Atma-Sphere Class D GaNFET Amplifiers

[Dweaton]

Hopefully I can get a pair of these in to hear.

 

[antcollinet]

Ive had numerous class d amps in my controlled listening room over the years.
Unlike most audiophiles here I work on music professionally and have a fully treated room. My speakers are set up in a perfect equilateral triangle and my tweeters are ear level. My phantom center is insanely good.

My speakers are modified Immedia Allegra that under went a full 9k crossover rebuild with cost no object parts. I use Benchmark, Bricasti, and Mytek conversion here.

My room: Not a few bass traps and thin panels like most of the consumers here but a full array of treatment to flatten out my room. My speakers are decoupled and overall it is a very hyper critical listening room.

(Btw I find it humorous how spec driven this website is even though I find it important to me it’s only part of story as system synergy, room treatment, and low level listening factor in) One of my favorite sounding AD converters is a JCF latte which doesn’t have the best measurements but has a really great/clean sound in analogue to digital capture that feels so musical and right) also worth looking into Playback Designs DACs and ADCs and what the designer there writes about specs…)

I guess I’m saying I appreciate this website but much of it I take for a grain of salt as most of the users here have untreated rooms. (Putting a few panels up and doing a system EQ is not a treated room..) I love some
The findings here though and see the merit overall.

Non-the less these minimal specs measurements done here don’t always equate to everything for me. For instance I enjoyed the new purifi modules in the nad c298 amp recently had it for 3months but felt at low volumes the music didn’t sustain) hard to describe) fyi I could live with them and work with them as they are very neutral/clean)…
these amps definably made me re-think class-d as every other amp I’ve used that has been class-d ended up annoying me sonically after time… almost like I was hearing a box of moving parts rather than music…

I’ve demoed Orchard amps, Wyred4sound (ice based modules) not my cup of tea…, and recently th e new AGD mono amps. (GaN) weirdly when we were switching between both the Orchards and the AGD monos. There was a strange fatiguing quality to the Orchards compared to the AGDs. Like in some chorale music we were listening to in the upper midrange it felt a little hard and grainy on the ears (note: the orchards are amazing overall and super fluid/fast and overall they really blew me away at first) and I think if we didn’t have the AGD amps we wouldn’t have noticed it. (This was even experienced in another room with other speakers through a high end MSB DAC)

All in all these new GAN amps really have a subtle different sound to them than the purifi based amps) it’s really like no sound almost like straight wire with gain… there is a fluidity and natural presentation to the music. I’m sold on them and thinking to switch now to using either a pair of AGD or the maxed out Orchards.
I’m not bothered by the specs of this amp…
Yet here we talk about specs of GAN amps and purifi modules… if you demo and listen to amps as much me there is clearly a different “signature” to these amp topologies… the sound I prefer is from the GAN amps… I know this is not a “feeling” forum. But it feels more like music… lol
Maybe I’m the only one here curious to demo these Atma amps…

Note: recently a few months ago I went to a local audiophiles house (70k amps, 20k DAC, and the whole 9 yards…) his room was bright and super fatiguing… no acoustics and really a painful experience overall. I was polite when I was there… long story short this guy is a big reviewer on audiogon… people send him equipment to review, he doesn’t even level match amps/dacs when he A/Bs by writes really flowery reviews of gear (not to mention R2R DAC promoter… I was disgusted… I appreciate this website a lot as there are many people like that spewing nonsense.

One the other side——> a month before that I went to an audiophiles house in Malibu… older man with endless money. Pure silver wired system(I looked up the speaker cables and they were 90k each), 300k audio note amps, and million dollar plasma coil speakers through horn loaded drivers, additional subs (forgot the models)… basically a 2-3 million dollar system… this system was amazing. 4 watts amps through 118db sensitivity speakers. I’ve never hear music float like that. Was it accurate? I don’t care. It blew me away. Music is wiggles in the atmosphere…

I'd love to hear your room. I've never had the opportunity to listen in a decently treated room.

Even so, I'd be really interested if you could still hear all those clear differences in a properly controlled blinded test.

 

[goryu]

I was initially curious as I am looking for 6 channels of high quality amplification for an active 3 way system. Unfortunately the manufacturer, Atma-Sphere hasn't been willing to publish the measurements. With the cost at 3x what I can buy a state of the art class d amp like Purifi or Hypex, I would like to see what I am paying all that extra money for...no longer interested.

 

[Dweaton]

I'd love to hear your room. I've never had the opportunity to listen in a decetnly treated room.

Even so, I'd be really interested if you could still hear all those clear differences in a properly controlled blinded test.

These were not blind tests done scientifically so you could call them subjective tests… and Probobly dismissed on this forum. I like to live with amps for 1-3 months before making deductions/decisions. However I do use the same references recordings and level match listening sessions. I often have another close friend with me too. Take it how you will… I’m curious if I could too… maybe it was all in our heads… we also had a pure class A Magnus audio amp in the fold that day… I’m sure we totally could hear the difference blind on that sucker. Had a lot of bass slam and drive.

 

[Dweaton]

I was initially curious as I am looking for 6 channels of high quality amplification for an active 3 way system. Unfortunately the manufacturer, Atma-Sphere hasn't been willing to publish the measurements. With the cost at 3x what I can buy a state of the art class d amp like Purifi or Hypex, I would like to see what I am paying all that extra money for...no longer interested.

Honestly for consumers I’d stay with Hypex, Orchards, or AGD or Benchmark. no need to get into some esoteric low watt class d ganfet… I wanna hear these amps though.

The new purifi modules really impress me more so than than other hypex/ice based amps I’ve demoed. I really want to hear the Mola Molas and the Merrill Audio amps sometime soon. The future is class D. I’m a believer now. They should post specs at least… I agree.

 

[GXAlan]

Again. what's missing is any evidence that your amps sound different than low distortion designs once impedance-related frequency response errors are accounted for. You've espoused the "distortion profile" hypothesis (as famously has Nelson), but at the levels your amps produce (relatively low compared to amps that are designed rather than engineered), the hypothesis begs for evidence, not just that it explains sonic differences but that those differences (frequency response aside) even exist.

So far, nope. I understand, you have your market and they don't care, so why bother? But hey, I'm a (now former) scientist, so the whole hypothesis testing thing is hard-wired into me.

I'm bringing up your old post, but running into a real speaker (JBL XPL90), I heard big differences between two integrated amplifiers. That could be impedance-related but I then measured them using a non-inductive resistive load with lots of appropriate negative controls and used DeltaWave to show that the measured difference between amps met the threshold of audibility whereas the differences between all sorts of appropriate controls did not, including one with the amp, running different sources.

This suggests that low distortion designs, independent of impedance-related frequency response can impart sound at exceeding low volumes.

Measuring the "sound signature" of two different integrated amplifiers.

@KSTR figured out that the left and right channels were swapped during recording! Presumably this must have been the case when listening too! The calculations had been done in stereo. This changes the numbers and shows smaller changes between amps when fed directly but still has a change...

www.audiosciencereview.com

@atmasphere @SIY

Negative Controls showing no difference once volume matched:
- three different setups at different gains measured against each other days apart
- two different high performance DACs at line output at different volumes
- three different sources into same amplifier, measured at speaker terminals

But amplifier A vs amplifier B did show differences with PK Metric's in the -48 dBFS or so. This was well under 1 watt of power as well.

I've given all of the test conditions to allow anyone to attempt to reproduce my results.

 

[SIY]

I'm bringing up your old post, but running into a real speaker (JBL XPL90), I heard big differences between two integrated amplifiers. That could be impedance-related but I then measured them using a non-inductive resistive load with lots of appropriate negative controls and used DeltaWave to show that the measured difference between amps met the threshold of audibility whereas the differences between all sorts of appropriate controls did not, including one with the amp, running different sources.

This suggests that low distortion designs, independent of impedance-related frequency response can impart sound at exceeding low volumes.

Measuring the "sound signature" of two different integrated amplifiers.

@KSTR figured out that the left and right channels were swapped during recording! Presumably this must have been the case when listening too! The calculations had been done in stereo. This changes the numbers and shows smaller changes between amps when fed directly but still has a change...

www.audiosciencereview.com

@atmasphere @SIY

Negative Controls showing no difference once volume matched:
- three different setups at different gains measured against each other days apart
- two different high performance DACs at line output at different volumes
- three different sources into same amplifier, measured at speaker terminals

But amplifier A vs amplifier B did show differences with PK Metric's in the -48 dBFS or so. This was well under 1 watt of power as well.

I've given all of the test conditions to allow anyone to attempt to reproduce my results.

Source impedance differences are certainly audible if they're not low. Fred Davis showed some interesting data on this about 40 years ago. Of course, those differences can be eliminated with some minor EQ trimming.

 

[atmasphere]

Unfortunately the manufacturer, Atma-Sphere hasn't been willing to publish the measurements.

This statement is false. To be true, the statement should read something to the effect of 'Atma-Sphere hasn't been willing to publish enough of the measurements for my satisfaction.' IOW we have published measurements; they were up as soon as we started selling the amps.

No-one is going to beat Bruno's Purifi modules distortion numbers any time soon. He controls the patents that allow one to get the loop gain needed for the kind of feedback he's running, while at the same time allowing the amp to restart correctly at the right frequency when its recovers from overload. That's harder than it sound and is several patents, making it challenging for anyone entering the field. So if distortion is your sole criteria get a Purifi; just be sure of several things- that it has a decent power supply using parts that will last, that the input buffer section is properly designed and includes a balanced input (because after all that's lower distortion...) and that its built well enough to not be ravaged during shipment. People ask why our gear costs what it does and quite simply our amp was built to last like everything else we've made.

lol...My understanding is the Orchard amp uses the flavor of the day GaN devices, which really don't offer any real improvements/advantages when used in class d amps at the lower switching rates (500-800kHz) most are using. The circuit topographies in all of these GaN amps are not to my knowledge as sophisticated/state of the art as that used in the Purifi.

This statement is problematic. GaNFETs really have nothing to do with how the amp is going to perform. OTOH topology has an enormous effect! The switching speed does not have to be all that high for low distortion BTW. In all class D amps you have something called 'deadtime' which is essentially prevents a power transistor from turning on until its mate has shut completely off. If you switch at a higher rate the amount of deadtime is a constant so will be the same amount; the output section will make more distortion at a higher switching speed since deadtime causes distortion. The allure of a higher switching speed is you can get more loop gain, which means you can run more feedback. I hope you can see that there is a bit of a carrot on a stick here- the extra feedback might only be cancelling the additional distortion of running at that higher speed. Of course the faster you switch the more headaches you have with parasitics.

The real advantage of GaNFETs is lower noise since there tends to be less inductive parasitics and less current required to make them switch due to lower gate capacitance. This means that the radiated noise of the module can be less than a lot of tube amplifiers. The concern here is meeting things like the EU Directives (CE mark) so the amp doesn't cause trouble when running. I had a cheap sub in my bedroom system for a while that was class D powered; when it was on it blotted out certain stations on the FM tuner in that system, which led me to the awareness that one way of obtaining the CE mark is by using an old technique called 'lying'. We were pretty concerned about radiated noise with this design since it was our first class D project.

 

[goryu]

This statement is false. To be true, the statement should read something to the effect of 'Atma-Sphere hasn't been willing to publish enough of the measurements for my satisfaction.' IOW we have published measurements; they were up as soon as we started selling the amps.

There is a clear difference between "specs" and "measurements". Your website has indeed published specs- a bare bones amount at that. There are no "measurements", which I consider data plots, rather than simple statements of performance as shown on your site. When I look at other manufacturers, like Hypex, Purifi, Orchard, etc., I see pages of measurements. You haven't published anything remotely similar. Instead, you deflect as below. Here is a link to Orchard's measurements for their GaN amp, which seems to measure very well indeed. I should add that the new amp from Hypex, the nilai500, coming out soon, measures even better than the Purifi.

Elevate your listening with our high fidelity audio electronics.

We are a boutique audio company that aims to provide an immersive listening experience by offering a variety of top-quality DACs, streamers, and amplifiers. Our products are meticulously handcrafted in the United States, considering the needs of music enthusiasts who prioritize high-quality...

orchardaudio.com

No-one is going to beat Bruno's Purifi modules distortion numbers any time soon. He controls the patents that allow one to get the loop gain needed for the kind of feedback he's running, while at the same time allowing the amp to restart correctly at the right frequency when its recovers from overload. That's harder than it sound and is several patents, making it challenging for anyone entering the field. So if distortion is your sole criteria get a Purifi; just be sure of several things- that it has a decent power supply using parts that will last, that the input buffer section is properly designed and includes a balanced input (because after all that's lower distortion...) and that its built well enough to not be ravaged during shipment. People ask why our gear costs what it does and quite simply our amp was built to last like everything else we've made.

Deflection/excuses. Others publish a full suite of measurements without deferring to Bruno. As I said, Hypex nilai500 beats the Purifi and there are many others who publish a suite of measurements without worry or fear of "beating Bruno".

Distortion isn't the sole criteria. There are many other performance indicators of interest. Your amp costs 4 times what a Purifi amp can be had for. I want to see why I should pay 4 times the price. I value performance as well as build quality. Both Hypex and Purifi seem to have excellent customer service and stand behind their products. I don't see why your product should last 4 times longer than those of Hypex or Purifi. The ncore line has been around for nearly 10 years I believe. I know people who are still using them without any issues. This seems like another red herring. Perhaps if you used a SMPS instead of a heavy linear power supply you wouldn't have to deal with product "ravaged during shipment". I have shipped several class d amps over the years, including to Japan and back from the US on several occasions and never had any issues.

This statement is problematic. GaNFETs really have nothing to do with how the amp is going to perform. OTOH topology has an enormous effect! The switching speed does not have to be all that high for low distortion BTW. In all class D amps you have something called 'deadtime' which is essentially prevents a power transistor from turning on until its mate has shut completely off. If you switch at a higher rate the amount of deadtime is a constant so will be the same amount; the output section will make more distortion at a higher switching speed since deadtime causes distortion. The allure of a higher switching speed is you can get more loop gain, which means you can run more feedback. I hope you can see that there is a bit of a carrot on a stick here- the extra feedback might only be cancelling the additional distortion of running at that higher speed. Of course the faster you switch the more headaches you have with parasitics.

The real advantage of GaNFETs is lower noise since there tends to be less inductive parasitics and less current required to make them switch due to lower gate capacitance. This means that the radiated noise of the module can be less than a lot of tube amplifiers. The concern here is meeting things like the EU Directives (CE mark) so the amp doesn't cause trouble when running. I had a cheap sub in my bedroom system for a while that was class D powered; when it was on it blotted out certain stations on the FM tuner in that system, which led me to the awareness that one way of obtaining the CE mark is by using an old technique called 'lying'. We were pretty concerned about radiated noise with this design since it was our first class D project.

The truth is in the performance. As Bruno and Lars have said, they see no real benefit to using GaN devices over traditional ones at present and based on their performance, I find their opinion hard to argue with. They have also shown it is possible to meet EU requirements for RFI, etc. with traditional devices, as have others. GaN devices can offer increased efficiencies, which we see with the Orchard measurements, and have other characteristics which, if implemented properly, can offer some advantages, but there doesn't seem anyone has yet found a way to exploit the possibilities. Maybe at some point there will be actual material benefits to using GaN devices for class d amps. I don't see anything material at present, rather most of the GaN amps seem to simply be using GaN devices as a marketing technique.

 

[atmasphere]

There is a clear difference between "specs" and "measurements". Your website has indeed published specs- a bare bones amount at that. There are no "measurements", which I consider data plots, rather than simple statements of performance as shown on your site. When I look at other manufacturers, like Hypex, Purifi, Orchard, etc., I see pages of measurements. You haven't published anything remotely similar. Instead, you deflect as below. Here is a link to Orchard's measurements for their GaN amp, which seems to measure very well indeed. I should add that the new amp from Hypex, the nilai500, coming out soon, measures even better than the Purifi.

Elevate your listening with our high fidelity audio electronics.

We are a boutique audio company that aims to provide an immersive listening experience by offering a variety of top-quality DACs, streamers, and amplifiers. Our products are meticulously handcrafted in the United States, considering the needs of music enthusiasts who prioritize high-quality...

orchardaudio.com

Deflection/excuses. Others publish a full suite of measurements without deferring to Bruno. As I said, Hypex nilai500 beats the Purifi and there are many others who publish a suite of measurements without worry or fear of "beating Bruno".

Distortion isn't the sole criteria. There are many other performance indicators of interest. Your amp costs 4 times what a Purifi amp can be had for. I want to see why I should pay 4 times the price. I value performance as well as build quality. Both Hypex and Purifi seem to have excellent customer service and stand behind their products. I don't see why your product should last 4 times longer than those of Hypex or Purifi. The ncore line has been around for nearly 10 years I believe. I know people who are still using them without any issues. This seems like another red herring. Perhaps if you used a SMPS instead of a heavy linear power supply you wouldn't have to deal with product "ravaged during shipment". I have shipped several class d amps over the years, including to Japan and back from the US on several occasions and never had any issues.







The truth is in the performance. As Bruno and Lars have said, they see no real benefit to using GaN devices over traditional ones at present and based on their performance, I find their opinion hard to argue with. They have also shown it is possible to meet EU requirements for RFI, etc. with traditional devices, as have others. GaN devices can offer increased efficiencies, which we see with the Orchard measurements, and have other characteristics which, if implemented properly, can offer some advantages, but there doesn't seem anyone has yet found a way to exploit the possibilities. Maybe at some point there will be actual material benefits to using GaN devices for class d amps. I don't see anything material at present, rather most of the GaN amps seem to simply be using GaN devices as a marketing technique.

Hm. It might be that I explained the cost of the amp on another thread. Its cost is based on a formula rather than what the market will bear; this is why our amp is less than a lot of our competition (for example Technics). The chassis is the most expensive part; its rugged enough that it easily survives UPS or FedEx ground handling. Having been docked plenty of times we made sure it has decent cosmetics so its not man-cave only. A toroid power transformer is used along with high temp filter caps- the power supply is designed to last. All the assembly including the boards is done by hand in-house. If we were to use someone else's modules the price would be several hundreds of dollars higher. Finally the pricing includes dealer/distributor markup; if you are an industry professional with credentials then any of our products are available at half price along normal industry accommodation guidelines.

You and I are on the same page with Bruno's reasoning. It has to do with how GaNFETs are turned off- and that specifically has to do with the output filter, whose inductive kick when its magnetic field collapses is actually what starts the shutoff of the output device in tandem with the gate being off. To this effect, the deadtime isn't for the output devices at all (they can switch far faster so if it was only about them there would be a lot less deadtime in our design). Plus the output device he uses is cheap and readily available. The downside is because its a leaded part there is more noise, but in the face of the distortion he's able to get that's not much of a downside. We've been thinking about going to MOSFET outputs on this account as well; it might allow us lower distortion since the deadtime influences that in the mid power range.

 

[goryu]

Hm. It might be that I explained the cost of the amp on another thread. Its cost is based on a formula rather than what the market will bear; this is why our amp is less than a lot of our competition (for example Technics). The chassis is the most expensive part; its rugged enough that it easily survives UPS or FedEx ground handling. Having been docked plenty of times we made sure it has decent cosmetics so its not man-cave only. A toroid power transformer is used along with high temp filter caps- the power supply is designed to last. All the assembly including the boards is done by hand in-house. If we were to use someone else's modules the price would be several hundreds of dollars higher. Finally the pricing includes dealer/distributor markup; if you are an industry professional with credentials then any of our products are available at half price along normal industry accommodation guidelines.

Well, there are always going to be manufacturers selling flash, the GaN amp build within a tube, for example, and charge pride of ownership prices, though I wouldn't put the Technics GaN amp in that category as unlike everyone else, they are running their amps at 1.2Mhz and have a lot of their own original tech. Whether the end result justifies the price is debatable but at least they are doing some real engineering.

There is certainly a certain snob factor in audio- a small, 10 lb amp the size of a cigar box that costs less than a pair of speaker cables can't possibly perform like a $25,000 90lb amp in a billet chassis. You have stated that you decided to produce a class d amp because you "saw the writing on the wall- class d is the future." I agree, but you seem to have missed a major factor driving this trend: light, small, efficient, ultra high performance, all at LOW COST. No doubt you have a loyal customer base after a long run marketing tube amps who will appreciate the overbuilt nature of your amp, couldn't care less about the lack of published measurements (if they were into state of the art performance they probably wouldn't be into tube amps in the first place), and responds to the dealer marketing model. On the other hand, there are many who are looking for state of the art performance without the frills and jewlery which drive up the price, transparency and full disclosure of the performance parameters, and a demonstrated commitment to value. The trend these days seems to be more the latter, judging by the success of companies like Nord, VTV, Apollo, Buckeye, Hypex, Purifi, Orchard, to name a few. I have a hard time justifying lesser performance at 4x the price, even with the possibility that the lower price might mean a shorter life before failure. Nothing to date has shown that these class d amps won't last 10 years or more. Who keeps an amp that long anyway the way technology advances? One could have 3 prematurely fail and still be ahead financially.

You and I are on the same page with Bruno's reasoning. It has to do with how GaNFETs are turned off- and that specifically has to do with the output filter, whose inductive kick when its magnetic field collapses is actually what starts the shutoff of the output device in tandem with the gate being off. To this effect, the deadtime isn't for the output devices at all (they can switch far faster so if it was only about them there would be a lot less deadtime in our design). Plus the output device he uses is cheap and readily available. The downside is because its a leaded part there is more noise, but in the face of the distortion he's able to get that's not much of a downside. We've been thinking about going to MOSFET outputs on this account as well; it might allow us lower distortion since the deadtime influences that in the mid power range.

I find little to fault with Bruno's reasoning, in general.

 

[atmasphere]

Well, there are always going to be manufacturers selling flash, the GaN amp build within a tube, for example, and charge pride of ownership prices, though I wouldn't put the Technics GaN amp in that category as unlike everyone else, they are running their amps at 1.2Mhz and have a lot of their own original tech. Whether the end result justifies the price is debatable but at least they are doing some real engineering.

There is certainly a certain snob factor in audio- a small, 10 lb amp the size of a cigar box that costs less than a pair of speaker cables can't possibly perform like a $25,000 90lb amp in a billet chassis. You have stated that you decided to produce a class d amp because you "saw the writing on the wall- class d is the future." I agree, but you seem to have missed a major factor driving this trend: light, small, efficient, ultra high performance, all at LOW COST. No doubt you have a loyal customer base after a long run marketing tube amps who will appreciate the overbuilt nature of your amp, couldn't care less about the lack of published measurements (if they were into state of the art performance they probably wouldn't be into tube amps in the first place), and responds to the dealer marketing model. On the other hand, there are many who are looking for state of the art performance without the frills and jewlery which drive up the price, transparency and full disclosure of the performance parameters, and a demonstrated commitment to value. The trend these days seems to be more the latter, judging by the success of companies like Nord, VTV, Apollo, Buckeye, Hypex, Purifi, Orchard, to name a few. I have a hard time justifying lesser performance at 4x the price, even with the possibility that the lower price might mean a shorter life before failure. Nothing to date has shown that these class d amps won't last 10 years or more. Who keeps an amp that long anyway the way technology advances? One could have 3 prematurely fail and still be ahead financially.

For decades now amps were not advancing all that quickly- it was a pretty mature art insofar as the technology development sigmoid is concerned. Only when class D became really practical about 20 years ago did the art advance more. Even so it appears to be at or near the top of the sigmoid curve so someone may well keep an amp made now 20 years.

We do exist in a different market I think. Apparently Technics is selling to that same market- their amp has similar power to ours and is not quite twice the price. BTW, as part of our foray into class D we have a patent that was issued about 3 years ago. We did do 'actual engineering' Anyone who has developed a successful module will have done 'actual engineering'.

In our market tube amplifiers are still being produced in fact we make some ourselves (I think the class D is a better amp). We see tube amps as something that needs to go away. After that, class A or AB amps too unless they can get the GBP to support their feedback properly. Most don't. We've been in business for nearly half a century so our perspective of what is important here might be a bit different. In any event we didn't design with price in mind, instead designed using parts that we knew wouldn't let us down. Having been around as long as we have I can tell you that there is a difference there. For example Bruno uses a circuit called a current pump to support the lower voltages needed for the front end of his circuitry; we found that to be noisier so popped for the few extra bucks to use a voltage converter/regulator. People have used the amp on speakers that are 105dB and report that its nice and quiet. Its so much easier to sell an amp and not have to get it back over something like that.

 

[sq225917]

There's plenty of decent class a/b amps out there with numbers far beyond audibility at sensible money so don't write them off yet.

People buy stuff for myriad different reasons, measured specs usually not being high up the list for the majority.

 

[restorer-john]

I had a cheap sub in my bedroom system for a while that was class D powered; when it was on it blotted out certain stations on the FM tuner in that system

Blocking AM, yes, FM- no chance.

 

[pseudoid]

The real advantage of GaNFETs is lower noise since there tends to be less inductive parasitics and less current required to make them switch due to lower gate capacitance.

Isn't one of the main advantages of designing with GaN also relate to the fact that it has some excellent slew rate (current) capabilities which can be suited for (higher) power amplifier designs?

 

[atmasphere]

Blocking AM, yes, FM- no chance.

Tell that to my FM-only tuner! In a class D design you can have parasitics at some crazy high frequencies. GaNFETs for example have no problem switching at 60MHz; ask me how I know. But you don't need the circuit to be switching that fast to set a parasitic into excitation. So yes, a poorly executed class D can easily interfere at FM radio frequencies.

Isn't one of the main advantages of designing with GaN also relate to the fact that it has some excellent slew rate (current) capabilities which can be suited for (higher) power amplifier designs?

No. If the amplifier can switch at 500KHz then its going to have plenty of slew rate. The advantage of GaNFETs IME is its a lot easier to make a lower noise circuit since parasitics are so much easier to control. That might have advantage to a higher powered amp, since with greater power you may well have greater possibility of noise from parasitics (which are usually inductive in nature).

 

[Mnyb]

Wonder if GaN would work in VFD’s lower losses are always welcome. The thermal problems are a limit in industrial drive systems ( and automotive too ).

 

[fpitas]

Wonder if GaN would work in VFD’s lower losses are always welcome. The thermal problems are a limit in industrial drive systems ( and automotive too ).

As I recall, SiC is the darling there. Not quite as fast as GaN, but still has good electron mobility and stands very high temperatures. Modern silicon IGBTs are pretty darn good too, if the ON voltage isn't a problem and you don't need blazing speed.

 

[Mnyb]

As I recall, SiC is the darling there. Not quite as fast as GaN, but still has good electron mobility and stands very high temperatures. Modern silicon IGBTs are pretty darn good too, if the ON voltage isn't a problem and you don't need blazing speed.

Thanks and sorry for the OT.
there was talk if SiC for a while , but our company uses IGBT’s currently , but developers are tight lipped so if one major company in the business switch to SiC or GaN we hear about it soon enough.
A concern is standard packaging so that several brands of semiconductor can fit the product .

 

[kipman725]

EPC's GaN isn't that great, Bruno should check out GaN Systems: https://gansystems.com/wp-content/uploads/2022/03/GS-065-060-3-B-DS-Rev-221004.pdf
Perfect for high power applications (apart from cost...).