Who tried Class D only to return to S/S or Tube

After a year and a half, I have finally divested myself from a pair of very good sounding Ncore NC1200 Acoustic Imagery Atsahs, but I have not settled in on their final replacement.

The original comparison was between the Class D Atsahs and a Class AB McCormack DNA-2 LAE that I own, which SMc Audio upgraded to their Signature Edition in 2014. The SMc-McCormack is an excellent sounding amp and, in comparison to the Atsahs, simply sounded more "real," primarily due to a better portrayal of spacial cues between musicians, a better sense of venue and perhaps a better ability to portray micro-dynamics. In addition to the upgraded DNA-2 LAE, I also have here a pair of Class A Lamm M1.2 Reference monos and, as of Monday, I will have a pair of Class A Clayton M300 monos. I plan to keep either the Class A Lamms or Claytons, and then decide whether I want to keep the Class AB SMc-McCormack too.

Reviews have been very positive about the Class D NC1200 amps, and I found them to sound quite nice, with standout features being a dense tonality and excellent (although possibly overdamped with some speakers) bass, as well as several very attractive ergonomic characteristics such as small size, low heat, low energy usage, and zero self-noise. Unfortunately, in comparison to the mentioned Class AB and Class A amplifiers, I felt the Class D Atsahs were lacking that last bit of lifelike ambience, as if music is not being played live or by a band in a studio, but rather as individuals cutting their own tracks and then merging the tracks to make the whole.

In my opinion, the reviewer over at Mono and Stereo actually got it mostly right (although too critical), with his review of the Mola Mola Kaluga, where he states,

"The familiar music didn`t sound much familiar through the MOLA MOLAs; in the midrange the voices did not posses enough dose of “human touch” to sound real.
All notes were there but the illusion of musicians standing in front of me wasn’t convincing at all. The music didn’t sound inviting and involving, it was just… there.
The emotional content was missing and the tonal colours were somewhat bleached.
For lovers of analog reproduction and concert goers the sound could also be quite fatiguing and plain boring."

And he concludes with .......

"As for the KALUGA monos…in my view the time has not yet come. Perhaps many people will find them good in what they do and will happily live with them for many years, but it should be pointed out that class-D amps offer a very different sonic perspective from what one hears live OR with good analog amplification, be it tube or solid state - regardless of the amp`s working class. If the sound of KALUGAs would be declared as very lifelike, then I fear we would be sending a wrong message to the audio amplifier industry, not to mention deny the reality. There is just no way one could consider both, the analog and switching amps equally capable of materialising that grand illusion of performers playing and singing in front of us - this is just impossible due to huge differences in sound."

One designer of Class AB amplification once told me, in his opinion, the Class D amps he had heard at that time had been "dynamically challenged." I believe he was talking about that micro-dynamic 0 to 60 thing. Some might call it sounding "overly smooth."

Based on my time with the Class D Atsahs and assuming (from the many positive reviews) that NC1200 is at or near the top of the Class D amplification chain, then the current state of Class D amplification has resulted in amplifiers that can sound very good, and that offer excellent ergonomic attributes, but still do not compete in every way with upper level Class AB or Class A amplifiers with regards to creating a musical whole, or a realistic illusion of performers and venue.

Hi Keith, doing well, and... Wow, I knew I was forgetting something important.... Fact is that Burmester is my other prefered uber-high SS brand, together with Solution and Rowland.

How could I forget, given that I was the one who pointed Matt onto Burmester?!

Only thing is... Seems I had a misconception. I thought Burmester ran in high bias class A/B, hence my original assertion that I had not found a class A amp that took my breath away. Well, seems that I had already found one after all... Burmester 911 and likely 909 at RMAF.

Burmies are an interesting case for me. In olden days, think about 15 years ago, they were not my cup of tea at all... I thought them to be both a little dark and a little hard sounding. Yet in the last several years they evolved into what for me are creators of true magic.

So now I know I have already found high magic in class D, Class AB, class A, and hi power tubes.... I am confident that my discovery of magic OTL will come eventually 

Saluti, G.

Hi Audiolabyrinth, I am absolutely vdelighted to hear that you love your class A amp. I feel exactly the same about my class D Rowland M925, which like your own device, appears to have a propensity for conveying feet shuffling, page turning, and.... Plenty of subvocalizations on old Glenn Gould and Andras Schiff recordings... Did I mention that it is so musical it makes me forget where I am?

Unfortunately, I have no idea how to evaluate amps according to parts count or soldering joints... I just listen to the music from components that I have had the fortune of owning, or at least listening to, with as little prejudice as I can muster in the process.

BTW, In SS class A/B, I truly adore Solution. in high power tubed amplification, ARC and VTL realy strike my fancy. In SS class A.... I am sure I will eventually find an amp that takes my heart away... I am sure it exists out there already *grins!*

 Y

Regards, G.

Hi ENIAC, your post could not be timelier. On Friday 11th, Marc Mickelson of The Audiobeat, posted his review of the Rowland M825 stereo amp, which sports  those very class D NCore NC1200 modules that you have experienced in your system.

Marc's findings are based on prolonged use of the amp in his system,, which protracted for a number of months... Yes, I estimate the device to have been fully broken in.

He appears to concur with your opinion that appreciation of musical neutrality in high achieving class D amps may require a paradigmatic shift for some audio lovers, away from some much beloved traditional warm sound.

Amongst other things, he expresses the following thoughts in his conclusions...

"Such a peripheral line of reasoning underscores what is very best about the Model 825 -- and potentially any great piece of audio equipment: it makes you forget that you're listening to a complicated and expensive audio system. This is more than the ability to suspend disbelief; it's a disarming of critical faculties, even when you're trying to be critical and unravel what you're hearing. In my experience tubes do this more readily than solid state, and class D almost never does it. The Model 825 does it as a matter of course -- it can't not do it -- and it happens not because of one or two or three of the sonic traits I discuss above, but all of them, in their exact proportions. If the Model 825 were somehow more natural, bordering on romantic, or more round and rosy, especially through the mids, it would be a different amp and perhaps a very good one, but not a great one. And the Model 825 is a great amp -- in numerous ways, greater than any amp I've heard. It speaks not just in its own voice but in a voice I always wanted to hear, such is the pull, at least for me, of the utterly clear yet composed way it reveals all that's on each recording."

http://www.theaudiobeat.com/equipment/jeff_rowland_model_825.htmSaluti,

As for Marc's caveat that "class D almost never does it", I respectfully disagree with him... And suggest that listening to a broad range of current high performing class D amps tends to reveal that class D in general has the same chance of sounding great or horrid as any other topology.   

Guido

If there was a way to plug in a speaker or headphone directly into the CD Media itself with nothing else in the chain you will most likely arrive at the same sound today's modern Class D is capable of given an equally transparent Preamp,cabling and speaker. As an example, the noise floor on the Hypex modules lies almost as low as many of todays SOA D/A converters and way below the majority of PreAmps on the market. Going D/A direct or having a very good $$$ Pre is pretty much a requirement if you don't wish to hear those devices influence at the output.

I used to own some very popular Class A & A/B amps in the past and then one day decided to try Class D despite hearing all the negative impressions from folks who are heavily invested in tubes & classic Class A/A/AB amps. I will admit that it took me a while to get my mind and ears around what I was hearing. The presentation was VERY different with a modern Class D design (I have used Hypex NC400 & NC1200 exclusively). The stripped down and crystal clear output via the Class D amps can indeed be too much change for many people to bare.

The truth is, once you get past this sonic change in presentation and begin to hear your music thru a much cleaner lens it then opens the door to adding your Salt/Pepper seasoning in much smaller doses to suite your final taste.

In most cases this Salt and Pepper can be introduced via cabling & isolation tweaks instead of via a sledge hammer by way of using inherently "warm" components that add too much seasoning to the point of being so far from the sound of the original media that its not even funny. This is especially true when you consider the combined total of seasoning added by component, cabling, tweaks, speakers and what ever else you can imagine.

Personally I like having a totally neutral set of main components that remain true to the source and then add my flavoring via cables and isolation as needed. Understandably folks like myself are the minority in this hobby and in the end as long as we all enjoy what we are hearing it doesn't matter how you get there.

George, the answer is... Yes, the current switching frequencies of approximately 500KHz in the power conversion modules are sufficient for some OEMs to implement some marvellous-sounding amps.... Kuribo and several others have already mentioned some example brands and models.

Having said this, and knowing how things proceed in technology, the word "enough" hardly ever applies, no matter where one stands in the evolutionary curve. Whether a switching frequency increase of 5X or 10X yields an audible enhancement or not, such featture will eventually be introduced at some time in the near/medium/long term future by module and SMPS manufacturers.

And with such next gen component parts, some OEMs will create even superior amps... While other ones will persist to develop "Creatures From The Black Lagoon", and all in between.

'Tis all in the handle, George!

G.

Once again I ask you the question, simple yes or no will suffice.

"Your saying is that there will be no higher switching frequency developed in the near future for Class D and what's now being used is enough"???

Cheers George

Your saying is that there will be no higher switching frequency developed in the near future, because there is no issue with at the moment, you need to re-think that one big time, seriously. 

Cheers George  

Can it be enhanced further?

Yes it can and soon I think, and I'll be there when it does, as soon as I see the technology about to become available from the big multinational component manufacturers, to supply the Class D manufacturers with. 

I'll get the jump and flick my expensive power hungry potential boat anchors before it's too late, and wait for the 2nd generation Class D to appear, even if it means I'm without music for a while.

Cheers George 

Thank you George, yes I have heard the screaches you describe, as well as the dark uninvolving sound several times at RMAF.... Quite consistently from some class D brands, and unfortunately equally consistently from some brands that produce otherwise well regarded class A, A/B, and a variety of OTLs and other tubed amps 

Luckily none of the amps of any class that I have owned since I sold an Aragon 4004 Mk.2 in the late '90s have had an even remote propensity of creating such audible horrors.

Somehow, my home is blessed by marvellous music... Yes, I hear music that is congruent with the sound of live acoustic instruments that I have experienced since I was six years old.

Can it be enhanced further? ... Of course!

The switching frequency guidocorona, may be 520khz, but it’s the amplitude as well of it not just the frequency and has to be filtered at the end with all that rms power by low order filters that have to take that power. 

From what I’ve been told by those in the know of Class D technology this has to be shifted up 5 to 10 times higher so the filtering of it on the output of a Class D amp can then also be shifted up higher, and therefore not be affecting the audio band, with audio band HF phase shifts or audio band HF roll-offs.

On most of todays Class D amps that try to get the highest frequency response they can get, you may hear a sizzle from a high bandwidth tweeter if you put your ear to it, if it’s not muted eg: in-between tracks on a cd.

Then there are those Class D’s that want to get rid of that sizzle which filter it even more savagely, then those ones can be starting to roll off the audio HF already at 5khz.

The sounds of the two can be then different in the upper-mids and highs, one being hard or harsh because it lets through some of the switching noise. The other sounding opaque or soft in the upper mids and highs.

Therefore to cure one or the other the switching frequency needs to be much higher so the filtering has little or no effect within the audio band.

Analogy: is to remember the early days of cdp’s with their brick wall filters, which on paper looked ok but sounded shocking, just because they wanted to show a flat 20hz-20khz frequency response. But in Class D amps this filtering is low order and happens at the end of the power amp at full rms wattage power levels, and the filters need to take all that power handling.

Then there's the SMP power supplies another problem again, that some Class D manufactures try to get around by powering with more expensive to make Linear power supplies.  

Cheers George  

Hi George, what would you deem to be a sonically safe switching frequency for future class D modules?

Do you know of any such "Upcoming Attractions" with higher switching rates preparing their entry to market?

Meantime, Yesterday I checked the NCore NC1200 switching frequencies... It ranges from 440Khz to 520Khz., which is almost 5 octaves above theoretical human hearing range.

Honestly, I cannot perceive any artifacts or shortcomings from my amps... But there may be some audible artifacts that I am not aware of. 

On the other hand, I freely admit that I would be just as happy with a wonderful Solution monoblock, or a major AudioResearch tubed amp... I mean, apart from the heat dissipation, and reliability anxieties from ARC amps.

PS... My class D monos are not light... 160 Lbs per side. They are not furnaces by any means, but are relatively toasty to the touch during Austin summertimes.

Saluti, G.

Well said Mapman, I myself am not ready yet as I outlined, but once the new (let's call it 2nd generation)  far higher switching technology happens, I'm jumping in with both feet, compared to my setup at the moment the bass/upper bass of todays good class D amps is already better.

I just have to time it right when I'm ready to make the jump as my two biamped power amps can re-coupe enough $'s s/h before they become boat anchors to get a pair of good 2nd generation class D's, and the same to a degree will happen to the 1st generation class D's as everyone will want to dump them also.

Cheers George