VTL • MB-450 Series III Signature and MB-185 Series III Signature Mono Amplifiers

". . .one or other of these amps might just be the pot of gold at the end of your own audio rainbow."

by Roy Gregory | November 29, 2014

he entire audio industry, from manufacturer to end user, enjoys a complex relationship with the duality of myth and reality. In one sense, the very object of the exercise of putting together an audio system is to re-create reality; in another, we construct elaborate justifications for intangible improvements and all-too-real expenditure. We fete legendary products (that few if any of us have ever heard) and succeed in glossing over or simply ignoring the operational realities of products we endorse, sell or own.

Nowhere is this last divide more keenly felt than amongst those manufacturers of tube amps. Between the realities of ownership and the myths that most customers attach to it there lies a gaping chasm. Of course, matters aren’t helped by the fact that the implications of owning a tube amp depend entirely on the nature of that amp, who you bought it from and the standard of engineering behind it. As a hobby that’s become an industry, when it comes to manufacturers we have more than our fair share of enthusiastic amateurs, and tube amplification attracts more of them than any category other than loudspeakers (although cables are coming up fast on the rail). But it’s a mistake to assume that all tube amps are created equal, and everything from the choice of tubes themselves to the people building the product, from the designer’s ethos to the marketing strategy, has a profound effect on the longevity, reliability and versatility of the product produced.

I think it’s fair to say that most customers (and a lot of dealers and distributors) consider tube amps to be less reliable, more troublesome, less accurate and more expensive than the solid-state alternatives. They are also generally held to be less capable when it comes to driving real-world loudspeaker loads and responsible for generating vast amounts of heat. Sooner or later you will suffer inevitable tube failure and then the fun really starts -- at least so the wisdom goes.

Now, this might seem like a strange precursor to a tube-amp review, but my point here is simple: don’t judge a book by its cover and don’t classify an amplifier by its output devices. Whilst there are plenty of tube amplifiers that would qualify for every facet of the characterization above, there are just as many solid-state amps that give cause for concern. Tube amps are inherently simpler than their silicon-based brethren, with fewer components to fail and generally less catastrophic results (for loudspeakers) when they do. The sheer range of available vacuum-tube output devices means that amps exist with power ratings ranging from one watt to hundreds of watts, which allows for some truly spectacular amp/speaker mismatches. But choose sensibly and there’s no reason that a tube amplifier can’t or won’t actually drive a loudspeaker better than a solid-state design.

What matters here is choosing correctly, and the amp/speaker match is far more complex than simply choosing tubes and solid state. After all, the ability to drive a car up a hill has never been any guarantor of audio-amplifier quality -- and in many cases quite the reverse. When it comes to heat -- well, you’ve got me there. But even that varies enormously with the number and type of output devices and the output topology. The universal power amp, the unit that will deliver the best available performance whatever the circumstances or loudspeaker, doesn’t exist. Instead, most amplifiers will work across a range of system contexts, to greater or lesser effect. When it comes to choosing an amplifier, what really matters is what speaker you are asking it to drive, whether the amp in question is fit for purpose and how much effort went into making it so. That has everything to do with tube amps -- and the amplifiers I’m reviewing here in particular. It’s not a case of tube or solid state, but which tube or solid state.

What’s in a name?

TL are clearly aware of the underlying public reservations concerning tube amps in general. Rather than denying that there’s a problem, or ignoring it and hoping that it will go away, they’ve met the challenge head on. You don’t get much more up-front about the issue than a tagline that states, "Making tubes user friendly." There’s the issue, neatly encapsulated in one four-word phrase. Recognizing that too many tube designs richly deserve their checkered reputation, the company realized that their amplifiers needed to be both easy to use and genuinely versatile and that those qualities should be self-evident. It’s an ethos that has reached its apogee in the Series III Signature versions of their popular and long-standing MB-450 and MB-185 monoblocks -- to what I consider spectacular effect.

Let’s look at the Series III Signature platform in detail to see just how this feat of engineering has been achieved. But first, let’s establish the ground rules. In essence, in order to go head-to-head with the solid-state competition, the VTL amps need to look as good, sound at least as good and do it across the widest range of loudspeakers. They need to be simple and fuss-free to operate, without demanding special tools or skills.

Sounds simple on paper, but just stop to consider the implications. The demand for tractable performance means decent rated output, which in turn means a large number of output devices. That leads to added complexity, a higher component count and greater vulnerability to tube failure. Back in the ‘80s, when I worked in retail, we reckoned that "double the number of output devices, quadruple the failure rate" was the rule of thumb for tube amps -- normally resulting in a costly, inconvenient and far-from-rapid trip to the service department. In order to overcome that reality VTL had to do something pretty special, and the Series III Signatures are it. Let’s take it step by step.

Pseudo-pro, rack-mount chic might have been all the rage back in the ‘80s, but it definitely doesn’t chime with current notions of classy décor. The challenge facing VTL was to overcome the governing open-chassis, communications-kit aesthetic of traditional tube amplifiers and approach the sleeker, more domestically acceptable presentation of modern solid-state gear. To make things even more difficult, the power requirements mandated chassis dimensions that were definitely on the larger end of domestic acceptability. The answer was a fully enclosed casework, with a svelte glass-and-aluminum front panel. The horizontal and vertical framework that surrounds the central window helps reduce the visual impact of what is a pretty bluff fascia, while the subtle curvature softens it further. The window provides a focus for the eye as well as a hint of what glows within. With controls limited to three soft-touch buttons, centrally mounted and contoured into the lower front face, the overall look is cool and classy -- and does an excellent job of disguising what is in essence a seriously large bent-metal box. In terms of actual metal work, this might constitute one small step, but aesthetically it really is a giant leap for tube-kind.

The other major issue that VTL have confronted is the whole question of housekeeping when it comes to tubes. The plug-and-play simplicity of cathode bias isn’t really an option in really powerful amplifiers. Instead, these tend to be (somewhat confusingly) referred to as fixed-bias designs -- by which they mean that the bias for each tube needs to be manually fixed, normally using a meter (handheld or fitted to the amplifier’s chassis) and a rotary pot. VTL have automated that whole process, via an onboard microprocessor. Each time you fire up the amp it assesses the bias requirement of each tube and adjusts the supply accordingly. It then continually monitors each tube’s draw, ensuring that they stay perfectly within their optimum operating parameters. So far so good, but VTL also take things to the next level, with auto fault sensing. If a tube fails, the amp uses its front-mounted LEDs to let you know, the color and behavior (steady or blinking, and if blinking, how fast) informing you of the nature of the problem and what to do about it. The tubes themselves can be accessed through two separately secured "hatches" in the casework, chassis-mounted LEDs indicating which tube(s) need replacing. Power the amp down, unplug the offending article and replace it, power the amp back up -- it will go through its self-diagnostic cycle -- and you are good to go. It really doesn’t get much easier or quicker than that.

With the appearance and practicalities taken care of, the company could really go to town on the sonic and musical qualities of the amp, extending its practicality beyond simple ease of use and into breadth of application. While the Series II iterations of these amplifiers had balanced input and phase-splitting circuitry to drive the push-pull output stage, the Series III Signatures employ differential circuitry from input to output, allowing greater voltage swing in the driver stage and a lower-impedance output for greater load tolerance. The screen and bias supplies are both precision regulated, while all capacitors in the signal path are Mundorf silver/oil types with film-type bypass caps used on the power-supply reservoir capacitors. At the same time the amp uses a shorter, faster and fully differential feedback loop and eschews global feedback altogether. The result is a circuit that remains unconditionally stable, irrespective of indignities perpetrated upstream or down. The output transformers are now even more heavily interleaved and closer coupled to deliver wider bandwidth without sacrificing low-frequency control -- another crucial consideration in powerful tube amps, where all too often high power and powerful bass are paid for with poor high-frequency extension.

Having made the amp bombproof to operate, the next stage was to make it "steerable" when it comes to speaker matching. That depends on three features of the Series III Signature platform: the choice of three different output tubes (the EL34/6CA7 in the MB-185, the 6550 or KT88 in the MB-450), the choice of triode or tetrode operation and a four-stage adjustable damping factor. In this way, the same basic platform serves up a choice of eight variations on the EL34 output tube and 16 6550/KT88 variations if you choose to go with the more powerful MB-450.

What’s the significance of adjustable damping factor? Far greater than you might imagine. The clue lies in the fact that it is derived from the degree of feedback, the higher the feedback level, the greater the damping factor. In this day and age it is easy to assume that all feedback is bad and that the less you have the better, but it isn’t actually quite that simple. There’s a world of difference between local or nested feedback (used within a circuit) and global feedback (that encloses it entirely). While feedback-free preamps are all the rage, feedback is critical to a power amplifier’s damping factor, just as Q is critical to a speaker’s voicing. Between the two, these factors have a huge influence over amp and speaker matching, and as Q is generally a fixed value (unless you happen to be using the large Focal Grande Utopias, with their adjustable-Q EM drivers) then being able to adjust damping factor to achieve superior matching is a major benefit, significantly broadening the type and number of speakers with which the amplifier can achieve really good results.

VTL offer four settings for damping factor: Low, Medium, High and Max. With any given speaker you will find that one setting is dramatically more musical, dynamic, involving and better integrated than the others. In my room and in most cases, I settle on either the Low or Medium setting. Those who crave a drier, more heavily damped sound might opt for the high setting, especially if the speakers are a little loose in the bass or the room is exaggerating the bottom end. I can’t really see anybody needing the Max setting, but it serves a useful purpose in establishing the continuum along which you are operating. Once you’ve heard what Max does to the music, you’ll treat the setting of the amplifiers’ damping factor with the appropriate caution and seriousness. It not only has a huge impact on performance, it offers a huge advantage in terms of choice and your amplifier’s longevity, should you (or should that be, when you) change your speakers at some point in the future. If the amp/speaker interface is the single most critical junction in your system, the Series III Signatures pull the neat trick of offering genuine adaptability, a serious benefit that’s not to be overlooked.

Take the VTL’s combination of overall stability, choice of output tubes, high rated power output (up to 225 watts into 5 ohms for the MB-185, up to 425 watts into 5 ohms for the MB-450) and adjustable damping factor and these amplifiers offer the real possibility of optimum matching with the widest range of accepted audiophile speaker designs. Okay, you might look elsewhere for something really efficient, like the Avantgarde Trios, or really hard to drive, like the monster MBLs, but within the realms of conventional dynamic designs and electrostatics, the Series III Signature is going to give you a way better than fighting chance of achieving something like the speaker’s true potential. That might sound a little lukewarm, but then it’s remarkable how few systems get even close to that limited goal! Using the VTLs I’ve achieved superb performance from speakers that range as widely as various Wilsons and Avalons, the KEF Blades, Marten Coltrane 2s, various Focal Utopias, Vivids, Rockports and MartinLogans. That’s quite a spread.

Other aspects of the Series III Signature platform that endear it to me include the provision of both balanced and single-ended input (the latter employing a dedicated J-FET current source to derive a balanced signal) a single set of speaker binding posts (allowing the transformer design to be optimized for a single set of output taps) and rear-mounted fuses (making replacement quick and simple -- you really don’t want to be lifting the lid on these beasts unnecessarily). In fact, at little short of 100 pounds apiece, you don’t want to be lifting them, period -- at least not on your own. They measure 18.5" wide, 18" deep and 9" tall, and their subtly sculpted fascia does a great job of making the amps seem smaller than they are, especially if they are placed in a rack. But perhaps best of all, owners of Series II units can have them fully upgraded to Series III Signature status, further future-proofing their already not-inconsiderable investment. Full marks to VTL for appreciating the value of their installed customer base, rather than simply working on creating product churn.

Finally, mounting hardware for 19" racks is available (if you must) although let’s be honest, the rack that can support these beasts is going to be even uglier than the front-panel extensions needed to perform the task. When something this big looks this good, I say, "Why ruin it?" Having said that the universal amplifier simply does not -- indeed, cannot exist, I’m forced to acknowledge that VTL’s Series III Signature series amps get way closer to that ideal than the vast majority of the competition. Not bad for a technology that is supposed to offer questionable versatility and reliability.

Fleet of foot(?): the MB-185 Series III Signature

n paper at least, the smaller brother in the Series III Signature stable makes little sense, a family afterthought that falls outside the plan. But life is rarely that simple, nor is the evolution of audio products. Identical in size and appearance to the MB-450 Series III, the MB-185 III uses EL34 (or 6CA7) output tubes in place of the beefier KT88 or 6550 employed in its big brother. This "costs" it around 50% of its rated output power for a monetary saving of around 20%. As I said, it’s not a deal most people would sign up to -- except that the '185 doesn’t use the EL34 to save money; it uses it because it offers a very different set of musical virtues to the 6550. This isn’t about the price or rated output of the amplifier. It is about how it sounds.

There are some products that you can sum up in a word or two. Those few words won’t tell the whole story, but what they will do is set the scene. For the MB-185 III, those words are "deft" and "beautifully balanced." There is nothing clumsy, ugly or rude about the '185. Even when provoked, its response tends to the arch rather than the uncouth, its manner and manners retaining an effortless sense of equilibrium. This is the Sir John Gielgud of amplifiers: accomplished, subtle and intelligent -- and possessing incredible range. Does that mean that it’s just another "nice" tube amp, incapable of getting down and dirty when the music demands it? Quite the contrary. When called on the MB-185 IIIs strike with a speed and grace that leave you wondering how it happened. No axe-wielding maniacs these; they’re quicksilver fast, whether it’s a case of cold-steel or rapier wit -- and believe me, reproducing music calls for both.

Enough of this verbal flim-flam -- it’s time to look at a few musical examples. Just as Sir John is quintessentially English (English you’ll note, not British), so too is the EL34, at least that’s the way I’ve always thought of it. So where better to start than that other great Englishman, Ralph -- Vaughan Williams that is, not Richardson! RVW had an ability to conjure an almost visual sense of landscape and its accompanying atmosphere; just think Sinfonia Antarctica and you’ll get what I mean. But’s its range and subtlety is perhaps best expressed through his various vignettes of English country life. His Norfolk Rhapsody somehow seems to capture the flat, farness of a landscape, defined by crops and agriculture rather than hill and dale, shaped by man rather than nature.

Playing the Boult reading (with Hugh Bean and the New Philharmonia [EMI ASD 2847]), the MB-185 III perfectly conjures that atmosphere and sense of distance, of contrasting stillness and industry. But it’s a natural sense of musical tone and grasp that reaches its apogee with "The Lark Ascending." To listen to the poise and control, the soaring delicacy of Bean’s melodic line, the pulse and soft echoes of the orchestral accompaniment is to be transported to the slightly drowsy warmth of an early summer’s afternoon in down-land England, with its muted sounds and strangely translucent light, a quality that both the composition and the performance capture precisely. As the soloist climbs towards the finale, his instrument describes the fragile, almost teetering poise of the ascending line, the drama of its sudden swoops, until higher and higher, almost impossibly high, it simply fades away into silence, leaving just that heavy atmosphere behind. Breathe again -- and marvel at the combination of texture and tonality, balance and delicacy that can produce such drama from something so diaphanous and insubstantial.

These short pieces illustrate perfectly what the EL34 brings to the party. It has a light touch, an ability to let the music flow and breathe that is built on its midband linearity. It does instrumental texture and it does individual instrumental tonality in a way that triode lovers will recognize, but it does them with a sense of focus, spatial definition and temporal authority and precision that is akin to ultralinear designs. Its innate sense of balance extends in both the vertical and longitudinal dimensions, seamlessly from top to bottom of the musical range, evenly through time, without hesitation or discontinuity -- qualities that the MB-185 Series III Signature exploits (and extends) to the full. Of course, all that lightness of touch and translucent beauty need a substantial underpinning if they are to amount to real musical substance, which is exactly what the Series III Signature architecture provides. Hugh Bean’s soaring violin takes its power from the stability and security of its anchor -- and that is lodged in the quality of the fully differential circuit, the power supply underpinning it and the sophisticated output transformer linking it to the outside world. The beauty of the MB-185 III is that it combines the sense of order and stability of the VTL circuit with the midrange coherence, delicacy and texture of the EL34 to create a whole that is even greater than the considerable sum of the parts -- a whole that can stretch that performance envelope, especially when it comes to scale.

Keeping things firmly this side of the channel (and the pond) you don’t get much bigger in terms of sheer scale and range than Walton’s sadly abused score for the 1969 United Artists’ film The Battle Of Britain. Ultimately only his startling "aerial ballet" sequence "Battle in the Air" was to feature in the movie, the rest of the music being composed by the more bombastic and populist/patriotic Ron Goodwin. But what does remain shows all too clearly what might have been. Recorded by Carl Davis and the LPO [EMI EL 27 0591 1], Walton’s music underscores the film’s climatic sequence and perfectly captures the exhilaration, desperation, fear and vast spectacle of the aerial battles that unfolded over the English Home Counties in the summer of 1940. The action covered the sky from one horizon to the other, with hundreds and hundreds of aircraft involved, and the score needs to reflect that. It’s a big orchestra, used to create huge drama and dynamic shifts, an emotional range that flits from the macro to the individual and back again, but the MB-185 IIIs take it in their stride, never glazing over the insistent high-tremolo strings or stumbling on the sudden rumbling bass explosions. As an exercise in controlled violence, this takes some beating, managing to combine the lethal beauty of the action with its devastating consequences. The Walton score has long been overlooked (although I believe a later DVD issue of the film was released that used it), but I believe it is one of his best and certainly most dramatic pieces -- easily outpointing the much-lauded Henry V in my opinion. I can’t think of a better advocate than the MB-185 IIIs to make that case.

That’s a pretty impressive endorsement, covering both ends of the musical spectrum, from solo violin right through to a large orchestra at full chat, drums and drama to the fore. But it comes with two provisos: I chose those particular musical examples because they play to the MB-185 IIIs’ (admittedly considerable) musical strengths. But like any amplifier, they possess their own particular blend of virtues and those may or may not dovetail with your musical tastes and system. For me, they offer a near-perfect balance of musical insight and nuance -- and I have the speakers to take advantage of those qualities. For my musical tastes and in my system, the '185 IIIs’ combination of musical grace, structural insight and articulation, their ability to reveal the interplay of musical phrases, textures and tonality, their sheer rhythmic dexterity and effortless ability to track changes in pitch and tempo, make them a musical joy. But in part at least that’s because I’m prepared to allow for their weaknesses in order to enjoy their strengths -- and so are my speakers.

Let’s be clear here: "weakness" is a relative term. In practice, the '185 III is a remarkably competent, versatile and accomplished performer. It’s just that its bigger (and twice as powerful) brother is even more versatile, even more capable when it comes to a wider range of speakers. That in turn relates directly to the choice of output tubes and the way the EL34 sounds. As I’ve already said, the '34 is remarkably seamless, top to bottom. It is extended and airy at high-frequencies and wonderfully open, coherent and tactile through the midrange. But to some extent, that midband clarity and agility are the result of a subtle trimming of the low frequencies, a gentle, almost imperceptible fade that tucks them under the rest of the range, at the same time ensuring that they don’t pollute, muddy or embarrass it. That’s what makes a good EL34 amp so responsive and immediate, detailed and translucently clear, fast on its feet and fast on the draw. But sit the '185 III side by side with an amp like the MB-450 III and for all its filigree detail and lucid musical expression, you can’t miss the extra weight and impact that the bigger amp delivers -- or the sheer physical presence that goes with it. It’s not quite as simple as grace or grunt, but it’s not far off.

I said there were two provisos, and the second is directly linked to the first. The extra weight, power and low-frequency control that come from the MB-450 III give it a far greater degree of control over larger drivers and awkward loads. Give it a speaker that likes to be kicked, or one that likes to kick the amp back, and the '450 III has an authority and drive that the '185 III can’t begin to approach. Does that make the '450 III a fundamentally better amp? No. It means that your amp of choice will be dictated by a combination of your musical tastes or biases and the speakers you need to drive. As well as my own Coincident PREs (meat and drink to the '185s, which had almost an embarrassment of power in this context) I was lucky to have Focal’s heavily revised Scala Utopia V2s in house at the same time as the VTL amps. This proved to be a marriage made in heaven, the French fancies having just enough of a load and just enough efficiency to really let the '185 IIIs get hold of them and take them for a ride. One of my recent guilty discoveries is Gravity soundtrack [Silva Screen Records SILCD 1441]. A heavily processed blend of synth and orchestra, voices and solo strings, it is full of texture and tension, drama and dynamic intensity, massive scale and huge crescendos that are snuffed out in an instant, with all the finality of an airlock slamming shut. The Scala/'185 III combination is quite remarkable faced with this intense and demanding music, ramping up the levels, ramping up the tension. Reticent low-frequencies? Not that you’d notice. Lack of impact and authority? You’ve got to be kidding! Which is the point. The '185 III is a thoroughbred. You don’t run a flat racer in a steeplechase, a sprinter over distance or a stayer on a baked-hard track over eight furlongs. This really is a case of horses for courses.

So what sort of speaker brings the best out of the '185s? Well, clearly the Scala V2 is a good point of departure. With a straightforward three-way crossover, an 11" woofer and a nominal 8-ohm load, the Scala could be a step too far, especially given a 3.1-ohm minimum impedance and a -3dB point at 27Hz. But countering that is a relatively benign frequency characteristic devoid of savage corners, a 92dB sensitivity and prodigious power handling. In short, with the '185s there was enough bass to really satisfy, enough power to test your headroom tolerance and enough thermal dissipation to let you crank the levels with abandon -- all that and a speaker that favors detail and texture, transparency and speed of response over sheer grunt. You can see why they make for a spectacular partnership. The lesson here is to avoid the really awkward loads and the sort of big, heavy bass drivers (or overly generous bass voicing) that demand an iron grip. Look for speakers that thrive on finesse and texture, detail and dynamic shading -- and look for a sensitivity of at least 90dB. Even with those strictures in place, you are going to be pretty spoiled for choice, with models from Focal, Vivid and Avalon featuring near the top of my own list of preferred options.

Actually, all amplifiers suffer from similar restrictions, especially if you want to get every last ounce of performance out of them. The point here is that, relative to its beefier sibling, the '185 III needs a shade more care when it comes to speaker matching, but just as importantly, it matches better with a different range of speakers. As it stands, the '185 is the perfect partner for many a musical journey, with just enough baggage (power and headroom) to make the trip, wearing its last outfit on the last day. Muscle-bound alternatives, weighed down with more power than you need slow your progress and limit your options when it comes to choice of route or destination. For me, the '185 IIIs deliver enough power, with enough headroom for both safety and satisfaction, to pair with a host of speakers I might choose to live with. Their ability to tease out the strands of music, to step behind the performance and give the performers their own voice makes them very special indeed.

Their lucid sense of musical structure and expression unravels the delicate strands of Corelli just as effortlessly as it allows Elvis Costello’s "Little Triggers" (This Year’s Model [Radar RAD 3]) to explode into the room. It’s this range that I find so satisfying -- the fact that their virtues serve all types of music with equal alacrity and without fear or favor. You might choose to have more grunt, or the speakers you own might demand more power, but carefully matched I really can’t see the '185s failing to satisfy even the most demanding listener. The subterranean rumbles on Gravity certainly plumb the depths, while the shape, texture and the air that the '185s define around the massive drum beats on "The Approach To The Line" (The Thin Red Line Soundtrack [RCA Victor 09026-63382-2]) more than make up for any perceived lack of weight -- the sort of weight that needs serious subwoofers to fully realize, irrespective of the speakers you use.

Acoustic music of any kind, whether we’re talking Julian Bream or Gillian Welch, is the '185 IIIs’ forte, if only because it depends on the natural expressive range of the instruments and players involved. But the same uninhibited dynamic and rhythmic qualities, the same abilities with tone and texture, are just as dramatically effective with rock or pop as they are with classical, just as captivatingly capable with complex jazz arrangements as they are with slabs of synth-based dance mayhem. Used with the Scalas in particular, this really is a go-anywhere, play-anything combination. Pete Tong mega mixes hold no fear, PSB with the volume wide open, or the rapid patter of India Tabla are all tackled with the same unintrusive grace, underpinned by the same absolute stability that renders the interwoven patterns understandable, that deciphers the heavy, stacked layers, that delivers the music in the right place at the right time.

Which brings me back to the question of balance and dexterity -- both qualities that allow an amplifier to step away from the signal, passing the music without leaving an imprint of its own. Let’s take the masterful Narcisco Yepes performance of the Rodrigo Guitar Concerto as an example (Argenta and the National Orchestra of Spain [Decca SXL 2091]). It doesn’t deploy massive orchestral forces, but with the need to accommodate a solo guitar, orchestral balance is critical (and perfectly suited to the simple Decca tree used for this 1959 recording). The '185s deliver a natural perspective, a beautiful sense of acoustic space -- including the slightly exaggerated depth produced by the tree -- and a beautifully separate and focused solo instrument. They allow Yepes his full expressive range, his notes and phrases their full shape and spacing, a master class in lucid precision. But they also embrace the sudden shifts in dynamic density that allow the music to jump and surprise, they traverse the astonishing changes in rhythm and tempo without hesitation or restraint. The third movement, its jangly Allegro coming hard on the heels of the plangent beauty of the Adagio, can sound jarring, almost inappropriate -- but not with the '185 IIIs. The change in pace, the change in voice, seem utterly natural, a contrast rather than a clash. It’s this ability to embrace music, whatever its language, whatever its idiom that makes the '185 such a fantastic audio tool. Sir John Gielgud and Ralph Vaughan Williams were both cut from the very fabric of England, but so too was Ian Dury, and the MB-185 Series III Signatures deliver his acerbic humor and biting lyrics, his complex yet catchy rhythms and lewd allusions with the same perfect equanimity that they handle the London Symphony. The '185s might never offend, but nor do they stand in the way of the Blockheads, and that’s their secret -- more of the music, more of the time. This isn’t an MB-450 III on the cheap, or a cut-down anything. This is an EL34 amp done right; in fact, make that done very right indeed!

Walkin’ tall: the MB-450 Series III Signature

ou know you are an audiophile when, confronted with a pair of amps this big, this heavy and this powerful, your first reaction is to reach for the biggest recording available and the smallest speakers! There’s no denying the sheer fun to be had from hooking up something like the Focal’s smallest Utopia, the Diablo, to the business end of VTL’s MB-450 III -- and it generates a truly remarkable sound. But whilst listeners might marvel at just how much can be projected from those diminutive enclosures, you are not really showing the '450 at the height of its powers. You actually need both more and less bandwidth to get a true grasp of its capabilities: more range from the speaker, less scale from the recording. Big amps doing big music isn’t that clever. Big amps doing small and subtle -- that’s far more impressive.

The track "Snowfall" (from Ahmad Jamal’s Alhambra -- the Alto 180-gram reissue [Alto AA005]) is a perfect musical microcosm: two and half minutes that encapsulate both Jamal’s magical touch and the '450 IIIs’ musical capabilities. What might seem at first almost simplistic is actually constructed out of layers of complexity and contrast, layers that cross dynamic and rhythmic divides and present an amplifier with the musical equivalent of simultaneously rubbing its stomach and patting its head. Picture an elephant attempting that feat and you’ll have some idea of just what happens when Ahmad Jamal meets all too many really powerful amps.

The soft, repetitive patter played by bass and drums anchors the piano’s wandering lines, its shifts in level and intent adding drama and surprise, engaging the audience, twice breaking into full-band ensemble before drifting away, capped off by the exclamation mark of Jamal’s characteristic musical full stop. The '450s are perfectly at ease, delivering the subtle drum work and nimble fingering of that softly pattering bass line, tracking the almost meandering notes of Jamal’s opening line. But when the piano starts to add attack and purpose, direction and intent, the amps are right there. There’s no lag or hesitation, no overstatement, just that carefully mapped, step-by-step increase in the weight and attack of the notes -- while leaving that softly laid underpinning consistent and undisturbed.

When the bass finally does transition from its simple, rapidly repetitive motif to a beautifully spaced and far more deliberately spaced walking line, the tempo picks up even though the notes themselves are more widely separated. The amps effortlessly reveal the change in tempo, the shift from the easy pace of the opening note patterns to the more insistent swing of the ensemble underpinning. But what’s special is the way that the amps manage to trace and reveal that changing relationship between the piano and bass, dealing with each musical strand independently but maintaining the links that bind them. "Snowfall" rises and falls in intensity, it upshifts and reverts, it evolves and develops, it speeds up and it slows down, and each instrument is doing its own thing in its own time. It’s about as rhythmically complex as a short trio piece can be -- but played through the MB-450 IIIs that complexity is laid bare. Rather than struggling to follow the sense of the track, you marvel at the level of understanding between the musicians, the way drummer Vernel Fournier can just lift his background fills to match the new urgency between piano and bass, the way the three instruments respond to each other without ever dropping an awkward note or clumsy step, the way shifts in tempo dovetail so perfectly that notes and bars never clash -- and with Jamal’s penchant for sudden dynamic shifts in the mix, that’s really saying something. This is as intimate as small group jazz -- that most intimate of musical forms -- gets, yet remarkably for such powerful amps, the '450s bring the performance to life, vivid without being forced, uninhibited and unrestrained yet perfectly stable and poised. It’s a listening experience that tells you a lot about the Jamal Trio -- and a lot about the MB-450 III too.

In describing the sure-footed and uncluttered clarity with which the '450s deal with "Snowfall," the word underpinning keeps bubbling to the surface. Key to the '450’s performance is the foundation provided by its unconditionally stable, fully balanced and heavily regulated circuit topology, the platform on which everything else rests. That stability is what provides its innate sense of order and musical organization, the clarity it brings to musical structure, rhythms and phrasing. With the '450s, recordings have a naturalistic perspective and presence that depends on having a place for everything and everything being in that place -- not in the clamped, pinched, over-damped and etched style of so many ultra-definition solid-state designs, but in the way that instruments and voices have a natural position and separation. They don’t overlap, blend, become confused or wander. They don’t crowd the front of the stage or rush it in crescendos. Instead, they stay just where they should be, both in space and in time, no matter what the shifting demands of the music. So when Ahmad Jamal throws in a sudden spray of notes, they don’t drag those soft, pitter-patter bass patterns out of shape. Everything stays just so -- and the magic of the music survives intact. It’s all about the relationships: the relationship between the notes, the relationship between the players. That’s what the '450 IIIs preserve -- and preserve so effectively that you can add more and more notes, more and more musicians or voices without the whole edifice crumbling and crashing down. It’ll get to big and bold, macrodynamic shifts and huge forces shortly, but just for now there’s more to be learnt by staying small.

The other thing that small, intimate recordings tell you about is absolute resolution of detail and the tiny dynamic shifts and inflections that tell you not just what is being played but how it is being played as well. Indeed, when it comes to sheer resolution the '450 is a fair but far from outstanding performer. It doesn’t deliver the absolute immediacy and the sense of contact point and pressure that you get from a product like the Lyra Connoisseur line and phono stages or the Berning Quadrature Z monoblocks. Instead it does something different and, in its own way, just as impressive and once again, found on that sense of stability and structure. The '450 might not resolve as much detail as some other amplifiers, but what is impressive is how it uses the detail it does pass. As I said, this amp has a place for everything and it gets everything in its place. That translates into a sense of concentrated energy, notes that are focused in space and in time, without smearing or bleeding. It also creates music with an effortlessly natural sense of presence and physical substance, solidity and dimensionality.

Rachel Sermanni’s Under Mountains [Turntable World TTWR001] is exactly the sort of album that audiophiles love to pull out when they need to impress their friends. A double 45rpm issue, beautifully pressed on 180-gram vinyl, it contains just over a dozen of those delicate, intimate songs built around female vocal and acoustic instruments. You know exactly the sort of thing I’m talking about: nice simple recordings, dynamic enough to impress, but not enough to get your system into trouble -- all the qualities to create that reach out and touch sound to impress your audio buddies or non-audio neighbors.

Except, Under Mountains is way, way better than the standard audiophile dreck that gets wheeled out on such occasions. This is no "great sound, shame about the music" album; these discs contain honest to goodness songs, performed by people who care -- and it shows. At least it does when you play it on the '450 IIIs. Take the song "Black Current" as an example. Beyond the wry pun of the bittersweet title, this is a carefully layered descent into the emotional risks of deeper relationships. The simple exposed vocal that opens the track, the way the backing builds with the careful addition of each instrument -- this is classic audiophile fare. But the lyrics take a turn to the darker side, the backing becomes fractured, with sudden shifts of tempo and density, and the vocal phrasing cuts across the natural line breaks and rhymes, adding a sense of dissonance. There’s many a high-end system that will make hay with the recording, the dynamic switches and instrumental contrasts -- but how many will make sense of the song? The MB-450 IIIs fasten on the vocal, building the track around the solid core and the lyrical twists. The disjointed phrasing and suddenly hurried lines mark out the pattern of the music, the instrumentation aligning with and reinforcing it. The VTLs might not deliver the last ounce of instrumental definition or resolve the exact space between performers, but the sheer presence and intent, the shape and purpose they bring to the song more than make up for any perceived shortfall. This is real music, from real people with an uncomfortably real message that the system makes it really hard to ignore -- just how it should be.

Likewise the album closer, "Circus Song": the sparse and spatial opening with its sporadic drum beats and simple bass part ushers in a deceptively gentle vocal, but as the track builds, so does the pace, until the singer is almost submerged in the torrent of the music. It’s easy to assume that the system is losing its grip, overwhelmed by the pell-mell energy of the track, but with big VTL monos doing the driving, you know that isn’t the case. This is entirely intentional, a case of the production reinforcing the sense of the song, the vocalist being swept away in the mix. Your system could lock everything in place, kept cool, calm and separate, but then it would be missing the point, and that point is the sense of the song -- which is not to be confused with the simple facts of the sound. The '450s don’t present that perfectly crisp, etched and carved-from-solid sound, devoid of life and motion. What they deliver is far more motive, dynamic and purposeful than that. What they are all about is the sense behind the signal, taking that signal and making it musically effective. After all, what use is detail if it doesn’t tell you anything? What the '450s do -- and do incredibly effectively -- is sort the wood from the trees. So "Under Mountains" might not have that ghostly, translucent "reality" that some audiophiles seek, but what it does have is the ability to move and engage the listener, to hit home and hit home hard on an emotional level. The imaging and presence, separation and immediacy are all impressive enough -- but not as impressive as the message they deliver. This isn’t "reach out and touch"; this is "bringing the music to you."

Okay, I’ve teased you enough. It’s time to unleash the '450 IIIs and let loose that sense of musical excess that lurks beneath the "It’s all about the quality" façade behind which we all hide. Big amps inevitably lead to loud music, like heavy beers lead to a headache the next day, and where better to start than the glorious vulgarity of the Saint-Saëns Organ Symphony? The massive and newly restored organ at London’s Royal Festival Hall has just turned 60, so what better opportunity to let the old lady really misbehave than the Saint-Saëns 3rd Symphony, with a full-roster LPO under the energetic baton of Yannick Nezet-Seguin? Which means that I have recent, firsthand, Row F experience of just how seriously over the top this music is! Turning to the Mehta/LAPO recording on Decca (a pretty substantial "filler" for his Planets on disc 23 of The Analogue Years boxed set [Decca 478 5437] and with the '450s hooked up to the Scala V2s, they do a remarkable job of not just matching the sheer scale and impact, the room-throbbing thunder of this monstrous work, but of keeping the orchestra firmly in their seats. Even in the glorious excesses of the fourth movement, with volumes pushing close to realistic levels, the sonic picture is astonishingly stable (establishing by the by just how effective a substitute solid presence can be for genuine bandwidth). The bass drums and timps are firmly rooted to the rear of the stage, as is the brass, even in the most florid tuttis. No, the '450s can’t match the imperturbable majesty and limitless headroom of the Siegfried IIs, but they get closer than mere mortals (with real-world budgets) probably have any right to expect.

Rest assured, the '450s do loud and they do dynamic. When a musician hits a drum it stays hit, and when an entire orchestral bass section is sawing away then the rumbling weight of their output really will move you, physically as well as emotionally. What all of this tells you is just how important the Series III Signature topology is to the sense of order, scale and structure that these amps possess, how critical that sophisticated and heavily interleaved output transformer is to extending that control and clarity to both frequency extremes.

So, with all that established, it’s time to talk output tubes. The MB-450 IIIs can be can be shipped with either Electro Harmonix 6550C or Tungsol Gold Lion KT88 glassware. But while the tubes might be interchangeable, their sound is not and materially affects the sonic character of the amplifier. Don’t get me wrong, the '450 running 6550s or KT88s is unmistakably the same animal, but the tube choice does affect its balance of virtues. How so? The 6550s deliver a big, warm, weighting and solidly powerful sound that seems to almost propel the music from the speakers. Performances are bold and dynamic swings exhibit enormous weight, power and impact. In contrast, the KT88 is arguably less emphatic at lower frequencies, but possesses greater texture, more air and high-frequency extension. For me that adds up to a more natural sense of musical shape, coupled to greater articulation and greater internal contrasts -- a sound I personally prefer. But -- and it is a very big but -- you may well disagree and so too might your speakers. Drive an Avalon Indra and the subtle textures and rhythmic insights this speaker delivers will thrive on the KT88. Turn to the Wilson Alexia and the sheer coherence and drive of the 6550 will come to the fore. At the end of the day there’s no right answer to this question, just as there’s no one correct setting for the switchable damping factor. The preferred solution will be system and listener dependent, but it is one option that you should be aware of, simply because, under the right circumstances it can deliver a significant benefit. Choosing KT88s over 6550s (or vice versa) won’t make or break the amp or the system -- but it can give it a very real and worthwhile lift.

At this point it might just be worth talking about the various, higher power KT88 "equivalents," most notably the KT120 and KT150. Neither tube is a true equivalent, requiring higher bias settings than the KT88 for optimum operation. They are also taller and, in the case of the KT150, larger in diameter, making it a seriously tight fit under the Series III Signature casework. The KT120 could be physically accommodated, but at this point in time the circuit isn’t designed to accept this tube and currently VTL has no plans to change that. Having worked so hard to create an amplifier that is powerful, stable and reliable, they are well aware that an equally reliable source of consistently repeatable tubes is an essential factor in that process. The KT120 is a single-source tube that comes from just one factory, way too fragile a supply chain for VTL designer Luke Manley’s liking. He prefers to stick with the tried and trusted. That may seem overly cautious when other companies are starting to fit the '120 in particular as standard, gaining what amounts to a free increase in output power, but are you really willing to trade consistency and reliability for a little extra power? It’s a question worthy of serious consideration -- which is exactly what VTL are giving it.

But this isn't the ultimate reason VTL eschews the KT120. Luke Manley: "The primary reason we don't use the KT120 is that we don't find their sound to meet our sonic requirements, with a grainy, forward sound, akin to that of the 6DJ8/6922 series of tubes. The KT120 seems to us to homogenize the sound, such that nuances and fine inner details get masked. There is a suppleness in the sound of the 6550/KT88 that seems to be lacking in the KT120." Incidentally, I’ll be looking at the contrasting performance attributes of various KT88, KT120 and KT150 tubes shortly. I can tell you now that it’s not nearly as simple as you might suppose -- and the power gains that exist on paper don’t always survive the translation into real-life audio circuits.

When I subtitled this section "Walkin’ Tall," I did so for a reason. So much of the MB-450 IIIs’ sound reminds me of the easy grace and quiet confidence exuded by a Jimmy Stewart movie character. Of course, his unshakable confidence and unbending will owed more than a little to having read the script -- and having the script writer on his side. The VTL amps might lack that level of behind-the-scenes support, but then they show no sign of needing it. The sound foundation provided by the Series III Signature platform is all the help the output tubes require. The result is a sound that blends real presence and power with the sort of order and clarity more normally associated with far smaller amps and the stability to draw a really convincing musical picture. For all the effort that goes into the signal, not one bit is wasted. The concentrated presence of the '450s comes from the effectiveness with which they harness their massive power potential to the job in hand. There’s no spurious detail or puff and bluster here -- things that can sound initially impressive but ultimately detract from the music. Play music that is delicate and depends on fragile interplay and big as they are, the '450s seldom overstep the mark. Play music with attitude and they back the performance to the hilt and, as we’ve seen, play huge orchestral pieces and these amps meet the challenge head on, bringing their sense of structure and dynamic control to the job, as well as their considerable headroom.

But if one album really sums up their capabilities it is Jackson Brown’s Running On Empty [Asylum 6E-113]. These live tracks are recorded in venues and situations as varied as the back of a bus, rehearsal spaces, hotel rooms and stadiums -- and in one case transition from a bedroom to live on stage. It’s a musical collage that demands nuance and intimacy at the smaller end of the scale, power, presence and a sense of space at the other extreme, as well as the ability to transition from one to the other without destroying the flow and continuity in the performance. Play "The Road" and the shabby, poignant sense of waste and loneliness in the lyrics is perfectly balanced against the understated backing of guitar and fiddle, the hotel-room acoustic locked between the speakers, the size and dimensionality of the image adding to the convincing presentation, adding access to the performance. Yet, as the venue migrates to the Garden State Arts Center Auditorium the acoustic simply seems to expand, first across the audience and then across and above the stage as the full weight and body of the band pick up the song. The '450 IIIs make what might be an awkward and disjointed shift appear utterly natural, testament to the skill of the engineers and producer, a decision that adds to the song rather than distracting or confusing the listener, as so often happens. Few amps make this transition make sense, spatially or musically; even fewer manage it with the poise and confidence instilled by the '450s. But the thing that really matters is not that the amps don’t stumble; it’s that the result is better music and a more convincing performance, factors that are at the heart of what makes these VTL amps so musically compelling.

The ability to work successfully with speakers that, for all their assets, are also adept at exposing weaknesses in driving amplifiers; their confidence with different musical genres and scales of performance; their placement of the musical performance front and center in proceedings: these are the attributes that make the MB-450 IIIs both supremely capable and so musically satisfying. Describing a product as a great all-rounder carries the whiff of compromise -- Jack of all trades but master of none. What the '450 offers is an almost preternatural sense of balance. It has enough power to drive most speakers at a price that is still (sort of) approachable. It has phenomenal musical integrity and a sense of ordered structure that make music both intelligible and engaging. It is versatile, reliable and tractable in use. But above all, it is that rarest of audio animals -- a keeper. The MB-450 IIIs cost you, but then once you’ve got them they’ll be in your system for a long, long time -- and in an industry where equipment turnover seems to be accepted as an unfortunate and expensive fact of life, that makes them a bargain. The '450s are survivors. They have survived in VTL’s range for several decades, evolving and upgradeable to the latest spec. They’ll survive changes in speaker (without limiting your choice) and changes in the system or room. They’ll survive evolutionary transitions in your musical taste and preferred source. But most of all they will, quietly and confidently, allow you to enjoy whatever music you choose, emotionally and intellectually. That makes the '450 a great amp to have in your corner -- a great amp to have in your system.

Squaring up to the competition

ore often than not, reviewing a product means placing it not just in the context of the system in which it will work to best advantage, but also in the context of competing products from other manufacturers. But in the case of the VTL MB-185 III and MB-450 III monoblocks, perhaps their sternest competition comes from within the VTL family. With so many similarities and yet such important distinctions, the most obvious alternative facing an MB-450 customer might well be the MB-185 -- and vice versa.

Now, high on the list of business "don’ts" are: don’t confuse your customers and don’t cannibalize your own sales. With those two caveats in mind, it might seem like an odd thing for VTL to do, offering both the '450 and the '185 in outwardly identical housings -- especially as the '450 allows customers to pretty much double the rated output for around a 20% upcharge. But that is to underestimate the impact that choice of output tubes have on the sound of an amplifier and the true (musical) costs of power. Indeed, rather like bass, the only thing that is worse than not having enough power can be having too much. So just what are the differences between these two amps? Which should you choose and why?

Time for a detailed comparison. Let’s start by using the Focal Scala V2 speakers -- which are, remember, a perfect partner for the MB-185 IIIs -- and the Marzendorfer/RSO Berlin recording of the Rodrigo Concert-Serenade for Harp [DGG SLPM 138118]. Not as well known as the Concierto de Aranjuez, this piece was written in 1954 and like the more popular guitar concerto, it follows a fast/slow/fast structure, contrasting quicksilver cut and thrust with a more contemplative central section. The '185s revel in the rapid instrumental interplay, the explicit dance rhythms of the opening movement, the more subtle exchanges between harp and guitar in the second. The joyous chaos of the carnival, the almost Gershwin-esque intrusion of car horns, the call-and-response structure between different groups of instruments -- all is characteristically Rodrigo, this most pictorial and impressionistic of composers (despite his blindness). The '185 IIIs never lose their way or their footing, the agile fingering of the harp and ostinato underpinnings unmistakable as Rodrigo’s work.

In swapping to the '450s the first and most important consideration is to move the speakers -- in this case, forward by around an inch. Why? Because the bass weight and extension of the '450 changes the spectral balance of the system sufficiently to make repositioning the speakers critical. Leave them perfectly placed for the '185s and hook up the '450s and the resulting sound will be heavy, slow and congested -- because the speakers will be too close to the rear wall. Of course, the same is true in reverse. Get the speakers just so with the '450s and the '185s will sound thin, lightweight and hurried. In fact, speaker positioning is a consideration you need to include every time you swap any major component in your system -- from a cable to a source component. They don’t all have the same sort of impact as the '185/'450 swap, but they will all change the spectral balance to some degree. Yes, you need to make single, repeatable changes -- but you also need the system to be working right in each case if you are going to make a valid comparison, a point these two VTL amps ram home with aplomb.

Get the speakers positioned properly and the heaviness that you start with recedes, replaced with a grounded authority and sense of purpose. The '450 IIIs deliver a more measured and arguably more substantial performance, dialing back the brilliance and ramping up the scale. The juddering bass passages take on a new tension and dark, almost menacing quality, the orchestra gains presence. But at the same time, the sheer fluency and immediacy of the '185s has been diluted. The easy conversations between (and separation of) the guitar and harp merge, creating at times a composite that has more of the harpsichord about it -- that combination of tinkling attack and body -- than the careful combination and contrast between the two different instruments.

But the biggest change is in the mood or atmosphere that surrounds the performance. The '185s offer a view that’s full of air, brilliance and light, sharp planes, angles and contrasts. The '450s are a more brooding, stolid presence, full of swelling power and a majestic stability and poise. Throw in those brass interjections and it’s fair to say that the '450s, in this instance, are more American, more reminiscent of Gershwin, while the '185s offer a performance that is unmistakably, quintessentially, Spanish in origin.

Now, I can change the music and you might think that that would alter the balance of virtues between the two amplifiers. But this isn’t a rock or classical, big or small, acoustic or electric conundrum. This is all about musical engagement, communication and the sense behind a performance. It’s all about the amp and speaker working together to step above the simple fact of the performance and into the realm of art -- because that’s what music is. On an artistic level, you’ll simply hear more, see further and appreciate the performance more deeply using the Scala V2s with the '185s rather than the '450s -- whether we are talking Leonard Cohen or Leonard Bernstein, Elvis Presley or Elvis Costello. Even the massive dynamic demands and sheer scale of the Gravity OST carry more drama and tension with the smaller amp. You might think that the Rodrigo’s rapid sprays of plucked strings play to the speed, transparency and immediacy of the '185, but there’s scale and dynamic swings, sudden crescendos and shifts in orchestral density too -- demands to challenge the amp’s stability and headroom -- and the '185s meet them all without fuss or bother. That’s the key: the blend of bandwidth and electrical demands presented by the Scala V2 is a near perfect match for the '185s available power and load tolerance, allowing them to work well within their comfort zone. The fact that the amplifiers’ lucid transparency and agility match the speakers’ characteristics too simply elevates the partnership still further.

But what happens when you step beyond those limits and things get a little less cozy? Enter the Wilson Benesch Square 5, a speaker that, whilst it’s still not a superbly awkward load, has nearly twice as many drivers as the Scala and locates two of them, isobarically arranged, pointing straight at the floor. It’s a topology that creates a surprising combination of weight and bandwidth from a speaker at its price (£8995 per pair), characteristics that value power and control if they are going to pay off. Add in the self-damped nature of the drive units and absolute immediacy will never be top of the agenda. Instead, the hybrid acoustic/electrical crossover and material consistency favor body and coherence. With the same positional caveats outlined above -- only even more critically in this case, given the bass reinforcement delivered by the floor -- I settled down to the same comparison with the two VTL amps.

Playing the '185s produced a strangely hesitant and disjointed performance. The fingering on the harp, the flow of its melodic lines, was at once smoothed off but strangely clumsy. The tonal brilliance and speed of the note runs were diminished, their attack and angular ripostes diluted. The orchestral underpinnings lacked conviction and the ostinato passages lacked drive. Even the slow movement, with its delicate finger work and nuanced musical conversation, lacked precision in its note placement, the way it interlocked the phrases, again robbing the playing of drama and tension.

Switching to the '450 IIIs after that was a revelation. Suddenly the playing took on purpose and intent, a sense of body and coherence that added to (rather than slugged) the musical intensity of the event. The separation of harp and guitar was clear, their interplay built on a single rhythmic foundation. The orchestral backing gained dynamic graduation and a sense of power abutted restraint, carefully balancing the fragile solo instrument. The dance rhythms of the opening movement were defined with a sure and certain step, the contrast to the slower second movement more marked and more effective, while the dynamic, tonal and rhythmic demands of the third movement built to a complex and impressive concluding crescendo. This was a very different but no less Spanish and barely less effective musical perspective than that offered by the Scala V2/'185 pairing. Big, bold and rich in color and pageantry, it might not be as quick or agile, sun-splashed or dazzling as what the '185s deliver, but it has its own earthy warmth and ruddy tonality. Where the Scalas and the '185s conjure the light and air, the Square 5s and '450s bring the landscape and the atmosphere.

So which is right? That’s where the listener (along with his musical tastes and biases) comes in. Let’s also put these comparisons into perspective: I’ve deliberately matched and mismatched speakers and amps. Ultimately, the junction between amp and speaker is the most critical in the system. Getting it right will be crucial to overall performance -- which makes it all the more astonishing how often you hear systems that have gotten it so badly wrong. A great amp and a great speaker do not necessarily make for a great combination. The whole point of this exercise is to show how speaker choice can make or break the performance of these (or any other) amplifiers.

Which brings us to the contrasting virtues of the MB-185 III and MB-450 III. In absolute terms the '185’s EL34s carry an edge in terms of immediacy, transparency, textural quality and contrasts, the easy, open separation of their midband clarity and the deft lightness of their rhythmic touch. They reproduce the structure of the performance and the musical relationships within it with a lucidity and almost tactile precision that is fascinating and engaging in equal measure, but -- and it’s a very big but -- only if you have the speakers that let them. In contrast, the '450 has a power margin and sense of musical authority that allows it to handle far more awkward loads with an easy grace, a potent low-frequency weight and extension to make the most of really wide-bandwidth speakers. Each excels in its own field.

So, which amp is better isn’t the question. Instead, you should ask which amp is better for you. That will depend on your choice of speakers and also on what kind of listener you are. If you have -- or will have -- Scala V2s or Avalon Indras, then the '185s are the amp for you. But if you lean towards the bigger Focal Stella Utopia (with its twin midrange drivers and the potent potential of its EM bass unit) or the Wilson Sasha 2 or Alexia, then you should probably look to the MB-450s. But also ask yourself whether you are the sort of listener who sticks with a system or twists? If you make a plan and pursue it, then opting for the '185 and a chosen partner (even if you don’t buy that speaker immediately) makes perfect sense. But if you prefer to churn your equipment, choosing each purchase from what’s new and what’s rated right now, then the '450’s sheer versatility, its ability to work with a wide range of matching speakers (not just because of its power but because of the output tube options and switchable damping factor too) are hard to ignore. Given just how critical the relationship between amp and speaker really is, in an ideal world it’s a pairing that should always be considered and planned as a single entity. But then we all know that life isn’t like that.

Summing up

TL’s MB-185 III and MB-450 III ably demonstrate the practical and musical benefits and tractability of the Series III Signature platform. Both are more versatile and more capable, more musically stable and engaging as a result -- meaning that you as an owner have more chance of realizing more of their performance. But in absolute terms, the MB-450 IIIs are the more adaptable of the two, combining that with serious musical scale and authority capable of delivering a commanding performance from even the biggest and most demanding speakers. Sure, Siegfried IIs or the S-400 II will take things a step further, but just because they can, it doesn’t mean you have to and the '450s can create some seriously satisfying pairings with many of today’s most highly rated audiophile speaker designs.

The MB-185 IIIs might lack the sheer grunt that comes from the '450s, but they more than compensate with subtlety and musical virtuosity. In this case, their adaptability is more about optimization and achieving maximum performance, rather than maximum versatility, and carefully executed with the right partnering speaker the results are genuinely extraordinary. Able to satisfy on both a musical and an emotional level, they don’t just justify VTL’s decision to offer the EL34 in the Series III Signature chassis, they can elevate the results possible from that topology to a whole new level.

Once again, we discover that in audio, there are few if any simple answers. What you have here is two excellent amplifiers. The difference between them delivering musical results that are very good or truly great comes down to how you use them and what you use them with. In this case, a little self-knowledge goes a long way. Be honest with yourself and one or other of these amps might just be the pot of gold at the end of your own audio rainbow.