OTL Amplifiers

  • Atma-Sphere M-60

    Atma-Sphere M-60

    Atma Sphere M-60

    Hi-End Audio Tube Amplifiers, 2 x 60 Watts, OTL monoblocks, Mk 3.3

    For years now the M-60 in its various forms has been the subject of the Soundstage! Hall of Fame Award, The Absolute Sound Golden Ear Award and Editor’s Choice, with numerous accolades in the press and on the web.

    The M-60 Mk. 3.3 continues that tradition with classic styling and its award-winning state-of-the-art performance. The M-60 gives you the features and precision performance of our larger models in a beautiful, 60-watt package. The amp operates class A and is unconditionally stable with reliability proven over many years.

    The power tubes are inexpensive, readily available and do not require any matching. Sporting a classic, open-chassis construction, the M-60 Mk. 3.3 sets the bar for hi-end amplifier performance.

    FEATURES

    – Balanced Differential Design®
    – Class-A2 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
    – Standby switch for long output tube life
    – 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
    60 watts per channel into 8 Ω load
    45 watts per channel into 4 Ω load
    80 watts per channel into 16 Ω load

    Impedance
    Input Impedance: 100 KΩ single-ended, 200 KΩ balanced Output Impedance: ~4.1 Ω

    Input
    3 V sensitivity ( for full output )
    RCA and XLR true balanced input

    Tube complement
    8 x 6AS7G output tube ( per channel )
    4 x 6SN7 driver tube ( per channel )

    Gain
    20dB (for 8 Ω)

    Power Bandwidth
    2Hz-75KHz within ½ dB

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

    Power supply storage
    140 Joules ( per channel )

    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
    1 dB

    Power consumption
    300 watts ( per channel )

    Dimensions & Weight
    13″ deep x 17″ wide x 8″ tall (33 x 43 x 20 cm) per chassis
    30 lbs (13.6 kg), per chassis, without tubes

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  • Atma-Sphere MA-1

    Atma-Sphere MA-1

    Atma-Sphere MA-1

    The best tube amplifier worldwide, 2 x 140 watts OTL monoblocks, Mk 3.3

    Recipient of The Absolute Sound’s prestigious “Golden Ear Award” in 2000, the MA-1 enjoys an enviable reputation. Now the Mk. 3.3 series builds on proven technology. An improved output section and enhanced driver circuit contribute to superior low-level detail, smoother sound, wider bandwidth and AC power immunity. The rugged, non-magnetic chassis features classic looks with superior layout. Setup of the amplifier is simple with it’s automatic biasing system. The controls and switches are ergonomic without sacrificing performance.

    The MA-1 is extraordinary in every way. Not only is normal operation easy on the vacuum tubes, the effect of a tube failure on the unit is entirely inconsequential. Despite its extreme performance, the MA-1 is known for remarkable ease of setup, ease of operation, day-to-day consistency and of course extreme musicality.

    Featuring our new custom wire, V-Cap Teflon coupling caps, custom resistors, and all the other extras for which we are known, the MA-1 shines as an example of why our amplifiers are the best amplifiers worldwide, regardless of cost.

    FEATURES

    – 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
    140 watts per channel into 8 Ω load
    135 watts per channel into 4 Ω load

    Impedance
    Input Impedance: 100 KΩ single-ended, 200 KΩ balanced Output Impedance: ~2.3 Ω (power method standard measurement)

    Input
    2.8 V sensitivity
    RCA and XLR true balanced input

    Tube complement
    14 x 6AS7G output tube ( per channel )
    5 x 6SN7 driver tube ( per channel )

    Gain
    25dB (for 8 Ω)

    Power Bandwidth
    2Hz-200 KHz within ½ dB

    Frequency response
    (1 watt, open loop) 20 Hz squarewave Tilt, unmeasureable
    1Hz-300KHz within 3 dB

    Power supply storage
    600 Joules ( per channel )

    Distortion
    Total Harmonic Distortion (THD) typically 0.5% at full power.
    Intermodulation (IM) distortion typically under .005% at full power.
    Phase shift less than 1° @ 20KHz

    Output section risetime
    600 V/µs

    Power consumption
    500 watts ( per channel )

    Dimensions
    18″ deep x 17″ wide x 8.5″ tall ( 46 x 43 x 22 cm)
    per chassis

    Weight
    36 lbs. ( 16.3 kg ), per chassis, without tubes

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  • Atma-Sphere MA-2

    Atma-Sphere MA-2

    Atma-Sphere MA-2

    Extremely powerful, hi-end OTL amplifier, 2 x 220 watts monoblocks, Mk 3.3

    Introduced in 1990, the MA-2 was the largest production triode amplifier and the largest production OTL in the world for nearly 12 years. In that time it set the bar for quality that has yet to be surpassed; it is one of the finest amplifiers made anywhere in the world regardless of price. Not only is it one of the most powerful production Output Transformerless amps available, it is also the most reliable. Audio purists have craved the design features of this amplifier since the beginning of Hi-Fi; only Atma-Sphere has succesfully put them all in the same place at the same time.

    Now the Mk. 3.3 boasts an improved gain stage with even wider bandwidth and greater transparency than ever before. We have added switchable feedback and automatic tube biasing to round out the package. Yet it remains smooth, detailed, and tuneful with a speed that belies such a large tube amplifier. Unlike many other amplifiers, it will stand up to constant playback without any noticeable artifact. And the improvements the MA-2 offers will be obvious on any system within seconds of powering it up; it sounds that good.

    The MA-2 is noted for its superior performance on Sound Lab, Wilson Audio, JM Labs, Magnaplanar and Avalon loudspeakers. These are speakers that need an amplifier capable of serious power. An amplifier that can fully utilise the full bass frequency range of the speaker with the proper control and impact, while simultaneously retaining detail, delicacy, and speed. This is an unusual combination but this is what sets Atma-Sphere apart from the competition.

    FEATURES

    – 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
    – Copper foil V-Cap Teflon coupling caps
    – Easily monostrapped for greatly increased power
    – Standby switch for long output tube life
    – Dual AC power circuits for each chassis
    – 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

    Output power
    220 watts per channel into 4, 8 or 16 Ω load before clipping

    Impedance
    Input Impedance: 100 KΩ single-ended,
    200 KΩ balanced – selectable to 600 Ω.
    Output Impedance: ~1.75 Ω (open loop)

    Input
    Selectable up to 600 Ω; 2.8 V sensitivity
    RCA and XLR true balanced input

    Tube complement
    20 x 6AS7G output tube ( per channel )
    6 x 6SN7 driver tube ( per channel )

    Gain
    26 dB (for 8 Ω)

    Power Bandwidth
    2Hz-150KHz within 1/2 dB

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

    Power supply storage
    1200 Joules in output section (per channel)
    100 Joules in Driver supply (per channel)

    Distortion
    Total Harmonic Distortion ( THD ) typically 0.4% at full power.
    Intermodulation ( IM ) distortion typically under .04% at full power
    Phase shift less than 1 degree @ 20KHz

    Output section risetime
    600 V/µs

    Feedback
    2 dB

    Power Supply Current
    80 Amps/channel

    Power consumption
    800 watts ( per channel )

    Dimensions
    28″ deep x 17″ wide x 10″ tall ( 71 x 43 x 25 cm ) per chassis

    Weight
    103 lbs ( 46.7 kg ), per chassis, without tubes

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  • Atma-Sphere MA-3

    Atma-Sphere MA-3

    Atma-Sphere MA-3

    The Best Audio Amplifier in the World. The most powerful OTL amplifier ever built!

    The MA-3 is the culmination of a massive project we began in 1998 at the behest of one of our customers. It was 7 years in design, with 15 different chassis and 12 different circuit concept explorations. The goal: to build the largest OTL amplifier the world has ever seen, while at the same time retaining the qualities our amps have made famous. The end result is arguably the the best amplifier in the world!

    There is clearly a need for such an amplifier that can make serious power while being completely transparent and musical; fortunately our OTL technology is well-suited to the task. Since we are not limited by issues that plague conventional amplifier designs, the MA-3 retains a wide bandwidth and low distortion simultaneouly. No transformer-coupled amplifier can produce 200, yet alone 400 watts and get it right at every audio frequency; yet the MA-3 makes 500 watts easily, without electronic artifacts. It’s high-power amplifier that is fast and truly musical!

    The MA-3 has all of the features as our other models, plus a few not seen in any other amplifier ever produced. It is class A, all-triode, and fully differential, with our patented direct-coupled output circuit and patented automatic bias control. There is only a single gain stage in the amp, so the signal path is very direct – something unknown in amps of this class. And with all it’s customised components, including custom precision Caddock resistors and tailor-made filter capacitors, it is one of a kind inside and out. The overall output power of the MA-3 can be varied by turning on or off banks of output tubes; the amp can operate on 1/3, 2/3, or all of the output tubes. This makes the amp very easy to live with! Of course, even at lower power levels, the MA-3 retains the innate authority and musical character that defines it as state-of-the-art.

    Furthermore, the MA-3’s power supply has a built-in AC line processor that regulates the line voltage coming into the amp! As a result, line voltage has no effect on the MA-3; it will make full power even if the AC line level has dropped to only 100 Volts.

    We included a very easy to use built-in tube tester (which can be used at any time the amp is on), allowing one to test the output tubes ‘on-the-fly’ in a matter of seconds. Bias and DC offset functions are automated, using an Atma-Sphere-patented method, with meters to monitor the tubes, output power, line voltage and other features.

    Output power
    500 watts per channel, 2-16Ω load before clipping

    Impedance
    Input Impedance: 100 KΩ single-ended, 200 KΩ balanced selectable to 600 ohms

    Input
    2.5 V sensitivity,
    RCA and XLR true balanced differential input

    Tube complement
    42 x 6AS7G output tube ( per channel )
    12 x 6SN7 driver tube ( per channel )

    Power Storage Capacity
    1/4 Farad per channel (more than any production amplifier)

    Power Bandwidth
    1Hz-100KHz within ½ dB

    Frequency response
    (1 watt, open loop) 20 Hz squarewave Tilt, unmeasureable even at full power. 1Hz-200KHz within 0.5 dB

    Output section risetime
    600 V/µs

    Distortion
    Total Harmonic Distortion (THD) typically 0.5% at full power
    Intermodulation (IM) distortion typically under 0.004% at full power

    Power Supply Weight
    152 lbs ( 68.9 kg ) per chassis

    Power Supply Dimensions
    34″ deep x 21″ wide x 12.5″ tall (86 x 53 x 32 cm) per chassis

    Amplifier Weight
    80 lbs (36.3 kg) per chassis

    Amplifier Dimensions
    31.5″ deep x 21″ wide x 15″ tall (80 x 53 x 38 cm) per chassis

    Panel Meter Functions
    VU level
    Individual tube condition
    Tube Bias status
    DC Offset status
    AC line voltage
    AC line regulator voltage

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  • Atma-Sphere Novacron Limited Edition

    Atma-Sphere Novacron Limited Edition

    Atma-Sphere Novacron

    Limited Edition

    Hi-End tube amplifiers, OTL monoblocks, 2 x 60 watts, Mk 3.3

    Originally introduced in 1991, the Novacron was the first US product to use the classic 6C33C Russian power triode. Just over twenty years later, Atma-Sphere is pleased to announce the return of the Novacron, now updated to Mk 3.3.

    In 1991, not only was the amplifier on the cutting edge of high-fidelity sound reproduction, it was an outstanding example of aesthetic industrial design. Today, the new Novacron combines the characteristics of the 6C33C triode with the same legendary circuit topology that has made our other amplifiers famous. Recent advances have rendered the Novacron even more reliable, easier to use, and inherently musical; maintaining the proper balance between sound and circuitry.

    Designed for reproducing music, not sine waves, the Novacron tracks dynamic waveforms faster than any other amplifier in the world. It naturally uncovers more detail than an ordinary amplifier, realizing your music as it was meant to be heard.

    FEATURES

    – Balanced Differential Design®
    – Class-A operation
    – Patented Circlotronic® direct-coupled (OTL) output stage
    – Dual-mono chassis construction
    – Copper foil V-Cap coupling caps
    – Teflon output tube sockets
    – Simple manual bias system
    – 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
    – Three-year general coverage warranty, one year warranty on output tubes

    Output power
    60 watts per channel into 8 Ω load

    Impedance
    Input Impedance: 100 KΩ single-ended, 200 KΩ balanced Output Impedance: ~2 Ω

    Input
    3 V sensitivity, RCA and XLR true balanced input

    Tube complement
    4 x 6C33C power triode ( per channel )
    4 x 6SN7 driver tube ( per channel )

    Gain
    24dB (for 8 Ω)

    Power Bandwidth
    2Hz-100 KHz within ½ dB

    Frequency response
    (1 watt, open loop) 20 Hz squarewave Tilt, unmeasureable
    1Hz-200KHz within 0.5 dB (-3dB @ 1 MHz)

    Power supply storage
    600 Joules / chassis

    Distortion
    Phase shift less than 1° @ 20KHz

    Output section risetime
    600 V/µs

    Power consumption
    400 watts ( per channel )

    Dimensions
    13″ deep x 17″ wide x 8″ tall (33 x 43 x 20 cm) per chassis

    Weight
    30 lbs (13.6 kg)per chassis, without tubes

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  • Atma-Sphere S-30

    Atma-Sphere S-30

    Atma-Sphere S-30

    High End OTL Tube Amplifier, 2 x 30 Watts, Mk 3.3

    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 those who seek the ultimate in amplifier design the S-30 gives you the same precision and sound quality for which Atma-Sphere is known. Featuring automatic bias and a large VU meter, operation is elegantly simple.

    Because it utilises 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.

    FEATURES

    – 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 Ω
    45 watts per channel into 16 Ω

    Impedance
    Input Impedance: 100 KΩ single-ended, 200 KΩ balanced Output Impedance: 7 Ω

    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 Ω)

    Power Bandwidth
    2Hz-75KHz within ½ dB

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

    Hum and noise
    Less than -75db below 1 watt,
    -95db below full power (30 watts)

    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 & Weight
    13″ deep x 17″ wide x 8″ tall ( 33 x 43 x 20 cm )
    24 lbs ( 10.9 kg ), without tubes

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