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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
mapman's avatar
mapman
23,602 posts
 

I’ve had many. Each is different but good.  Generalizing adds no value.  

bluethinker's avatar
bluethinker
324 posts
 

@hilde45 - During during Covid, I decided it was time to invest in a sound system. Little did I know I was embarking on an expensive journey exploring all sorts of equipment - class a, class ab, and tube amps. Luxman, Gryphon, Conrad Johnson, Qualiton, Linear Tube Audio…  Let’s just say I have tested my wife’s patience.
 

As I grew tired of tube amp maintenance, I recently purchased a pair of used AGD Audion mkiii class d amps. I had grown used to the rounded glow and warmth of tubes, so it took me about a week to finally honestly assess the AGD amps on their own merit. 
 

Going through your list, the frequency balance is wonderful, the image specificity is great, and transient speed makes the music exciting and energizing. I just find myself drawn into the music. These AGD class d amps sound as good - and better in many ways - than my class an amp. I’m no longer fixated on listening to my system and driving my self crazy. 
 

If you have not already, check out the AGD amps (I’m sure Ralph Karsten’s class d amp is also great btw)… I’ll keep a tube amp to swap in every once in awhile, but the AGD mono blocks are now my reference amps in my living room. 

yyzsantabarbara
5,557 posts
 

I got this amp today for my office setup.

GaN FET Amp: Premium 6.5 Class D Audio Review ($995)

I am going to assume it is not broken in yet, and it already sounds very good. My office Magnepan Mini speakers, which need power, sound excellent with them. I had a CODA #16 amp on them before I rotated it for the GanFET amp.

At the moment it is not as good as the mostly Class A CODA #16 but very impressive, nevertheless. This amp likely will sound different in 2 months of playback. That is going to be interesting given how good it sounds already.

I am using the imersiv D-1 DAC direct to amp.

Switched over to the less resolving and slightly warmer Meitner MA3i DAC also direct to amp and that seems a bit better match. Sounds more like the CODA #16.

fatdaddy2
534 posts
 

A useless exercise.

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.

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