Balanced Audio Technology VK-55SE power amplifier
I love audio shows. Of all those people gathered together to commit hi-fi, a handful of them actually get it right and make it look effortlessBalanced Audio Technology's Geoff Poor, for example. You can count on the latest BAT products to sound better than the room should allowPoor never sweats, just pulls out disc after disc of great blues, making it hard to release the sweet spot to the next needy audiophile.
Such was certainly the case at the 2009 Consumer Electronics Show, where Poor was driving a pair of Wilson Audio Specialties WATT/Puppy 8s with an all-BAT system comprising a VK-D5SE/Superpack CD player, a VK-32SE preamplifier, and the brand-new VK-55SE, a 55Wpc amplifier ($5995). At the time, I had a pair of W/P8s in my listening room and had driven them with a wide variety of components, but I'd never heard them sound like that. Geoff Poor chuckled. "That's what David Wilson told me, too."
I simply had to review something from that system, so we arranged that I would receive the VK-55SE, which, in the fullness of time, I did. Of course, the reviewing gods saw to it that when the VK-55SE arrived, I was auditioning a pair of loudspeakers whose impedance extremes did not favor tubed-output amps; it took some more time to replace them, then familiarize myself with the new speakers and a few other system changes, before I could install the VK-55SE and really audition it. And therein lies the tale . . .
What I dream of is an art of balance
BAT tends to release components as stock models, and later offer them as Special Editions (SEs), and as SE upgrade packages. What changes turn a stock BAT model into a Special Edition? Higher-quality parts, for one, such as replacing the polypropylene capacitors used in the VK-55reviewed by Robert Deutsch in May 2005with paper-in-oil caps. Usually, BAT also increases the energy-storage capacity of the power supplyin the case of the VK-55SE, by fivefold over the VK-55. The SE also replaces the '55's resistive current sources with vacuum-tubebased (6922) current sourcesa change that, BAT claims, provides "a more soulful portrayal of musical texture and instrumental timbre."
Perhaps the biggest change over the stock '55 is the '55SE's use of the 6H30P "super tube" as the amp's first gain stage. BAT designer Victor Khomenko favors the 6H30P over the more conventional 6922 or the 6SN7 used in the VK-55 as a gain stage because the former substantially improves plate resistance, transconductance, and amplification factortripling or quadrupling the "goodness," he says. Using Khomenko's proprietary Unistage topology keeps things simple: no buffers or cathode followers are used.
In addition to the 6H30Ps, the VK-55SE employs a pair of 6SN7s, the aforementioned 6922s, and four 6C33 output tubes. (As only 8 tubes are visible on the VK-55SE's top panel, the other two must be inside.)
Because the VK-55SE is the first BAT component I've reviewed, I feel obliged to observe how superlative its fit'n'finish aretrue of every product in the BAT line. The metalwork is substantial, and the black, textured livery is flawless. And while I know I should be above such petty considerations, I would frequently find myself gazing at the glowing 6C33 tubes during late-night listening sessions, much as I would at a fireplace. They were lovelyand sounded it.
To keep your balance you must keep moving
Setup of the VK-55SE is straightforward. It has, of course, balanced inputs and your choice of binding posts: Low, Medium, or High output impedance. Other than an IEC mains socket on the rear and a power switch on the front, there are no switches, controls, or other embellishments. The tubes are auto-biased. True, the amp weighs 50 lbs, so it must be placed on something solid; and it throws off a fair amount of heat, so it needs air circulationbut satisfy those conditions and you're good to go.
I auditioned the VK-55SE with Klipsch Palladium P-39F, Thiel CS3.7, and Vienna Acoustics Klimt The Kiss loudspeakers. With the P-39Fs and the Kisses, I slightly preferred the High output transformer option. With the Thiels, it wasn't closeLow was the way to go. Your mileage may vary, especially with different cables.
Balance is the perfect state
As I listened to Arturo Delmoni's superb disc of solo violin works by Ysaye Kreisler, and Bach (CD, John Marks JMR-14), the character of the BAT was immediately apparent: the sound was vivid, relaxed, and liquid. Delmoni's 1780 J.B. Guadagnini violin has an unusually big sound, and the '55SE reproduced that bigitude, and the Guadagnini's timbral impact, with clarityit didn't sound too big or too bright, but just right.
Ditto for the supporting acoustic, which was, properly, simultaneously of and not of the instrument's tone. That sounds all Zen and everything, but it's not. With live musicand with great recordingsyou're always aware of an instrument's interactions with its acoustic environment, but are very seldom confused as to which is producing what. Many audio systems kinda sorta smoosh the two together. The BAT, however, presented that interaction with about as balanced [ahem] a nuance as one gets in reproduced music.
On the Horace Parlan Quintet's Speakin' My Piece (CD, Blue Note/Audio Wave AWMXR-0002), from the latest batch of XRCD24 reissues produced by Joe Harley, I was struck by the BAT's dynamic ease. In contrast to the rhythm section, Tommy Turrentine's trumpet leapt out of the soundfieldas did brother Stanley's tenor sax. The piano, bass, and drums were the recording's steady state; the tenor and trumpet both had that sense of infinite gradations of sound that all too frequently distinguishes live music from its re-creation.