Atma-Sphere MA-2 Amplifier

Ron Resnick

Site Co-Owner, Administrator
Jan 25, 2015
6,589
1,002
113
Beverly Hills, CA
#1
I think we need to spend more time on the Atma-Sphere MA-2 Class A, 220 watt, OTL amplifier.

http://www.atma-sphere.com/Products/#MA-2

http://www.theaudiobeat.com/equipment/atma_sphere_ma2_mk31.htm

http://www.atma-sphere.com/Reviews/tas/workshop/index.html

http://www.soundstage.com/revequip/atmasphere_ma2ii3.htm

http://www.soundstage.com/revequip/atmasphere_ma2iii_followup.htm

From these reports and WBF members' reports there seems to be a consensus that these amplifiers, like other OTL amps, are capable of amazing transparency, but, unlike other OTL amps, you can get these in 220 watt and 500 watt versions.
 
Jul 16, 2011
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#3
I owned MA2 Mk II.3s for a number of years and I loved them. Never a glitch with a tube or any other issue for that matter...Problem is I live in Texas. In order to be comfortable I would have to turn the ac way down a few hours ahead of a listening session in the summer...In the winter the amps pretty much kept our house cozy when the amps were on...
 
Mar 18, 2019
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#4
I am new to Atma-sphere gear (and tubes). I recently purchased, from audiogon, a MP3 and MA2. I am coming from a Plinius cd-lad and Sa-103. I was very happy with that system for 12+ years. A recent move and having everything in storage for over a year sparked a new interest in the hobby. After lots of research here I am!
I sent the MA2 to Ralph for updates to current specs. Over the last couple of months I have been getting to know them. So far I can say that I’m impressed. It’s a lot of work messing around (tube rolling) for the right tubes to set the tone your after! I can say that this system has far better transparency, dynamics, and soundstageing. The upper mids and highs are better. I’m roiling tubes to fleshout the lower mids and bass. I would be interested in hearing from others concerning there experience with tubes and placement in the amps.
The MA2 have Sylvania chr domes, gta’s, syl vt231, psvane, followed by syl yellow label gta’s from back to front.
MP3 has cbs Hytron 5692 and a Brimar 12au7.
Oppo sonica had a Siemens which made the sound to thin. I placed the EH it came with and that improved the tone greatly.
I just bought a Mazda 7308 for the Oppo and a couple pair of RCA 6sn7gta’s to try in the ma2’s or mp3. I’ll report on the results once I have them.
 

Folsom

VIP/Donor
Oct 26, 2015
3,708
317
83
Eastern WA
#5
The ones I heard were pretty nice, forget the models.... not as big as the MA-2. If you can get a chance to audition, I would.
 
Dec 16, 2018
50
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Phoenix, Arizona USA
#6
Doc, if you're looking for a little warmth, body, etc., in the lower MR, spend the money for Tung-Sol oval-plate 'N7GTs/VT-231s.. I've tested dozens of types of 'N7s and kept dozens of TSOPs over the decades, and those are what are in the 1st-stage-Voltage-gain positions of my M-60s and MA-1s.. Check with Ralph on which tubes in your amps are the 1st-gain-stage, which are the cascode-gain, and which are the cathode-follower(s).. I'd use the TS-OPs in the 1st stage and of your tubes, maybe the RCAs in the cascode-gain, and whatever you have lying around in the CFs.

I bought two batches of BRIMAR CV1988/6SN7GTYs from Upscale this winter/spring.
https://www.upscaleaudio.com/products/brimar-cv1988-6sn7gt
(The tubes pictured are the clear-glass, curved-gray-plate versions.. Note Upscale's warning that these are NOT 'preamp' tubes; these are lower-quality, poweramp-frontend tubes.. Mine are very quiet and highly satisfactory.)

The first quad had blackened glass and, an inspection using a very bright flashlite revealed, curved gray plates; the 2nd tubes had clear glass and the same curved, grey plates; and the 3rd tubes, tall, rectangular black plates.. I THINK the black-glass and gray-curved-plate ones are close in overall character to the TSOPs; I use two of mine in the cascode-gain positions while I'm still using the TSOPs in the initial-gain positions..

TSOPs claimed to be NOS are frightfully expensive, as in $300 or more; all of my old ones test relatively poorly but sound fabulous and are quiet and NOT microfonic.
 
Last edited:

Ron Resnick

Site Co-Owner, Administrator
Jan 25, 2015
6,589
1,002
113
Beverly Hills, CA
#7
Congratulations, Doc nowack!

Ralph makes unique, and uniquely wonderful-sounding, products!
 

tima

Industry Expert
Mar 4, 2014
838
408
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#8
The ones I heard were pretty nice, forget the models.... not as big as the MA-2. If you can get a chance to audition, I would.
The M60 is a real sweetheart. It may have the purest tonality of all four of Ralph's amps if you have the right speakers.
 

Atmasphere

[Industry Expert]
May 4, 2010
822
18
18
St. Paul, MN
www.atma-sphere.com
#9
I’m roiling tubes to fleshout the lower mids and bass. I would be interested in hearing from others concerning there experience with tubes and placement in the amps.
The four tubes in the rear are the voltage amplifier tubes- the two 6SN7s closest to the front panel are the driver tubes.

So the driver tubes, if you want to try rolling, should have -GTA or -GTB suffixes as they are subjected to higher voltages which will shorten the life of a GT.

The voltage amplifier tubes are the most important to the sound of the amp. The voltage amplifier is where all the gain of the amp occurs. It is a differential cascode circuit aided by a constant current source, resulting in fairly high CMRR (Common Mode Rejection Ratio) over 100dB.

There are three 6SN7s in a differential and parallel arrangement which drive the cathodes of the 4th 6SN7 which is the top of the differential cascode. So those first three tubes have the most sonic impact. Yyou don't have to replace all three when auditioning a tube brand (although the cumulative effects will be easier to hear if you replace all three). The top of the cascode IOW has less effect on the overall sound than the bottom, so you replace the first three 6SN7s from the rear panel first, then the 4th.

We've got very good reports of the Psvane and TJ Music 6SN7 variants. Note that they should not be used in the 5th and 6th locations as they don't have the additional voltage rating of the -GTA and -GTB suffix. People report that these tubes have all the best character of the best NOS tubes (Ken Rad being the best, followed by the metal base chrome dome Sylvania after that probably the RCA red base or CBS Zalytron)) without any of the weaknesses! Pretty powerful statements IME.

On tip: have fun- don't drive yourself crazy. I go for a good musical presentation; if I'm getting that I spend the rest of the vintage tube money on more LPs ;)
 

MrC.

New Member
Feb 16, 2019
8
7
3
#10
If you are interested in the MA-2's I would definitely suggest finding a place to audition them with the speakers of your choice. I'm running a set of MA-1 Deluxes, which seems a rare bird and probably made as a custom order for the guy I bought them from, having the power supply of the MA-2 running 12 output tubes in the older MA-1 configuration. If you look at the specs of the various models from atma-sphere, the added tubes give more power and headroom but also give a lower output impedance to run a wider range of speakers. If you don't need ear drum splitting power, you can, and I do, use an autoformer by the speaker to up the reflected impedance from the speaker to the amp. This gives an easier load to the amplifier and also makes the amp sound its best from a lower impedance speaker with less than the MA-2's load flexibility. Paul Spetz of Anticables fame makes an autoformer for just such a purpose, and probably something that would be useful for tuning many amps for the speaker they are intended. McIntosh amps have this autoformer output feature to connect various impedance loads. With an Atma-Sphere amp and the Zero autoformer you have a wider range of speakers that can be used to amazing effect. Anyone put off by the cost of the MA-2 and looking to run a smaller pair of monitors or mildly efficient floor standers would be well advised to try out the MA-60s with the autoformers that can raise a 4 ohm load to a 12 or 16 ohm load that would be loved by the Atmas. A side effect of the higher impedance seen by the amps is that your speaker cables are suddenly less burdened by the effects of a tough speaker load and thinner or longer runs of wire can be used without detriment.
 

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