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Equipment Review

July 2005

Stello M200 Mono Amplifiers

by Doug Schneider

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Review Summary
Sound "Velvety and textured," "with bass that’s reasonably tight, but a little warmer, fuller, and bloomier than I’m used to hearing from most solid-state amps." "The highs…are an interesting blend: as extended and pristine as those of the best solid-state amps, but with a little bit of the politeness and ease that I hear from the very best tube amplifiers." "The M200 is the perfect amp for someone who wants the high power that solid-state amplifiers can provide but doesn’t want the cold, clinical, and almost sterile presentation that so many modern solid-state amps still exhibit."
Features "The M200 is a solid-state design with J-FET devices on the input stage and bipolar devices for the output stage. Stello rates the M200 at 140W into 8 ohms."
Use "Also on the back are two 12V trigger inputs and one of two power switches. This switch is intended to be always left in the On position, which keeps the M200 in standby mode and its circuitry warm. To turn the M200s on for real, you use the push button on the front panel."
Value "A terrific product and a very good value."

Mono amplifiers make a lot of sense, whether they're used for stereo playback or in a multichannel system. First, you get true channel separation right back to the wall plug. If you’re a purist, you’ve got to like that. There’s simply nothing shared between one channel and another as there is with a single-chassis stereo or multichannel power amplifier. Second, by separating each channel into its own chassis, you can place each amplifier close to the speakers or preamplifier, or wherever else you want to, which is not only convenient but also allows you the flexibility to use the length of interconnect or speaker cable that best suits your setup.

I suspect that these are the some of the reasons Stello developed the M200, an ambitiously designed mono amp intended for stereo and multichannel systems. A pair of M200s costs $3495 USD with silver-finished chassis covers, $3695 with olive-finish covers (which is what the review pair came with). While the M200s are hardly cheap, even by the standards of high-end audio, when you consider how versatile these amps are, how striking they look, and how wonderful they sound, a pair of M200s represents startlingly good value and can find a home in even the finest music systems.


Each M200 weighs 35 pounds and measures 12"W x 6 1/2"H x 17 1/2"D -- moderately sized and light enough that you’re not likely to hurt your back taking them out of their boxes and positioning them in your room.

The M200 is a solid-state design with J-FET devices on the input stage and bipolar devices for the output stage. Stello rates the M200 at 140W into 8 ohms -- not huge power, particularly when today you can find affordable, high-power stereo amps like Anthem’s P2 (325Wpc for $2500), but 140W is way more than enough power for the majority of speaker systems. The M200s never ran out of steam on me.

On the backside are single-ended and balanced inputs -- I used the single-ended ones. Even though the M200 has balanced inputs, it is not a fully balanced design. According to Stello, "From the point of sonic quality, balanced design during the passage from the source to the power amp is very reasonable. That's why we insist on the true balanced design for the source and preamplifier. But, the power amplifier is different." Also on the back are two 12V trigger inputs and one of two power switches. This switch is intended to be always left in the On position, which keeps the M200 in standby mode and its circuitry warm. To turn the M200s on for real, you use the push button on the front panel.

Not surprisingly, the M200 shares the same kind of styling as the DA220 that I reviewed last year. I really like it. There’s a decidedly simple and elegant look to the pieces -- the faceplates have a very light texture and rounded edges, and the chassis covers have a brushed finish that looks slick. On the M200s there’s just a single heat sink mounted on one side. The DA220's and M200’s understated looks are in direct contrast to the overly-built-to-the-point-of-being-gaudy appearance of many amplifiers that seems so desirable to some. Give me the simplicity and elegance of the Stello gear any day.

For the price of these amps, I have no complaints about their build quality, styling, or functionality. They look great and worked flawlessly for the entire review period. However, I have to put one con alongside a long list of pros. The warranty, which is just two years instead of the five years that are more or less the standard here in North America, is too short in my estimation. There’s just something more reassuring about a lengthy warranty, and it’s the one thing I wish the M200 had. Who knows -- maybe my comment here will have an impact.


I primarily used the M200s with Stello’s DA220 DAC, my Theta Data Basic transport, and Song Audio’s SA-1 preamplifier. For a time, though, I also used the M200s with the Benchmark Media DAC1 in order to take advantage of the DAC1’s onboard volume control, which allowed me to eliminate one set of interconnects, and the SA-1, to get a better idea of the amps’ sound in a more minimal setup.

The speakers alternated among MB Quart’s Vera VS 1F, PSB’s Platinum M2, and ACI’s Sapphire XL. Interconnects and speaker cables were either Nordost Valkyrja or Nirvana S-L. I used the M200s plugged into the ExactPower EP15A and also directly into the wall socket in order to assess the sound with and without power conditioning.


The M200 is the perfect amp for someone who wants the high power that solid-state amplifiers can provide but doesn’t want the cold, clinical, and almost sterile presentation that so many modern solid-state amps still exhibit. You’ve probably heard the kind of amps I’m talking about. They have a powerful, visceral presentation that can stun with vividness and immediacy, but they also sound icy and rigid rather than warm and inviting. The M200 is far more velvety and textured than that -- in fact, some might even call the M200's sound tubelike. A solid-state amp that sounds like tubes? Sort of, but not entirely. Here's why.

The M200 does have a somewhat warm and rich sound, a characteristic of many tube designs, with bass that’s reasonably tight, but a little warmer, fuller, and bloomier than I’m used to hearing from most solid-state amps. If someone didn’t know the inner workings of the M200s and you told them they were listening to tubes, they may well believe you. The highs, though, are an interesting blend: as extended and pristine as those of the best solid-state amps, but with a little bit of the politeness and ease that I hear from the very best tube amplifiers. In the end, tubelike or not, the M200 is a solid-state amp with a unique set of sonic characteristics. You don't come across such an amp very often.

A "tubelike" character

Every so often I encounter a solid-state amplifier that has some characteristics of tube amplifiers, such as a higher output impedance or lower damping factor, soft clipping, and a tendency for the damping factor and distortion to stay more constant with frequency. The soft-clipping characteristic is such that distortion increases more gradually as clipping is approached, in contrast to the usual solid-state character whereby distortion suddenly increases from very low values at the onset of clipping. This soft clipping is usually a result of low amounts of global negative feedback being applied. The low amount of feedback also helps to keep distortion and damping factor more constant with frequency.

In the case of the Stello M200, the damping factor is a bit higher than that of most tube amplifiers, which will help control woofers better. Further, the damping factor is essentially constant with frequency, as is the amount of distortion.

As a result of all this, the M200 may exhibit a more tubelike sonic character than the usual solid-state power amplifier.

...Bascom King

One afternoon I was listening to Césaria Évora’s Voz d’Amor [Bluebird 82876-54380-2]. The engineers did a bang-on job of capturing Évora’s voice on this recording. There’s a rich, resonant quality that, along with loads of detail,  really helps to show off what a high-resolution system can do. The sound from my system, with the Platinum M2 speakers at the end of the chain, was voluptuous, but not overly so, and wickedly detailed, but not to the point of being clinical or cold. Half the time I was caught up in the music, and the other half I was impressed with just how good the sound was from this system, made up of moderately priced, overachieving components that can stand tall with the cost-no-object crowd. Do you have to mortgage your house to get fantastic sound? No way.

Bruce Springsteen’s latest, Devils & Dust [Columbia 93900], is one of his best releases in years, both musically and sonically (far too many of Springsteen’s albums are recorded so poorly that no matter how good they are musically the engineers should be jailed for the steely sound the recordings display). Devils & Dust is a rather somber, downbeat album that showcases Springsteen at his minimalist best, relying heavily on closely capturing his voice, which benefits greatly from the M200’s rich and textured presentation. Play the third track, "Reno," to know what I’m talking about. It presents Springsteen’s voice so forward and so present that it sounds like it is trying to squeeze through the speakers' grilles to get into the room.

While the Évora and Springsteen discs do a good job of showing off the M200s' tonal balance, detail, and finesse, this is the kind of music you play at low or medium volume levels (at least I do), so it hardly taxes the M200s’ power capabilities. So I turned to Johnny Cash’s America IV: The Man Comes Around [American Recordings 440 063339-2] to give the M200s a more vigorous workout. For this test I used primarily the MB Quart Vera VS 1F speakers, which will play to astonishingly high volume levels -- louder than any other speakers I’ve used in my system.

I’ll cut the story short and just tell you the relevant information: My patience with painfully loud music gave out long before the speakers and amps did. I played the opening track on The Man Comes Around, which is also the title track, and nudged the volume higher and higher until I just couldn’t take it anymore. The walls vibrated, a few things around the room shook, my wife peeked in to figure out what kind of mayhem I was up to, and the neighbor even turned off his lawnmower to hear where all the racket was coming from. At the point where I could hardly stand to be in the room any longer, I could still tell that the system was remaining remarkably composed and wasn’t near straining. Did I need to go further? Not really -- the point was proven. The M200s may not be the most powerful amps you can buy, but do you really need more than their 140 watts? I don’t.

Back to something simpler and less raucous, I popped in my ol’ soundstaging-and-imaging standby, Ani DiFranco’s Up Up Up Up Up Up [Righteous Babe RBR013], and played "Everest." While the bulk of a system’s ability to produce a credible illusion of performers in the room has to do with the speakers, their placement, and the room itself, the amplifier and other associated electronics can have a fairly significant effect, especially with the subtle cues that allow for more exact placement of the performers left to right and front to back.

Indeed, the M200s acquitted themselves well. Ani was placed precisely in the far left of the stage and just back from the speaker plane, as she should be. There was absolutely no wavering or image instability, and the sense of depth and soundstage envelopment were wonderful. Complaints? None. Not with this music, anyway. But I do have a caveat about the M200s that could affect some potential purchasers’ fondness for them.

I’ve harped on the fact that the M200s have a rich, smooth, velvety sound, something I really like and that drew the reference to their being somewhat tubey-sounding. But the M200s aren’t the most incisive or visceral amps you’ll find, and the bass, while bloomy, doesn’t have rock-‘em-sock-‘em punch that some solid-state jobs do. In other words, although the M200s have plenty of power and can unravel loads of detail, they’re more laid-back than they are in-your-face and immediate, including in the bass region.

The M200s are solid-state amps with a bit of flavor. My own experiences, with the components I mentioned, were very positive, so the M200s' flavor suits me well. With the M200s in your system, your admiration will depend on your listening preferences and likely the characteristics of the components with which you use the amps.


At the same time I was listening to the M200s, I was also using Song Audio’s SA-300 MB mono amplifiers, which both Jason Thorpe and Marc Mickelson wrote about last year. The SA300 MBs retail for $4000 per pair -- in the same price range as the M200s. The two amps make for an interesting comparison -- contrast is more accurate. On the one hand, an amplifier doesn’t get much more esoteric and tubey than the SA-300 MB, with its low power and 300B output tubes. On the other, the M200s are powerful solid-state amps with more than a touch of tube ease and delicacy. In most outward ways, these two mono amps are about as different as two amps can get, but in terms of their sound, there is some common ground.

While the M200s are rated for 140W into 8 ohms, the SA-300 MBs are said to produce less than 8W into an 8-ohm load. For people used to solid-state amps, that’s hardly any power whatsoever; for fans of single-ended-triode amps, though, that’s more than enough power because they’re likely to match the SA-300 MBs with a high-efficiency speaker that will help to compensate for the low power output. This is part of the tube-amp ritual -- careful consideration of what speakers you use in terms of sensitivity and load. Tube amps aren’t usually as powerful or as load-friendly as like-priced solid-state amps.

Still, while 8 watts aren't much, I was surprised to find out that the SA-300 MBs could drive the Vera VS 1Fs quite well, even to loud levels. In fact, a couple times I found myself reaching for the volume control to turn the music down. It doesn’t take much power to get speakers humming along nicely -- generally, you need real power for excessive volume levels and lifelike dynamics. This is where the SA-300 MBs fell short.

But, despite the low power and limited dynamics, the SA-300 MBs sounded downright glorious, particularly through the mids, where there was a rich, full and almost bulbous sound that added weight, heft, and life to vocals. It was in this area that the SA-300 MBs outperformed the M200s, and most solid-state amps I’ve heard regardless of price. There’s just something about the midrange of a SET amp -- you need to hear it to understand. Still, tube amps -- at least low-powered tube amps -- aren’t for everyone.

Although the mids were spot on, the bass of the SA-300 MBs wasn’t as deep, full, or tight as that of the M200s -- not surprising, really, because solid-state always excels there, even if the M200s don’t have the most solid bottom end in the world. And although I could admire the SA-300 MBs’ treble for its clarity and natural ease, the M200s had better extension and, therefore, more air around performers. Again, the frequency extremes are generally the domain of solid-state amps, although some listeners will give up ultimate extension for the pristine sound up top that tubes can offer.

In terms of soundstaging, it was a toss-up. Both amps presented a stage that was bristling with life and had an admirable sense of width and depth. The main difference came with voices and guitars, which tended to be projected farther forward in the stage by the SA-300 MBs, most likely because of the way those amps handled the mids -- with greater fullness and weight.

Obviously, each amp has its virtues. For someone who wants real tube sound, only tubes will give that, and Song Audio’s SA-300 MB offers some of the best of tube sound at what still can be considered an affordable price. However, tubes need care and feeding -- they need to be replaced from time to time, and, in the case of the SA-300 MBs, they need to have their bias checked and adjusted every so often. Tube owners know this and are used to fiddling with their amps in the same the way that some people tweak high-performance sports cars. Solid-state designs aren’t necessarily perfect, but they do give their owners freedom -- freedom to use whatever speakers they want, and freedom to play music at higher volumes. And there are no maintenance issues whatsoever. Turn the M200s on and engaging music comes out -- simple as that.


When I reviewed PSB’s Platinum M2 speakers last December, I called them, along with Paradigm’s Signature S2s, "the pinnacle of common-sense two-way bookshelf-speaker design." By that I meant that while it’s possible to spend more money on speakers, you might not be spending money wisely. When using the Stello M200 mono amps, I couldn’t help but think of them in the same way. For well under $2000 a channel, the M200 has the looks, build quality, and performance that will satisfy a good number of audiophiles itching for cost-no-object sound but don’t have cost-no-object bank accounts. For those audiophiles who can’t afford to spend more, an amplifier like the M200 is a godsend and should be on their must-audition lists. For those who can afford to spend more money, they’ll be faced with the dilemma: Is it really worth spending more than what the M200s cost?

I certainly know it’s possible to spend more and get better amps than the M200s, but it’s also possible to spend more and not do nearly as well. That, to me, is the mark of a terrific product and a very good value, which is precisely what Stello’s M200 mono amplifiers are.

...Doug Schneider

Stello M200 Mono Amplifiers
$3495 USD per pair.
Warranty: Two years parts and labor.

April Music, Inc.
Seorae Bldg., 773-1 Bangbae-Dong
Seocho-Gu, Seoul 137-829
South Korea
Phone: 82 2 3446 5561
Fax: 82 2 3446 5564

April Music, LLC
1512 Windmill Place
Chula Vista, CA 91913
Phone: (619) 591-9665

E-mail: info@aprilmusic.com
Website: www.aprilmusic.com

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