Class D = Trash?

georgehifi,

     Let me get this straight:

     When  I initially asked you:

"1. Does any scientific evidence exist that in any way supports your theory that the current class D switching frequencies are too low and result in sonic anomalies that are audible?

2. Have you personally ever heard these sonic anomalies listening to good class D? If so, please explain what these theoretical sonic anomalies sound like. Apparently, you currently may be the lone known human believing in, and claiming the audibility of, these sonic gremlins."

  Your response, is to post quotes from a very forgettable 10yr old roundtable discussion that actually is more concerned on the relative merits of class D amps than on the existence of audible affects caused by the switching frequencies utilized?  And the panel consists of 9 traditional linear amp (both tube and solid state) designers and a single designer actually designing his amps around class D amp power modules that he did not design but purchased from another company?

 Come On, Man!  You didn't come anywhere near answering either one of my clearly straight-forward questions  by quoting from the comments of a stacked deck panel of traditional linear amp designers, 90% of whom have absolutely no experience designing a single class D amp  

    Who's the genius who picked out this ridiculously unbalanced panel of participants?  Is he the same one who selected the participants for that infamous 'A Remarkably Unbiased Roundtable Discussion on Christianity' that consisted of those 9 adamant atheists and that single choir boy?
     I would have found that Class D Roundtable a lot more informative, interesting and worthwhile had the genius invited an actual class D amp designer, such as Brruno Putzeys, the inventor of both the Ice and Hypex NCore class D amplifier technologies.
     Due to the complete absence of ANY evidence that even vaguely supports your theory, the complete lack of ANY description of what these theorized sonic anomalies  actually sound like,  you're reluctance to state whether or not you've ever actually heard them yourself and my personal experience of never hearing even a hint of sonic anomalies from my class D amps,  I think you understand the reasons you need to come up with a new fake theory/boogieman to further your mysterious agenda.
     How about claiming they spontaneously combust?

Later,
 Tim 

^^ one of the artifacts of Class D is is that there can be intermodulations between the scan frequency and the the signal being amplified.

You can see this in the specs if the spectrum of distortions is graphed. So there isn't a lack of evidence!

In the digital world, they call this 'aliasing'. In the analog world (and since Class D is an analog process) we call it 'inharmonic distortion' to distinguish it from 'intermodulation distortion'; the latter being intermodulations between tones being amplified.

This is why the artifact of Class D is different from traditional solid state. The artifacts are similar to those of digital and you see many of the same complaints leveled against it- cold, sterile, that sort of thing.

Its a simple technology, and that seems in a way to belie the issues of how to correct the artifacts, which is rather tricky. Like digital though it is a rising star in high end audio (many think its already arrived but the fact that this thread exists is evidence that it has a ways to go, otherwise it would have completely supplanted tubes and traditional transistors; since it hasn't, we know without needing to know technical issues that its got a ways to go) and its potential can't be ignored (which is why we've been investigating and working on class D ourselves).

Hi atmasphere,
     Thank you for your explanation.  I know your credentials and trust your comments have no hidden agenda.  Unfortunately, I don't know georgehifi's credentials and whether he has a hidden agenda against class D.
     Okay, so you're stating that there can be intermodulations between the scan frequency and the signal being amplified in class D amps.  Amp designers call this 'inharmonic distortion' and its affects may be a cold and sterile sound.  I just have a couple questions about this:

1.  Is there a consensus among amp designers that current switching frequencies (what I believe you're calling 'scan frequencies') being too low is the primary cause of 'inharmonic distortion'? If so, is there also a consensus that raising switching frequencies to the 3-5 MHz range would reduce 'inharmonic distortion'?

2.  Can you explain why I, and apparently many other class D amp users, do not perceive our class D amps as being cold or sterile?  Do you think the ability to perceive  the affects of 'inharmonic distortion' differs among individuals or do you think it's more likely the degree of 'inharmonic distortion' varies by amp?

3.  Are there any current methods of measuring 'inharmonic distortion'?

Thanks.
  Tim

of course, you can measure all sorts of distortion products - inharmonic means non-harmonic

@noble100  and @randy-11

I suggest you ignore some of these criticisms before listening. There are like a billion claims, many old or outdated or downright false.

I can tell you I cannot, blindfolded, or sighted distinguish between my current amps based on Class D and my previous, Parasound Halo A23's. The latter are linear, hi bias AB. I've also heard megabuck class A amps and mine sound as good (within their volume / power envelope).

For this reason, I completely discredit anyone who claims Class D must have x or y artifact.

Best,


E