]

In a linear supply, the output voltage and current are determined by the ratio of primary to secondary windings on the transformer, the size of the wire used to wind the transformer, and the amount of iron or other magnetic material in the transfomer.

In a switching supply, the power is first turned into high voltage DC with a rectifier and then it gets turned back into AC at a much higher frequency. The duty cycle of the oscillator turning the high voltage DC into AC is adjusted by feedback from the secondary of the switching transformer to keep the output well regulated. If a switching transformer is connected straight to the power source and without the switch (usually MOSFETs), it will burn up in seconds. :shock:

Switching supplies are able to reduce the amount of iron required in the transformer by huge amounts because transformers are VERY inefficient at 50 or 60Hz and they get much more efficient as the frequency rises. Simply raising the frequency from 60Hz to 400Hz reduces the amount of iron required by 80%. Switching supplies typically operate at frequencies from 50KHz to 200KHz but they are also found with lower and higher switching frequencies.

Cheap switchers may operate at frequencies down into the audio range. This is where you run into problems because the output will have a good deal of noise at the switching frequency.

If you get a switcher that operates at a high frequency and has good filtering, it will work fine. You get what you pay for.

[Paul Perry (Frostwave)]

A well-designed switcher is good. ( a bonus is that, by design, ALL switchers give a regulated output).
But as a pessimist, I feel that the world is about to be flooded by REALLY CRAPPY switchers. For example, i had a power surge burn one out (didn't happen to the 10+ linears on the same circuit).
Also, if the switching freq gets out as interference, even if it is above audio, it can cause interference to some gear.

[Connoisseur of Distortion]

i have had decent experience with the switching power supplies. people calim they can interfere with your signal, but this problem only seems likely if you are using a reeeeeally picky pedal

[gurutzeta]

Thanks peter for the explanation and the rest for their coments.

[Tubebass]

I've been using a couple of tiny Panasonic 5 volt switchers with their outputs in series to power my pedals for over a year with no noise  or any other problems.