Thursday, May 26, 2011

S6 - Irresistible Force

Gutsy sound

Like most modern amplifiers, the S6 keeps things simple. It offers five unbalanced line inputs, a set of tape outputs and a single set of loudspeaker outputs. There’s no built-in phone stage and no socket for headphones. The volume and input selector knobs have a nice solid feel and the amplifier comes with a handsome wood-clad remote control that looks like a late ‘80s mobile phone.

Six El 34 output tubes are used (three per channel) along with a pair of ECC 82s. Each output tube features user-adjustable bias and there’s a moving-coil meter to help the value to be set correctly.

Crisp dynamics

The S6 produces a very rich smooth alluring sort of sound that is found immediately likeable. It delivers a big weighty sort of presentation that’s full-bodied and solid. There’s something ‘right’ about the combination of incisive clarity and rich pungent depth it offers.

At the same time, bass and treble extremes remain beautifully balanced and integrated, so that the higher frequencies never ‘lead’ the midrange and bass. The bottom end is clean and firm – maybe not quite as deep and powerful as certain direct-coupled transistors designs, but solid and weighty when it counts and free smearing and boominess.

Absolutely gorgeous

Unison Research’s S6 sounds absolutely gorgeous, delivering that sweet glowing richness that tubes are famous for, without loss of bite or immediacy. Indeed, it’s the combination of silky smoothness and crisp immediacy that is so alluring.

S6 is one of those tube amps that’s very good at covering its tracks. It recreates the music with little sense of strain and sounds as though it has power to spare.

Wednesday, May 11, 2011

TAS Editors Choice Awards 7 to PSB

Leading audiophile magazine, The Absolute Sound, honours PSB Speakers with a total of seven awards for loudspeakers and subwoofers in its annual Editors' Choice Awards. Reviewer Neil Gader is left questioning, "How does he do it?" as Paul Barton continues to introduce outstanding speakers. PSB scooped up awards in multiple price categories, cementing our reputation for designing high-value, high-performance speakers.

Loudspeakers From $3000 - $5000

PSB Synchrony Two

A sonic extrovert, with dark voluptuous tonality, the Synchrony Two Tower offers bone-rattling dynamic exitement in a sleek, four-driver, two way, bass-reflex design. Two of its woofers high-pass to the tweeter at differing frequencies, giving this PSB marvelous coherence and extension from bottom to top... Neil Gader, Issue 177

Loudspeakers From $2000 - $3000

PSB Imagine T

Tonally neutral and Dynamically turbocharged, this short, two-and-a-half-way Tower offers a balance of audio virtues that is classic PSB. from the vivid midrange to the powerful midbass, nothing seems out of joint - and that goes for the Imagine T Tower Loudspeakers seamless curvilinear enclosure. Not as nuanced as the Synchrony but more then good enough to make you feel like a big spender. Neil Gader, Issue 189

Loudspeakers From $1500 - $2000

PSB Synchrony Two B

Another Brilliant two-way compact from Paul Barton and crew. The "mini-me" to the larger Synchrony Two Tower, the Synchrony Two B Bookself Loudspeaker is more of a classic "voice" speaker and windfall for chorale listeners and singer / songwriter aficionados. Capable of solid 60Hz extension... Neil Gader, Issue 177

Loudspeakers From $1000 - $1500

PSB Imagine B

Think Imagine T Minus a midbass driver and a floorstanding enclosure. There's the same voice in the expressive midrange and treble and, with only minor exceptions, the same superb balance. The B can't quite quite chew on bass lines like the Imagine T loudspeaker can, but as if to compensate the B seems a bit lighter and fleeter of foot in the upper mids and lower treble. Neil Gader, Issue 189

PSB Image T6

Paul Barton's latest creation again sets a standard for performance in this class. The Image T6 Tower Loudspeaker's dual 6.5" woofers deliver realistic bass down to 35Hz (-3dB) coupled to a very clean, pure, transparent midrange. The bass tends toward the warm and "boomy" rather then dry and tight site. The treble is clean and extended, albeit with a bit of exess energy. Th Image T6 Tower Loudspeaker's low-diffraction cabinet has paid off in outstanding imaging; the Image T6 Tower Loudspeaker's easily disappear into the soundfield. Robert Greene, Issue 200

Loudspeakers Under $500

PSB Alpha B1

Yet another "how does he do it?" loudspeaker from the prolific mind of Paul Barton. The new, more curvaceous Alpha combines mind-bending dynamics and rich mids in a speaker barely a foot tall. Even the midbass has power and pitch definition rare in this modest price range. Neil Gader, Issue 170


PSB SubSeries 5i

At this point no one should be surprised at what this Canadian speaker company can do in the lower-price range. Even so, the performance of this econo-sub is semi-unbelievable. Extension, dynamic slam, and good musicality from this 10" bass-reflex design make it the perfect match for misers with the Midas touch. Neil Gader TPV Issue 48, and CM, TPV, Issue 69

Tuesday, May 3, 2011

VTL MB-450 Series III Signature monoblock power amplifier

The VTL MB-450 series began life in the late 1980s as the Deluxe 300, a pair of which I once owned. Over the years the basic design has been improved and modified, in the forms of the MB-450 (1996) and the MB-450 Series II (which I reviewed in January 2008). The tube complement remains the same: eight 6550s in the push-pull output stage, a 12AT7 input tube, and a 12BH7 driver. Into a 5 ohm load, the MB-450 III is claimed to produce 425W in tetrode mode or 225W in triode, from 20Hz to 20kHz.

The Series II added VTL's Smart Tube technology, also found in the company's flagship Siegfried line. This optimizes tube performance through the use of logic-controlled auto-biasing, which continually monitors each tube, and adjusts its bias on power-up as well as when the system is idling. It also includes a diagnostic system: If a tube malfunctions, the amp indicates that with an adjacent LED and shuts down if the tube draws excessive current.

VTL's goal for the Series III Signature revision was, first, to improve the MB-450's ability to better drive a wider range of loudspeakers. These changes include a redesigned, fully balanced differential input stage driving a differential phase splitter, and a lower-impedance push-pull output stage terminating in an output transformer that is now fully balanced, and claimed to be "dramatically improved." The Series III also has a shorter, faster, fully balanced negative-feedback loop. VTL claims that this circuit completely eliminates ringing and maintains phase integrity without using capacitor compensation.

Precision-regulated power supplies for the output tubes' bias supply and screen voltage maintain the tubes' operating-point consistency, even when the AC supply fluctuates. VTL claims that this produces tonal stability and "sonic integrity" in the reproduction of complex, dynamic signals.

A front-panel button allows the MB-450 to be switched between tetrode and triode operation for the output tubes. Although there is a Mute button, switching the operating mode can be performed without having to mute the amplifier. The four settings of the Damping Factor toggle switches behind the glass window on the front panel vary the MB-450's output impedance by changing the amount of negative feedback in the circuit. The Low setting minimizes damping and to produce the "most natural sound," per VTL, while Med (Medium) has a minor impact on the overall sound but produces somewhat better speaker control. The Hi setting further improves speaker control, but has a greater impact on the sound; and Max applies the iron fist of maximum feedback, but with a noticeable negative sonic impact, according to VTL.

VTL claims that the addition of pricey premium Mundorf silver-oil capacitors produces a sweeter, more extended top end, a more relaxed-sounding midband, and superior midbass control. An MB-450 Series II can be upgraded to Series III status.


The Series III looks very similar to the Series II, with one significant exception. Now, to access the tubes, instead of removing the entire cover, which was unwieldy, VTL has cut from it a pair of small L-shaped sections directly above the output tube sockets, making them far easier to remove and replace.

Otherwise, with its gracefully curved front panel of matte brushed aluminum and tinted glass, the MB-450 remains a substantial piece of kit built to an extremely high standard—which is what you should expect to get when you plunk down $18,000 for a pair of them. The beefy speaker terminals can take a hard torqueing, and everything else on the rear panel, as well as what's inside, is industrial grade.


While VTL's instructions suggest that unpacking each MB-450 Series III Signature is a two-man job, I managed it myself (thanks to the gym). No doubt your dealer will do this for you, but if not, be careful. Not only does each amp weigh 93 lbs, but because its transformers concentrate most of its mass in the rear, lifting and carry can be awkward and tricky.

The manual is usefully detailed, helpful, and informative, but sometimes makes the simple seem complicated: "For the MB-450 amplifier, there should be a total of 8 sockets for the output tubes. . . ." Should be? Is someone at VTL worried that a tech might have omitted a few sockets?

The output-tube sockets are numbered 1 through 8, but all of the 6550C tubes, which were separately shipped in another box, were labeled "#2," while two spares packed with the amps were labeled "#7." This caused some confusion, particularly as the instructions tell you to "Insert the output tubes into each of the output tube sockets from tube #1 to #4 on the left side of the cover and 5 to 8 on the right side of the cover."

VTL's CEO, Luke Manley, told me that the manual was written by his wife, Bea Lam, who feared that a more direct tone would sound bossy. I say go for it, girl! Don't be afraid to write: "Remove the covers and insert output tubes into the eight sockets." We'll know not to insert more than one in each socket. Of course, the auto-biasing circuit makes matching the tubes irrelevant, a point Manley reiterated when he visited my listening room to make sure everything was going well. Why even mention the socket numbers?
Manley had brought along four spare B+ fuses, and extra input and driver tubes. Better to be prepared in the event of a tube failure, in which case the MB-450's microprocessor-controlled design helps ensure that, at worst, you'll be replacing a tube and a fuse instead of shipping the amp back to the factory for more extensive and expensive repairs.
The MB-450 Series III Signatures were in my system for three months, during which we experienced a severe windstorm; the power came and went, and there were many brownouts. The amps proved completely reliable; they ignored the brownouts, while each interruption of power caused them to revert to Standby mode.

Pushing the Power button turns the amp on. Hitting Mute both mutes the input and draws down tube current to a trickle. VTL suggests leaving the amps in Mute mode overnight, if you plan on listening the next day. Then, on startup, they'll be warmed up and ready to go. For extended non-listening periods, hit the Power button to completely shut down the amp. From a cold power-up, don't expect the MB-450 III to sound its best for an hour or so.


Luke Manley switched among the four settings of the Damping Factor control so I could hear the results of each from my listening position. Low sounded too sloppy for my tastes and my Wilson Audio MAXX 3 speakers, but Med tightened things up nicely. The other positions sucked the air out of the room, so Med it was. Your preference may vary with your taste and speakers. It's nice to have the flexibility.

Going from a megawatt solid-state amp to a powerful, competently designed tube amp no longer produces a seismic sonic shift—at least in tetrode mode. In fact, there was somewhat of an unexpected role reversal. Forget about warm, soft, rolled off—the MB-450 Series III's top-end extended smoothly out to the highest reaches. By comparison, my big Musical Fidelity Titan reference sounded somewhat less exuberant in the high treble, if equally refined.

Overall, in tetrode mode, the MB-450 Series III ran a fast, tight, lean, rhythmically nimble ship—the opposite of what "tube sound" is supposed to denote. Running the amplifier in triode mode did indeed produce the soft, tubey sound some like, but I don't. I ran the VTL in tetrode throughout the review period.

Do you like gobs of air and superior spatial projection? Do you like it when everything floats effortlessly in space, freed from the confines of the speakers? The MB-450 IIIs did that with ease. Their top end was as generous and expansive as you'd expect from the best solid-state amps, with unusually fast, precise attacks, but without any of the grain, glare, and etch that often accompany those attacks in the solid-state realm. The MB-450s didn't miss a molecule of air or a single cymbal rivet. VTL's specs show flat response to 20kHz. I believe it.

The clarity, transparency, and physical refinement of the VTL's reproduction of high-frequency transient information produced realistically sharp edges—the kind I don't normally associate with "tube sound," or with all that much solid-state sound, either. The MB-450's sustain was what I do expect from tubes: extended and expansive, with overall decay structures that were graceful and generous, even if the fade was more to dark gray than to the black you get from the best solid-state amps. I'd noticed this quality of the MB-450 in VTL's room at the 2010 Consumer Electronics Show, and now I heard it in my listening room.

Classic Records' reissue on nine single-sided, 200gm, 45rpm LPs of The Royal Ballet: Gala Performances, with Ernest Ansermet conducting the Royal Opera House Orchestra (RCA Living Stereo/Classic LDS-6065), puts the listener in the airy space of Kingsway Hall, the orchestra arrayed on an ultrawide and ultra deep stage. This recording lets me hear into the stage's deepest recesses, and layers ranks of instruments from front to back with great precision, and the MB-450s reproduced all that it offers.

The MB-450 III's crystalline finesse in the treble never ceased to excite. Cymbals, bells, and celeste were reproduced with effervescent precision and sophistication: tiny when appropriate, but always precise. It's almost impossible to go ice-crystal precise on top and not pay a price in terms in the richness of string tones lower in the audioband, but the MB-450s managed a fine, realistic sheen on massed and solo strings alike, producing an ideal balance of bow on string and the resulting woody resonance.

Like the Series IIs, the Series IIIs produced "enhanced holographics" compared to my current reference amp, the Musical Fidelity Titan, which couldn't match the 450's airy expansiveness. While the VTLs' reproduction of space was more generous and their soundstage wider, deeper, and more vivid, it was never bloated, nor were images on that stage diffuse or lacking in weight or body. Still, the solid-state Titan was superior in the latter regard, producing greater body and weight and, especially, image solidity. Which you'd prefer would be a matter of taste.

Like the MB-450 II's, the III's low-frequency extension was seemingly complete—deep, solid, and especially well controlled—with the result that the sound of the III was rhythmically nimble and texturally revealing. It gave ground to the MF Titan in terms of bass weight and, especially, bass dynamics, where it seemed lighter and somewhat more polite, and less able to produce visceral, stomach-slamming drive. Of course, one listener's "drive" and "weight" are another's "sludge."