Competitive class D amp suggestions

@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.  

@rsf507 thanks for the link. I have a bit better idea about Atmasphere amps than before. I may also ask by email. As to the distortion, I don't know what THD really means. As noted in this thread, my class A tube SET amp with THD 0.5 gives notably cleaner sound reproduction than my class D amp with THD of 0.001. 

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). 

A 5-6 watts SET integrated amplifier can give you enough power unless your listening are is extremely large and your speakers are too non-sensitive. Then there is no real need in hybrid setting. 

I have a SS preamp which gives very comparable soundstage to a tube one. I mean not necessarily a tube preamp will give you better results. I am inclined to think that power amplifier is more important. A preamplifier can give you an additional flavour and it's up to you if you like it or not. If you have an integrated amplifier then you "get rid" of such kind of care, at least you don't need to search for a best preamp for your setting trusting to the amplifier designer.  

We will see. 

In my second system recently i was using Cherry Megaschino (which now needs a repair of one channel), Mankey Stingray tube integrated, PS Audio Stellar S300 and most recently, since about one week or so, Nuprime ST-10. The latter is better than S300 in almost all aspects except that it does get hot. If the Voyager will be notably better than ST-10 then I may try it in the main system with my tube SET integrated. So far, the latter amp could not have been bitten, unlikely Voyager will surpass it.

As I have mentioned  I am fond of class D, but so far I did not audition a class D amp that sounds as natural and as clean as set class a tube amp that I'm using.y

Which class d amplifier you consider sounds more natural and clean than SET class A ones?

Jerry, VTV Purifi might be a reasonable choice (for me). I did not try yet  a Purifi (or GAN) based class d amp. Could you help with more detail on auditioning this amp  (in particular compared to your SET amp)? 

Thanks for the suggestions, indeed. It is a hard task to choose an amp without auditioning it. But since i decided to try another class D amp, it may take time and more efforts to come to decision. For example, I still have no clear idea yet on the sonic differences  between Purifi and GAN based amps, roughly (was not able to audition any of such amps).  I will check the other suggested options, but so far, I have no clarity. Would be helpful if you could be more specific on which features of the amp(s) you suggest you like or dislike. 

My first class D amp was PS Audio Stellar S300. I was really surprised how one can get that good sound for $1.5k.  I enjoyed it, it sound the best on live recordings, i like its compact size, the weight and it works completely cool even does not get warm. It is not an ideal class D amp for me, i think it lacks a bit mid-low frequencies. Exaggerating too mach, it sounds a bit like a megaphone, but it gives quite deep low and clear  high frequencies. My next class D selections were still not  ideal. The class D amp i am using now is Cherry Megaschino, the one I like the most among ones I had. It is not so traditional class D amp though because of its considerable weight, also it gets quite hot (hotter than my 200 watts integrated class AB McIntosh). But I think Megaschino is a better sounding amp, it somehow sounds more realistic and complete. Although the sound is somewhat clear and natural, compared to mu SET amp, exaggerating again, its reproduction is still a bit "dirty".  

As to the speakers, I use 3 pairs of Thiel speakers in different systems, CS6 in the main system with the 5.5. watts SET integrated, the bookshelf MCS1s with a Thiel subwoofer (that I currently use with the Megaschino) and CS3.6s. All of them are excellent speakers, I even never though to replace them. 

@embolek, how would you characterize, roughly, sonic differences between Ncore, Purifi and GaN amps ? Why you decided to try Peachtree 400 if you already had another GaN module amp? 

@tweak1 , did you sell the Voyager, why, did you get a better class D amp? 

Thanks again for the input. 

Based on your suggestions, current possible selections are (in the priority order)

Peachtree Gan400, March audio P262 (which indeed seems to be well built - just judging by photos), VTV Purifi, and i may check the other suggested options as well.

Thanks @twoleftears for your comment. Though my question could not be so stupid; e.g., it is a common point of view that Ice Power amps sound natural and less analytical then many class D amps. But of course, this does not classify them as the best class D amps.

@smargo, your explanation was very useful, especially when you compare three amps with different type of modules in a comprehensible may. I also owned Cherry desktop Maraschino (STM). Its main attraction is the size (and power it gives for that size). I think the AGD amps somehow borrowed the desktop concept of STM, at least, in the design. The Megaschino is considerably better (and also it costs about 5 times more i think).  

Do you mean any particular JR class d amp?

As to Nuprime, i am not aware about STA 9 but still have HPA 9 preamp which is class a. Quite well sounding preamp by the way.

Thanks everybody for your comments and passion to class D amps, a challenging alternative way of sound reproduction. 

Analyzing your suggestions, if i am not mistaken, Jeff Rowland Model 125 is ICE Powered. Since I already had an ICE Powered amp, this might not be an attractive option for  me (given that this amp not cheap, perhaps just good-looking). 

Peachtree GAN 400 can be an interesting choice. I have emailed them a few days ago, did not get an answer (not a nice way to "answer" questions). Then i called them. They say that  they do not ship outside US or something similar (a bit inflexible answer, i would say). Orchard Audio GaN mono blocks is an alternative  (also less expensive) option . I just emailed them. 

As to Rogue Hydra and Dragon amps, Hydra's power would be fine for me unless Dragon sounds different. Somebody mentioned AGD Audion monoblocks. Both, Rogue and ADG are hybrid, AGD is about twice more expensive and twice or more times lighter, do they sound better? 

Honestly, I am not too convinced with an idea to combine tubes with SS in one unit. If I want tubes, I go and listen to my tube amps. 

My homework turns out to be not easy -  I may end up with buying nothing.  

Anyways, your further inputs and highly appreciated!

Then it seems that i have no clear idea on what the "hybrid" actually means and how it is implemented. How GaN output is "packed with tubes", just for an additional flavor or for an additional power? Which architecture is "preferable", hybrid or this one? I have no idea how AGD amplifiers sound, but in general i prefer as less flavor as possible. 

Atmasphere class d amps can also be interesting. I did not find them on the site and have no idea on preferences made in their design. Neither i know if there are already completed models. Can Ralph provide  more detail? 

@kuribo , thanks for your input on Peachtree Gan 400. It is important to have different opinions here and your arguments seem reasonable.  

@orchardaudio and @atmasphere thank you for your comments and the link. I read them with an interest, they sound convincing. 

Class D offers a way around that, by allowing for profound amounts of feedback that is very difficult to do even with modern devices in AB circuits! With such high amounts of feedback its possible to build an amp that is both low in distortion while relaxed and detailed better than the best tube amps. To some this last statement might seem a bit weird but the experience of amps with low distortion not sounding all that good is common. At this point (and take this from someone who has been at this over 50 years) I'm very convinced that tube power amps are on borrowed time.

This is a very strong and challenging statement, especially from a tube amplified producer (i appreciate it very much). I did believe in this a few years ago. Nevertheless, so far, as mentioned earlier in this thread, i did not find a class D amp that sounds as good as  my 5 watts tube SET class A amp. Perhaps, Orchard and Atmosphere  already produce such class D amplifiers... 

@orchardaudio and @atmasphere, do you expect to have a further breakthrough is the design of your class D amps in near future? 

I realized that i don't have an answer on the following (perhaps stupid, forgive me) question. Would it make a sense to combine somehow GaN transistors  with Purifi modules in a single amplifier? 

@agdproduction , thank you for your input. 

@ricevs, your comments were very useful, at least i clarified some things for myself. Design issues also have some (superficial) importance. These "tubes" and the AGD amps look look attractive to me. I would now wish to know how they sound, especially, given that they are about twice more expensive then most of the comparable amps.  (..."making money is good..."  (:  😉) 

@clio09 , thank you for this post. 

In comparison to the LSA, the LSA came off grainy in the upper frequencies, it was clearly heard after listening to the Atma-Sphere amps.

 What you precisely mean with "grainy in upper frequencies", can you be a bit more specific on sonic differences between Atmasphere class d and LSA Voyager amps in different frequency ranges?

@clio09 can you help with another feedback before I take the final decision

do you think that Orchard GaN monoblocks (150 or otherwise 500 watts) can be any better than Voyager ( in particular in terms of the distortion in high frequencies)?  Which of these amps you would choose?

@clio09 , clean highs is very important. At the same time, this sale came out now and somehow is motivating me to take this choice. At least, i will know what can be wrong and will see how critical this issue is, thanks again. At this moment, perhaps, i am not still convinced/ready to pay twice more for something that i have never heard. In any case, i have the 5.5 watts SET amp here in my main system. 

@tweak1 , thanks for the suggestion. Is the vibration you mentioned caused by CD players and speakers (I understand that amplifiers cause no vibration)?

with the possible exception of the sound at overload (but for that just make sure you have enough power).

Thanks Ralph, your point of view is clear. The last is a delicate question for me, at least: How one can know that it has "enough power"? Strange things happen. I have tried large Thiel speakers with a 200 watts class AB amp and i felt that, may be, the power was not enough since it sounded a bit "forced" at moderately high volumes (if this a correct way to judge if the power that an amp can give is enough for a speaker). But i don't observe similar things with a tube SET 5.5 watts amp connected to the same speakers. Perhaps, there is a more reliable way to check whether the power of an amp is indeed enough for a speaker?

@axo0oxa thanks for a detailed overview on your Vivace.  I think your points of view with be taken into the consideration, certainly it does not sound like a joke. Why you decided to go with Vivace and not with less expensive Audion ? Anyway, apparently you realized your dream, which is the most important thing.

 

IMO/IME the breakthrough has already occurred- you can now finally buy a solid state amp that sounds better than the best tubes can offer (with the same liquidity, no harshness but with greater detail including depth)

@atmasphere this is what I always wanted to hear!  It only remains to experience it unless it is taken as faith (unfortunately, none of us saw the God, even ones with the strongest faith, so less probably that i will be able to see him ever on this land).

Its easy enough to hear. You don't have to take it on faith.

@atmasphere, this would be true if i were living in the US (it is too complicated to import equipment to Mexico for trial test, each time you receive a gear, you have to pay quite a lot of $$$ due to the duties/taxes). 

Meanwhile, as a "temporary solution", i got a Nuprime ST 10 amp from a local dealer, a reasonably priced used one  (i was left with no class D amp - the right channel in my Cherry Megaschino is almost silent, i  tried to contact  Tommy O'Brien lately without any success so far. the site is there but the emails come back, the telephone is out of service. He was personally dealing with most things, i suggest there is nobody else that can reply or take care of support. Hopefully Tommy is fine (a nice guy), but have no idea on what is happening with his company). 

After 3 days of auditioning, i decided to keep the amp. In fact, it has surpassed my expectations. It is quite fast, dynamic, airy with a considerable sound stage,  frequency extension is good, details are fine. The sound is extremely very clean but still the distortion is tolerable. It is a non-standard class D design, it does get quite hot. The sound is slightly colored, the base is a bit exaggerated, heights are clear, but a bit colored. The overall sound characteristic resembles Pass amps, if you like them, you may like ST 10 (much cheaper, much less power consumption...). This amp can be better than all (more expensive) class D amps i had except the Megaschino (which is broken now). 

After a few days of auditioning,  I suggest that this amp deserves  consideration,  it is a serious piece of gear. In fact, the reviews i read more or less objectively describe  performance of this amp. I wonder how much better could the overall sound be with other available options including more or less reasonably priced Voyager 350 and Orchard amps.  

"The sound is extremely very clean" ---> "The sound is *NOT*  extremely clean"

@axo0oxa thanks for this complement. You may still have more successful jumps, you never know. I made similar jumps also replacing amplifiers, and am not sure if more jumps are required. Compared to your tube SET amplifier, what exited you the most in your Vivace amp (except its cool look, i understand that these "tubes" looking as candles at night, may give an intimate peace-like feeling)?

Lately he had some problems with  suppliers, and he was intensively working on a new MK3 Megaschino...

Ralph, thank you very much for this, very, very, sad information. I didn't know him personally but we communicated a lot by email. One can say how a person is based on a letter exchange. He was always positive making good things and was doing that practically alone. He was, really, a very nice guy. Just to tell you that i am writing this message with tears in my eyes, a person whom I never knew personally. He had two daughters  i think. I will miss him...

P.S. He was relatively young, do you know what happened with him?

I ordered LSA GaN Voyager 350, should be here by Thursday. I will try it first in my second system. If I would like it then I may try it also in my main system. I will post what I will see. 

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.

@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)?

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). 

@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. 

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. 

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. 

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.

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) 

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. 

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.

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.

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. 

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.  

@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. 

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 have a small update on the LSA GaN 360 Voyager amp. it should have now a bit over 100 hours of burn-in (I used it more than usually in my second system basically leaving it on most of time). I did not note any essential improvements after 80 hours or so. Perhaps, it may still get a bit better. 

I can say now how the Voyager compares with the Cherry Megaschino  in my second system. The sound of Cherry is cleaner, more open, less "forced" and more alive and natural (even with half-working right channel, I  adjust the channels taking an extreme balance position). 

To me,  Cherry  does not sound like a traditional class D amp, while Voyager sounds like a good class D amp, perhaps the best one I have heard  so far except Cherry. No doubt that it is a very good value performance/price. 

I suggest that Atmosphere and AGD  amps may sound somewhat similar to Cherry, but cannot be sure of course. For me, Cherry just sounds like a good class A tube amp, point. So pity that Tommy passed away!

Soon I will move the Voyager to my main system. I will let you know about my impressions in a few days or so. 

@twoleftears and ​​​​@atmasphere , thanks for additional explications! I did not reilase, from the beginning, that different pics were different harmonics, a very useful image. But now I do not understand what the blue curve stands for. 

​I used the LSA GaN Voyager  in my main system for a few days. Not surprisingly, it didn't sound worse in the main system, which is a good characteristic. At the same time, the main system revealed some technical problems related to the amp. I noted this before in my second system as well but I suggested that the problem could have been in the preamp. 

First, the amp just does not sound well  with the balanced inputs - there is a quite notable lack of the middle and high frequencies with the balanced inputs ( i tried two different quality  balanced cables). Fortunately, one of the RCA inputs has no such problem. 

Second, a quite strange thing happens. With both XLR inputs, the left channel is too weak.  And with both RCA inputs the right channel is too weak. I mean, even if i stand in front of the speaker, the sound coming from the other speaker is dominant. The preamp in my second system has the balance control, so this issue was somehow "settled" by reducing the volume in the normally sounding channel by about 40%. The T&A DAC/preamp in my main system has no balance control, so it was just impossible to use the amp with either XLR or RCA inputs. ​Then i used the rear switches to put the right channel in XLR and the left channel with RCA modes . This was the only way to achieve a more or less balanced sound. 

Third, i think the amp has some phasing problem. Apparently, it is made out of phase. But when I swapped the positive and negative speaker outputs, the amp remained out of phase. Perhaps, this is not a big problem but something may also be wrong with this. 

Based on my small experience with the combined XLR-RCA auditioning in my main system (thanks to the rear amp switches that permitted me to use such an option), i think there is nothing particular to complain about  the sound quality of the amp (judging analytically). At the same time, there is no point in comparing it with my SET tube amp that just sounds more real, full and alive. This can be subjective. But perhaps, not. Just take one of the CDs I used to compare the SQ of the two amps. It is Keith Jarrett's "Buy buy blackbird" (hey @jjss49 !). It is a particularly well recorded CD. Although it is a studio album, one can feel the studio environment and the musicians on each of the instruments, just as if it were a live recording. The SET amp gives this feeling, the Voyager does not (so far as it is  now). 

Perhaps, the Voyager may still improve (it should have about 110 hours of burn-in). I will be able to judge once I get it back from Underwood Hi FI. I am going to ship it for repair today. 

@twoleftears , I wonder how this integrated amp sounds with this speaker impedance correction feature. E.g., the distortion at higher order harmonics (the pick at 1k and the following ones at 2k etc) is considerably higher than that of the first, 2nd and  3rd order harmonics, they should be audible. Given that, it is really interesting how this is reflected on the SQ. 

The diagram is  "unusual" also because it shows  a big difference between the two channels where a little distortion is observed in the blue channel as there are only two blue picks.

Just an update on my earlier post on my LSA Voyager GAN 350 map. Mr. Walter from Underwood hifi was so kind to replace it with another new one. So far the new one works without showing similar problems. Walter has also recommend an SPL Elector SS preamplifier, which I think is a good match, it compensates a bit a lack of the body and "inanimateness" in the sound reproduction of the Voyager. 

@rolox Thanks for your post. Looks and sounds interesting. Would be nice to try it.