About Us
Atma-Sphere music systems, Inc. is a small company in Saint Paul, MN that has been making world-class vacuum tube music amplifiers since 1976.

We are known for our unique approach to circuit design, resulting in multiple patents and the creation of the first, truly reliable Output TransformerLess (OTL) amplifiers. We made the first balanced-line products in the world of high-end audio, including the MP-1, which was the world's first balanced-line preamp.

All of our amps and preamps are hand-crafted and made-to-order according to each customer's needs. All of our components are hand-selected, and often custom-manufactured especially for us, right down to the wire we use.

The resulting products are unique in the world with an unmatched capacity to reproduce music with intrinsic reliability.

The Absolute Sound interviews Ralph Karsten
Atma-Sphere Music Systems, inc.
1742 Selby Avenue
St. Paul, MN 55104
(651) 690-2246


USA Tube Audio

  • 8355 E Butherus
  • Scottsdale, Arizona 85260
  • 1-800-676-1085
  • Charlie




Audio Solutions

New Hampshire

Sounds of Silence

New Jersey

HiFi Logic

New York

Triode Picture & Sound

Signature Sound




CN Thomas-Acoustics

  • Fonthill, Ontario, L0S 1E5
  • +1 905-687-2341
  • Chris

High End Audio Exchange

  • 1426 Sierra Ave
  • Kingston, Ontario
  • K7P 3H2 Canada
  • (613) 767-4321
  • Francois


Guang He Rui Xing

  • No.1 Qu, Xiang Ti Man Bu
  • Shun Yi District
  • Beijing, P.R.China
  • Tel. +86 133 6688 9363
  • Mr. Li Xuan



  • Felixvej 47
  • 4200 Slagelse, Denmark
  • Tel. +45 40841115
  • Henrik


Himmlisch Hören

  • Merianstr. 20, 44801
  • Bochum, Germany
  • Tel. +49 0234 / 70 80 43
  • Fritz



  • Lucas Stephanides
  • 35, M. Mercouri St.
  • Kordelio, Thessaloniki 56334
  • Greece
  • Tel. +30 2310 773001
  • lucastef@otenet.gr


Jorge Deman


Phantom Audio

  • Pondok Jaya
  • Bintaro Sector 3A
  • Tangerang, Indonesia
  • Tel. +62 (813) 800 94990
  • Zahir

ProAudio Italia srl

  • Via Bari, 110 int. 10
  • 70022 Altamura (Ba)
  • Italy
  • Tel. +39 080 314.32.24
  • Michele

Revinylized BV


Loddefjord HiFi

  • Gamle Mathopsvei 22b
  • 5173 Loddefjord, Norway
  • mob.phone: +47909 92 551
  • Kjetil Melvik

Serbia and Montenegro

Sretenovic Audio

  • Vojislava Ilica 131
  • 11050 Belgrade
  • Serbia & Montenegro
  • Tel. +381 11 3223 854
  • ssret@eunet.yu


Connoisseur Audio

  • The Adelphi
  • 1 Coleman Street, #03-40
  • Singapore 179803
  • Tel. +65 96954004
  • SP Lim

Audio Concept


Audio Revolutions

West Indies

Semprie and Mitchell

  • 18 Laurier St., Morvant
  • Republic of Trinidad and Tobago
  • West Indies
  • Fax +1 868 624-3847
  • sempriemtt@yahoo.com
[M-60 Mk3.3] I am really enjoying the M-60s. These are, I think, a much better match for my 92.5 dB efficient Coincident Super Victory II’s. The Frankensteins just don’t have enough to really make them sing, and the reduction in THD at my normal listening levels is very much noticeable and appreciated.

Imaging is as good as the best I had from my Frankensteins, there is a nice sense of air, the tonality is spot on, in short, I think giving the M-60s a try was an experiment that ended very well. The M-60s are staying and the Franks are moving downstairs to my 2nd system.

In addition, I am powering the M-60s straight from the wall without going through the PS audio P-10. It was working pretty hard to keep up with current demand and was running pretty hot. We have pretty clean power here, and I have dedicated circuits to my listening room, so I don’t think I am noticing any adverse effects from removing the P-10.

Every time I listen to these amps I like them a bit more. They really are quite special.

William M