Quality and power are watchwords for Atma-sphere OTL amplifiers. High end audio will never feel the same again when you experience the technology of hand selected made-to-order components provided by Ralph Karsten and his team of committed professionals atAtma-Sphere.


Atma-Sphere are dedicated to bringing lovers of beautiful sound only the best in audio and their individually hand crafted units are the envy of audiophiles the world over. What listeners get are exceptional amplifiers without the need for a transformer, advanced and durable technology and superb quality audio which is guaranteed to last for decades.

Because of their innovative approach to audio technology, inventive transparent circuit designs and the desire to achieve accurately reproduce great sound, distortion and noise are practically eliminated resulting in an audio experience for listeners which is nothing less than awesome.







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.









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, with innovations that were breakthroughs at the time and remain so today. With decades of refinement, patents and awards, the MP-1 is a paragon of the audio world.

The Mk. 3.3 update has affected the MP-1 more than than the rest of our lineup. More about that later… if the MP-1 is something you’ve not encountered before, it is unique in the world of preamplifiers. It easily outperforms conventional line stages and any passive or transformer volume control on account of its patented direct-coupled output which allows for greater transparency while also preventing coloration from interconnect cables. With only three stages of gain in the entire preamp (including the phono section), our Balanced Differential Design® is an elegant signal path that assures low distortion, wide bandwidth and dynamic range. No matter what you thought was the best, the MP-1 is an audible improvement.


OTL Power Amplifiers


OTL Tube Amplifiers





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.


Founder & Owner

Ralph Karsten is renown for taking the lead in the world of OTL amplifiers, verified by the fact that only three patents have been issued since the 1950s and two of those were to Atma-Sphere. They have also been the first to lead the way when it comes to preamps and were the first manufacturer to produce an all-tube preamp with a direct coupled balanced output.

Connoisseurs of fine music savour the experience provided by components designed by a master of supreme sound. With over 40 years experience in the audio industry focusing on high end audio, Ralph Karsten is simply the best at what he does.

Phantom Audio United Kingdom