Class D is just Dandy!

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

You know what I like about my Class D (Primare I32)?
It sounds really, really good. I have no idea if it has ICEpower or NCore, or Hypex in it, and I'm really not sure I want to learn enough to know if it matters. Every time I get more educated on the technology of HiFi it causes gear-lust costs me money. I'm much better off listening in blissful ignorance.
Seeya, fellas.

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

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

randy and george,

     I believe I understand george's often stated theory that the current typical class D switching frequency is too low at about 500kHz and results in sonic anomalies within the audible human hearing range of 20 Hz to 20 Khz. This theory further claims that raising the switching frequency to the 3-5 kHz range will cause these sonic anomalies from affecting any frequencies within the audible range of human hearing capacity. 
 
     My issues surrounding this class D switching frequency theory, that apparently both of you now support, are twofold:

1.  Whether to believe 2 people on an audio forum named randy and george, of uncertain class D technical knowledge and credentials,claiming this switching frequency theory is valid but offering no supporting evidence

 OR
 whether to believe the actual inventor of class D amplifier technology named Bruno Putzeys who seems to assign no validity to this theory and has stated that "500 kHz is a completely reasonable class D switching frequency".
 Written down like this,  it seems like an especially silly and obvious choice to me concerning whose advice I should rely upon in evaluating this theory.  Are you two really suggesting I simply ignore the inventor of Ice and NCore class D power modules and just trust your viewpoint instead?
   If it was empirically proven that these sonic anomalies exist and are audible to a significant number of humans, I admit I would be curious to determine if it improved the sound of my system once the price was much more affordable  As it currently stands, however, I'm not convinced I should care since I've never even heard a hint of any sonic anomalies from any of the class D amps I've used in my system or any I've ever listened to in any system.  
   
     As Aristotle so famously asked Plato so astutely long ago:
"If  your class D amp had a switching frequency proven too low and it caused audible sonic anomalies, but you could not hear these anomalies,  would they even exist to you?"

    That hipster Plato then replied to his teacher in the following lesser known and less famous manner:
 "Mr. Astute, if I cannot hear them pollute then it does not compute and I know the point is thus moot so I properly cease to give a hoot."  True story. 

       I'm with Erik and Plato on this one; I've been living with dreamy sounding amps for a while now, too. I don't need my switching frequency increased to have what I consider the best, either.

Later,
 Tim

At $17k a pair? No. No thank you.

I’ve heard current linear amps that were about that expensive and I wouldn’t switch to them either. To me the idea that we need super technology to finally fix the Class D problem just wont’ fly.

Blame my tin ears if you must, but this was solved a decade ago.

Best,

E