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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
hilde45's avatar
hilde45 OP
6,005 posts
 

Thanks for the additional comments. 
Some replies:

 @fatdaddy2    – You say it's useless, but then drop it without any explanation. What makes it useless in your view? And if you've had experience with class D amps worth sharing, that would actually be useful.

 @yyzsantabarbara    – I tried THAT GaN FET amp a while back and didn't keep it – it had a really harsh glare that I couldn't get past. That was a few years ago though, and maybe they've improved since. Interesting that you're finding the warmer Meitner a better match; that tracks with what I'd expect.

 @bluethinker    – Thanks for the detailed account – that's exactly the kind of real-world journey that helps. I'm increasingly convinced about AGD. One thing I keep coming back to is how they compare to Atmasphere's class D. We know AGD has iterated three times on their design, which suggests they're actively refining it. Ralph, on the other hand, has said his amp doesn't need improvement – which could mean he got it right, or could mean something else. Would be curious to hear your take if you've had any exposure to the Atmasphere.

 @mapman   – That's actually the whole point of the thread. I agree completely that generalizing adds no value – which is why I'm asking people  not  to generalize. You've had many; great. What were the differences between them? That's where the value is.

  @ted_b    – Thanks for adding context.

mahgister's avatar
mahgister
15,050 posts
 

My comparative experience with class D and tube amp and class A or class AB is too modest to be really in the knowledgeable  audiogon group ...

But my actual low cost class D Edifier  active speakers+integrated active sub if well optimized score very well on your list. ( keep in mind that i dont claim to beat Audio GD or Ralph class D amp ).

All the factors  you described are tight to the system/room as much as to the choice of an amp class then i cannot say anything comparatively wise.

Optimization for me transformed a low cost system into a good one... I include DSP in the 3 main working dimensions...

My goal was not the exploration of the best comparative at high cost but how to create a low cost system/room with zero frustration...

my conclusion: class D is one of the greatest innovation in engineering audio...

 

bluorion
524 posts
 

I'm currently in the process of downsizing and have a Bel Canto e.One stack (Pre5 and 501s amp). I had a BC amp (s500) about 6-7 years ago but traded it in for some other equipment I wanted at the time. Once I traded it in, I started to regret it and got another on a few months ago as a demo. I heard quite a few of BC and other class D amps at Axpona last year and they all sounded amazing---they were some of my favorite rooms.

As I get older, I'm getting tired of lugging around heavy integrated amps etc. These amps are so easy to move around and DEAD quiet (I keep them on 24/7 per BC recommendations). All I do is turn on my source and turn up the volume. The e.One stack has great reviews online too. I use them with a pair of Revival Atalante 3 speakers. I find the combination has great synergy and are very musical. It's not fatiguing and it's fun to listen to streaming or CDs. The sound is quick, full with good bass response. It has great soundstage and it has plenty of power reserve. Actually, I'm going to try it with a pair of KEF R3 Metas I have from my other system. I'm sure it will also be a good match. The BC e1x is also a great integrated amp.

fatdaddy2
534 posts
 

Useless, in that the question(s) posed by the OP involve too many variables for the collective response to tell anyone anything. Yes, I've owned class D (Crown, 600 wpc), along with AB, A, push-pull and triodes. Most class D are based on modules from a handful of manufacturers, so the end result always relies on effective implementation. Class D is not my cup of tea, but YMMV.

decooney
2,565 posts
 

"@fatdaddy2 Yes, I’ve owned class D (Crown, 600 wpc),". ..

.

Crown Class-D:  Pro Sound, PA system use, fans involved, design is not as low noise, no real input stage refinement, primarily used for PA, HT, subwoofers. If you like PA sound, great. Not a great reference for home audio use or critical listening. A limited and fairly useless comparison example for Class-D Hi Fi in musical home audio.

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