Competitive class D amp suggestions

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..

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.

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??!

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?

@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.

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

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. 

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 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) 

@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.

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.

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?

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.

+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.   

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..

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. 

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. 

a lot of player with quality sound.

new bel canto 600m

merrell audio

agd

mr ralphs class d.

".."…..

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...

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

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

What about the Marantz Ruby PM KI...?  

Thanks agdproduction I'll have to see if my dealer can get one in for evaluation. I've been waiting over 3 months for the Atmasphere amp and each time they say it's almost ready another 3 - 4 weeks go by and nothing. 

Step by step, it can be more relevant now to compare an AGD amplifier with LSA Voyager GaN350. I didn't see any negative feedback on the Voyager so far on Audiogon  from people who own it (including myself), whereas I read some on an AGD amp (that costs a few times more). Once we know what are objective advantages of AGD over the Voyager (if there are some), we may consider other more expensive candidates; otherwise, it seems to be just a kind of subjective  speculation. 

Not sure what your budget will allow but I've owned the Rogue;

Sphinx 2

Cronus Magnum 2

And now the Pharaoh II integrated.

Rolled RCA Clear Tops in it and couldn't be happier. 250 watts into 8 Ohms and 400 into 4 Ohms. New Class D Hypex N-core amp and tube preamp. Breathtaking! 

@rsf507 

Hello, just let us know.

Both models,  Audion and Tempo, are ready to ship

I've been anxiously awaiting to hear the Atmasphere class d amps from my dealer in NH for months now. He keeps telling me soon but I just might look at AGD instead. 

If anybody has the Atmasphere classD amplifiers in the Seattle area, let’s get together and do a comparison.

I have the AGD Tempo di Gan.  It's excellent.  I too would be curious to hear it pitted against Atmasphere's amps under controlled conditions, but there really isn't anything I want to improve at the moment, so that's not a priority.  Either it, or the Audio Envy Mega PC that I put on it, took a little while to break in, but then everything snapped into place.

Think there may be one or two who were not blown away with AGD.

But the comments of AGD owners are unanimously raves.

If you don’t need mono blocks (and/or are not a fan of the “tube” output stage)

the stereo Tempo is uses the same technology as the mono models and is said to sound virtually the same as the Audions for $2K less.

I believe that the much more expensive Vivace also sound very much like the Audions. Just a bit more full sounding. And the top line Grande Vivace is also very similar to the lower models just another bit more full and twice the output.

If going for the upper models, the Grande Vivaces are the ones to get.

I do agree that they are revolutionary. 

I took a chance on a used pair of Audions because they don't come up that often and I wanted to hear them.   Count me highly impressed.  Totally black background, very fast, neutral tonal balance, good spatial representation - I do think they are revolutionary.  From my perspective, the current top contenders are the AGD and Atmasphere Class D amps (Ralph, I may be giving you a call).  I would love to hear Ralph's Class D amps and the Vivaces as well. The AGD Audions sound great with my VAC Signature IIse preamp and my Tekton Encore speakers.  Have yet to feed them into my Avalon Eidelon Diamonds.

Would love to hear people's experience of the Atmasphere Class D.  From what I've heard, people who have heard them very often end up buying them, and they are flying off the shelves...

I gather Jason Lim shut down production of the Evolution monoblocks because the Evolution STA offered 90-95% of the performance at just over half the price, so it is now their flagship product.  I can't seem to find out whether the STA uses proprietary modules or ones purchased from an OEM.

It would be interesting if there are some comparisons, in particular, between Nuprime ST-10 stereo, ST-10 mono blocks  and Evo STA amps. I suggest ST-10 stereo may have the highest value performance/cost. 

As to the Voyager, it made the first "improvement jump" after about 20 hours of use. If following 10 jumps will be equally significant, then this amp is a great amp,  a perhaps, with a best value performance/cost. So far, i use the same setup with RCA cables and Nuprime HPA-9 preamp (if i mentioned it earlier,  the HPA-9 was better than the W4S STP 2 preamp hooked up with the Nuprime ST-10 amp). 

I'm kind of surprised there hasn't been more discussion of the Nuprime Evolution STA.  Anyone heard it?

@mglik 

Thank you for your very kind words.

@tweak1, @rc22 Thanks for the suggestions. In fact, I also read in the manual that a better power cable is recommended. I replaced the supplied PC of the Voyager GaN 350  with Audience Forte f3 PC. perhaps, there is some improvement in power and in base (I have to return the other cable and audition the amp again to be completely sure).  But the most important thing that needs improvement remains a little dryness and lifeless in sound. Hopefully, this can be improved with break-in.

So far, my analytical thinking tells me that this is a very good amp. Pre-consciously, i am not still too attracted to the amp, all is good, but something (the soul) is still missing. May be i need to spend more time with the amp and this might be changed. For the final verdict, I will wait until it is fully broken in and then will try it in my main system (with better cables, transport, dac, acoustics, etc). This weekend I used it more than i usually do, it should already have close to 15 hours (in some amps, i was observing an improvement already after 10 hours). As to the other interconnect cables, honestly, i don't understand how a transport  interconnect cable may influence on the performance of the amp (it may improve how the transport sounds of course). I have never tried spring pods but will bear this possibility in mind.

Later this week i may try the amp's balanced inputs with W4S STP 2 preamp. 

@mresseguie, thanks for sharing your experience with Nuprime Evo monoblocks. My earlier idea on these amps was that they are more accurate than ST-10 amp but also more analytical. Based on your comments, apparently, this might not quite be the case. The ST-10 gives a tube flavor, nice sound stage but the distortion is a bit notable. If the Evo amp inherited the former features but eliminated the distortion without being analytical, they should be very good amps (I think this was a key consideration in the design of new @atmasphere class D amps).  It could be interesting a direct comparison of these two Nuprime amps.  

@niodari 

I only just discovered this thread last night, and I see you've purchased an amp. Even so, I'd like to suggest a Class D amp no one has mentioned. Nuprime announced its Evolution STA dual-mono amp in January. I had already been researching the various new Class D and GANfet amps, and knew the only way I could hear this or that amp, was to go ahead and buy an amp in order to listen to it in my system. Because the Evo STA was the newest of the bunch, I decided to take a chance and buy one. 

The EVO STA needed a solid 250 hours of burn in before I was satisfied that there were no more obvious changes to its sound. This amp has a warm tube-like character to it yet simultaneously is very revealing and clear. I love how it sounds in my system.

I have no idea how it compares to the various other above mentioned amps, but I sure do love its sound. I think it's worth considering if you haven't finished your search. The MSRP is $4995. However, if you check with your dealer, he/she may have 'confidential' pricing. 

Michael

@ghdprentice 

Your AR 160 Ref stereo is not just the best AR I have heard, it may be the best amp I have heard. The monos must be threw the roof.

So cool of your dealer to let you hold on to them.

What I heard at your house was superb and definitely had the “organic” sound of tubes. Although I would not say that it was “tubey” at all. 
My Class D AGD Audions do not approach or attempt to recreate that tube organic sound. They produce a more “clear window” into the music. I would say a more neutral take rather than organic. However, I don’t necessarily miss what your tubes do. It is very satisfying.

I decided to swap PCs between my transport and my Voyager. The Voyager had a boutique PC from Tek Line Cables (15 yo, then $500, no longer in business), I also have one on my preamp/dac outboard PS. 

The new PC was better top to bottom with more defined bass umph. Looks like I need 3 more PCs; transport, dac/pre and CorePower PLC

+ @tweak1

— A good power cord on the Voyager is a is a must.

—spring pods are such a deal (mine are autocrast. Same as nobsound.

Inexpensive and so effective).

Autocrast spring pods under my speakers are by far the best of the 4 vibration-management products i’ve tried.

I am utterly thrilled with the Voyager and the sound of my system now. But I Look forward to hearing better things still, when I improve my Dac, Pre and USB in the near future and also continue to build on the significant improvements in room acoustics I’ve realized lately.

@niodari 
I leave all my SS electronics on 24/7. Have not found the Voyager to get more than mildly warm.

@niodari

Congrats. Do not worry as it will definitely break in. Now, that said, I did not like the the supplied footers, replaced them with inexpensive Nobsound + added ~ 5#s of weight to the top. The W4S (XLR>XLR) makes a lot sense, but quality XLRs and PC will matter. Replacing a Marantz HD CD-1 (used as a transport) with a Audiolab CDT 6000, was another excellent upgrade, as was improving the coax and PC cables to it. Feed it HQ ancillaries and it WILL reward you

hth

I was able to audition my new Voyager LSA  GaN 350 for a couple of 

hours this morning. I let it warm up for just 30 minutes or so (this is a completely new unit with no burn-in). I hooked it up with Nuprime HPA 9 preamp using its RCA outputs (it has no balanced outputs), bookshelf  Thiel MCS1 speakers (sensitive 91db) with a Thiel subwoofer and passive crossover, Krell Kav 300 CD player used as a transport with a Cherry DAC.  

During these two hours, I compared it with the Nuprime ST-10 amp that I was recently using in the same setup. These are my first impressions. 

I didn't find the Voyager  bright, still a little harsh and slightly dry perhaps. Although it is 500 watts in 4 ohms, it gives notably less power than 150 watts ST-10 amp, at least with HPA 9 preamp (perhaps, impedance issues). I found its sound clear, natural, unaltered, in some sense, a bit fuller than with ST-10 since it goes a bit deeper into orchestral passages. The middle range is a bit more defined than in ST-10. The soundstage, so far, is a bit flatter than that of ST-10, but Voyager has a bit more details. The heights are clean (despite that some measurements claim that there could have been distortions in high frequencies).  The base extension is less than in ST-10, still it sounds natural. The sound of this amp somehow resembles to me  a class A amp sound, still not as rich and complete (yet? - this may change with break-in hours). 

The amp has no standby mode. I left it on without using it, and it  got quite warm. I would not leave it on all the time (Cherry Megaschino has also no manual standby switch, but it goes standby automatically after 8 minutes of idle time, and stay completely cool). 

I think I need to use the amp for more time to understand how much i like it. I may stay with it and use it in my third system with Thiel CS 3.6 speakers.  Meanwhile I will leave it in my second system for break-in (i use that system  for 1-2 hours in the mornings so it may take some time). I may also try its balanced inputs with Wyred4Sound  STP 2 preamp. Now, i see no point in trying the amp in my main system (where i use my 5 watts SET tube amp). I may try it in the main system after the break-in of 200 hours or earlier if an essential improvement will occur. 

I will post my further impressions in case my thoughts and feelings will be changed compared to what i think right now (first impressions might not be very objective). 

@blkwrxwgn , unfortunately, Tommy O'Brien has passed away...

In fact, i also like the Cherry Amos faceplates, at least the dark red one if my Megaschino. Does anybody  know if there is someone who is able to deal with Cherry amps now (my Megaschino needs a repair of its right channel)?

The Voyager just arrived today, i hope will connect it tomorrow and will post my first impressions. 

I have only two preamps, Nuprime, HPA 9 and Wyred4Sound STP 2, will try first HPA 9 with the Voyager (class A, quite a good preamp). I am not sure if ST 10 is of the last generation, perhaps not, it is produced about 2 years ago, i will ask. 

@mofojo , given two amps, one class AB and the other class D of about the same price, most likely, the  class D amp will be better.

Only class D I ever liked was a Lyngdorf 2170 but that was totally due to the room correction and only with some speakers. 
 

Not heard the new Gan stuff or any “high end” stuff but of the  medium priced class D vs medium priced AB or tubes I’ll take the latters all day. Haven’t heard a class D that gets the highs right or really the upper mids either. 

Which version of the ST-10 ? New, it would be version 4, which in reading, is the best of the 4.....I believe there were 4 versions.

I have the Voyager GaN 350 in my main two-channel system and the Wyred4Sound 1000r monos in my home theater room. Love 'em. Never going back to Class A.