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Atma-Sphere M-60 Mk. 3.1 OTL Monoblock Amplifier Review

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Setup

Setup was quite simple. I set each amp just to the inside of my Teresonic Ingenium Silver, connected the Teresonic Clarison speaker wire to the M-60s and connected the monoblocks to my Shindo Giscours preamp with Teresonic Clarison Gold interconnects. The rest of the system simply consisted of the Shindo 301 Vinyl Playback System. Because of the auto-biasing, setup was as simple as could be.

I tried these amps with three different speakers, the first being the Ingenium I mentioned above which uses the 8-ohm version of the Lowther DX4 with silver voice coils. Then I used them with Teresonic’s wonderful little Magus, this time with Lowthers A55 drivers with Alnico drivers with an impedance of 16 ohms. Lastly, I used them with a pair of B&W 805S mini-monitors. With all three speakers this amp sounded superb, but it was almost a perfect match for the little Magus with the DX55 Alnico drivers.

Listening

If you have never heard an OTL amp, it can be very difficult to imagine how they sound. The Futterman amps, for instance, had a big soundstage, with a very quiet background. The Joule-Electra amps carry this a step forward by adding speed and refinement to the equation. The M-60 Mk 3.1 sounds different from either of these amps, but there is no mistaking it for an OTL. Well designed OTL amps sound remarkably neutral, almost colorless, and clearly let you hear the textures of music. They are also some of the most spectacular soundstaging amps I have heard. They lean toward a full and powerful lower midrange and bass. These are big sounding amplifiers with really quiet backgrounds. Yes, they are OTLs, but they also sound like good class A tube amps. With the right speakers the sound can just float in space and allow the music to become part of your listening environment.

Midrange and top-end

I don’t think at this price you’ll find any other monoblocks with a top-end that’s more open, alive, and detailed than these amps. They come close to my $30,000 Wavac’s delicate, lovely, alive sounding midrange, though they fall a little short in the ability to let individual voices or instruments sound genuinely alive. It is an unfair comparison of course, because my amps cost five times as much and produce only 8 watts per channel.

I think when you consider their power and price it is simply amazing how delicate the midrange and highs sound. This delicacy comes from the amp’s ability to play extremely fine details. At first, I thought they were slightly rolled-off in the highs, but the longer I listened the more I discovered I was wrong. One recording after another, all the treble was there in a very natural way. This is a sound that very much reminds me of the top-end I hear at live acoustic musical performances. The midrange has a very realistic sense of openness with good speed, but not so much lightening faster as with a speed that was very natural with good timing and pace.

The M-60 3.1’s midrange is somewhat dependent on which speakers you use it with, but whether I used it with the Teresonic Ingeniums, Teresonic Magus, B&W 805S, or Genesis speakers I always found the midrange and top-end very musical.

Bass and Lower Midrange

The lower midrange is lush, full, yet still quick with good pace. The bass is big, powerful, deep, with quite a wallop. Of course, with their power the M-60s can deliver bass that enhances one’s enjoyment of all genres of music. Upright basses came through with plenty of texture and very solid. Likewise, drums sounded very solid and full when played on these amps.

As much texture and detail that the Atma-Sphere amps have, they don’t quite unravel and layer bass instruments the way the Wavac EC300B does; but the power, the dynamics, and scale of the overall lower-end is really something special.

Scale, Soundstage, and Imaging

The Atma-Sphere M-60 Mk 3.1 has huge scale. With some speakers the scale may be a little bigger than life, but with the Teresonic Magus with the 16-ohm, Alnico Lowther drivers, they had near-perfect scale. The scale was life sized, well fleshed out, and with plenty of weight. This sense of scale is very lifelike, and I think part of the factor for this weighty scale is the very efficient implementation of an OTL design.

Likewise, the soundstage is wide, deep, tall, and big. This is not the kind of soundstage that you expect from mini-monitors with modern tube amps, but much more like what I hear with my Wavac EC300B. By that I mean a very coherent soundstage where the instruments and singers are part of the air and sound of the room. To me, this is much more the sound of live music than individual instruments, and voices floating in air as if they have been painted on black velvet.

Conclusion

The Atma-Sphere M-60 Mk 3.1 gives you great sound for the money. For many speakers, these amps will be about as good as it gets. Truth is, I found the sound on all three speakers I tried them with to only be bettered by amps that cost three and four times as much. Thus, you should consider them very highly recommended.

4 Responses to Atma-Sphere M-60 Mk. 3.1 OTL Monoblock Amplifier Review


  1. Steve Harrison says:

    I am reading and enjoying some of your equipment reviews. However I find myself frustrated because the review states that the amplifier gives you “great sound for the money” but fails to state the amplifier’s price! I noticed the same omission in some of the other reviews I read. This is a simple problem to address and I urge you to do so.

  2. Steve, thank you very much for your email and readership. Our apologies for the omission. As we continue our relaunch transition since Jan 1, we ask you and our readers for your help in identifying similar issues and shoot us a note. Meanwhile, enjoy the new Dagogo Experience!

  3. Alan says:

    Enjoy the reviews. I read with interest since I have a pair of Quad ESL-2805s. There seems to be a cult following of the OTL amps with the Quads. Any thoughts on the differences between the AtmaSphere M-60 and the Leben CS-660?

    Also, did the M-60 mono blocks work well with the Shindo Giscours? I am thinking of upgrading to the Shindo Masseto and wonder if you think this would pair well with the Atma-Sphere M-60 and the Quads. Thanks

  4. Jim says:

    I was wondering why the reviewer failed to mention the only person, outside of Futterman 60 years ago, to get a government patent for his outstanding OTL amplifier design, Bruce Rosenblit at Trancendent Audio. His OTL amps are awesome, reliable, affordable, and probably there are 20 time the number of his amps in use today. But then I noticed Transendent Audio is not a “Sponsor” of this website and Atma-Sphere is. That answers all my questions. This review should be taken with that obvious omission in mind.

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