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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
mike_in_nc
1,250 posts
 

>> My main point was just to say that there can be sonic designs that do not sound warm which are nevertheless the product of someones intentional, artistic, sonic preference.  <<

I’d definitely agree with that.

It’s been a few posts ago, but could I go back to the characterization of an amp as "shouty"? I would appreciate getting a clearer picture of what’s meant by that by @hilde45 . I would consider a setup to be shouty if there was an emphasis (even if not measurable) around 1 kHz to 3 kHz. But I am not sure that’s the same thing that was meant here.

 

hilde45's avatar
hilde45 OP
5,993 posts
 

@mike_in_nc 

It’s been a few posts ago, but could I go back to the characterization of an amp as "shouty"?

Clumsy phrase on my part. 

Here’s a better way to say it. I’m describing upper midrange forwardness or presence region emphasis — a boost or lack of control roughly in the 2–5 kHz range that causes vocals, brass, and attack transients to project aggressively. These are loud moments that feel stressed rather than effortlessly loud. Another way to describe it would be "hardness on peaks" or glare in the upper mids. In short, the sound becomes irritating or fatiguing precisely when the music demands the most from the amp.

Better?

mike_in_nc
1,250 posts
 

@hilde45  - Thank you for your explanation of "shouty", which does make clearer to me what you are describing. It's something I have experienced, though I always associated it more with recordings than with amplifiers. That's not to take sides in this; I would have to say, I honestly don't know.

Surely, an amp that could suppress that "I have to turn this down NOW" feeling on some recordings while not reducing the pleasure of playing others would be musically desirable.

Do you use specific recordings to detect shoutiness? The ones that came to my mind immediately were some old recordings of violin concertos, made in the LP era and transferred (badly, I'd say) to CD. On occasion, I've resorted to EQ to make those more listenable.

hilde45's avatar
hilde45 OP
5,993 posts
 

It's something I have experienced, though I always associated it more with recordings than with amplifiers. 

What allowed me to attach the adjective is that the same recording, decibel level matched, sounded shouty with one amp but not another.

Typically, shouty is a female voice belting out a note or a horn. 

niodari's avatar
niodari
378 posts
 

To me, this "shouty" in the sound reproduction is most evident on  symphonic recordings, when a considerable amount of string instruments (violins) play together. It is more notable on old types but even on new ones. I suggest this is a most difficult type of music for amplifiers. In fact, I use to compare the amps based on this measure, in particular.   

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