Atma-SphereAtma-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 have 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. Furthermore, 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 both an unmatched capacity to reproduce music and an intrinsic reliability heard nowhere else.

Atma-Sphere website

Will my speakers work with Atma-Sphere OTL amplifiers?

This question comes up. We can't guarantee every speaker will be a good match but are happy to chat with you on the topic and demonstrate some that do work well.

There's also a lot to be said for trying the products at home, and we're here to help with that, too. So give us a call!  773-809-4434

Preamplifiers: MP-1  MP-3  UV-1

Amplifiers: S-30  M-60  MA-1  MA-2  MA-3  Novacron

Atma-Sphere MP-1

In 1989, the first MP-1 introduced balanced line technology to the world of high end audio. It was the first balanced, fully-differential preamp ever made, and it included a range of innovations that were breakthroughs at the time, and remain so today. With a history of years of refinement, patents, and awards, the MP-1 is a paragon of the audio world.

The MP-1 Mk. 3.2 is unique in the world of preamplifiers. It easily outperforms any passive or transformer volume control as well as conventional line stages. This is because of a patented circuit that prevents coloration from interconnect cables. And with only three stages of gain in the entire preamp (including the phono section), our Balanced Differential Design® not only assures an elegant signal path, it assure low distortion, wide bandwidth, and dynamic range. No matter what you thought was the best, the MP-1 is an audible improvement.

Our unique, patented circuitry solves a major preamp problem: the output coupling capacitor. This capacitor has to be large to play bass, but large capacitors can't play the mids and highs properly. Getting rid of it is a transparency and bandwidth breakthrough. Transistor preamps often use direct-coupling, but they sound like transistors! Thus a lot of audiophiles have gone to using passive devices, thinking they have found the answer. This is only because they have not heard technology that works. The MP-1 and the MP-3 stand alone in the world of active preamps that work!

The Balanced Line system was created to eliminate interconnect cable coloration, which is why the recording and broadcast industry has used it for the last 50 years. This is how high fidelity recordings existed before exotic (high end audio) cables existed. The balanced line system is better as it resists RF, hum, noise, cable artifacts (sound changes with different cables) and cable length. This eliminates the need for an exotic cable (and its cost) to achieve state of the art performance.

The MP-1 nicely complements our balanced-line amplifiers, but works well with any amplifier. Phono cartridges are naturally balanced sources; since audio is recorded in the balanced domain, it only stands to reason that you should play it back that way, too. The MP-1 works well with very low output moving coil cartridges (less than 0.2mV), and even doubles as a state of the art headphone power amplifier.

  • Balanced Differential Design®
  • XLR connectors for phono and aux
  • XLR output connections
  • Patented direct-coupled Circlotronic® output
  • Fully regulated supplies featuring proprietory circuitry
  • Zero feedback design
  • Dual-mono construction
  • Differential passive phono equalization
  • Precision 24-position stepped volume control built from a Shallco® custom switch
  • Two tape monitors (tape functions use RCA's)
  • Precision components used throughout
  • Total system phase switch
  • Teflon® custom coupling caps
  • Low-noise "star" grounding topology
  • Power supply isolated in seconds chassis
  • headphone compatible with a simple connector
  • Three-year general coverage warranty with one year warranty on output tubes

Line stage frequency response
.1 Hz - 400 KHz, +0 dB, -3dB (-0.5 dB @ 250 KHz)

Line stage gain
14 dB

Line stage input impedance
100 KOhms single-ended / 200 KOhms balanced

Line stage output
32 V into 600 Ohms

Output impedance
30 Ohms

Phono stage input impedance
47 KOhms, adjustable with rear panel loading strip

Phono stage Input Overload
300 mV

Phono stage Max Output
(at clipping) 120 V peak-to-peak

Phono gain
~66 dB

Phono bandwidth
.5 Hz - 100 KHz, -.5 dB

RIAA accuracy
Within .07 dB

RIAA Phono sensitivity
(for 0.5 V @ 1 KHz) 0.15 mV

Power Supply storage
170 Joules

Tube complement
8 x 12AT7
10 x 6SN7

Dimensions
(per chassis) 13" deep x 17" wide x 5.5" tall (33 x 43 x 14 cm)

Faceplate dimensions
(standard 3U rack, sans mounts) 19" wide x 6" tall (48 x 15 cm)

Weight
(per chassis) 42 lbs. (19 Kg)

Warranty
Three year, transferable
One year for tubes

Available with both phono and line stage, or line stage only.

Optional Features
Remote Volume Control
V-CAP Copper foil capacitors for line stage
V-CAP Copper foil capacitors throughout
Caddock resistor package
Caddock volume control
Low output Moving-Coil step-up transformers for cartridges under 0.2 mV
Damping package
Dual outputs

Front Panel finish options
Black
Silver
Brushed Gold (Anodized)
Custom panel finishes available upon request

Accessories
Balanced to Unbalanced adapters
For use with single-ended amplifiers or sources. Specify input or output.

Cables
Balanced Interconnects
Balanced phono cables
1 meter, DIN to XLR or RCA with ground post to XLR

Atma-Sphere MP-3

The MP-3 preamplifier is based on the concepts pioneered by our MP-1 preamp, now in a single-chassis package. Recently updated to Mk 3.2, the MP-3 is a fully differential all-tube preamplifier, with a direct-coupled high current output capable of driving low-impedance balanced-lines. Like our MP-1, the MP-3 easily drives interconnects over 200 feet long! The MP-3 extracts more ambient information with greater image specificity, bass definition and dynamic range than any single-ended preamplifier. Furthermore, it perfectly complements the balanced design of our Music Amplifiers or any balanced power amplifier. The patented innovations, developed specifically for this preamplifier, have allowed the MP-3 to rise to the top.

Balanced line technology has been in use in the recording and broadcast industry for decades, and is why the high fidelity era began in the early 1950s, long before exotic interconnects existed. Balanced lines work better than single-ended cables, being dramatically more resistant to RF, hum, cable artifact and cable length. In essence the low impedance balanced line system is a means of preventing your interconnect cables from affecting the sound of your stereo. The MP-3 supports this system, so you can run long cables with no need for exotic interconnects.

In addition to its remarkable line section, the MP-3 works well with low-output moving coil cartridges and uses a minimum of connections in the front panel wiring and controls. A low number of gain stages (only three from phono input to line level output) insures the low distortion, wide bandwidth and superb dynamic range. The result is a truly musical package with exceptional value.

  • Balanced Differential Design®
  • XLR connectors for phono and auxiliary inputs
  • XLR output connections
  • Patented direct-coupled Circlotronic® output
  • Zero feedback design throughout
  • Balanced differential passive phono equalization
  • Precision 23 position stepped volume control built with 96 resistors on a custom built switch
  • Two tape monitor inputs, tape functions use RCA jacks
  • Precision components used throughout
  • Total system phase switch
  • Low-noise "star" grounding topology
  • Three-year general coverage warranty with one year warranty on output tubes

Line stage frequency response
1 Hz-200 KHz, +0 dB, -2dB

Line stage gain
15 dB

Line stage input impedance
100 Kohms single-ended / 200 Kohms balanced

Line stage output
12V

Output impedance
250 Ohms from 2Hz to 400KHz

Phono stage input impedance
47 K O, adjustable with rear panel loading strip

Phono stage input overload
500 mV

Phono stage max output
(at clipping) 120 V peak-to-peak

Phono stage gain
55 dB

Phono bandwidth
.5 Hz-90 KHz within 1/2 dB

RIAA accuracy
Within .1 dB

RIAA Phono sensitivity
(for 0.5 V @ 1 KHz) 0.2 mV

Power Supply storage
50 Joules

Tube complement
7 x 12AT7
2 x 6SN7GT
2 x 12AU7

Dimensions
13" deep x 17" wide x 5.5" tall (33 x 43 x 14 cm)

Faceplate dimensions
(standard 3U rack, sans mounts) 19" wide x 6" tall (48 x 15 cm)

Weight
19 lbs. (8.6 kg)

Warranty
Three years, transferable
One year for tubes

Available with both phono and line stage, or line stage only.

Optional Features
NEW! Remote control volume
V-CAP Copper foil capacitors for line stage
V-CAP Copper foil capacitors throughout
Caddock resistor package
Caddock volume control
Low output Moving-Coil step-up transformers for cartridges under 0.2 mV
Power Supply Regulation
Damping package
Dual outputs

Front Panel finish options
Black
Silver
Brushed Gold (Anodized)
Custom panel finishes available upon request

Cables
Balanced Interconnects
Balanced phono cables
1 meter, DIN to XLR or RCA with ground post to XLR

The Absolute Sound
Sue Kraft, April 2009
Sue Kraft, 2004

AudioReview.com
Various, user submitted

Enjoy The Music
Wayne Donnelly, August / September 2006
Todd Warnke, April 2001

Revue Du Son Et Du Home Cinema
Jean Hiraga & Robert Lacrampe, October 2002 (in original French)
Page 1Page 2Page 3

Soundstage!
Vade Forrester, October 2008
Ken Micallef, June 2002

Atma-Sphere UV-1

The UV-1 (UltraViolet) preamplifier is based on a circuit that we have used for many years, but never marketed before. About 40 years ago, Ralph Karsten began developing his own circuit for use for friends on a budget but with high end audio aspirations. Over a period of decades, the circuit has seen a lot of refinement. It is a simple circuit (and obviously a complete departure from our other products), based on a very capable and refined 6SN7-based line section with a simple phono section based on 12AT7s. We have seen this preamp best preamps costing up to five times more; when we say 'refined', we mean it!

We never really considered marketing the circuit though, as it is so different from the rest of our product line. But friends and associates convinced us that we had something special, especially for its price so here it is.

The preamp is available in three forms: a basic line stage, a full function preamp with high output MM capability, or with the addition of of a set of Jensen stepup transformers works with any low output moving coil cartridge as well.

  • Simple zero feedback line section
  • Cardas RCA connectors used thoughout
  • standard dual output connections, optionally reconfigurable
  • Shunt-style balance control
  • heavy-duty seamless aluminum chassis
  • Precision components used throughout
  • Low-noise "star" grounding topology
  • Three-year general coverage warranty with one year warranty on tubes

Line stage frequency response
2 Hz-200 KHz, +0 dB, -2dB

Line stage gain
15 dB

Line stage input impedance
100 KOhms single-ended

Line stage output
12V; 17VRMS at clipping

Output impedance
400 Ohms from 2Hz to 100KHz

Phono stage input impedance
47 KOhms

Phono stage input overload
500 mV

Phono stage gain
70 dB (Low Output Moving Coil version)

Phono bandwidth
5 Hz-90 KHz within .5 dB

RIAA accuracy
Within .1 dB

RIAA Phono sensitivity
(for 0.5 V @ 1 KHz) 0.15 mV

Tube complement
2 x 12AT7 phono
2 x 6SN7GT line section

Dimensions
15 3/8" wide x 7.5" deep x 5" high

Weight
7 lbs.

Warranty
Three years, transferable
One year for tubes

Atma-Sphere S-30

The S-30 is the unchallenged state-of-the-art in low power vacuum tube amplifiers. With its simplicity of operation, small footprint, and all the features of our larger amps, the S-30 represents the high-water mark of compact OTL design.

For audiophiles who seek the ultimate in amplifier design and are realistic about their budget, the S-30 gives you the same precision and sound quality that Atma-Sphere is known and recognized for. Featuring automatic bias and a large VU meter, operation is elegantly simple.

And because it utilizes decades-proven patented handwired circuitry, it is stable with any load and both performs and sounds better than any single-ended amplifier ever produced, let alone conventional push-pull designs. Its fully-balanced design and proven class-A triode operation make the S-30 the ideal choice for the discriminating audiophile.

  • Balanced Differential Design®
  • Class-A operation
  • Patented Circlotronic® direct-coupled (OTL) output stage
  • Dual-mono chassis construction
  • Automatic bias - no adjustment needed
  • Built in VU meter for tube and output monitoring
  • Easily monostrapped for greatly increased power
  • Uses only one gain stage for supreme clarity of sound
  • Proprietary precision components used throughout
  • Low-noise "star" grounding topology
  • Fully hand-wired point-to-point electronics - no circuit boards!
  • Stable with all input and load conditions
  • Exclusively uses Octal-Triode based vacuum tubes
  • Classic open chassis construction with Wrinkletex™ finish
  • Three-year general coverage warranty, one year warranty on output tubes

Output power
30 watts per channel into 8 Ohm load
45 watts per channel into 16 Ohm load

Impedance
Input Impedance: 100 KOhm single-ended, 200 KOhm balanced
Output Impedance: 7 Ohms

Input
3 V sensitivity
RCA and XLR true balanced input

Tube complement
10 x 6AS7G output tube
6 x 6SN7 driver tube

Gain
23dB (for 8 Ohms)

Power Bandwidth
2Hz-75KHz within 1/2 dB

Frequency response
(1 watt, open loop) 20 Hz squarewave Tilt; unmeasureable
1Hz-200KHz within 3 dB

Distortion
Total Harmonic Distortion (THD) typically 1% at full power
Intermodulation (IM) distortion typically under .04% at full power
Phase shift less than 1° @ 20KHz

Output section risetime
600 V/µs

Feedback
2 dB

Power consumption
400 watts

Dimensions
13" deep x 17" wide x 8" tall (33 x 43 x 20 cm)

Weight
(without tubes ) 24 lbs (10.9 kg)

Warranty
Three year general coverage
One year for output tubes

Optional Features
Power Supply Boost option
V-Cap Teflon® coupling caps
V-Cap Copper Foil Teflon® coupling caps
Caddock® resistor package

Meter Panel finish options
Gray hammertone
Brushed anodized black
Brushed anodized silver
Brushed anodized gold
Custom finishes available upon request

Accessories
Jumper plugs for high efficiency speakers
Replaces tube in the voltage amplifier section of Atma-Sphere power amplifiers, thus reducing gain for high efficiency speakers. Recommended when efficiency of speaker is over 100 dB.

Cables
Balanced Interconnects

AudioReview.com
Various, user submitted

Extreme AV
Vangelis Lazarou (in original Greek)
Page 1 • Page 2 • Page 3 • Page 4

Revue Du Son Et Du Home Cinema
Jean Hiraga & Robert Lacrampe, October 2002 (in original French)
Page 1 • Page 2 • Page 3

The Sensible Sound
Tom Lyle, Issue #96 June/July 2003

Soundstage!
Vade Forrester, March 2007

Making the Atma-Sphere M-60

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