Tube Power Amp Reviews

Sitting in my usual seat at the center of Avery Fisher's 20th row, I concentrated on the sound. When I got home, I played the Milstein LP, which proved far quieter than the coughing and choking accompaniment provided by the hall full of alter kockers earlier that evening. The first thing I realized was that I'd had the system cranked up way too high during previous listening sessions to ever realistically reproduce the sound of a concert as heard from that hall's 20th row. Turned down, the system achieved remarkably believable, lifelike sound from this disc, though Milstein had been purposely spotlit to a greater degree than you'd ever hear in concert.

However, the instrumental textures produced by the MB-450s, particularly the "softness with speed" quality of the strings, was remarkably lifelike, though the overall sound was somewhat more vivid than the "solid-state" sound of Avery Fisher Hall itself—which is named for a man who made his fortune building tube gear.

A matter of reliability
During the months the MB-450s were in my system they proved totally reliable, though all of their tubes were not. Though Luke Manley may not agree, this was a good thing—it gave me an opportunity to put myself in the shoes of anyone considering buying these amps. The LEDs of the MB-450's diagnostic circuits can tell you when there's a power fault (fuse) or a variety of tube faults. I'll spare you the details, except to say that the system automatically zeros in on the defective tube by illuminating the LED next to it. It also tells you whether the fault is excessive current draw (in which case the amp also shuts down), or low or no current draw (in which case it continues to play).

Once during the two-month review period, one MB-450 failed to power up. Its Mute LED began to rapidly blink red, indicating an excessive current draw that the auto-bias system was unable to cope with. A rapidly blinking green LED next to one of the output tubes identified the culprit. It needed to be replaced.

Removing the cover led to my only complaints about the VTL MB-450 Series II Signature. First, the use of Phillips-head screws doesn't strike me as a good idea. The heads are too easily stripped, and chances are, with eight output tubes, that cover's going to be coming off more than a few times during the tubes' expected lifespan. Hex-head screws would be better.

Furthermore, removing the top cover also requires removing the 11 screws—nine Phillips and two hex-head—that secure the front panel. That's a lot of screwing, and not the kind I like. Putting the front panel and cover back together proved a bit of a jigsaw puzzle in terms of aligning the holes in the cover with the holes tapped in the chassis. A hint: Don't fully tighten any screw until they're all screwed in a bit (footnote 3).

Other than getting the cover off and finding plastic tube sockets—which, over time, can deform more easily than ceramic ones—I have no complaints about the VTL MB-450 Series II Signatures. In fact, I loved them. I miss them already.

Conclusion
After the MB-450s had left the building and my Musical Fidelity kW solid-state monoblocks were back in the system, I had a listen. The sound was very different from what I'd got used to in my two months with the VTLs.

The kWs' soundstage was more compacted, but was more solid and better focused than the VTLs'. Everything tightened up but much was lost, including the grand, floating sensation I'd experienced with the VTLs, the gloriously transparent midrange, and the harmonic richness (which some would call third-harmonic distortion). The kWs' bass was tighter and punchier, but I wouldn't call it "better." It was a different but equally compelling sound.

The MB-450s never sounded restricted or strained, but when you're used to more than 1000Wpc, it's difficult to cut that to less than half—even if, subjectively, tube amps tend to sound louder and more powerful than they actually are. I'm sure a pair of 800Wpc VTL Siegfrieds would really light up my system, literally and figuratively, and provide the full dynamic expression I've grown accustomed to with the Musical Fidelitys. But the MB-450s came close enough.

When I played the Tchaikovsky concerto via solid-state, Milstein's violin retained its supple, transparent sound, but was somewhat more restrained harmonically, and recessed within the stage. The same was generally true of the strings, and the entire picture receded farther back on the stage and took on a slightly cooler cast. The kWs' solid-state sound was actually more true to what I'd heard at Avery Fisher Hall, while the VTLs' picture was richer, grander, more involving. Then again, no one says great things about Avery Fisher's cool, dry sound. Perhaps, had I heard the concert at Carnegie Hall, I'd be saying the VTLs sounded more correct.

With my solid-state amps once again settled in, I'm more than satisfied, though I miss certain aspects of the VTLs' performance, and could be happily living with them as well. Maybe I'm too easily satisfied—but I think it's more about how well the VTLs performed in my system than about how easy I am to please.

When you consider that the MB-450 Series II Signatures cost a bit more than half the cost of the Musical Fidelity kWs, that says a lot for the VTLs. They are yet another indication that while tube and solid-state electronics each have their own sonic signatures, the gap has narrowed considerably—and, thanks to VTL's auto-bias circuitry, maintaining consistent sonic performance from tubes could hardly be easier.

The VTL MB-450 Series II Signature monoblock power amplifier is easy to listen to. It's even easier to recommend.

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Footnote 3: I learned that working on cars, but how many audiophiles have done that? How many Jews, for that matter? I'm probably one of six Jews outside Tel Aviv who's done his own car work and probably one of fewer audiophiles. How many instruction manuals offer that hint? None.