BAT VKP-10 Valve Phonostage
Excellent
The VK-P10 is a versatile, true all-tube, differential, high-current phono stage. Its well-vented case is identical in size to that of BAT's VK-5i remote-control couch-potato preamplifier. (RD, having reviewed the original VK-5 line-level preamp, brought you word of this upgrade in April (Vol.20 No.4, p.245). Suffice to say, it's a terrific piece. The user interface is severely habit-forming!) An on/off toggle switch protrudes from the left of the VK-P10's aluminum faceplate, while a discrete blue power-on LED peers out from the center. After a 45-second soft-start ramp-up with two relay clicks, you're ready for signal.
I was interested to note the polarity switch on the right side of the front panel. With a differential circuit, phase inversion comes almost free. The signal path is the same either way, the only penalty being an additional switch in the signal path.
Around back, the unit sports both single-ended and balanced input jacks, but only XLR outputs. Not to worry; BAT provides the finest XLR/RCA adapters I've ever heard. (Check out my Sidebar interview with Victor for his interesting thoughts on mixing single-ended and balanced equipment.) As for the two types of input, Victor explained, "Jonathan, you know, you'd have a balanced input if the cartridge was a balanced device. But since it only has two leads, the cartridge doesn't know if it's balanced or single-ended. The fact is, you get better noise performance when you connect the cartridge in single-ended fashion. However, we recommend balanced connections from that point on."
The back panel also carries a ground connector, a fuse port, and an IEC receptacle.
Layout
In general terms, the VK-P10 is a fully differential three-stage zero-feedback device with a passive differential RIAA network. Peering into the exposed chassis, I noted that it was efficiently laid out and obviously built to a high standard. Two current-source 6SN7 tubes dominate the boardscape, with two rows of four 6922s each ranked to either side. All tubes are Russian: the big 'SN7s branded "Sovtek."
One of two toroidal transformers is mounted vertically on either side of the front case. (The VK-P10 is dual-mono from the power cord on.) A number of squat black capacitors carpet the forward section of the circuit board, bristling with over 200 Joules of get-up-'n'-go. (That's more than some medium-powered amplifiers, Victor tells me.)
The caps filter and smooth the DC in what Victor describes as a Double-Pi configuration. Pi filters are essentially two caps to ground with a resistor in between. The cap/resistor/cap assembly looks like the sign for Pi. Remove one cap, and you're looking at an L filter! We're demystifying science here.
These two Pi filter stages are linked in series. Post-Pi, as it were, the smoothed DC branches three ways: to the output stage, through an additional L filter to the second stage, and via another L filter to the input stage. Input each side is handled by a single 6922. The second stage—another 6922—functions as a simple differential pair with the 6SN7 providing the current source. This stage boosts the signal and provides buffering for the differential passive RIAA network that follows. Two more 6922s are paralleled together per channel in the output stage.
I've given you the gruesome details regarding circuit topology because it's one of the defining elements in the overall design. You see, many high-end preamps use heavy regulation in their power supplies. But regulation implies feedback, and that's something Victor doesn't care for.
"Throwing feedback in improves measured performance," he explained, "but I simply don't like the way it sounds. You know, it's something like your ideal body weight. Let's say that's 160 lbs..."Victor: "We also believe plate-loaded triode circuits always sound best, so there are no cathode followers in the VK-P10's output. And no cascoded circuits either. Still, the output impedance of the phono stage is low enough not to be a concern in 'normal' systems. By that I mean a typical line-stage preamp, such as our VK-5, with an input impedance of at least 10k ohms, and interconnect under 100' or so."
Build considerations
I was surprised to learn the VK-P10 is built up of galvanized steel, an inherently magnetic substance. According to Victor, this offers a degree of attenuation of the 60Hz component that surrounds us all. (New York is such a radiated environment, it's a wonder we don't wake up toast some mornings. Perhaps we do...)
I learned that this build sensibility is reflected everywhere in the design. For instance, mass-damping the chassis top cover might give the unit a more substantial "feel" but have little actual effect. Rather, Victor uses an "intelligent" approach to vibration control. For example, the bottom chassis is coupled to a ½" vibration-absorbing plate, which is an integral part of the structure. The PC board is bolted to this plate in 17 places! BAT analyzed the vibration modes and found the nodes and antinodes. Once these were known, sensitive components—such as the tubes and the potted paper-in-oil capacitors—were positioned at the antinodes.
BAT also uses ceramic tube sockets with silver contacts, and...the list goes on and on. I strongly suggest all interested parties contact BAT for a copy of their various White Papers. They do a terrific job of explaining, in very cogent fashion, the engineering and implementations featured in their designs. It is truly fascinating reading.
Versatility
The input stage incorporates most of the elements responsible for the VK-P10's versatility. That includes user-selectable cartridge loading of resistance (100, 1k, or 10k ohms, or User Selected) and capacitance (100 picofarads, 470pF, 1000pF, or User Selected), or any parallel combination. A 47k load resistor is permanently connected to the cartridge input as the default. Female posts are provided, along with pin terminations for your favorite audiophile cap or resistor. The factory will be happy to oblige you in these matters.
There's a switch to choose between high and low gain modes. Low cuts the output by 6dB for cartridges with afterburners. There's yet another switch to choose between Direct and Step-Up modes, which introduces a pair of transformers into the outputs. The trannies feature both 12 and 18dB taps, chosen...by throwing a switch, of course!
Overall, this provides the user with a range of between 50 and 83dB of gain to work with. The phono stage should function with cartridges ranging in output from 0.1mV to 5mV powerhouses. If you can't get your cartridge to settle in, give it up.
Loading
Because the VK-P10 is so flexible, I futzed and fiddled with its many settings. I tried the board-mounted values of 100, 10k, and 100k ohms. I also tried a few Holco resistors of differing values that Victor had left with me. My conclusion is that there are no hard'n'fast rules when it comes to cartridge loading. Try it with your cartridge of the moment and listen for the result. Trust me on this-you will easily hear the difference. My advice is to find what pleases you and go with that. Don't read me or anyone else who dictates what you should do in every case. There is no "every case."
Take the Symphonic Line RG-8. Well...let's leave it here for now. It likes a bit of loading, but it's not very happy at 100 ohms. I preferred the 1k ohm setting I used throughout the test period, with no capacitance switched in. An input impedance of 10k or completely unloaded at 47k ohms was even better, but rather too noisy for RFI-rich New York. It's better to let things be what they are, what?
Sound
I eyed the system as I sat down to do some critical listening. (Can we find a less clinical way to describe this, I wonder?) Yes, it's true, analog is a pain in the ass, it takes up a lot of time, and one has to be completely obsessed and demented to go through it all. But when everything's just right...ah, the wonder.
I settled on the RG-8 for most of the review period. It made a wonderfully synergistic match with the VK-P10. The cartridge sounded impressive at an initial 1.4gm VTF. With a dab of Mortite on the headshell, the palpability and "body" improved. (I keep 1/10-gram Mortite boogers handy for this purpose. Can you say, "Get a life!"?)
Let's start with Beck! (He won a Grammy, you know. There's hope for the world.) When I spun Odelay (Bong Load Custom Records BL30), the illumination, clarity, and air were astounding—as was the imaging. Big Boogie Factor, lots of pace, and terrific dynamics. Before too long that old sense of analog awe fell over me, and I yearned to drop something serious on the platter.
That would be Patricia Barber's Café Blue LP (Premonition 737). Small adjustments of VTA brought her into astonishing focus and presence. It was a snap finding the balance between sharpness of focus and harmonic integrity that I look for when setting VTA.
I sat back and wallowed in the burnished textures, reveled in the coherent, transparent soundfield. The Symphonic Line cartridge was strutting its stuff, dishing out detail, dynamics, and timing right on the button! It had a snap-factor even Martin Colloms would like.
If you don't "associate" the RG-8 with the finest of amplification blocks, it's bound to sound bad. I'm not being a snob—some components are, by their nature, more revealing than others. It can be both a blessing and a curse.
But during extended listening sessions, it came to me that I'd never heard the RG-8 sound so good. The burnish and shimmer of the cymbals at the end of "Too Rich for My Blood" was so apparently real to the event that it just wasn't possible to differentiate. The midrange textures were filled with velvety nooks and crannies. The bass and dynamic slam gave me goosebumps.
You think that happens all the time in a reviewer's system? Forget it. Work, work, work... Yet surely worth it, I thought, as I sat back in the Ribbon Chair, stunned by the soaring emotional energy pouring out of the Ascents at the climax of the cut.
Something else came to me during an extended analog orgy I enjoyed one evening after scoring a dozen or so OJCs in perfect shape for $8.98 each in the East Village. Just to tantalize you...Monk and Coltrane; Kenny Burrell and Coltrane; Red Garland with Trane and Donald Byrd; Art Farmer's Farmer's Market; Gene Ammons with Byrd, Jackie McLean, and Mal Waldron; Clark Terry with Monk; and Dexter Gordon's Tower of Power!
But the prize of the evening was "The Timekeepers": Count Basie Meets Oscar Peterson, on Pablo 2310-896. (I'm always saying, "Oh, it's just a Pablo." But Pablos are great. They deliver more quality for your analog buck than practically any other jazz label out there. Look for them.) "I'm Confessin' (That I Love You)" jim-jam-jimmies along so well, and with such an engaging warmth of purpose, that I felt like Oscar Peterson at his keyboard as I tapped out my listening notes. The music came across perfectly good-natured, emotionally warm and inviting.
Is finding that emotional component part of re-creating the live event in the high-end sense? Or is it simply a sense of communing with the music? Can home reproduction ever get a listener back to the original acoustic event? Look at the equipment Kathleen and I have the privilege of auditioning, and still I'm asking the question!
Back to the music. Let's consider the last cut on side A, "Rent Party." This marvelous set piece contains one of the sweetest piano duets ever recorded. The two instruments are, of course, set to the left and right of center. One could be pessimistic and expect nothing more than early Atlantic/Blue Note ping-pong stereo. (I'm beginning to see that these same recordings in mono may hold the true key to the music.) But as I settled into my chair to listen, the sense of total ambience was very strong.
The music began as I scanned the back cover. I picked up a few phrases from the notes by producer Norman Granz, who describes Basie and Peterson as having very different (if complementary) styles: "Peterson's technique is prolific and flawless, Basie's sparse and flawless." So I think I'm on strong ground when I say that it's Basie on the left, Oscar on the right. Basie just sketches a theme to start with, one so natural and gentle that I hardly noticed it. Soon after, Oscar rings in, taking the theme and polishing it in that filigreed style of his. As his first notes sprang out of the soundfield, I was startled enough to involuntarily turn my head to the right. How'd that piano get in here?
You could hear the thunk as I fell into the magic of the moment. Peterson's piano was placed closer to the listening position, sounding altogether BIGGER. As a result of the more close-up perspective, the strike of hammer and string was more pronounced, becoming part of the fabric of sound from that instrument.
Basie appeared to the left and more to the rear of the soundfield. His piano, while still potent and colorful, emphasized less the initial strike and more the coherent tonal balance.
At some point in the ceremonies Basie begins to tap his foot. This comes through the rich tapestry of sound quite naturally—he's not hitting us over the head with it. It's just a suggestion, but it's completely irresistible. If you don't find yourself nodding or keeping time with at least one of your appendages, you're just not with us.
When Louie Bellson finally comes in on drums with John Heard on bass, it's all in the family. The charm and warmth are undeniable, no matter how big a grouch you might ordinarily be. Heard's bass sounded wonderfully acoustic, not bloated at all: natural, full, tight, pitch-differentiated, expressive, and very present. Bellson's restrained drum work perfectly balanced the quartet's harmonious tonal comings and goings. This, my dears, was a little slice of analog heaven.
Conclusion: It's alive!
The BAT VK-P10 allowed every part of the amplification chain to work its best. The P10 was clearly a device that remained transparent to its purpose at all times: not the omigawd transparency of the Avalon Radians or the limitless view deep into the soundstage that the YBA 6 Chassis offers, but rather a sense that the phono stage was transparently letting the 'table/cartridge/interconnect combo develop their sound to their best ability, and sending their signal along to the line-level preamp.
The combo of the VK-P10 and the VK-5i wasn't "ruthlessly revealing," as I've described the CAT SL1 Signature (a heavily regulated cathode-follower design) in the past. Nor did it present the lush, beautiful imagery of the Jadis JP-80. Actually, if this phono front-end sounded similar to anything at all in our experience, it would be the four-chassis Jadis JP 200...which costs a cool $25k or so!
During the course of the review, I threw everything I had at the VK-P10: Big Symphonic, Big Rock, Big Band, and lots of smaller, sweeter recordings of all kinds. The P10 never failed to deliver the musical goods. Its character was always the character of the associated components.
By virtue of its design, its power supply, and its eschewal of feedback, the BAT breathes. In so doing, it effortlessly lets the music through. This is one fine effort, worth every penny of its asking price.
Description: Tube phono preamplifier. Tube complement: two 6922, two 6SN7. Inputs: RCA single-ended and XLR balanced. Outputs: XLR balanced (RCA adapters available). Gain adjustable between 50 and 78dB. Loading switch adjustable for 100 ohms to 47k ohms. Capacitance switch adjustable between 100pF and 1000pF. Power consumption: 150VA maximum.
Dimensions: 19" W by 5.5" H by 14" D. Weight: 35 lbs.
Serial number of unit reviewed: OP100050.
Price: $4000 (1997).
