Class D is just Dandy!

randy-11
higher switching frequency moves it further from the range of human hearing and enables "kinder, gentler" filtering

+1 many times over Randy, seems like your one of the few that get it here!

Just to add to that, the "gentle" filter is on the output speaker terminals, and has to take the full grunt (wattage) of what the amps gives out, it has to be "gentle" (low order), if complex it would soon fry up.
Or as Mark Levinson tried with $$$$ the No. 53 monoblocks, a higher order filter and massive to take the grunt, (as you can see by the 4 x chokes on each monoblock), but that has problems also as well as expensive, it wasn’t received very well.

http://www.stereophile.com/images/1212levin.side.jpg

Cheers George

Always fun to talk tech.... but I've been living with dreamy sounding amps for a while now. I don't need my switching frequency increased to have the best.

E

I'll lay money on it Eric your the one of the first to change to the higher switching speeds when they come available/affordable, hopefully soon, judging by Technics lead in this area of higher switching speeds.
 
I know I will sell my inefficient, hot, heavy, boat anchors just before it happens, before they become worthless, as will today's Class-D amps.

Cheers George

I always thought the gentle filter slope was b/c steep "brick wall" filtering caused audible distortions...

I do agree that the amplifier is the closest component most of us have that is near perfection.  Speakers, room tmts, DACs, source material... all are in more need of improvement on a relative basis.

It’s because a simple low order output filter can take the amps full power, but it’s effects reach down into the audio band and still leave some switching noise left overs, hence the need to take it up much higher as Technics did with far higher switching frequencies, so they can be effectively removed, without effecting the audio band.

These days when Stereophile tests a Class-d amp, they put on an external output filter, the Audio Precision’s AP0025 filter, which has a -50db rolloff after the audio band so the 1khz square waves look half decent without the switching noise embedded right across it, (good for sales) 10khz square wave still looks a mangled mess though, trouble is this AP filter can only take very low power, would be real nice to leave it in to listen to, but it would blow up in a micro second.

http://www.stereophile.com/content/class%C3%A9-sigma-2200i-integrated-amplifier-measurements#31YFAPfYVDGeowzZ.97

And yes steeper filters as you said do have their own set of problems re sound, as ML found out with their No.53 monoblocks.

Cheers George