CLASS D MONO AMPS buy ATMASPHERE MUSIC SYSTEMS

When will the specs/measurements be available?

All the specs he wants to share now are on his website. He has never published measurment graphs......most companies don’t. If you want more detailed specs than I suggest you contact him directly.

http://www.atma-sphere.com/en/classD.html

I think that if he wants to compete with the likes of Hypex and Purifi, he needs to publish measurements along the likes of the competition.

Don’t think so. His market is for people who REALLY listen and value how an amp SOUNDS and value his take on harmonic structure of the distortion versus super low standard measurements of distortion. All versions of Purifi and Hypex sound different from each other yet most measure the same. I have no doubt his amp will "sound better" than anyones Purifi....including my modded ones....of course, at a different price point. Some believe the measurements at ASR really mean something.....they do mean something....just not much in the way of how something sounds. Those guys do not listen so they have no idea if their measurements correlate to sound. Ralph has made state of the art tranformerless tube amps for years and his amps have been compared to other amps over and over....so he has a great reference for sound. ASR guys have no reference for sound....they just have some measuring tools.  I am pretty sure Ralph won't send his amps to ASR to be measured.  Maybe in a few years someone will send them their own pair and then you can whine about the fact that it does not measure as good in some ways as something.else.  Meanwhile, those that have the amps will be grinning because of the beautiful sounds it makes.

We all have different takes on things....vive la differance. Joy to you and everyone.

@ricevs thans for the link - I did not find class-D yesterday.

@kuribo I don’t think he is competing with Purifi.
I was thinking that his amps are all current amps, but the specs suggest a voltage amp.
All of his other amps are low feedback design, but this one is 35dB of feedback gain.

I am not sure what Hypex and purifi are in terms of feedback gain.

I wonder how well this new product will work with 16 ohm speakers? Sure, it will work, but, how effectively. This is a surprise for folks who have cherished the OTL designs for use with 16 ohm speakers. 

@ricevs you hit the nail on the head. The only similarity will be that they are D Class.

 

The website lists power specs into 16 ohm. Ralph has clearly articulated all amps make less distortion into higher impedance loads so I would anticipate that is a driver still for his design. Will be interesting for someone to measure how these operate into different loads. Yes the M word….. I would expect these to work better with more speakers which would open up some new sales paths for Atmasphere.  Has potential to make me a customer which would not have been likely  with OTL tube amps given my speaker preferences. 

I wonder how well this new product will work with 16 ohm speakers? Sure, it will work, but, how effectively. This is a surprise for folks who have cherished the OTL designs for use with 16 ohm speakers. 

My speakers at home are 16 Ohms as well as our speakers at the shop. Any amp driving 16 Ohms will have lower distortion.

So he is adding distortion to please a certain group of people? And those who don’t prefer his particular distortion preference, not so much.

@kuribo In most class D designs, the distortion sources in the design are caused by dead time and non-linearities in the encoding scheme. In our design these result in lower ordered harmonics- its not been tailored.

 

 

@kuribo In most class D designs, the distortion sources in the design are caused by dead time and non-linearities in the encoding scheme. In our design these result in lower ordered harmonics- its not been tailored.
 

There are many sources of distortion in class d amps, not only those you have mentioned, but also in the output filter. Do you use post filter feedback?

Please share some measurements of the frequency response with load, THD+N with power and frequency, FFT's and IM. Also, can you share the switching frequency used? Lots of claims made here (not all by you) so it would be enlightening to see a more complete picture of how this amp performs in actuality, not how it sounds to those who haven’t heard it yet.

@kuribo a large segment of the market likes state of the art design, excellent objective performance, as well as a neutral and transparent sound.

Slightly circular I think, because those words define the "market" as being those who like state of the art design, excellent objective performance, as well as a neutral and transparent sound. That is actually quite narrow, by my reading, and so large segment is correct but moot.

My own definition of "market" would be substantially wider, and would include other variables, without necessarily excluding those mentioned. Perhaps a different weighting scheme, for as is conceded, everyone has different tastes.

Perhaps by choice like yourself, or for other reasons.  Irrelevant.

Slightly circular I think, because those words define the "market" as being those who like state of the art design, excellent objective performance, as well as a neutral and transparent sound. That is actually quite narrow, by my reading, and so large segment is correct but moot.

My own definition of "market" would be substantially wider, and would include other variables, without necessarily excluding those mentioned. Perhaps a different weighting scheme, for as is conceded, everyone has different tastes.

Perhaps by choice like yourself, or for other reasons.  Irrelevant.

 

 

My comments don't define the market in its entirety- I am simply noting that there is a great number of people in the market who like state of the art design, excellent objective performance, as well as a neutral and transparent sound- in other words, objective and subjective criteria are of importance, not just one or the other. The success of Hypex and Purifi, both commercially and critically, attests to this market dynamic.

I couldn't care less what others think of the sound of this or any other amp. What matters to me is my own opinion, in my room, in my system. The rest is simply noise. I want an amp that outputs a signal as true to the input as possible, only larger. I appreciate good design as verified and vetted by measurements as do others.

@kuribo From the website -

The Class D amp has the same kind of distortion signature {as tube amps}, but at a much lower level.

This, to me, is reasonably unambiguous. From what I understand of Hypex and Purifi (and others, of course) amplifiers, they make no such claim about harmonics. I suspect measurements may confirm this. I’d bet on it.

I’m as concerned about the definition of the market as you are with your amplifier preference. "in the market" would be the worldwide production and sale and availability of stereo amplifiers. Within this there are many other more narrowly defined markets like an overlapping mess of circles on a page, each with their own and overlapping characteristics.

So the "great number of people" must be taken in this context.

People, forget about Hypex, Purifi, et al.

The obvious point of comparison/competition here is the AGD Tempo di Gan.

Consider this.

Atmasphere: proprietary GaNFET module, 100W into 8, 200W into 4, $5400.

AGD: proprietary GaNFET module, 100W into 8, 200W into 4, $5500.

If anybody could get both amps in the same room at the same time, then they would really have my attention.

People, forget about Hypex, Purifi, et al.
 

Why? They are the current state of the art in class d amplification.

@kuribo From the website -

The Class D amp has the same kind of distortion signature {as tube amps}, but at a much lower level.

This, to me, is reasonably unambiguous. From what I understand of Hypex and Purifi (and others, of course) amplifiers, they make no such claim about harmonics. I suspect measurements may confirm this. I’d bet on it.

No, Hypex and Purifi are more concerned with producing a wire with gain, free from any coloration, tube like or otherwise. Their measurements bear this out as the harmonics, etc., are buried below audibility. If the maker of this amp provides similar measurements, we can make that assessment.

 

 

@twoleftears  That AGD price is for the stereo unit.    The Atmasphere are monos.

The AGD monos (Audion in satin)  are $7500. 

But even then, one coould speculate.....The question is how much of the difference in price is due to the bling factor and other stuff - the AGD bloke reckons somewhere that the cost associated with sticking a small city into the KT88 tubes is significant..  I'm not surprised.

Compare the pics, if you may, at you leisure.

@kuribo If the maker of this amp provides similar measurements, we can make that assessment.

But Ralph specifically says that his amp does have 2nd and 3rd harmonics at some level..

If I’m interested in buying a car that is grey, I don’t even think to bother the dude who is selling a red car for details about it.  That’s just me. I can’t speak for we.

But if I did wish to ask about why the red car is so much better than a dull grey car, I would do so politely and with due respect for the red's superiority.

Here are the facts that Kuribo/ASR miss.

1. No amp has ever passed straight wire bypass testing.

2. All Purifi amps sound different.....based on their input stages, power supplies, wires used, connectors used, damping ,etc. etc.........yet, they will all measure about the same.....with all these different parts and execution.  So, if you can change and improve the sound of an amp without affecting its distortion measurements.....this actually proves that measurements by themselves are really not that important to really KNOWING what an amp sounds like.

3. No one who has listened to a bunch of serious amps has ever declared a Purifi based amp is the best amp in the world.

4. The Benchmark amp also measures like ASR people want.  It has its own sound (improved by using audiophile fuse in it) and again, no one would say it is state of the art that has listened to many high priced serious amps.  On Jay's thread right now there is a guy who just listened to 4 different amps and the Benchmark was not the best.

5. Discrete op amps do not generally measure quite as good as integrated circuit op amps.  VTV sells a version of their Purifi based amp that you can interchange various op amps on its input....including integrated circuit ones.  The discrete ones just plain sound better and each brand of discrete op amp sounds different from every other one.

6. Static standard distortion measurements do NOT tell you how transparent (like a striaght wire with gain) an amp is.  This fact alone does not resonate with measurement obsessed people.  The only way to know how transparent an amp is......is to listen to it.  Listening rules....measurements are just a mild indicator of something....nothing else.

Here is another factoid.  You cannot change anyones addiction by stating truth.  In order to stop your addiction, you have to admit you are addicted......the ego does not like to be WRONG.  I am sure Kuribo will fire back with his usual response.  We have played this game before.

The dance of truth versus ignorance is an eternal dance.  On every level there is truth......and on some level eveything is true.  So, hopefully, we can speak our truth in peace without making someone else wrong.  People are beautiful.....but sometimes we think and act out of alignment with our beauty.  This is called "being human"......However, we are also divine and can re-align with our beauty at any moment......we make the call.....every breath we take can be filled with joy or whatever else you choose.....choose wisely my friends.

The mind is a "make wrong machine"........the heart is a "make beautiful kissy thang"

I send you all big wet kisses.

Here are the facts that Kuribo/ASR miss.

Not a single fact, just more guru babbling not worthy of further consideration or comment.

But Ralph specifically says that his amp does have 2nd and 3rd harmonics at some level..

If I’m interested in buying a car that is grey, I don’t even think to bother the dude who is selling a red car for details about it. That’s just me. I can’t speak for we.

But if I did wish to ask about why the red car is so much better than a dull grey car, I would do so politely and with due respect for the red’s superiority.

"At some level"

What does that mean exactly? Nothing really.

If I’m interested in buying a car that is grey, I don’t even think to bother the dude who is selling a red car for details about it. That’s just me. I can’t speak for we.

Indeed, that is just you. If I am considering a $5000 amp, I would like to know a little more about it than the color. But that is just me, and probably the majority of people.

 

But if I did wish to ask about why the red car is so much better than a dull grey car, I would do so politely and with due respect for the red’s superiority.
 

Superiority? That has not been proven by any measure.

Thanks for the unsolicited advice.

 

@atmasphere ,

Will the Class D amps be upgradable?

Bob

There are many sources of distortion in class d amps, not only those you have mentioned, but also in the output filter. Do you use post filter feedback?

Yes.

Please share some measurements of the frequency response with load, THD+N with power and frequency, FFT's and IM. Also, can you share the switching frequency used? Lots of claims made here (not all by you) so it would be enlightening to see a more complete picture of how this amp performs in actuality, not how it sounds to those who haven’t heard it yet.

The frequency response is load invariant within 1/10db from 20-20KHz, with 0 degrees phase shift at 20Hz and less than 1 degree at 20KHz. The invariance due to the output impedance being a few milliOhms, the low phase shift due to the feedback value, which allows the amp to correct for phase shift at the bandwidth extremes.

THD from 20Hz- 20KHz  is < 0.1% at full power (200 W into 4 Ohms) and about 0.005% at 1 watt. We think it might be lower but finding a decent filter to knock out the residual has been tricky during the pandemic. We  found one about a week ago and are interested to see how things differ once its integrated into our test setup. The distortion is lower into 16 Ohms.

The switching frequency is just shy of 500KHz, depending on load. The input is entirely direct-coupled.

The filter I mentioned is an Audio Precision device and is used to knock out the residual to prevent it messing with the distortion analysis. If I got this right its 8th order(!) and puts the residual down about 60dB... This is why we've not posted any more distortion data since the residual throws the readings off.

 

 

 

@kuribo No. Purifi is last year's news, even if he is now working on a higher powered module, and Hypex... well.  GaN is state of the art--and not the generic stuff being put out by Peachtree and LSA.

And @noske, I disagree and would maintain my point.  As regards proprietary modules, power output, and price, the two products are directly comparable.  The fact that one is housed in two cases is secondary.  The Audions are nice but not only considerably more expensive but also less powerful than the Tempo di Gan.  My proposed comparison seems to me to offer the levelest of playing fields.

The frequency response is load invariant within 1/10db from 20-20KHz, with 0 degrees phase shift at 20Hz and less than 1 degree at 20KHz. The invariance due to the output impedance being a few milliOhms, the low phase shift due to the feedback value, which allows the amp to correct for phase shift at the bandwidth extremes.

THD from 20Hz- 20KHz  is < 0.1% at full power (200 W into 4 Ohms) and about 0.005% at 1 watt. We think it might be lower but finding a decent filter to knock out the residual has been tricky during the pandemic. We  found one about a week ago and are interested to see how things differ once its integrated into our test setup. The distortion is lower into 16 Ohms.

The switching frequency is just shy of 500KHz, depending on load. The input is entirely direct-coupled.

The filter I mentioned is an Audio Precision device and is used to knock out the residual to prevent it messing with the distortion analysis. If I got this right its 8th order(!) and puts the residual down about 60dB... This is why we've not posted any more distortion data since the residual throws the readings off.

 

I look forward to plots once you get your filter worked out.

At only 500Khz, what is the advantage of using GaN? None of your specs appear to be anything not already achieved or bettered by amps using good old fashioned mosfets.

Thanks for the info.

@kuribo No. Purifi is last year's news, even if he is now working on a higher powered module, and Hypex... well.  GaN is state of the art--and not the generic stuff being put out by Peachtree and LSA.

Until bettered, ncore and purifi are still the peak of class d design and performance.

GaN is a state of the art device but has yet to be implemented in a class d amp in a way that improves upon what has been already done by ncore and purifi using mosfets. Maybe some day, but not yet.

I was a scientist and for a long-time I had myself convinced that I could find better equipment by knowing more facts about the gear I might buy. And sure, I still think some audio facts can be a useful guide. At some point, however, you’ve just got to kick the tires and see how it sings.

Glad to see some people are loving the new amps Ralph.  Congrats.

 

I guess Kuribo will have no more to say on this thread because this design is not as good as Purifi (according to him).....so

Now we can get back to the actual reality of .....How does it sound? Will be interesting to get the feedback from more listeners when these amps are produced in more quantity and compared to other amps besides older OTLs. So far, we have two raves. Enjoying the ride....I hope you are too!

I guess Kuribo will have no more to say on this thread

 

no more to say to you anyway.

This Kuribo is the same person that was going off on Ric for mods to the LSA Voyger.

He is here to argue and he is not buying anything.

 

An Intergrated Class D Amp with Tube Pre-section would be a good idea??

Rouge and Gold Note are building Class D Hybrids with Tube pre.

An Intergrated Class D Amp with Tube Pre-section would be a good idea??

 

Not in my opinion. The benefits of class d done right are neutrality, low power consumption, cool running, etc. which is sort of the antithesis of tubes. Kind of like ordering a diet coke with your two big macs.

The frequency response is load invariant within 1/10db from 20-20KHz, with 0 degrees phase shift at 20Hz and less than 1 degree at 20KHz. The invariance due to the output impedance being a few milliOhms, the low phase shift due to the feedback value, which allows the amp to correct for phase shift at the bandwidth extremes.

THD from 20Hz- 20KHz  is < 0.1% at full power (200 W into 4 Ohms) and about 0.005% at 1 watt. We think it might be lower but finding a decent filter to knock out the residual has been tricky during the pandemic. We  found one about a week ago and are interested to see how things differ once its integrated into our test setup. The distortion is lower into 16 Ohms.

The switching frequency is just shy of 500KHz, depending on load. The input is entirely direct-coupled.

The filter I mentioned is an Audio Precision device and is used to knock out the residual to prevent it messing with the distortion analysis. If I got this right its 8th order(!) and puts the residual down about 60dB... This is why we've not posted any more distortion data since the residual throws the readings off.

I understand amp pretty at the freshman college level. And I appreciate the new designs and designers bringing new stuff to market.

But I really appreciate venerable designers, like yourself, bringing their expertise to bear on these things.

[/scratching the chin(s) and watching]

@twoleftears As regards proprietary modules, power output, and price, the two products are directly comparable.  The fact that one is housed in two cases is secondary.  The Audions are nice but not only considerably more expensive but also less powerful than the Tempo di Gan.  My proposed comparison seems to me to offer the levelest of playing fields.

This is impeccable logic, and I agree, thankyou.  Ralph is much more forthcoming about certain design features than AGD bloke.  This is important to those of us who are curious, bearing in mind the words of @cal3713 ,above, which I concur with.

@jerryg123 I seem to remember reading somewhere that the tubes in the Rogue Dragon were not in its input stage.  Can anybody confirm?

@twoleftears

"If anybody could get both amps in the same room at the same time, then they would really have my attention."

Indeed!

I would also add the LSA Voyager 350 @ 3+ times the wattage but has an MSRP of $3000, though usually available for $2500

When you wrote this  "GaN is state of the art--and not the generic stuff being put out by Peachtree and LSA."  were you referring to LSA/Peachtree's NON GaN products, but not their GaN products?

 

@twoleftears not sure was just checking the spec on their website very unclear..

From AS.

Not surprisingly, with this much power on tap in a standard-sized chassis, DragoN is a hybrid tube/Class D design. However, the rogues at Rogue emphasize that it’s not “simply a tube circuit placed in front of a Class D output section.” They describe their proprietary “tubeD” circuit topology as one that integrates the tube section (a pair of 12AU7 tubes) into the amplifier’s output stage. Additionally, three massive linear power supplies built around large, high-performance toroidal transformers power the amplifier circuitry, and top-shelf parts mounted on a heavy (two-ounce) copper circuit board are used exclusively throughout.

The AS Review.

https://www.theabsolutesound.com/articles/rogue-audio-dragon-power-amplifier

At only 500Khz, what is the advantage of using GaN?

@kuribo 

In a nutshell, reduced distortion and less heat than MOSFETs, not like that's much of a thing. The faster speed of GaNFETs requires less deadtime, which has to be increased at higher switching frequencies (when we first started doing this, I thought the deadtime would be constant regardless of the switching frequency and learned otherwise; either way deadtime becomes a greater distortion influence as you increase the switching frequency).

 

Would the dead time be more like, or analogous to, crossover distortion, slew rate distortion, or neither?

Here is the opinion of the Purifi team as discussed in an interview:

Bruno: Well, with the sort of audio performance we’re getting I’d say that we’re asymptotically approaching “perfect”. One could argue that we passed the point of diminishing returns a few years ago already. I’m not saying that a next step won’t have any audible benefits, but in the grander scheme of things, the margin is shrinking.

 

Lars: That’s if you stick to audio performance alone. Otherwise we wouldn’t have bothered going to class D to begin with. You don’t do that for audio quality. You do that to get better efficiency, make the amp smaller and yadda. And then you get a new set of problems to fix, such as what it sounds like. And then there’s reliability, manufacturability and so on. I wouldn’t say that GaN is going to be the answer to those things, and neither is upping the switching frequency.

 

Bruno:  Well for a given efficiency you could probably increase the switching rate, but if I’m going to shell out as much for a pair of FETs as what you’d normally pay for the whole amp, I’d rather benefit from that in terms of higher efficiency. Of course, not everyone is able to make that choice. I’ve spent my career honing control loops, most audio designers haven’t and so have to rely on simpler control loops. In that case, increasing the switching frequency is definitely helpful to reduce distortion.

 

Lars:  We’re as fanatic about audio quality as anyone else, but because we’ve got feedback down to a T now we’re not forced to resort to higher switching frequencies.

 

Bruno:  If we need to be geeky and I guess that the folks who are going to read this interview can handle that -eh Thomas?- lets grab the specs for the FET in our 400W Eigentakt module and its closest GaN equivalent. So that’s the FDP42AN15A0 (OnSemi) on our left and the EPC2033 on our right. Rdson: 36mOhm vs 7mOhm. Clear win for GaN here. 

 

Lars:  It’s also got a higher current rating (24A vs 48A) so if we want to be fair we should be scaling by about 2:1

 

Bruno: Oh erm well, that’s still a minor win for GaN because after scaling it’d come up at 14mOhm. Gate charge is of course magnificently low (30nC vs 6nC after scaling) so driver losses would be low and you can turn them on fast. GaN also has zero Qrr so you can do that if you want. But the main thing that sticks in my throat here is output capacitance. Our good old FDP42, which is from 2002 mind you, has an output capacitance at 100V of 70pF whereas the EPC device puts in a whopping half nanofarad (or 250 puff after scaling). That means your idle losses will go up, or you will have to increase dead time to allow the output inductor to recover the extra stored energy at its leisure. And isn’t it just idle losses that more or less determine real-life power consumption in full? And if power consumption isn’t something to care about, why not just stick with class A…?

 

Lars:  And high dead time combined with high switching frequency sounds even less attractive. That just increases open-loop distortion.

 

Bruno:  In applications like motor controllers and high density SMPS GaN and SiC devices are a breakthrough, mind you. It’s just that audio is this weird application where average power is very low and where dead time actually affects performance.

 

Lars:  And GaN is going to mature so this picture is bound to shift at some point. Just not now.

 

Bruno: True. On the other hand, silicon is doing the same. More recent devices are getting frightfully close to GaN. Sadly they only come in SMD packages that require fairly expensive methods to get the heat out. Like most GaN devices. It looks terribly ancient, but the good old TO220 package is still a neat compromise in terms of performance for the price.

 

Lars:  It’s just a game of tradeoffs. The fact that we’re using normal parts, and the reason why we chose to do so doesn’t make for a sexy story. We all like to believe in a magic bullet but when you’re an engineer you have to make choices based on tangible grounds. So the sexy story we’re trying to push about Eigentakt is that we think it’s a bloody clever design.

In a nutshell, reduced distortion and less heat than MOSFETs

I guess we will have to wait for your distortion plots to determine if your amp measures less than the ncore or purifi amp, which is already far below audibility. As for less heat, that seems like a small advantage, if any, at best, which you have noted. Personally, I don't really see a compelling case for GaN at this juncture.

Class D outperforming tubes is nothing new. It happens! Has happened for a number of years. It all depends....   Class D stopped me from going to tubes over 10 years ago.    Smart of @atmasphere to open some new horizons when he felt the time was right!

I am in Baltimore/DC metro area. Looking forward to an opportunity to hear these. Have heard Atmasphere OTLs many times in the past at Capital Audiofest. Maybe next one but hopefully sooner.

Would the dead time be more like, or analogous to, crossover distortion, slew rate distortion, or neither?

Neither. At least in our design, its responsible for lower ordered harmonics. We can see that there is a cubic non-linearity, as (like our tube amps) the 3rd harmonic (treated by the ear the same as the 2nd) is the dominant distortion product.

 

 

@atmasphere...Ralph, is your design a module like most of the others?  I ask because I would assume the money would be in selling that module to others?

 

Wonder how much B&O has made off of their ICE modules?

Ralph, is your design a module like most of the others?

It is a module; because of noise concerns that's really the best way to do it.

@atmasphere Any plans to develop a higher power version of these amps, or a stereo ~350 wpc doubling into 4 ohms class D (similar to bel canto black ex) with the same sonic profile as your new monos?  I'm asking because I wonder if these 100 watt class D monos have enough testicular fortitude to drive <89 dB efficient speakers with grunt and authority. I would completely understand if you chose not to answer the above question ;)

 I'm asking because I wonder if these 100 watt class D monos have enough testicular fortitude to drive <89 dB efficient speakers with grunt and authority. I would completely understand if you chose not to answer the above question ;)

Generally speaking I'm not a fan of low efficiency and hard to drive speakers. This is simply because the harder you make any amplifier work for a living, the higher the distortion, and with that distortion comes a less relaxed presentation (due to the generation of higher ordered harmonics) and less detail (since distortion obscures detail).

89dB is borderline low efficiency. A lot depends on the room and your listening habits as to whether 100 Watts is enough power or not. The speakers in my bedroom system are about 90dB and I play them with an amp that only make 5 Watts with power to spare, no worries. You have to take the room into account.