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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
5,994 posts
 

I had Claude AI do an analysis of Axpona, and here's what it came up with:

Axpona 2026

Definitely Class D:

  •     AGD Productions (Room 724) — Guerra's own GaN Class D monoblocks (Vivace, Audion)
  •     Atma-Sphere (Popori Acoustics, Room 690) — the GaNFET Class D monoblocks we've been discussing
  •     Bel Canto (Room 1130) — long-established Class D specialist (REF series)
  •     Buckeye Amplifiers (Room 712) — builds exclusively around Purifi Eigentakt Class D modules
  •     Devialet (Rooms 318, 550) — Class A/D hybrid topology (ADH)
  •     Dutch & Dutch (Rooms 472, 476) — active speakers with built-in Class D
  •     Fosi Audio (Rooms 558, 560) — budget GaN/TPA Class D amps
  •     Gato Audio (Room 731) — Class D integrated amplifiers
  •     Hypex (Madisound, Room 348) — the NCore and Fusion Class D module maker itself
  •     Kii Audio (Room 1441) — active Class D speaker systems
  •     Lyngdorf Audio (Kyomi Audio, Room 1527) — Class D with RoomPerfect DSP
  •     Mola Mola (GTT Audio, Room 1627) — Kaluga Class D monoblocks
  •     NAD (Lenbrook Group, 1-Schaumburg E) — Masters series using Purifi/Eigentakt Class D
  •     Orchard Audio (Philharmonic Audio, Room 705; VPE Electrodynamics, Room 502) — GaN Class D specialist
  •     Purifi (Madisound, Room 348) — the Eigentakt Class D module maker itself
  •     Aavik (Audio Group Denmark, 2-Epiphany) — Class D integrated amps

Very Likely Class D:

  •     Anthem (Room 394) — their STR and MCA series use Class D
  •     Axxess (2-Epiphany) — Audio Group Denmark's Class D integrated line
  •     PS Audio (1-Schaumburg A) — Stellar series uses Class D
  •     Primare (Fidelity Imports rooms) — Class D amplification throughout their electronics line
  •     T+A (1-Schaumburg G) — their MP 3100 HV and PA 3100 HV use proprietary Class D

 

decooney
2,564 posts
 

What’s interesting is just how many rooms still run tube amps at Axpona. If this breakdown is even remotely true, it’s a surprise.  Seeing more tube amps on walk-thru videos than prior years.  There were like 220 listening rooms listed. 

Amplifier Type         Estimated %      Approx Rooms
Tube                               50–60%               ~110–135
Class A / AB                  30–40%                ~65–90
Class D / Hybrid            10–15%                ~20–35
mapman's avatar
mapman
23,588 posts
 

Tube amps are traditional high end audio’s great last stand really in terms of offering something still unique and different, even if based  on old 20th century technology that no longer measures up.  Measuring up is not required in this space, it just has to sound good and maybe offer some bling.  Tube gear shines (literally) in that area.  Plus tube rolling can be fun and gives people something to do.  

hilde45's avatar
hilde45 OP
5,994 posts
 

@mapman Good points! I have been wondering "Why so many tubes at Axpona if the technology is on the way out and tube supplies are in greater threat?"

@atmasphere Ralph, I hope you had a good show! I am thinking about your comments about the days of tubes being numbered vs. the the kind of experiences and conversations you had at Axpona. Did what you see at Axpona jibe with your general sense of where the industry is headed? Or is an audio show a bad place to read the tea leaves, at least in some respects? 

@decooney  Very interesting analysis. I had Claude AI run an analysis. I’ll spare the details here but here’s the prompt and results:

PROMPT: "How many rooms at Axpona on the distributor list  contain or were headed by manufacturers of tube amp or preamplifier gear?"

ANSWER: There are roughly 40+ tube amp/preamp brands versus around 20 Class D brands. That’s about a 2:1 ratio in favor of tube gear, which suggests that despite all the Class D momentum in the audiophile press, tubes still dominate the high-end show floor in terms of sheer brand count. The Class D presence is notable and growing, but the show remains heavily tube-weighted, which tracks with the demographics and purchasing habits of the traditional high-end audiophile market."

Even with counting errors – and there are probably several, I’m guessing – the conclusion is interesting.

Regarding the tube market, this report is interesting and hopeful, though larger changes remain problematic (the Shuguang factory closure in 2019, the small number of sources for audio-grade vacuum tube glass, the shift in the pro market).

https://dataintelo.com/report/global-electronic-tube-amplifier-market

chrisoshea
578 posts
 

If anyone here is surpised at the amount of tube gear at AXPONA...Keep attending future hifi shows and maybe you won't be surprised.

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