Class D Technology

George, I looked at the link you provided.  Yes they use filters for the purpose of measurements to eliminate residue of switching frequency that is otherwise completely benign. This small residue (about 1%) has no effect on the sound.  Speaker membrane will react (move) to its average value only.

I don’t buy the "gas guzzler" A/B vs. "green" class D arguments for the latter. Kilowatt hours are cheap and relatively clean until you pile up a WHOLE lot of ’em. With typical audiophile usage patterns, and the fact that we’re a VERY small segment of the population, there’s no significant ecological impact here. 

According to this pouring used car engine oil to kitchen sink is OK (does not have environmental impact) since very few people do it.

And as far as ecological impact, class D probably makes things worse overall, due to the fact that audiophiles ship ’em over, decide they don’t like the sound, and then ship ’em right off again

That's funny.

This small residue (about 1%) has no effect on the sound

Put your ear to a wide bandwidth tweeter, you will hear it’s poluting artifacts. If not the filter effects is set very low to cut way down to 10khz or even less, creating all sorts of other problems.

Cheers George

Let me add that while I do concede that my engineering knowledge falls short of what many of you possess, there's still a lot of bat guano peddled on these forums.   I like it here, and there are some very smart, very cool, very interesting people that I've learned a lot from, but oftentimes this forum is to audio knowledge what Fox News is to global news coverage.  Sometimes after I visit I have to remind myself that I didn't just spend 10 minutes on Shutter Island.

Here is just one of many that Stereophile tested, not using their test filter. It’s more than 1%.
And this Class D had a linear power supply as well, most use smd now which creates even more other noises as well.

http://www.stereophile.com/images/archivesart/805CIAfig2.jpg

Cheers George

Just a couple of quotes from other Stereophile measurements personel.

I dislike measuring amplifiers with a class-D output stage. This is because such designs can throw out enough ultrasonic noise that you can never be quite sure that what you’re actually measuring is the input stage of your analyzer being driven into slew-rate limiting. What I do, therefore, is to insert, when appropriate, a sixth-order low-pass filter set to 20kHz or 30kHz between the output of the amplifier and the analyzer.
But you can see from this graph how the amplifier’s ultrasonic output rolls off rapidly, presumably due to the low-pass filter necessary to minimize the HF noise produced by the switching output stage

Cheers George