Explain Class D amps to "non audiophile friends"

Fascinating technology!

The main thing I wonder about is how much better even will it get over time for hifi audio purposes.

There would still seem to be some practical upside in maturation of this particular technology though I would say it has clearly evolved to the point of being highly competitive with others already in hifi audio. I expect it could widen a lead practically over time moving fore ward if it has not to some extent perhaps already. The bigger question will be how much will it matter? Similar to the discussions about value of high res digital audio sources I would think.

"Semiconductors are getting much faster every year including high current Mosfets."

Exactly!

Much technological progress over the last half century has evolved around the speed of semiconductors as evident in the myriad of increasingly functional electronic devices that never stop coming and likely will not in the foreseeable future either I would bet.

A quick look around today versus 5, 1, 20, 50 years ago quickly confirms that!

I look forward to the day when I might consider replacing my current Class D amps with something that is even better perhaps even for a fraction of the current cost.

Might high end audio be the one frontier so advanced that advances in semiconductor technology might fail to conquer it along with the rest?

I think not.

Time will tell even if it has not already started to do so for some.

Tony,

If you are not accepting due to a pre-conception about what a good amplifier looks like, or even how it works, then I might venture to say you are on the wrong path.

IF you have heard a Class D amp and are not convinced, then I would say your conclusions at this time are justifiable based on your personal needs and preferences. If you hear several over time and still are not a fan, then you have done due diligence in making a valid determination.