Tube Power Amp Reviews

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.

Sound
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."