Class D Technology

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

Great thread. I'll add that Class D amps are extremely sensitive to power source and power supply. To hear the best the technology can offer, you would have to pair it carefully with a matching quality power cord and possibly a power conditioner. This took my NCores to a whole new level (refinement, bass, micro detail, etc) and brought out the musicality that had been lacking. 

Ok George we get it.  You aren't sold on class d yet.  Others are. Mine sound great and no faults I could point to when listening.  They just make sweet music as said. 

I am going to chime in here in favor of current class D amps, with a big thumbs up! I have been in the tube amp camp (both SET and others) for 20+ years, and now I am happy as can be with my Red Dragon S500 amp. No, it's not like a tube amp, but it's not SS sounding either.  It does so many things right, and hardly anything wrong, that I can easily live with it. All topologies have their pros and cons.  Throw a tubed preamp in front of a Class D, and there you go!