What is an AV grade switching power supply?

Most cheap, poorly designed SMPSs are noisy.

ifi audio makes a series of high quality SMPSs at several price points.

Here's an example: iFi audio iPowerX

Buy these at Amazon. If you don't hear an improvement, return it.

The item you speak about is not available from Amazon. 
 

Question is about an AV grade Power adapter. What is av Grade?

Linear power supplies are much better .For example, high-end DACs have them and are a key differentiator between the mass market sub $1000 offerings and high-end units.

They are designed for low noise and are often considered quiet since there is no high-frequency switching. They are used anywhere that excellent regulation and/or low ripple is required as well as needing low electromagnetic emissions and excellent transient response.

AV grade? Is that like a black one?

Yes I think an AV grade power supply is one that has better noise filtering on board. Like the IFI stuff as was mentioned.  Switch mode power supplies are notoriously noisy, so for AV use, I would think they put in various filters to quiet the noise so the music or video signal isn't affected.

@jumia

iFi audio IPower X Power Supply

Problem with linear power is that the circuit is always on and this creates noise. A switch power is fine if the filtering for high frequencies is done well and should not be a problem.

So linear power for switches it's not a good idea.

Let's go with mainly marketing BS. Bet they don't provide specs. Any quality PS has validated FCC class B test results. Most critical thing in audio is ensuring the switching frequency stays out of the audio frequencies and preferably high to make filtering easier.