VTL ST-85 power amplifier Page 2

Inside, it's a classic "keep it simple" VTL design, using a pair of EL34 output tubes per side in a tetrode configuration (footnote 1). (Unlike some of the higher-priced and -powered VTL models, the ST-85 can't be switched into triode mode.) Four 12AT7s wrap up the tube complement.

The output transformers aren't the Signature models found in VTL's higher-priced amplifiers, but they're similar (though simpler) in winding layout and construction—and, of course, smaller. Removing the metal cage that protects you from the tubes (and vice versa), one finds bias-measurement points and trim pots. Adjustment is straightforward, and is profusely explained in the owner's manual.

The power of one
Initially, I didn't see why Luke was concerned about the power provided by a single ST-85 except while driving the Joseph Audio RM-7si speakers. The bass is the place where a lack of power is most often felt. The littlest "Joe Audio" monitors aren't the last word in the lowest octaves, but they do manage to reach down lower than one would suspect, and said reach wasn't limited or dulled by the ST-85.

A quick bass-is of comparison was established with the 150Wpc Audio Alchemy OM-150 solid-state amplifier. The ST-85 produced less prominent low- and midbass, which is to call it more accurate. (The OM-150 tends to be a little overwarm in the bass.) The ST-85 also exerted more control over the bass. Such results run counter to what one expects when comparing a lower-powered tube amplifier with a higher-powered solid-state model—to the ST-85's favor.

Listening to "Cumbanchero," from the outstanding you-are-there-and-"there"-is-Havana Introducing...Ruben Gonzales (CD, World Circuit/Nonesuch 79477-2), I was taken by the rich textures produced by the ST-85. I wouldn't say that the midrange was lush, as that would imply too much of a good thing. No, this was just enough of a good thing. The one area in which the solid-state OM-150 bettered the tubular ST-85 was transient snap—the cowbell punctuating the rhythm jumped out of the mix more convincingly with the OM-150. However, life is a series of tradeoffs; along with that speed came a wee too much bite in the brass. The ST-85 replayed the brass more convincingly, with a better-proportioned level of "blat."

I gave a listen to one of Stereophile's own recordings, Serenade (CD, Stereophile STPH009-2), through both the ST-85 and the JoLida SJ 502A integrated tube amplifier. The ST-85 did a better job of rendering the sense of the performance as happening in a well-defined space—I've never been inside Santa Fe's St. Francis Auditorium, but I could imagine what it's like. The VTL also demonstrated a degree of air and sparkle—or, to put it another way, top-octave extension—that the lower-priced but higher-powered JoLida integrated couldn't match.

The VTL's ability to create a more coherent, highly delineated, three-dimensional soundscape was even demonstrated by Deadbolt's Zulu Death Mask (Cargo HED-074), an unnatural recording of an unnatural act, throbbing with reverb-laden guitars, creepy organ, and demented psychobilly mumbling. Deadbolt ain't heavy metal, but they are heavy—what else would you call a band that claims to be "The Scariest Band in the World," has guys with names like Harley Davidson, 3rd Degree Burns, and Les Vegas, and features two bass players? When it comes to heavy, there's no substitute for horsepower; the JoLida provided a tad more low-end weight, which is important when you're trying to raise the dead.

Ah! Maybe adding another ST-85 would help close that gap...



Footnote 1: No, it isn't an ultralinear circuit, formerly the norm for VTL. Luke Manley says that none of the current stable of VTL amps is an ultralinear design.
COMPANY INFO
VTL
4774 Murietta Street, Suite 10
Chino, CA 91710
(909) 627-5944
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