Atma-Sphere Class D Mono blocks

[LL21]

Ok, I have had the Atmasphere running for a couple weeks. They have only been out of the system a couple times for a day or 2.
I have played them back to back with my 12 year old Dartzeel NHB108 model 1 with SCNP network. First thing is to say, they are very close in sound. Its not easy to tell them apart. What I do feel I notice is the Atmasphere is more clean and has a tad bit tighter bass. The Dartzeel seems to have just a touch more background noise and plays a little smoother. The Dartzeel may have a hair more richness, but that may also be the perceived background noise.

The space around instruments and sound stage is almost exactly the same.
The bass to treble extension seems the same.
Neither have any perceived peaks, dips, hardness or fatigue.
Both are very balanced and musical.

You would not mistake either of these for a tube amp.

If you like SS amps, I was very surprised at how well the Atmasphere plays. I had preconceived notions of class D. I don't think you could tell it from any Class A or AB amp, outside how the manufacture of any other amp has decided to tune their equipment. In other words, there is nothing to let you know what Class amp this is. It could be Class A, AB or D.

The build quality reflects the price. Its a solid amp but has no flash. I have no idea the quality of components inside the case. If Ralph wanted he could add a lot of anodized aluminum or copper fins and up the price by thousands. But I doubt it would make the sound different. I perceive nothing saying heavier metal or damping would impact the sonics.

I did very little to try different foundations under it. I did put a set of feet under it and heard nothing. They currently sit on my wood floor.

I am going to be bummed to send them back to the owner. In all honesty, I may sell all the amps I have on hand and get a set of Atmasphere monos. I like the fact I can leave them on 24x7 and never worry. They are always warmed up and ready to go. There is nothing I hear to say the quality of sound is less than the Dartzeel. I actually like the clean and speed in the bass.

Wow...in some respects, none of us should be particularly surprised despite the [pardon the pun] stereotypes about Class D. It is Ralph Karsten we are talking about, renowned designer of Class A, OTL legends.

Will be interesting to see if you end up actually selling everything and getting these monos. Meanwhile, enjoy them!

 

[nquery]

You would not mistake either of these for a tube amp.

While they don’t necessarily sound like a tube amp, I replaced a Line Magnetic SET with these about 3 weeks ago and do not miss the tube amp whatsoever.

The space around instruments and sound stage is almost exactly the same.

The Atma-spheres do a 3D image better than my LM, and the space/clarity/depth around instruments is outstanding. One of my favorite things about them.

While I haven’t listened to amps in the Dartzeel price bracket, it’s really hard to fault these in any way at all.

 

[microstrip]

(...) I have played them back to back with my 12 year old Dartzeel NHB108 model 1 with SCNP network. First thing is to say, they are very close in sound. Its not easy to tell them apart. What I do feel I notice is the Atmasphere is more clean and has a tad bit tighter bass. The Dartzeel seems to have just a touch more background noise and plays a little smoother. The Dartzeel may have a hair more richness, but that may also be the perceived background noise.

The space around instruments and sound stage is almost exactly the same.
The bass to treble extension seems the same.
Neither have any perceived peaks, dips, hardness or fatigue.
Both are very balanced and musical.
(...)

Interesting that you found them to sound overall so close - I have owned the Dartzeel NHB108 model 1 and although I loved it a lot it had a clear sound signature - and its measurements show higher than usual distortion for a solid state design. It was very different sounding from Atmasphere OTLs, I would say more forgiving and less transparent.

 

[Kingrex]

I can also note, the Atmasphere is a little more picky than my Dartzeel when it comes to grounds. If I plug my tape deck in which is not on the Torus transformer, the Atmasphere will hum from the ground loop. The Dartzeel is quiet.

If my digital is playing, the Atmasphere will also play music very quietly when my preamp is off and in mute. But only when in mute. I actually turned my pre off at night and would put a rip on loop and let the Atmasphere run music all night that way while breaking it in. If the pre is on and in mute, the system is muted and quiet.

The Atmasphere responds to a power cable the same as my Dartzeel.

I look at all the pressure connections inside the Atmasphere and want to use Deoxit gold on them. Its not my amp so I have not. But I bet it would like it and maintain its performance many years longer if treated as such.

 

[ACHiPo]

Ok, I have had the Atmasphere running for a couple weeks. They have only been out of the system a couple times for a day or 2.
I have played them back to back with my 12 year old Dartzeel NHB108 model 1 with SCNP network. First thing is to say, they are very close in sound. Its not easy to tell them apart. What I do feel I notice is the Atmasphere is more clean and has a tad bit tighter bass. The Dartzeel seems to have just a touch more background noise and plays a little smoother. The Dartzeel may have a hair more richness, but that may also be the perceived background noise.

The space around instruments and sound stage is almost exactly the same.
The bass to treble extension seems the same.
Neither have any perceived peaks, dips, hardness or fatigue.
Both are very balanced and musical.

You would not mistake either of these for a tube amp.

If you like SS amps, I was very surprised at how well the Atmasphere plays. I had preconceived notions of class D. I don't think you could tell it from any Class A or AB amp, outside how the manufacture of any other amp has decided to tune their equipment. In other words, there is nothing to let you know what Class amp this is. It could be Class A, AB or D.

The build quality reflects the price. Its a solid amp but has no flash. I have no idea the quality of components inside the case. If Ralph wanted he could add a lot of anodized aluminum or copper fins and up the price by thousands. But I doubt it would make the sound different. I perceive nothing saying heavier metal or damping would impact the sonics.

I did very little to try different foundations under it. I did put a set of feet under it and heard nothing. They currently sit on my wood floor.

I am going to be bummed to send them back to the owner. In all honesty, I may sell all the amps I have on hand and get a set of Atmasphere monos. I like the fact I can leave them on 24x7 and never worry. They are always warmed up and ready to go. There is nothing I hear to say the quality of sound is less than the Dartzeel. I actually like the clean and speed in the bass.

Rex,
I feel similarly about the Benchmark Class H amps I bought for Summer use. They are so good that I have yet to put the MA1s back in the system. I can only imagine Ralph's Class Ds would be a further step up in performance while keeping the easy-to-live-with SS features.

Now if I can only get my hands on a Sound Labs-sized AtmaSphere Class D...
Evan

 

[Gregadd]

"Sound Labs-sized AtmaSphere Class D..."
Evan
Could you please explain what that means for s dense audiophile? Thanx.

 

[Atmasphere]

I can also note, the Atmasphere is a little more picky than my Dartzeel when it comes to grounds. If I plug my tape deck in which is not on the Torus transformer, the Atmasphere will hum from the ground loop. The Dartzeel is quiet.

If you are running the amp single-ended, try placing a jumper between pins 1 and 3 of the XLR input.

 

[Kingrex]

Are sound labs small? I bet you could stack the Atmasphere. Its a toroid inside so there should only be a horizontal spray of emf where the windings exit the coil. Otherwise it probably emits very little noise.

Ralph told me its not pickey about the platform it sits on. I agree. It did not respond to footets as I noted above.

I would think the next step is to make a much higher wattage unit, clap some fancy metal around it an up the price. Of course that is all just a marketing decision. And I don't know if that will change the sonics.

That reminds me, I heard no difference when it comes to Ease, or Air or Finess. But they are both 100 watt amps.

 

[ACHiPo]

"Sound Labs-sized AtmaSphere Class D..."
Evan
Could you please explain what that means for s dense audiophile? Thanx.

@Gregadd The Sound Labs are inefficient and
need lots of power. I don’t think the current Class D is big enough to drive them.

 

[Gregadd]

The Merrill amps will melt your tweeters.
Not to worry. Iam sure Ralph is working on it

 

[thomask]

While they don’t necessarily sound like a tube amp, I replaced a Line Magnetic SET with these about 3 weeks ago and do not miss the tube amp whatsoever.



The Atma-spheres do a 3D image better than my LM, and the space/clarity/depth around instruments is outstanding. One of my favorite things about them.

While I haven’t listened to amps in the Dartzeel price bracket, it’s really hard to fault these in any way at all.

Did you have LM 508 or 805?

I am happy with the sound of LM 508 fitted with vintage tubes.

But I consider using class D amp for longer listening hours.

 

[nquery]

Did you have LM 508 or 805?

I am happy with the sound of LM 508 fitted vintage tubes.

But I consider using class D amp for longer listening hours.

Yes 805ia. I found that tube rolling progressively resulted in the amp sounding less and less 'tube-like', all in a good way. Getting the Atma-sphere class D's just took this process to it's ultimate conclusion ... I had even thought I might need to keep a tube pre-amp in the chain to compensate, but I found that using my tube DAC + a buffered line-stage is best. I leave the class D's on 24x7 and not having to worry about warming up the LM tubes or frying my cats is a bonus.

fyi I was a frequent poster, alongside yourself, on the LM 508/805 thread on Steve Hoffman forums. Feel free to PM me if you want.

 

[Atmasphere]

@Gregadd The Sound Labs are inefficient and
need lots of power. I don’t think the current Class D is big enough to drive them.

One customer of ours in Europe reported that they worked pretty well on the Sound Labs. But we don't have much information on the size of the room and the like.

 

[Tuckers]

I just don't like living with something that takes 30-60 minutes to warm up before it sounds it's best, how I have to manually bias them a couple times a month, how their sound is always slowly degrading over time and must be replaced every few years

This is one of the main reasons I put tubes to bed a few years ago as well. Welcome to the club

 

[Gregadd]

This is one of the main reasons I put tubes to bed a few years ago as well. Welcome to the club

You have heard of the Princess and the Pea.

 

[PYP]

You have heard of the Princess and the Pea.

This one?

 

[Gregadd]

Yes, sometimes it takes a lot of high-quality mattresses to get a goodnights sleep. If you get my drift. Besides, tube rolling is a hobby unto itself.

 

[PYP]

Yes, sometimes it takes a lot of high-quality mattresses to get a goodnights sleep. If you get my drift. Besides, tube rolling is a hobby unto itself.

for some, the pea is digital, for others vinyl, or Roon, or streaming, or streaming with Roon, or speakers that cost > $200k, or speakers that cost < $200k, or non-SET amps, or class D amps, or non-horn speakers, or multi-cone speakers in a box with a complex crossover, or tubes, or non-NOS tubes. To say nothing of MQA!

 

[Gregadd]

I get your point. But some of those are not nearly as subtle as a pea.

 

[PYP]

I get your point. But some of those are not nearly as subtle as a pea.

depends upon your mattresses and personal sensitivities...

To put this thread back on the original track, the picture above is of a princess after listening to Atma-Sphere Class D mono blocks all day long.