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.
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:
- Frequency balance — Is the tonal response even across bass, mids, and treble, or does it favor certain regions?
- High-frequency texture — Are the highs extended and smooth, or edgy, grainy, and fatiguing?
- Bass definition — Is the low end tight and articulate, or loose and bloated?
- Midrange character — Does the midrange feel present and natural, or recessed and thin?
- Transient speed — Does the amp respond quickly to dynamic attacks, or does it sound sluggish and rounded?
- Dynamic range — Does it scale convincingly from quiet passages to loud ones, or compress the difference?
- Soundstage width and depth — Does it create a convincing three-dimensional image, or sound flat and narrow?
- Image specificity — Are instruments and voices placed precisely, or do they blur and wander?
- Background noise floor — Is the silence between notes actually silent, or is there grain, haze, or hash?
- 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.
- ...
- 355 posts total
@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:
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 |
Probably a good prediction. You might have missed that this is not really about surprise. We’re trying to explain it, given various circumstances mentioned in other posts. Got any theories? |
@devinplombier If you want the most out of your amplifier investment dollar, avoiding loads like this is a very good idea. All amps make more distortion driving lower impedance, which is heard as not as smooth, not as detailed (and speaker cables become for more critical!). You always want the amp to be loafing for its job, allowing it to have a lot in common with sitting on a park bench. That's when the amp, regardless of its technology, will sound its best.
@hilde45 FWIW Dept.: With this comment he really showed he didn't know what he was talking about. Dead time is a device used in any class D amp to prevent the output section overheating and failing very quickly. It is the same amount of time needed to keep a given device (MOSFET or GaNFET) cool and does not vary with switching frequency. So when the switching frequency is higher, the dead time makes up a greater and greater portion of the pulse train- essentially increasing distortion. So you have an increasing need for feedback as switching frequency is increased. You do get more loop gain with higher switching frequencies, so its possible to have more feedback.... At any rate, the reason to use GaNFETs isn't speed so much as being able to reduce switching noise because you have far less parasitic inductance in the output section. To give you an idea of how much lower that noise can be, our class D is between 60 and 70dB below the value set by the EU Directives (for which you obtain the CE mark), and that is caused by the power supply rectifier in the amp rather than the output section! As a result there are a lot of tube amps (like the Dynaco ST35) that radiate more noise than our class D. Keeping noise down is vital if you want associated digital gear to work properly!
That really depends on who you talk to. I can point you to some people who say quite the opposite. FWIW. AI really can't be trusted!
@hilde45 I think its a bad place to read the tea leaves. That is because the musical instrument amplifier market (guitar and bass amps) consumes 90% of tubes made worldwide. Class D is now invading that market too; Fender, using the Sunn marque, has just released the Sunn Beta Lead amp, which is class D. Since most guitar players use effects pedals to create their 'sound', all the guitar amp has to do is not be annoying. Its not like it was decades ago when Jimi Hendricks got his sound by overdriving his Marshall amps! It makes a big difference if you are waiting for the headlining act to get done with their set so your band can finally move its gear out of the venue at 3:AM, that your amp weighs 15 pounds instead of 85! So in ten years the tube market is going to look at lot different. The larger tube producers are going to have to sort out what to do when 90% of their market is moving away from them.
It closed because it burned down. It got rebuilt about two years ago and is producing tubes once again. I don't intend to stop playing with tubes since its fun. We're actually working on a tube prototype right now but I've got no illusions it will be better than our class D. But some people still can't make that leap, so we'll have something for them (that also uses tubes that will be easier to find as sources dry up).
|
- 355 posts total