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Expanding the Class D Conversation: How Would You Characterize Their Differences?

Expanding the Class D Conversation: How Would You Characterize Their Differences?

I'm currently trialing the NAD M23 (1st gen. Eigentakt-based), and I find it intriguing enough to want to understand it better — which means understanding the broader sonic landscape of class D. So I'm crowd-sourcing.

In a recent exchange, the estimable Ralph Karsten (Atma-Sphere Music Systems) made two comments that stopped me cold. For those who missed it, here's what he said:

"IME, class D amps vary in sound more than tube amps, which is to say, quite a lot."

"IMO there is a bigger difference between various class D amps than you hear between various tube amps. IOW just because you heard one class D amp says nothing about how the next one might sound."

Link: https://forum.audiogon.com/posts/2885828

As I think through this more carefully, these are genuinely important claims. My own experience with tube amps confirms that they produce audibly distinct characters across topologies and designs. If Ralph is right and class D exceeds that range, then generalizing from one class D experience to another is even more hazardous than I assumed.

One specific question for Audiogon members:

If you have a Class D amp or have compared class D amplifiers, how would you describe their character(s)?

Here are some criteria I use:

  1. Frequency balance — Is the tonal response even across bass, mids, and treble, or does it favor certain regions?
  2. High-frequency texture — Are the highs extended and smooth, or edgy, grainy, and fatiguing?
  3. Bass definition — Is the low end tight and articulate, or loose and bloated?
  4. Midrange character — Does the midrange feel present and natural, or recessed and thin?
  5. Transient speed — Does the amp respond quickly to dynamic attacks, or does it sound sluggish and rounded?
  6. Dynamic range — Does it scale convincingly from quiet passages to loud ones, or compress the difference?
  7. Soundstage width and depth — Does it create a convincing three-dimensional image, or sound flat and narrow?
  8. Image specificity — Are instruments and voices placed precisely, or do they blur and wander?
  9. Background noise floor — Is the silence between notes actually silent, or is there grain, haze, or hash?
  10. Long-term listenability — After an extended session, do you want to keep listening, or has something been quietly fatiguing you?

If you can include relevant system context — room, speakers, preamp — please do. Those variables will help me interpret what the amp itself is contributing.

I'm less interested in rankings than in understanding what Ralph mentioned, namely the [vast] range of sonic signatures class D is capable of. Eigentakt, Hypex, Pascal, Purifi, GaN-based, etc. — all fair game.

Price is no constraint here — I'm interested in the full range of what's out there.

hilde45
bluethinker's avatar
bluethinker
324 posts
 

@hilde45 - I’m looking forward to your observations on the AGD Audion MKiii and the other amps. I have heard great things about that Pass amp… I’d love to hear it at some point. 

For whatever it’s worth, I did feel they took a few days to settle in my system. I asked ChatGPT if there would be a legitimate reason a class d amp would need time to adjust to my system and it did provide a legit (at least it felt so to this non engineer) explanation. Of course it also reminded me that my perception of the sound was changing over time, which I heartily agree with.

It was really after a week where I felt comfortable comparing the Audions (paired with the spectacular LTA premap) to my Luxman class a solid state and CJ and Qualiton tube amps. 

 

 

parkergetdean
1,048 posts
 

why would you ask chatGPT that question? How would it know? There is simply not enough info out there for it to train for any non-BS, intelligent answer.  

bluethinker's avatar
bluethinker
324 posts
 

@parkergetdean - Are you using AI for work everyday? I have worked in technology my entire career and have found this new phase of technological evolution to be the fastest and most disruptive yet. I really only started to adopt it for my personal life once I had to use it daily…

ChatGPT actually had a pretty coherent explanation. I’m not an electrical engineer, so maybe it was totally bogus. But these tools are synthesizing information from vast stores of data, so more often than not the responses are in the ball park. I’m always looking for obvious hallucinations and inaccuracies, but these machine learning tools are getting better by the day. 

 

mahgister's avatar
mahgister
15,050 posts
 

I discussed with Grok(4.2) for 15 hours almost straight about linguistics,mathematics,philosophy etc all fields integrated in my own perspective (i sum this discussion in 450 pages PDF 2 days ago ) and Grok analysed  as meaningful all my work and criticize it but without being able to dismiss it... Anyway i dont know anyone able to discuss this with me, i am retired since 2015... smiley

I just  also discussed today the whole geopolitical situation Us/Canada and his effect on the world... I learned a lot from Grok but only because i use it as a mirror for my own thinking not as a "truth" delivering machine... A.I. is a machine not a god. The fact that he knows every mathematical theorems in existence did not means he can create new one because it do not properly understood and cannot  gives new conceptual schemas... But a machine can look at a pattern no human eyes or mind can look at...it is you who must guide it and then interpret his results...

Conclusion :  A.I. cannot be more intelligent than your own question...The extreme danger: you risk making his answers your own jail...

For acoustics principles and concepts interaction it is better than a book but beware it cannot replace certain important book , for example it cannot criticize acoustics theory as  a human genius will do, but A.I.,once this genius had communicate his theory, will be able to synthetize his ideas and even gave interesting suggestion...

But A.I. will make simplistic errors and worst simplificayion you must learn to track...

No Machine replace human thinking , the only one who think the opposite are those who sell it, they are crooks (Altman) , or techno-cultist thinking they do science when they develop already existing  technology, they use science.

Here as an exemple a Grok Analysis of the acoustical theory book i use as my fundamental scripture so to speak, (it is not room applied acoustics  but it help to understand it at a core level) The author is a Nigerian genius who put at shame many Western acoustician and his book is completely unknown and Grok read it in seconds and approve my opinion about the author theory:

https://x.com/i/grok?conversation=2026515540827623676

«My brain is a machine,washer and dryer,but only God knows where the linen fabric come from»--Groucho Marxcool

 

 

@parkergetdean - Are you using AI for work everyday? I have worked in technology my entire career and have found this new phase of technological evolution to be the fastest and most disruptive yet. I really only started to adopt it for my personal life once I had to use it daily…

ChatGPT actually had a pretty coherent explanation. I’m not an electrical engineer, so maybe it was totally bogus. But these tools are synthesizing information from vast stores of data, so more often than not the responses are in the ball park. I’m always looking for obvious hallucinations and inaccuracies, but these machine learning tools are getting better by the day. 

parkergetdean
1,048 posts
 

@bluethinker I have been using ML for 10 years now, tweaking it for AI, for a client I would not disclose. The AI response is based on the information it is fed, and the algorithms it runs on. You can’t make a gourmet dinner from stuff taken out of the trash. The information on audio gear is wildly subjective, heavily influenced by vendors, sales objectives and pure BS. (On top of the topic being wildly subjective with a funny jargon that gives a normal person a headache) For every honest and expert review, there are 10-20 entertainment piece that will be weighted the same because AI can’t distinguish between relevant and fake (nor its custodians want it to). If it could and would, we would not be fed with lies and propaganda every day in the name of news and facts.

In short, for audio, the sample is so small, AI can just use proper English to sound convincing ("coherent explanation") but it is largely clueless. And it is true for any niche subject. I asked fun questions like best pastry shops in Budapest or best swimming pools in Munich, which movies is more romantic: A or B, the responses were disasters. And THERE IS sufficient info on those like decades and centuries of literature. A couple hours of reading, filtering, iterations and critical thinking yields better results.

It can improve, A LOT, will it, I guess?

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