Reviewer: Ken Micallef
Digital Source: Audiomeca Mephisto IIX [in for review]
Analog Source: Rega P2/Grado Prestige Gold cartridge
Preamp: Shindo Monbrison, Atma-Sphere MP-3 [on loan]
Amps: BAT VK-75
Speakers: Gallo Nucleus Reference 3 [in for follow-up review]
Cables: Primary - Omega Mikro Planar A-VII interconnects (CD to Pre), Omega Mikro Planar IV Silver LCX speaker cables and jumpers, Nordost Quattro Fil interconnects (Pre to Amp); Secondary Stealth PGSX ICs and speaker cables [on loan]
Stands: Salamander 5.0 rack, Mapleshade platforms, cone points and isoblocks
Power line conditioning: BPT Model BP-3.5 Signature Ultra Isolator, JPS Kaptovator and Omega Mikro Planar I and III power cords, Shunyata Black Mamba and Anaconda Vx Powersnakes
Sundry accessories: Ceiling treated with 8 x RPG ProFoam damping panels, Mapleshade HeavyFoot cone points under speakers
Room size: 24' x 12' with 10-13' sloped ceiling, short-wall setup
Review component retail: US $9,950/pr
In this addled age of consumerism when you can easily lose your mind trying to assemble the ultimate system; when a multitude of amplification options are available from flea-power 8-watt SETs and brawny solid-state behemoths to curious digital amplifiers, not to mention wares from start-up manufacturers that either look like they were built in (a), a NASA lab or (b), in Elmer Fudd's garage... why would anyone desire the possibly troublesome ownership of a pair of often maligned OTL (output-transformer-less) monoblocks?
No output transformer? One must use 8-ohm-or-higher speakers? After all, don't OTLs blow up with the wrong impedance load? Isn't there the danger of burning down not only your home but more importantly, your finely tuned audio reproduction center? What gives?
Okay, so I am leaping off the deep end of audio hyperbole but long ago and far away -- before OTL masters like Atma-Sphere's Ralph Karsten entered the game -- there were real concerns about the viability of the OTL design. A little history thus before we proceed with the goodies.
It was sometime back in the 1950s that Julius Futterman designed the first widely available OTL amplifier. OTL amp designs are the heart of simplicity and audio honesty. OTLs lack the bulky output transformers necessary for most tube amps to step down voltage and match impedance to speakers. Minimalism rules. And just as the "straight wire with gain" motto applies to preamps, OTL power amps go a long way in getting you closer to the music.
Ralph Karsten founded Atma-Sphere Music Systems in 1978 and soon introduced the first reliable OTL amps. The Futterman amps had a tendency to belch and blow up, taking down power tubes and speaker drivers and with them, your audio humility. Ever ingenious, Karsten found a way around this problem and produced his first M-60 OTL amplifiers in 1980, just as the audiofools of the world were abandoning solid state en masse for the glory of pure tube amplification. Now more companies produce tube amps than ever before and Atma-Sphere is one of the most famous, honored and awarded makers. Karsten's M-60 has become a very popular amp; heck, even I owned a pair for a while.
The M-60s' transparency, purity of tone and serious jump factor were their best traits, a stubborn inability to handle anything less than 8-ohm loads their worst. Pairing the M-60s with my then-speaker compliment of Audio Physic Virgos was not an electrical match made in heaven. They sounded pretty damn fine together though. The M-60s kicked out the Virgos' rich, plummy bass with decent authority but the top end could sound strained when I felt like listening at 'In A Gaada Da Vida' levels. Ultimately, the ohmage mismatch made the M-60s blow power tubes when driving the 4-ohm Virgos. Thank God those 6AS7 power tubes were cheap.
But the MA-1 MkII.3 Silver Edition, an updated version of the MA-1 MkII.2, does not in any way resemble the M-60. While it does use the same tubes 14 x 6AS7s and 5 x 6SN7s -- that's where the similarity ends. To quote the Atma-Sphere website regarding the 25th anniversary MA-1 MkII.3 Silver Edition OTLs:
"The MA-1 Mk. II has been replaced with an upgraded version that is built on the same circuit concepts but features an enhanced driver circuit for lower distortion and wider bandwidth; driver supply regulation, again for lower distortion and enhanced AC power immunity; and a new chassis with welded and polished corners for a seamless look. [Its] musical design has yet to be equaled by any amplifier except our own MA-2 Mk.II.3. The best way to describe the design is much like a pair of single-ended triode amplifiers wired together differentially. It is the world's first Class-A all triode fully-differential zero feedback output-transformer-less amplifier (the original MA-1 was introduced in 1987). Thus it can reproduce greater depth, the lowest, most precise powerful bass, with sumptuous, revealing midrange and highs yet remaining tonally neutral... the MA-1 tracks dynamic waveforms faster than any other amplifier in the world."
The MA-1 MkII.3s can be run in either Class A or A/B, feature a standby switch (like the M-60) for longer output tube life, use both XLR and RCA input connectors, custom-built Teflon coupling capacitors, a patented Circlotronic® output circuit and Karsten's very own 'star ground circuit'. The MA-1 MkII.3s weigh in at a mere 35 pounds each, a welcome fact when you live in a seven-floor walk up as I do. (Fellow moonie Jules Coleman has scaled those Olympian height on a few occasions and is a better man for it!)
Before I describe my listening experience with these Atma-Spheres preceded by a brief Q&A with Ralph Karsten, let me go ahead and just get something out of my system - er, my head. These amps are exceptional pieces of audio art. It took a lot of fiddling around and playing with different ICs and speaker cables to get them to lock into a presentable sound but once all the ancillaries were right, the sound which the Atma-Spheres produced was massive, vividly lifelike, extended in the frequency extremes and generally so enjoyable that I was soon able to simply set the bias, power up the preamp and forget 'em. That is until I thought about their hefty 10K price tag. "What can I sell, beg for or borrow to be able to purchase these magnificent but dangerously (to my health) heat-generating amplifiers?" But first, a few questions with that pioneer designer of OTLs which neither smoke, fume nor fire up - Ralph Karsten.