Atma-Sphere Nirvana OTL Monoblock Amplifiers

[Phantom-Audio]

This has been Ralphs's Masterpiece Amplifier, a no-compromise design, Which retails now at 65K but is built to order only. I thought il post in this group as it's a rare build and commission upon request.

Iv owned all of Atma-Sphere Amplifiers and Pre-Amps. and have evaluated all his amps carefully; this is by far the best sounding Amplifier Ralph has ever built.

I hope Ralph can chime in and explain the complexity or the spec of how this differs to the rest of his other amplifiers.

 

[earlinarizona]

How many Watts?

 

[ACHiPo]

With 6 power tubes per side I’m guessing ~90 into 8 Ohms?

 

[DonH50]

They are 120 watts into 8 ohms. Full power from 2Hz to 100KHz within 1/2dB. THD is about 0.5% when the amp is set up properly (this can be affected by tube choice since it is a zero feedback design). Its nice and quiet so no worries on speakers with 105dB efficiency. It runs regulated power supplies for the driver high voltage and filament circuits.

From another thread... https://www.whatsbestforum.com/threads/atma-sphere-nirvana-amplifiers.32871/

Looks like Phantom has them for sale. https://www.audiogon.com/listings/l...ralph-karsten-masterpeice-otl-amplifiers-tube

They are monoblocks with (I think) 12 output tubes per amp.

 

[BlueFox]

Not being into tubes, any idea how long these will work without any repairs, tube replacements, or any other fixes? I deplore the heat my Pass amps create, so how much heat do these generate?

 

[Phantom-Audio]

From another thread... https://www.whatsbestforum.com/threads/atma-sphere-nirvana-amplifiers.32871/

Looks like Phantom has them for sale. https://www.audiogon.com/listings/l...ralph-karsten-masterpeice-otl-amplifiers-tube

They are monoblocks with (I think) 12 output tubes per amp.

Correct about the item being for sale, it is not something i want to get rid of but being forced due to some circumstances.

Ralph Claims 120 watts per channel on the provided tubes, but this can go up to if I recall correctly, about 140 watts if used better power Tubes.

I have NOS RCA and a few other NOS tubes which will produce more power, but iv not tried them as the provided tubes with the amps are still going strong.

 

[ACHiPo]

From another thread... https://www.whatsbestforum.com/threads/atma-sphere-nirvana-amplifiers.32871/

Looks like Phantom has them for sale. https://www.audiogon.com/listings/l...ralph-karsten-masterpeice-otl-amplifiers-tube

They are monoblocks with (I think) 12 output tubes per amp.

I remember that now

 

[Phantom-Audio]

Not being into tubes, any idea how long these will work without any repairs, tube replacements, or any other fixes? I deplore the heat my Pass amps create, so how much heat do these generate?

Iv owned them for about 3 years the original tubes are still going strong, If you know of Atma-Sphere the Reliability one of the best in the industry. From my experience, you will not likely ever have a failure apart from tubes or fuses.

Iv never had any issues with any Atma-Sphere Amps or Pre-amps so they are solid reliability so far. Iv owned all his amps. The most you will get is a popped fuse if the tubes arc.

 

[DonH50]

By all accounts Ralph (@Atmasphere ) is a solid engineer (as well as a great guy all around) and his amps have a great rep for reliability (unlike some earlier OTL amps ) and sound. You can ping him about the expected tube life and such; he is very accessible. If I were in the market, these would get my serious consideration.

FWIWFM - Don

 

[microstrip]

Not being into tubes, any idea how long these will work without any repairs, tube replacements, or any other fixes?

Tubes will last for long. But if you get a tube tester and test the tubes every six months you probably will never need a repair.

 

[Atmasphere]

I hope Ralph can chime in and explain the complexity or the spec of how this differs to the rest of his other amplifiers.

Beyond the obvious metalwork, this amp employs a fair amount of regulation in the driver section- regulated filament supplies and high voltage. The driver and output sections are built on sub-chassis within the main chassis. The power transformers are all overbuilt to an extreme for the application. We used a high performance Panasonic capacitor in the output section that uses multiple connections to minimize inductances in the part.

 

[Phantom-Audio]

Ralph could tou explain what are the Hexfred? and how much quieter this is against the other amps. i beleive you mention it was over 9db quieter ?? or more

 

[Atmasphere]

Ralph could tou explain what are the Hexfred? and how much quieter this is against the other amps. i beleive you mention it was over 9db quieter ?? or more

The amp does use HEXFRED rectifiers throughout. That's not unique in our amps- our S-30 is built that way too. Most of our amps have HEXFREDs in the driver power supply and regular silicon in the output section. Which one we use depends on the resonance formed between the power transformer and the junctions of the rectifiers and in the S-30 that means we have to use the HEXFREDs there. We did that in the Nirvana as a bit of overkill. The lower noise IMO has mostly to do with the regulated supplies.

 

[Phantom-Audio]

How much power does the Nirvana produce?

 

[Atmasphere]

Its 120 Watts into 8 Ohms.

 

[Phantom-Audio]

Snippet from a Email conversion with Ralph over the Nirvana Amplifiers.


The reason it is so much quieter is all the regulated power supplies. At the time that amp was conceived Tenor and Einstein both made amps with a similar price tag and neither sported any particular circuit advantages. They got away with it on bling alone. We figured we could do that only with the internals to match.

I think the Nirvana is a better amplifier and may be the best sounding we have made ( He was quoting against the MA Series and Novocron)

The Nirvana was built to see what was possible if everything in our OTL design were pushed to the limits. So everything in it is over-built, for example the power transformers are built with the least DC resistance allowable in their windings to prevent voltage sag while under load and also to run cooler. Sub chassis were used for the output and driver sections; filament and high voltage power supplies are regulated and ultra high performance filter capacitors employed in the output section. HEXFRED rectifiers are used for all the supplies and properly snubbed for ultra low noise operation.

On account of these measures the amp is silent on horn speakers and has very low intermodulation distortion, resulting in a very clean and musical first Watt. The sockets were custom built by Ebe, the last American manufacturer still making tube sockets. They will last decades. If course the amp is built with V-Cap Teflon coupling capacitors and high end resistors, custom wire made just for Atma-Sphere; every aspect of the amp was given this sort of attention. Naturally the chassis shows this off with super-polished and chromed machined panels showing it off.

All the Best,

Ralph

 

[gleeds]

A stunning-looking amplifier and a departure from Ralph's usual design esthetic. I would love to hear these amplifiers one day, but I am sure they sound terrific. Congratulations Ralph!

I have long been a fan of Atmospheres Novacron, also a departure of sorts.

 

[Sphere1]

I have owned Atma-Sphere amps and preamps for over 20 years. I never knew these Nirvana amps even existed. Just stunningly beautiful. Would like that kind of bling on my MP-1 preamp.

 

[Phantom-Audio]

It is an expensive and time-consuming build process hence the reason why Ralph is reluctant to put them up on the site. Out of all the Atma-sphere Gear, this is by far the best amp Ralph ever made. Iv also owned the novacrons.

The Nirvana are for sale. However, I am putting up all my Field Coil Speakers and Amps for sale.

 

[Atmasphere]

A stunning-looking amplifier and a departure from Ralph's usual design esthetic. I would love to hear these amplifiers one day, but I am sure they sound terrific. Congratulations Ralph!

I have long been a fan of Atmospheres Novacron, also a departure of sorts.

The Novacron came into existence as the first amp made in the US to use the Russian 6C33 way back about 1993. Since then we've tried to include some of its design elements in other products (such as the M-60 Mk3) but the number of tubes always sat squarely in the way of really doing that. That is why the Silver Edition amplifier used a different aesthetic as it allowed the greater number of tubes to be present (we still make an updated version of that FWIW). The Nirvana was another approach to that.