Competitive class D amp suggestions

What about the Marantz Ruby PM KI...?  

The T+A A200 Class D (Purifi) also looks interesting.

https://www.ta-hifi.de/en/audiosystems/series-200/a-200-power-amplifier/

for sound quality among class d/gan fet amps, for me it is agd - one and done

bargain seekers may look at other less costly models if they are on the hunt for better value... but that would be the reason for the hunt, not sound quality... imho

caveat -- i have not yet heard ralph’s new amp which seems to a head to head competitor to alberto’s...

a lot of player with quality sound.

new bel canto 600m

merrell audio

agd

mr ralphs class d.

".."…..

Might well be the case. But then there should exist some objective evidences that these amps are essentially superior to other more reasonably priced ones including LSA Voyager GaN 350. Honestly, i would not order one costing a few times more without having such an evidence. 

Who here actually heard in their own system the Atmasphere class d amps? I'm in line to hear a pr when my dealer gets his demo set. 

I'd like to ask Ralph two questions about class d in general but I will use his class d to ask the questions:

1.  How do I equate a class d amplifiers power output with its power draw.  So for example, your class d amp is capable of producing 100 watts at full power...at full power, how many watts would it draw?

2.  It seems that most class d amp designers are going for the lowest distortion possible. I think I've read correctly that Nelson Pass said that if 2nd harmonics are dominate, an amplifier will sound very musical for music that is not complex and 3rd harmonics are probably preferable for complex music.  I also believe I've read that your goal was to get distortion as low as possible and to have 3rd harmonics be the dominate of any remaining distortion.  Is there a particular reason for 3rd vs a blend of 2nd and 3rd?

I hope I've represented all of the above correctly..

+1 @snapsc

I just heard Mr. Pass mention 2nd order harmonics in an interview. But your question about whether 3rd order harmonics is pleasing for complex music is interesting.

And, while it may seem intuitive to presume that a system that can do complex material can easily tackle less complex music, maybe there is more to it than that.

And now for a movie reference that hopefully someone besides me, gets…

Bueller, Bueller, Bueller?   LOL.  I mean, Ralph.   

Nelson Pass is correct about the 2nd harmonic, great for simple music, but not for complex music. Here is a quote from the late Roger Modjeski on the topic as well:

"Once again, I remind people that 2^nd harmonic is not benign on complex music, i.e. anything more than a solo. What people are missing is that large 2^nd harmonic distortion also means there is large IMD and here I'm talking of the good old SMPTE test, 60Hz and 6kHz mixed at 4:1. The nice treble note riding on the 60Hz bass gets crushed in the valley of the 2^nd harmonic wave. Doesn't anyone think about this? It's so obvious and easy to hear."

I have read a number of times where Ralph talks about 2nd and 3rd harmonics being pleasing to the ear, and where higher ordered harmonics are not. I have his Class D amplifiers and also his M60 monoblocks, as well as a Music Reference OTL and David Berning Quadrature ZOTL amps. The Atma-Sphere Class D is right there with all of them. In fact I have said to Ralph and a number of people who I have had listen to the Class D amps that they in some ways make the OTLs sound obsolete. There is some really cool things that Ralph is doing in his circuit that other Class D manufacturers are not, and it's evident in the sound.

Don't be concerned if Ralph does not pop in here. He is off on a month long bicycle trip riding along the Continental Divide. So his access to the Internet as well as time to respond on this thread may be limited.

Good for Ralph...life can't just be about music and Gear 🤣.

I can't seem to find it now but I think Ralph said that his goal with the Class D Monos was to get the distortion as low as possible and be sure that any residual distortion was dominated by the 3rd Harmonic....and based on how you describe the sound, I wouldn't be surprised if this is exactly what Tommy Obrien was doing at Cherry Amp...although he never actually said it.

What about the wattage draw question...if a class d amp is 90% efficient, does that mean that it draws 110 wats to produce a 100 watt output?

There is some really cool things that Ralph is doing in his circuit that other Class D manufacturers are not, and it's evident in the sound.

Something similar could be said about Cherry amps, these amps have something special, they sound different to other class D amps. They have some kind of a special flavor. The distortion of Megaschino  is 001% and this can be perceived. It sounds cleaner than my push pull class AB tube amp, but the SET class A tube with 5% of distortion at 5 watts, 2-3% at my usual listening volume of 2-3 watts, sounds remarcably cleaner, which is very difficult for me to explain.

@snapsc , it would be great if you compare your Cherry amp with Atmasphere class d, they may have something in common indeed.

@niodari 

I suspect that the difference between the Set and the Megaschino is both the amount of distortion and the profile of the distortion with the SET amp having more 2nd and 3rd harmonic giving it a tonal difference.  In my case, with the 2Cherry, I've never owned an amp that was as clear, tonally correct and presented music in a life like way.

I pretty much change my system up every 2-3 years...I guess because the gear is as much fun for me as the sound.  Most of the time, I sell the current piece to make space for the next piece, although lately I've just given gear to my son as his interest in the hobby seems to be growing.

I've got my eye on a couple of amps and as such, will sell the 2Cherry...and usually there is an overlap of the old with the new so a comparison may be possible.

That would be very interesting, please keep us posted! 

I will not sell my Megaschino, also because no Cherry amp will ever be again produced (on this land, at least; perhaps Tommy is doing that in heaven) and it will be a benchmark for me. But I do wish to arrange the problem in its right channel! (so far,  i have no idea  who could help me with that) 

Who here actually heard in their own system the Atmasphere class d amps? I'm in line to hear a pr when my dealer gets his demo set. 

I have a pair incoming.   I currently use a Pass XA30.8 so it will be a very interesting comparison!    I love the Pass but my listening room doesn't have AC so if I can find something I like as well but runs cool, that would be great :)

That could be a conceptual change from Pass labs XA amp. If you like how Pass Labs  amps sound, you may also like Nuprime class D ST10 monoblocks, but they do get a bit hot in long run.

Let us know your first impressions on Atmasphere monoblocks vs XA 30.8. 

Speaking of 2nd and 3rd order harmonics and their influence on what we hear...this is an interesting post/analysis.....

@snapsc Thankyou for that link, that is tremendous information.

This leads me to wonder about the virtues of Purifi module Class D amps. Tests reveal the near total absence of any audible 2nd and 3rd harmonics.

I guess it depends on the maker using Purifi technology, but I have recently been reading all I can about March Audio.

So "good" is bad. True.. While I haven’t auditioned, I remain cautious.

I am very sad that Ralph’s Class D is designed only for Nth America and Canada (and perhaps a few others) electricity supply, otherwise I’d be placing my order.

AGD? Hmm. If I really have to, kinda thing.

I'm not an engineer but I suspect that the Purifi is similar to the Benchmark....drive the distortion as low as possible...period, the end...and obviously a ton of people really prefer that sound.

Since very few designers talk at length about what their 2nd or 3rd harmonics strategy is...you don't know for sure what you are getting unless the amp has been tested or the designer will tell you.

I have a buddy who posts here pretty often...he has a Purifi amp and a few other amps as well.  He says that the Purifi actually sounds fantastic...strong low end, really nice top end...good sound stage...BUT...he says that compared to his other amps, it is emotionally uninspiring which to him means that while it technically sounds good, it doesn't seem nearly as musical as his other amps that are know for actually having some 2nd and 3rd degree harmonics.

Is this real?  Is this imagined?  I don't know but since there is more and more being written now about something that Nelson Pass identified 20 years ago...maybe we will all learn more in the years to come?

Very curious to hear the difference between my AGDs and the Atmas.

In chrome, my Audions are $8400. The Atmas are only &5400.

@clio09 

Your Berning OTL is something like $80k… is it not? And the Atmas go head to head??!

Thanks for sharing to this link!

I had a brief look at this information, and may have a more detailed look afterwards. I understand now more about harmonics and the distortion. I  general, much depends on which particular mathematical model is used . Here using merely a third degree polynomial might not be a most refined  way to model this   problem.  But it's always difficult to find a precise mathematical model. Like in quantum physics, the quantum equations somehow work. The outcome though is difficult to explain from our Newtonian point of perception of the world. Something similar maybe happening in distortions and measuring the distortions. In fact the formula that I just saw for measuring total harmonic distortion is a bit rough to me. So based on that formula the measurement might not say too much or even could be not really relevant. But there is an immediate practical observation that the second order  harmonics somehow amplify middle and high frequencies making them sound softer, and the third order harmonics in fact amplify the amplitude so the sound becomes more dynamical. Based on these practical observations mekes me to think  that both kind of distortions are good.  Auditioning now my set tube amplifier and analyzing what I have just read I understand and feel more what is happening. 

From here on THD will be irrelevant for me to judge about audio gear. Purifi model will neither attract me any more. As I suspect, it is hard to achieve 100% of linearity, i e., an ideal natural sound preproduction. In this regard, the second and third order harmonics could be helpful. I guess this is merely the reason why many people including myself like tube amplifiers. 

Actually, I don't know how the second and third order harmonics are dealt with in class d amplifiers in general, and in GaN class d  amplifiers, in particular. Any input on the subject would also be appreciated. Thanks again for your input.

Actually, I don't know how the second and third order harmonics are dealt with in class d amplifiers in general, and in GaN class d  amplifiers, in particular. Any input on the subject would also be appreciated. 

Perhaps because they are there but rather inaudible to mortals.  This review puts a March Audio (Purifi based) amp through the tests.  Some lower order harmonics *do* exist (maybe contrary to what I said previously) but at barely there levels.

I have not seen any GaN tests.  Some may exist, but not for AGD or Atmas that I am aware of.  I can't recall the dude at AGD even mentioning harmonics in his rather infrequent announcements..

+1 to the Elacs.  1U format, cool running, sound great and the price is nice.

The interesting thing from the March Audio review/test is that although the distortion is very low, the remaining distortion is mostly 2nd and 3rd.  The question  becomes "although it has great bass and an extended top end, is it musical"...or is possible that the distortion possibly too low for optimal musicality?

Of course "musical" means different things to different people...from lush harmonics to no fatigue to open and airy...and then there is the whole issue of how much influence is being put forward by the specific speakers and room.

The important thing is that with more of these tests, people can begin to draw their own conclusions at to what might be more appealing to them individually.  In my case, I never really understood what CherryAmp was doing to get a less sterile and more musical/harmonic/lush sound...now, I have a suspicion that since Tommy was an admirer of Nelson Pass, he got the 2nd and 3rd harmonics where he wanted them while driving total distortion low.

Perhaps what we need is an amp with variable second and third harmonic controls, so that we can dial in the exact mix that we prefer.  

Perhaps what we need is an amp with variable second and third harmonic controls, so that we can dial in the exact mix that we prefer.  

This can be done with digital signal processing, or something similar. I think its a good idea - that is I think what Nelson Pass used on test subjects to reach his optimal tweaking of included harmonics.

I don't know how difficult it would be to realistically implement in an analogue amp intended for home use.. Probably would be expensive - just a wild guess.

@mglik, the Berning Quadrature Z are $33k list. I'm not one of those people that feels the higher the cost the better the sound. While the Berning amps are quite good, and I respect David Berning as an innovative audio engineer, I'd never pay $33k for them. Too much out there at a fraction of the cost that is a better value in my opinion. So yes, the Atma-Sphere Class D were right there with them, so much so that I packed the Berning Quadratures up today to get them ready for sale, to be followed by the Atma-Sphere M-60s. I am keeping the Atma-Sphere Class D, as well as my Music Reference OTL-1, RM-10, and RM-9 SE amps.

I am very sad that Ralph’s Class D is designed only for Nth America and Canada (and perhaps a few others) electricity supply, otherwise I’d be placing my order.

@noske We recently documented that our noise emissions meet EU directives; we always had intention of selling overseas.

The interesting thing from the March Audio review/test is that although the distortion is very low, the remaining distortion is mostly 2nd and 3rd.  The question  becomes "although it has great bass and an extended top end, is it musical"...or is possible that the distortion possibly too low for optimal musicality?

I have just realized that i don't really know which order harmonics  THD measures. My rough  believe now is that if it is high for 2nd and 3rd order harmonics then its fine (i found the article from your latest link particularly useful and well argumented).

I have a suspicion that since Tommy was an admirer of Nelson Pass, he got the 2nd and 3rd harmonics where he wanted them while driving total distortion low.

We will now never know that... I suggest  this can be a best way to deal with the distortions! Such an SS amp could also sound like a tube amp. 

I just recalled the third degree polynomial from the article. Not sure but it might be the case that THD takes a mere weighted sum of gain, the second and third degree harmonics. More refined parameter would measure the distortion of the gain, second and third order harmonics separately.

@niodari THD takes a mere weighted sum of gain, the second and third degree harmonics. More refined parameter would measure the distortion of the gain, second and third order harmonics separately.

Yeah, and SINAD. This is probably not the right forum to discuss issues of specific weightings as it is quite a mathmatically beguiling issue. This, I think, is understood.

I look at a threshold metrics. Should they be met, then a visual of what else is presented is worthy of further examination - this is perhaps three or four other parameters, on a good day.

And this is becoming reasonably well understood by many inquisitive folk, with thanks to a small number (one?) of .educational resources that did not exist until recent years,  Plus valued contributions by exceptionally knowledgeable people.

@clio09 ”Too much out there at a fraction of the cost that is a better value in my opinion.”

Yes you pointed out you are a value shopper and it is not a good value. Some people are going for the the best sound they can get. This is their market. But for them it is completely worth the cost. Hence, fr them it is a good value. Values are personal.

@ghdprentice, maybe I should have stated my point a different way. I know too many people who when doing comparisons think along the lines of, "Well it cost $100,000 so it must be better...". To your point, I do go for value, but I go for the highest quality of sound I can attain as well. In addition to moderately priced components I have some very expensive components in my system. All components in my system were chosen for their value, regardless of their price, and because they contribute to the overall enjoyment of my system.

@noske So far,  for me this is a most relevant forum to discuss this since am not aware of other possibilities and i know nothing about electronics. As i have already mentioned, i was not aware of these things before i had a look on the article which seems to be very useful and well written. 

An average is no good if you wish to have an information about the distortion of the harmonics of a particular degree, unless you adjust the weights respectively,. but then you will have different functions, i.e., using current terminology different  "THD" for different harmonics. If ones wishes to have a single universal measure, we may give a large weight to the gain and relatively small or 0 weight to the second and third degree harmonics. But then we will practically ignore the higher order harmonics, which we know are good for may people (who likes tube stuff)! Or a manufacturer may decide which of the "THD"s specify in their products. 

@snapsc , you may be correct about the design strategies of the Cherry amps, Tommy also liked tubes. I think these are second and/or third order harmonics that made me enjoy so much the Megaschino, and my tube SET amp as well. I suggest that it is precisely this tube-like effect of the higher order harmonics that makes the sound so enjoyable. 

Creating alternative "THD" measures seems to me to be a best simple solution to reflect a more precise picture of what is really happening. In fact, we have here a kind of multiobjective and threshold  optimization problem. Our first objective is to minimize the first order harmonics that is also referred to as the gain if i am not mistaken, and also we aim at somehow maximize (!) the distortion in higher order harmonics. Or we may try to maximize the distortion of 2nd and 3rd degree harmonics where we wish to keep the distortion  of the first degree harmonics (the gain) no larger than a certain claimed threshold (for example, 0.001%). Redefining THD in this way,  the producers of the tube amplifiers will  bravely be able to put real distortions that their equipment have.  I don't know about electronics and the limits of the distortions, i.e., would a very large distortion of the 2nd and 3rd order harmonics be good, and what is an ``ideal'' balance between the second and the third order harmonics? 

At this point, with my humble knowledge, i suggest that all this THD (and perhaps other spec parameters) theory is just a b*****t (created by engineers who do not know much about mathematics). It is a non-relevant and non-informative parameter which does not disclose actual balance between the harmonics of different orders.

Electric engineers succeed to develop exceptionally sounding equipment, but the existing parameter for measuring their ``distortion'' seem to me to be useless. 

Electric engineers succeed to develop exceptionally sounding equipment, but the existing parameter for measuring their ``distortion'' seem to me to be useless. 

Engineers have other measurement tools: distortion vs frequency (rising distortion is an indication brightness and harshness may be present), distortion spectra at one Watt and also at 06dB of full power and distortion spectra measured at different frequencies.

If you know what you are looking for, these measurements can tell you how the amp will sound. I agree THD isn't a good marker.

Engineers have other measurement tools: distortion vs frequency (rising distortion is an indication brightness and harshness may be present), distortion spectra at one Watt and also at 06dB of full power and distortion spectra measured at different frequencies.

If you know what you are looking for, these measurements can tell you how the amp will sound. I agree THD isn't a good marker.

So the situation is not completely hopeless. Ralph, how these distortion parameters reflect the distortion of the harmonics of each degree?   I think that now i know that i am looking for an amp with small first order distortion but large second and third order distortions, roughly. But, as I have also mentioned, i don't really know how large they can or should be, no idea at all.  

@niodari 

the numbers might get you in the right theater but you will only find the perfect seat by trial and error because the amp has to mate with the source or preamp and speakers in a way that sounds great to you. 

So for the trial and error process you either buy new and return or preowned and resell if the amp ends up being a bust.  The key is to enjoy the journey knowing that perfect is the ultimate unobtanium.  

So the situation is not completely hopeless. Ralph, how these distortion parameters reflect the distortion of the harmonics of each degree?   I think that now i know that i am looking for an amp with small first order distortion but large second and third order distortions, roughly. But, as I have also mentioned, i don't really know how large they can or should be, no idea at all.  

In a nutshell, if there's enough lower ordered harmonic distortions, they can mask the higher orders. The higher orders otherwise cause harshness and brightness. Either the 2nd or 3rd can predominate, but if the 3rd dominates then it has to be at a lower level to begin with- about 1/10th what you might see if the 2nd were dominant in the design.

For example almost any SET makes 10% THD at full output- most of which is the 2nd harmonic. If you have an amplifier design that makes the 3rd instead of the 2nd (which can happen if the amp is fully differential and balanced, since even orders are cancelled throughout the design) then the THD will and must be much lower. This isn't that hard to achieve since a design that exhibits a dominant 3rd harmonic will tend to have less distortion overall anyway.

On top of that the distortion cannot rise as frequency is increased, which is a problem with most solid state amps made (and with tube amps employing feedback). Class D offers a solution for this- you can have the distortion vs frequency look like a straight line, and you can run a lot of feedback at the same time. In this way you can achieve distortion levels that are several orders of magnitude lower than you might see in a tube amp ye the actual distortion signature (2nd and 3rd vs the higher ordered harmonics) can look quite similar to a tube amp.

This allows greater transparency (since distortion obscures detail) yet the same kind of smooth mids and highs you associate with a really good tube amplifier- IMO, the best of both worlds.

In case you don't get my drift, I'm drawing a very straight causal line between the distortion measurements and how the amplifier actually sounds; IOW its predictable based on sufficient measurement! The tech to do this really didn't exist 40 years ago but it does now. A lot of audiophiles don't know that yet; like so many industries tradition plays an enormous role in this.

In unrelated news, Topping has recently released a new version of its D90SE DAC, called the D90LE, and that is unremarkable in the current context.

What may be of interest, perhaps for educational purposes only, is that included in the new firmware is the option to simulate either tube harmonics or transistor harmonics (or neither).  Specifically, just 2nd and 3rd harmonics, fixed for either option.

Scroll over three quarters way down here to "Sound simulation", and there are images of the fundamental and its two prominent harmonics spikes (sadly the images are not very clear).

Ralph, your distortion discussion is very helpful. What can you say, generally speaking about the distortion make up for class A and highly biased Class a/b solid state amplifiers?  Are they generally the higher distortion 2nd harmonic type or the lower distortion 3rd harmonic type.. or have I missed the mark completely???

What can you say, generally speaking about the distortion make up for class A and highly biased Class a/b solid state amplifiers? Are they generally the higher distortion 2nd harmonic type or the lower distortion 3rd harmonic type.. or have I missed the mark completely???

Most of them tend to have unmasked higher ordered harmonics at a low level, and because the ear uses the higher harmonics to sense sound pressure, its keenly sensitive to their presence! Also because the ear assigns a tonality to all forms of distortion, this causes most of said amps to sound harsh and bright even though they might have less higher ordered harmonics than a tube amp! This is how important the masking that the 2nd and 3rd provide can actually be.

The reason so many class A and AB solid state amps have this issue is they lack the required Gain Bandwidth Product to support their feedback at all frequencies. This is why they can play good bass, since at those frequencies the feedback is enough to do the job. But at some higher frequency the amp runs out of GBP and so the feedback decreases: and with it the distortion at those frequencies rises. That is why distortion vs frequency is an important measurement. The distortion simply should not rise at all if brightness and harshness is to be avoided.

There are a few A and AB amps that appear to have enough GBP to get around this problem and I think most of you know of one of them- the Benchmark- but you still have the issue of the distortion spectra itself. Most of the measurement guys that poo-poo subjective listening will tell you that the distortion is inaudible if about 100dB down. I personally doubt that; if it were true there would be no controversy around the ’sound’ of these amps. Since getting the distortion that low (< 0.005%) is pretty hard you can see that the distortion spectra still plays a role.

One thing to keep in mind is that the distortion spectra at 1 Watt doesn’t tell the whole story! A classic example is SETs, which at lower power really do quite well. But when you get over -6dB of full power the higher ordered harmonics become more prominent. This causes the amp to sound ’dynamic’ at first (as power is increased) since the power needed is on the transients. So the ear reacts to the loudness cues on the transients, converting the result to ’dynamic’. I’m convinced that when audiophiles use the word ’dynamics’ to describe what they hear in an amplifier or stereo, that you can safely replace that word with ’distortion’ and not change the meaning of the conversation at all.

In many class A and AB amps what happens is not quite the same- as power is increased the distortion spectra changes but the result is more harshness and brightness, since that’s a problem with them even at lower volumes.

BlueSound PowerNode.

2nd and 3rd harmonics pretty much same level.

Well my dealer tells me "soon" that he will be receiving his pr of the Atmasphere Class D amps for his own showroom, then off to interested customers. I've heard this for almost 3 months. I understand production issues but still always the same thing. Time for me to move on sad to say.  

Ralph your tutorials are helpful!  At lease i understanding now better what is or can be happening with the sound delivered by audio equipment (why knows about electronics may also understand why is this happening). I still am not sure about some basic things. Now i suspect that the "higher order harmonics" are not second and third order  harmonics but 4th, 5th etc order harmonics (just to clarify, in my earlier posts i referred to "higher order harmonics" as the second and the third order ones!). Do 4th, 5th etc order harmonics also exist? Is the goal then to suppress 4th, 5th etc order harmonics with the second and third order harmonics, or also suppress the first order harmonics ? Why a high distortion in the first order harmonics cannot suppress the  4th, 5th etc order harmonics?

Independently of what is the answer, it is clear that an average of  some order harmonics and hence THD makes no sense (see my earlier posts) merely because it does not take into account the rules of acoustics.  

This allows greater transparency (since distortion obscures detail) yet the same kind of smooth mids and highs you associate with a really good tube amplifier- IMO, the best of both worlds.

I did not understand that. Are you saying that by obscuring the details greater transparency is reached ? 

@twoleftears this diagram, a proof of a nearly the same behavior of the  second and third harmonics is nice to see.

I still am not sure about some basic things. Now i suspect that the "higher order harmonics" are not second and third order  harmonics but 4th, 5th etc order harmonics (just to clarify, in my earlier posts i referred to "higher order harmonics" as the second and the third order ones!). Do 4th, 5th etc order harmonics also exist? Is the goal then to suppress 4th, 5th etc order harmonics with the second and third order harmonics, or also suppress the first order harmonics ? Why a high distortion in the first order harmonics cannot suppress the  4th, 5th etc order harmonics?

Let's be clear about something: 'masking' is where a louder sound (like a 2nd harmonic) can obscure a quieter sound (like a higher ordered harmonic). "Supress" suggests reducing the harmonic. So the lower orders do no suppress higher orders, but they can mask them if their amplitude is high enough in relation to the higher order(s) to be masked.

The higher orders are the 5th and above.

Are you saying that by obscuring the details greater transparency is reached ? 

No. I am saying that with lower distortion there is greater transparency; distortion obscures detail.

@twoleftears Interesting. That 18th harmonic (9KHz) looks increased. There also appear to be some intermodulations present (inharmonc; not positioned directly on a graticule or directly in the middle of two graticules). 

@niodari The first harmonic is the fundamental frequency of the note itself.  So that's the big spike to the far left.  Thus the other harmonics begin with the second.

The reason why the same note/frequency played on a violin and a clarinet sounds different is--simplistically--because different instruments produce different combinations of harmonics... rather like different models of amplifiers!

@snapsc 

The interesting thing from the March Audio review/test is that although the distortion is very low, the remaining distortion is mostly 2nd and 3rd.  The question  becomes "although it has great bass and an extended top end, is it musical"...or is possible that the distortion possibly too low for optimal musicality?

They sounded pretty darn good and musical when I heard the older 120W/ch version.
But I am more in the camp of “give me a wire with gain”, and not in the “spice to taste” camp.
Did hear some Devore O/98s with a Jadis that  sounded nice in LA (SoCal). I did not bust out the iPhone for an SPL reading, but they sounded loud.
They were musical, but not overly quiet in the “low distortion” way.

Horses for courses I suppose??

And as Ralph says here:

Most of them tend to have unmasked higher ordered harmonics at a low level, and because the ear uses the higher harmonics to sense sound pressure, its keenly sensitive to their presence! Also because the ear assigns a tonality to all forms of distortion, this causes most of said amps to sound harsh and bright even though they might have less higher ordered harmonics than a tube amp! This is how important the masking that the 2nd and 3rd provide can actually be.

The speaker (and amp) had a quietness about them.
(And the speakers having low distortion is likely a very big part of that.)

Historically I have usually found it rare to find quiet speakers. It is always a sign that something magical is happening.
I usually find this when I cannot hold a conversation and bust out an SPL measuring app and find it is playing 90-100 dB(A).
But it does not sound as loud as a system playing at 80 dB(A) in a somewhat perplexing way.

I only have found that happening when the speakers and amp have a low distortion, so I have no reason to suspect anything else than what @atmasphere is saying about “the ear” using the harmonics to determine loudness as being likely true.

Personally I do not likely opt for musicality via high distortion over having low distortion electronics and drivers in a speaker that is also not plagued by resonances. While both can sound good with most music… it just seems easier to get good piano and vocals out of a system that is lower distortion and more free of resonances.

But, then again… I have only heard a limited number of systems, and never heard Atmasphere gear in person. I am intrigued by his electronics… so it is (IMO) a low risk decision.
Similarly with the MA gear, it measures very well… and… I have heard it and it also sounds very nice.

Ralph, thank you for the explanation. One thing I’m still not clear about is why people describe class a and high bias a/b as being warm sounding especially if their overall distortion is on the higher side?