VTL MB300 & MB450 Signature monoblock amplifiers Michael Fremer 1999
Whenever I switched to the Conrad-Johnson Premier Twelves from the far more powerful VTL MB450s, I never felt as if I was losing dynamics, authority, or control. In fact, the C-Js sounded faster, tighter, and punchier overall, particularly on the bottom—like bouncing a quarter on a bed made with hospital corners instead of one whose sheets have merely been tucked in. The Twelves elicited the best bass I've gotten from the Audio Physic Virgo speakers.
The VTLs created a bigger soundstage and did a better job of giving the listener the sense of being in a large space—when that was the venue. The C-Js excelled at focusing images throughout the soundstage, and at delineating them from the reverberant backdrop. Overall, the 450s sounded warmer, riper, and more laid-back, particularly in the midbass—which may account for much of the difference in soundstage size. The Premier Twelves were faster, tighter, and more forward, but never sounded edgy or bright.
Both amps sounded accomplished, and neither committed any serious errors. Neither suffered from grain, etch, or electronic artifacts of any kind. Both are likely to please most listeners, but in different ways. The Premier Twelve clearly had the edge in excitement and rhythmic drive. The C-J and VTL don't sound alike, but the differences aren't in the same league as the differences you'll find between speakers or phono cartridges.
Yet when I switched from the C-Js to the VTLs and replayed Neil Young's "I Am a Child," the VTLs disappointed—they slowed the pace, took some snap off the snare and kick drum, and reduced the delineation between the images and the ambience behind. Moving to Gershwin's Concerto in F, though, the VTLs better suggested the hall, and offered a slightly more diffuse presentation that some may find more akin to being there live. As one manufacturer said to me about an update of an unrelated product, "You know what? I like the original version better. I go to a lot of live concerts, and live, you don't get that kind of focus."—Michael Fremer
Michael Fremer wrote again about the MB450 in April 1999 (Vol.22 No.4):
Is Vacuum Tube Logic's MB450 a "new" product, or an upgrade of the MB300? "New!" said VTL's Luke Manley, lobbying for a full review. But since the 450 is essentially a 300 with a new, far more sophisticated output transformer, cleaner circuit layout, improved parts, better build quality, and more graceful cosmetics, our decision was to do a Follow-Up.. This should actually redound to VTL's credit: ongoing refinement grants a confidence-building air of continuity. At least that's what I think.
Like the original late-1980s VTL 300, the MB450 uses eight 6550 output tubes (now sourced from Svetlana) in place of the NOS GEs used on the original. A later version of the 300 substituted the somewhat brighter- (some would say edgy- and glary-) sounding KT90 output tube, and added a front-panel meter for convenient bias checking and adjustment that gave the amplifier the look of a laboratory instrument.
The meterless 450 shares the rest of the VTL amplifier line's understated cosmetics and boxy, "industrial" geometry. Nothing flashy, but not unattractive. Only owners of the original 300 will truly appreciate the subtle but significant changes Luke Manley and his design team have made to the amplifier's construction.
With the original 300 I reviewed almost a decade ago for The Abso!ute Sound (and reviewed in Stereophile, October 1988, Vol.11 No.10, by J. Gordon Holt, with a Follow-Up by Russ Novak in July 1996, Vol.19 No.7), the main circuit board was attached to the chassis via a pair of standoff pillars that left one side of the board loose to flap around in transit. Exacerbating the situation was a small transformer on the board's untethered end that made it flex like a diving board. When my review sample arrived, the filaments didn't glow on one 6550. Removing the chassis bottom, I found that two wires had been ripped from the tube socket by the flapping board. Not a great way to commence a review!
When I removed the MB450's bottom cover I found a cleaner, much improved layout on a higher-quality board, with broad traces connecting better parts, including large polypropylene caps. In place of the original's tangled wires were crisply routed, nylon-tied harnesses. The board itself was well secured to the chassis, and the soldering had been done neatly and with care. So while I understand the schematic probably hasn't changed all that much, the execution takes the product to a much higher level of quality.
The original 300 I reviewed did not feature a fused B+ rail, which meant that a blown output tube could take out board components. The MB300 added that protection, and the MB450 has it as well, along with an XLR input jack for convenience's sake—it's wired directly to the pins of the high-quality, gold-plated RCA jack.