Gallium Nitride GaN Class D Amplifiers

In my recent research for a possible upgrade to my current amp (Benchmark (AHB2) I was reading about the new higher end design for Class D. I'm very interested in learning more about these new GaN(Gallium Nitride) designs. Three companies are offering some very well reviewed products and they are not going crazy with Watts per channel:

Orchard Audio offers a 250 watt Amp

AGD a 100 watt

Atmos-Phere also a 100 watt

What's interesting  is while Orchard is a new company AGD and Atmos-Phere have been around a while producing high end Tube amps. In almost every review it is noted how these newer designs sound like Class A or Tubes with all the benefits of Solid State. One reviewer couldn't go back to his tube amps after extended listening to the Orchard. No wonder AGD and Atmos-Phere are getting into this technology. It's very exciting as these amps are highly efficient turning over 90% of the power they draw into sound compared to about 78% with A/B designs and I believe even significantly lower for Class A. They run cool and usually weigh between 10-28lbs. I plan to do more investigation. Small size and light weight with decent power is very attractive. There are also mono block offerings for more power if needed. These are not cheap Class D products. They are well designed and constructed.

Orchard Audio's base model is around $2700and their Dual mono version with larger power supplies is $5500.

Both AGD and Atoms-Phere are $5000

Mono blocks for each are about twice the cost.

Has anyone had any experience, demos, etc ., with these types of GaN Class D amps?



Atma-sphere are exclusively mono and run about $6000 the pair. The other two vendors offer both stereo and mono as far as I can tell.

I’ve auditioned the Orchard Audio and AGD Productions GAN amps in my system. To my ears, they did not sound alike, and other than being GAN chip amps were not sonically comparable.

The AGD Audion amps were natural, extended, and transparent with a large sound stage. Not dissimilar to my SET tube amplifiers, and to Atma-Sphere OTL tube amplifiers that I also auditioned for an extended time, although both lacked the elusive 3D depth of the tube amplifiers.

The Orchard Audio amplifiers sounded sharper and more precise. They skewed away from my listening preferences.

I don’t think one can price shop in the GAN amplifier arena and think they’re getting the same (or similar) sound for less money among available products.

The benchmark is top notch.  Nothing wrong with the others using GaN but hard to call a clear “upgrade”.  Depends on the specific amp not what transistor technology used and what you prefer mostly.  Atmasphere and AGD are popular with tube amp lovers otherwise.    GaN has advantages but alone does not guarantee “better” at least based on objective measures alone. 

A friend of mine brought over a set of AGD monoblocks to try in my system for an afternoon. They performed extremely well for their cost (?$8K). Natural sounding and dynamic. I was comparing them against my Audio Research Reference 160m monoblocks. With the rest of the system being Audio Research Reference, the substitution was not a huge difference in sound quality. The AGD did not render the treble as well.. but for the price great deal. I would probably identified more differences if I had them in my system for much longer… but they did a good showing for themselves.

The reason I mention that the rest of my system did not change is that if you substitute one component of a carefull crafted synergistic system and substitute one component, it can often maintain its character. But switch two or three and the whole can fall apart.

@jfrmusic, the dual mono stereo (DMC) unit is $4000, not $5500.

I do sell ultra monoblocks as well that are more expensive and can be configured to be $5500.

Reach out with any questions.



Since you have had direct experiences with these two amps I would be very interested in more specifics of the SQ and character of the Atmosphere and AGD amps. .Did you auction the AGD Tempo or the mono blocks?


From the many reviews theses amps may provide a more Class A / Tube like sound character which would be attractive to me.

I had demo of Atmasphere Class D followed by Atmasphere tube amps at CAF 2022. The two sounded more similar than different so that is a good omen for the tube amp camp.

i also heard AGD at another Audiogoners house who also ran Linear Tube Audio amplifier. LTA is a tube amp that does tubes in a way that resembles very good SS or Class D amps in general. Very good sound but more towards the tonally neutral side. Atmasphere amps have just a bit more touch of tube like “PRAT” which many audiophiles will find very desirable and harder to find outside of actual Tube gear.


@jfrmusic of course the speakers matter a lot as well. Did you mention what speakers you are running? Thanks.

@jfrmusic, I have not heard the Atma-Sphere GAN amps. I mentioned having auditioned Atma-Sphere OTL amplifiers; specifically, M-60 mono blocks.

I auditioned AGD Audion mono amplifiers.

They share common characteristics of naturallness, tonal richness, excellent frequency balance (actually I think the AGD Audion had slightly better balance), and an expansive image. It’s been a few years, but my fuzzy recollection is the AGD Audion amps were more tonally neutral. The Atma-Sphere M-60 always struck me as pleasingly warm in tone, but not syrupy. This is a wonky comparison, though, because I have no idea if the Atma-Sphere GAN amps convey the same house sound. Maybe someone who has heard both will respond  

Preamp was SMc Audio VRE-1C. Loudspeakers were Audio Note AN-E/SPe HE (95db, 6 ohms).


Totally a swag guess based on personal experience but I suspect the Atmasphere Class D would sound somewhat more different from Benchmark than AGD, but the only way to know for sure would be to try both and compare. All three are very good amps so I think it mostly comes down to personal preference and how much change you seek. Sometimes you just have to go with your gut feel, or which product and company strikes you best.  I think you have identified two very good alternatives. 

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The Atma-Sphere M-60 always struck me as pleasingly warm in tone, but not syrupy. This is a wonky comparison, though, because I have no idea if the Atma-Sphere GAN amps convey the same house sound. Maybe someone who has heard both will respond.

I own both sets of amplifiers. I have owned the M-60s for over a decade and purchased the Class D around the time they came out. The Class D gives up very little to nothing compared to the M-60s, simplifies ones set up quite a bit, and if you care about saving the environment and some cash on your utility bill there's that too.

From the average audiophiles perspective the description of the M-60s by @tvad might sound nice, although I wouldn't use the term "pleasingly warm in tone" myself. From my perspective I would say both the M-60s and Class D have low coloration characteristics due to their low distortion, especially in regard to higher order harmonics which tend create unnaturally bright tones. They are both well balanced amplifiers (with AES48 compliant balanced differential circuits) that will pass the "truth" to your speakers. You will most likely find your speakers and components upstream from the amps introducing more coloration. The amplifiers themselves not so much.

As a long time Atma-Sphere customer and authorized dealer feel free to take my comments with a grain of salt.


The Orchard products sound more compelling to me than the Atma-Sphere monos.

More power maybe? Not heard the AGD gear yet. Class D with GanFet or something along those lines is the future. The Euros have been doing it well for sometime now.  It is better with warmer speakers for my money.

I have both a LSA Voyager 350 GaN amp and a EVS 1200 IcePower 1200AS1s. Both are dual mono in a single chassis. Both are excellent, and as good as any of the many amps I owned over the decades be they tube or SS. Sadly, the EVS is no longer made, but the Voyager is and it's a real bargain (MSRP ~$2700), AND, Ric Schultz modifies them


I owned the AGD Gran Vivace and they were spectacular. I had an Aesthetix Calypso linestage (tube) preamp in the chain and it was the best sound I've had in my room to date, save for one aspect - low end (reverb). Back to this in a second... what set AGD apart from the others is that they purchased all of the GaN modules that were designed for audio applications whereas all others only had access to modules for other purposes. I do not know if this has changed, but it seemed to be a true story a year or so ago. Back to where GaN fell short for me -

Enya "O Come, O Come, Emmanuel" - Opening deep synthesizer and second, John Rutter: "Pie Jesu" around the 1:02 minute mark. Both are Qobuz. What is missing? Power and emotion. My question is, why? I do not think other amps are embellishing the sense of power and scale. I am wondering what it means that GaN is not accomplishing the same? Is it more accurate? Controlling the drivers too well? 

I have had Audion MK 3’s for a few weeks now. It is the most educating experience I have ever had with a component. The difference that different cabling makes is much more apparent than it used to be. Moving around different brand cables within the component mix results in some quite unexpected advantageous relationships which were not so clearly audible in previous set ups. These modifications extend throughout the component mix.

The amps also very quickly educate you about what treatment the listening space requires. "Room nodes" are now distinctly audible to me across the spectrum. Bass nodes in particular are now more obvious as to where they are in the room and where treatment should focus.

With these amps volume can be turned up higher without bleeding the music or wearing the listener out. I feel that I have been learning more things about musical reproduction in general.

Interesting, @izjjzi. I have the stereo AGD and feel the same about the bass. The sound is as good as anything I’ve had but the bass is light compared to others...or is it more truthful? I think it’s tad light but everything else about it is spectacular. Alberto, the owner/designer, sometimes chimes in around here as does Ralph at Atma-sphere. Maybe that’s how they sound so good everywhere else in the spectrum. SET’s often have the same issue, but I thought that was due to power. The AGD’s can handle difficult loads like Maggies and Quads.

When some of you are writing about AGD are you referencing the non-tube Class D? Or the Hybrid Class D with tubes?

AGD does not make a Hybrid Tube GaN amplifier. The GaN circuits are located in the tube and it is 100% solid state GaN, pure gimmickry with some functionality.

@bhvf, in my system, bass was not light from AGD Audion amplifiers. It was deep, resolved and tonally balanced. More truthful might be an accurate description.

The "tube" in the AGD amplifiers contains the GAN chip, and was designed to allow easy chip upgrade by an owner without opening the amplifier’s chassis. An owner simply pulls the tube, unscrews the base, pulls out the GAN chip and installs the new chip, screws the base back on and re-installs the tube. Albert has written that he also did it because it’s reminiscent of tube components and looks cool, but it has a practical purpose. I'm not aware at this time if a new GAN chip has been designed that necessitates an upgrade.

Gold Note of Italy has GaN mono blocks also that are quite spectacular and have sound quality that rivals the boutique builders and will save you $1 to 3k. PA-10s are well reviewed and received. Search the pages in this forum. 

My question is, why? I do not think other amps are embellishing the sense of power and scale. I am wondering what it means that GaN is not accomplishing the same? Is it more accurate? Controlling the drivers too well? 

The sound is as good as anything I’ve had but the bass is light compared to others...or is it more truthful? I think it’s tad light but everything else about it is spectacular

@bhvf I've heard a lot of class D amps that were light in the bass. I have a hypothesis as yet unproven which is that many designers think that since the amp is so efficient that they don't have to have a beefy power supply. IME a beefy power supply is pretty important since the amp's current draw can vary quite a lot and the supply must be able to handle it with no worries. 

@izjjzi The 'sound' of any amplifier has more to do with its distortion signature than anything else. If you know this then you also know as a designer to keep the distortion spectra (which is very measurable) as benign as possible.

If you get all the parameters right class D will have just as much impact in the bass as any other amplifier class. GaNFETs are not any more 'accurate' as they are switching devices. The design and how well its executed is what is important.


On my GanFET Audions the bass was so impactful that I had to disconnect one of the two hot wires to the REL S812's. This was advised by REL if your system has so much bass that is cannot play louder than position 5 on the REL volume knob without creating excess bass.

No experience with Orchard or AGD, but I owned a pair of Atma-Sphere M-60s for a number of years, fully upgraded to 3.3 including V-Caps. After procuring a pair of the Atma Class Ds, the M-60s were sold and I've never looked back. The Class Ds are smoother in the top end, have better control of the bass, and are equal in the midrange, all of which is high praise as the M-60s sound great. I don't at all miss the heat output or the 24 tube anxiety of the M-60s; the Class Ds never even get warm, and I can leave them on all the time.

Speakers are Zu Druid V, which I've driven with 2 watts but sound way better with 50, regardless of room size.

@atmasphere Respect and regards to you and to Alberto.

Please, it is not bass I am referring to but low-end reverb(?). The two tracks I previously mentioned involve a synthesizer and organ, not bass guitar or other. I own a pair of REL 212SX and yes, Billy Eillish tracks and others hit my chest like a truck. What I am describing is the emotion of deep notes, resonance (reverb?) that you can feel. My Accuphase A36 and PASS LABS x260.8s knocked those tracks out of the park, but were muted... benign with GaN. If this piece can be solved by GaN amplifier manufacturers, GaN will be my last stop. That said, I will soon be auditioning a new player in the GaN space (ArgentPur) some time this month or so.

@izjjzi I can't speak for other class D designs. The sound varies from one class D to another more than it does with class A amps or tube amplifiers- IOW quite a lot.

But I know how our stuff sounds.

For reference I use LPs and CDs that I recorded- which helps since I know how they are supposed to sound. The bass issue you seem to describe doesn't sound challenging to me- I also play bass and keyboards (most of which are old school synthesizers) if that helps...

I believe Most Class D amps have low output impedance which can contribute to damping factor compared to higher output impedance tube amps. That can make a big difference in how bass sounds in many cases (not all) in that the driver is better controlled and distortion lower. When I first heard my first Class D amp in my system, Bel Canto ref1000ms, it sounded like the bass was gone. Shortly after when my ears adjusted I realized it was all there but more defined and articulate than ever compared to several prior SS amps. A decent quality sound meter app is all that is needed to put any bass level question to rest. Ears alone may well not cut it in this case.

@mapman +1, I also own the Bel Canto REF1000Ms and use them to power my distributed bass array for a bi-amp set up. No shortage of bass there and it's very fast and articulate.

When speaker designers of yore were making speakers with 32 and 16 ohm impedance damping wasn't quite as important. Back then tube amplifiers, zero feedback SET in particular known for high output impedance, were by far the norm. Nowadays with speakers being of lower impedance things have changed. It's been said by a few people I know who make tube amplifiers that the popularity of solid state amplifiers using feedback came about due to speaker designers making 4 ohm impedance speakers. Makes sense when you think about it as damping should be higher with that type of load. However, these same tube amplifier makers have said to me that anything over a damping factor of 20 makes very little if any difference. So the damping factor spec should be taken with a grain of salt as well.

I have no experience with AGD, Orchard or Atmos-phere but I have owned a Peachtree Audio gan. 400 for a year, my local HiFi dealer had it in stock and I was able to audition it and bought it, 400 watts into 8 or 4 ohms.  I am quite happy with it, very detailed, but not bright, neither forward or laid back, more neutral. Wanted a little more power for my Magnepans than I had with my old 150 watt Threshold amp.  There may be better gan amps for a higher price but I can’t complain, quite happy with the gan. 400. I think class D is the amp of the future and they are constantly evolving and getting better, and the days of the 150 lb space heater class A/AB amps are growing shorter.  

@atmasphere I would love if you could try the two tracks I mentioned with your various amps and report findings. Maybe PM me? I am super curious. 

Another thing I had change with the Audions - the 10 gauge "western electric" speaker wires I had been using with the previous set up had to be changed over to 16 gauge. With the 10 gauge wires the sound was way too overbearing and difficult to get right. Sounded like a run-away horse.

I would not let GAN transistors be your deciding factor ,that is just one small influencing part of a big chain of parts . Much has to do with how substantial the power supplies are , quality of build ,and output stage . Some build pretty boxes 

look at Merrill a fine product but  put a pretty face on it with nice machined cases 

and then $25-$30k I was shocked ,just 3 years ago they were around $10k .if I am going to spend over $10 k  AAvic from theDanish Audio group makes Outstanding 

gear That get get very $$ ,But they have a entry level line that is very refined with lots of trickle down technologies  that is reasonable a integrated starting around $6k. The Danes  are known to build excellent products .I owned a class D product 

I regret selling from Gato audio very natural and musical. I think they have a Canadien distributor .their 150 monoblocks with a meter is very well respected .

check these guys out . Sorry I cannot remember everything here but it’s a good starting point.

Check out audio group Denmark , they have very good products ,even their entry level has technologies their brilliant designers have that most Donot .

well worth checking out ,their entry level is better then most of any type of amplification per $$ dollar spent. Lots of cutting edge technologies.

I wanted to give an update. I needed to drop off a couple DACs I was trying at my local AGD dealer. I mentioned this thread and told him about my thoughts on bass. He said he never heard that nor experienced it in his own systems with their amps. He speculated it may be my speaker cables so gave me something to try. There's a huge difference on the bass side between my regular cable and the ones he gave me. I'm shocked at the difference. I bought the cables when I had a totally different system so they may just not work with this amp and speakers as well. Crazy hobby/addiction.

I recently purchased a Hifi Rose RA180 that I have paired with Focal Diablo Utopia standmount speakers and an SVS sub. It also utilizes GAN transistors and had some interesting features such as bi-amping capabilities, BTL mode for difficult speakers, selectable tone controls, and a dedicated sub out.

I also really like how it looks on the rack and stacks up well with the highly rated and equally gorgrous Hifi Rose RS130 streamer. 

@bhvf , care to say what the old and new cables were?  It might help others who happen to be using similar cables

I own the Peachtree Gan 400 amp.....Match it with a nice tube preamp and you have a beautiful , musical sound. Nice.  OR go with the Pascal Module that Aavik , Axess and Gato have for a step up in SQ.

My Audions are fronted by a Primaluna EVO 400 pre which has been in my stack for 2 years. This sounds good, but in a few weeks supposedly I will be receiving a Holo Audio Serene KTE pre. My DAC is a Holo May KTE, and the Serene is supposed to compliment the May quite well. However, I am a little apprehensive. New Record Day’s Youtube review of the Serene said something to the effect that the Serene took the totally clear window of the May and smashed that window out of the way which is what the Audion already feels like it is doing. Clear I like - "clear light" as in the famous old time LSD could be harmful to your health. LOL

I have the Technics SU-G700M2 which uses GaN FETs and it's really nice sounding. No etch, great extension, slightly warm, lots of PRAT, great tone, you name it, it's got it. A keeper if there ever was one and it got me off the audio merry-go-round.

All the best,

Just commented on your too heavy to lift thread. Do yourself a favor and just find the right amp. I went the GAN Class D route and now sorry other than it will probably be my summertime amp. It just amazes me how to some people they sound like tubes, or even better. They just don’t. Of course that’s just my opinion like everyone else’s. YMMV.

Do yourself a favor and just find the right amp.  I went the Class D route and now sorry other than it will probably be my summertime amp.

@marco1, you have made this comment in different threads.

I respect your opinion, and I made a similar decision, but I hope you won't mind if I ask you to share some details.

It's helpful to readers if specific Class D amplifier(s) are discussed, because akin to other audio components, chip amps (I use the term chip amps, because not all are Class D) don't sound the same. At least the chip amps I've heard in my system had different presentations and characteristics.

Which Class D amp(s) are you referring to that did not meet your expectations?

@tvad The three Class D amps that did not meet my expectations were AGD, Orchard and Atma-sphere, the 3 amps brought up by the OP.  I currently own A/S OTL and Conrad Johnson amps and recently sold some Pass amps all of which I am comparing to.  Over the years I’ve also owned quite a few other amps, both tube and solid state, so I do have some foundation to compare to.  Like I’ve also said in other threads the GAN amps imo are getting close to the sound of tubes.  They’re just not there yet. Whether they ever will is not for me to say.  The easiest way to explain it and what I have also said before is that they don’t have the “soul” of a tube amp. There are of course several pluses.  They’re light weight, run cool, and in some cases a good value if that is what you’re looking for.  Again, sorry to say they just don’t sound like tube amps.  I had hoped they would.

@marco1, thank you for specifying the amps.

Interestingly, two of those...AGD Productions and Orchard Audio...were two I also auditioned about four years ago.

I arrived at the same conclusion as you did.

Nevertheless, I believe AGD Productions GAN amps (and I suspect Atma-Sphere GAN amps as well), are worthy of recommendation and audition.