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

Researching and comparing any online notes that can be found for studying Tube / Class A amp designs vs. different ClassD designs while attempting to understand any loss that still might occur through the Analog signal → pulse encoding → switching → analog reconstruction process. 

Reference to good old standard Tube / ClassA SS amps, with:

• Continuous waveform (no encoding)
• Natural harmonic structure (2nd/3rd order) harmonics
• No switching or reconstruction

Hearing in midrange: Flesh-and-blood vocals, wet texture, where decay trails linger naturally, slight bloom around, close to "realness"

-vs-

Reference to "older" ClassD architecture and designs, having:

• Tiny timing errors = loss of microtexture
• Harmonics don’t decay as naturally
• Can sound:
  • “dry”
  • “flat”
  • or slightly “synthetic”

-vs-

Reference to newer ClassD architecture and designs, having:

• Faster switching (GaN)
• Lower dead time → fewer timing errors
• Higher switching frequency → easier filtering

Listeners reportedly hearing:

• Much better "inner detail"
• Cleaner "harmonic structure"
• Less “digital glaze”

But still:

• Not truly continuous like tubes or Class A
• Still a reconstructed waveform

👉 Findings:  "approaches analog" flow — but "doesn’t fully become it"

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AXPONA 2026 - ClassD?

It will be interesting to read and view show reports after Axpona ends to learn just how many ClassD amps are presented in the show rooms.  So far, still seeing lots of tube amps and Class A/AB amps there viewed on the walk-thru videos over the past few days. Hoping others who attended post more here with updates, Thx. 

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

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. 

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.  

@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