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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
kirkwallace's avatar
kirkwallace
286 posts
 

@hilde45 i thought I’d come back to the Pascal module driven Gato Audio DIA 400-S (NPM) class D integrated amp I received in February.  It has over 100 hours of playtime on it now and while it sounded fine out of the box, i think it is now performing exceptionally well.  Driving my tiny DALI Menuet SEs, it just makes them sing with very clear, unstrained, never harsh treble and pretty marvelous bass for such tiny speakers.  But the real fun was connecting them to my Joseph Audio Perspective 2 Graphene’s this weekend.  Totally transformed the speakers. Gave them that last 5-10%  musicality and harmoniousness that they had so far lacked — and for which reviewers always praise them — when driven by a very well regarded Class AB integrated amp. (This was not using the Gato’s internal streamer and dac, but rather my Stream1/Phoenix USB reclocker and LTA Aero with TungSol round plate NOS tubes that the JA normally rely on.). Never fatiguing, sibilant, shouty or harsh, regardless of volume.  (At 400 wpc, I have to be careful about not turning them up too much!). I perceived no loss of detail or dynamics compared the AB that normally drives them. I am really delighted with this little (13kg) Gato! 

It is probably unlikely you can get to audition the DIA 400-S, but if that chance does arise, I hope you take it and add here your experiences with it compared to your other amps.

Thanks again for a terrific thread and all the work that went into it!

kirkwallace's avatar
kirkwallace
286 posts
 

I can’t figure out how to post a pic of the Gato DIA 400S, but it is a handsome devil to boot. If anyone is curious, here’s the link 

Gato DIA 400-S product page

hilde45's avatar
hilde45 OP
5,997 posts
 

@kirkwallace  Thanks so much. Glad you’re enjoying it. An important fact about my speakers are they’re 97 db and are above 8 ohms mostly. They roll off at 60 hz. A super easy load. This is why Class D does not have that much advantage over other amps. Class D has wonderful power but my speakers are very easy loads. They can be driven with a handful of watts with alacrity. 

The speakers you mentioned benefit mightily from class D. The DALI Menuet SE
is I think 86 dB and 4 ohms. The Joseph Audio Perspective2 Graphene is, I think 84 dB, 8 ohms with a nice high minimum of 5.5 ohms. Though a bit less sensitive (~83.6 dB measured by Stereophile, nominal 84 dB), the Joseph’s impedance profile is benign, I read.

But either way, these speakers can show off the benefits of a Class D amp’s power and invariance. I happen to have speakers that are easier and show the benefits of Class D less easily – and probably the reason why, overall, I still see the Class A amps I have heard as better, overall. Most people don't have my speakers. Most people can benefit from the power in Class D. And it's great that makers like Ralph and AGD and others are thinking hard about how to implement with musical ends foremost in mind. I would like to try Ralph's amps next. Just have to bite the bullet. I'd be excited to write them up after some time with them. 

kirkwallace's avatar
kirkwallace
286 posts
 

Make complete sense, @hilde45 .  What shocked me was that, at least in my room, with my other components, for the JA speakers, the DIA 400-S was clearly superior to my big Class AB amp.

I’d love to see your write up of @atmasphere ’s Class D monoblocks.

decooney
2,564 posts
 

To @kirkwallace looking at the power amplifiers, interesting how the mono, four, six channel amplifiers from Gato Audio are all listed for the exact same price. 

One might normally expect the mono amps to be lower cost, but I guess not for now, all the same price at E4495 ea. I wonder if any rooms at Axpona will have them playing for people to listen to and check them out there?

https://www.gato-audio.com/eu/electronics/power-amplifiers.html 

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