What is so tricky with SMPS in audio?

[solderdude]

Thank you very much! Why would introducing leakage reduce emission? As the result of putting a low impedance pass for HF between your secondary and your primary?

Yes, without it the secondary output would just be a huge antenna. The small cap between output and input 'grounds' it for HF reducing emission.

A question remain: why did it took so long to transition from linear to SMPS? Only 20 years ago, it seems like SMPS were not the norm in high end products.

Availability of fast switching devices with a high voltage and current capability in huge numbers and thus low prices.

 

[kevin gilmore]

especially as amplifiers get bigger and bigger, the sweet spot is a switcher, followed by a lc filter and then a really good linear regulator. noise ends up in the sub microvolt range.
when you need 10+ amps to drive your planar headphones, you save at least 40 lbs in mains transformer and large caps.

 

[egellings]

What about the fact switching noise is inaudible? Why would you need to filter it in the first place, beside EMI compliance (which is usually of secondary importance in the amateur world)

The noise may well be inaudible, but it could still interfere with the amplifier's operation by causing sensitive input stages to be driven out of their linear operating region. Rectification effects could also shift the operating point of a stage. Best way to prevent that is to remove the amplifier from the noise source, and if that's not possible, then add adequate HF filtering right at the input stage. If not that, then tell the darn switch-mode supply to shut up!

 

[TRDK]

In Germany this product is used be many audio users:

EMD 503

https://www.amazon.de/-/en/AUTH-9kHz-Universal-Broadband-Protection-light-grey/dp/B07TTNQL8W/

and

EMX 506

https://www.amazon.de/-/en/NachrichtenTechnik-Universal-Broadband-Mains-Filter-White/dp/B0B3MZJ8CN/

Torben

 

[TRDK]

This is my current setup:

Torben

 

[dfuller]

What about the fact switching noise is inaudible? Why would you need to filter it in the first place, beside EMI compliance (which is usually of secondary importance in the amateur world)

It is entirely possible for it to be demodulated by the audio path especially if it's high impedance.