Balanced Audio Technology VK-P10 SE Tube Balanced Phono Preamp with nicely upgraded NOS tubes (will list them soon).
OUTSTANDING SOUND & Fully Balanced. Well Reviewed.
Just fully serviced to factory specifications.
Balanced Audio Technology VK-P10 phono preamplifier Jonathan Scull
Some of the most innovative thinking on hybrid circuit design these days seems to come from Russian designers. As a group, they are technically very well educated, pragmatic, and unfettered by American high-end didacticism.
Balanced Audio Technology's Victor Khomenko, late a citizen of Leningrad, emigrated here with his wife Anya in 1979. Most of his working experience has been in the field of instrumentation for the military and aerospace industries. He and soon-to-be partner Steve Bednarski met while pursuing careers at Hewlett-Packard. They found their commonality, high-end audio; Victor built Steve one of his custom amps; they both took deep breaths; the rest, as they say was Balanced Audio Technology.
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.
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..."
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Balanced Audio Technology VK-P10 phono preamplifier
I looked down at my paunch, sighed heavily, and fixed Victor with my best "Pray continue" look.
"...so you do nothing but diet and exercise like crazy; you have no life, but you get down to 160 lbs. Or you don't do anything drastic, enjoy yourself, and wind up at 170 lbs, a little above of your target. Which would you prefer, Jonathan?"
Yup. So BAT builds symmetrical, bipolar power supplies that let their equipment breathe. (Symmetrical means the power supply generates both plus and minus 150V rails rather than relying on the ground—full of schmutz as it often is—for the return.) Light regulation but heavy filtering is the word of the day.
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."
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.
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.
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?
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!"?)
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Balanced Audio Technology VK-P10 phono preamplifier Page 3
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.
Balanced Audio Technology VK-P10 phono preamplifier Equipment & Setup
Sidebar 1: Equipment & Setup
I began my auditioning with the VK-P10 sitting on its own rubber feet atop a Signature ClampRack. As I began to listen, I mixed and matched components and adjusted gain and loading.
The final optimized playback chain included the Symphonic Line RG-8 on the Forsell Air Force One, XLO 3.1 phono cable with single-ended RCAs at both ends into the P10, then balanced runs of TARA Labs Decade line-level interconnect to the VK-5i preamp. The Forsell Air Force One, after a small service by the factory, was once again spinning its magic tune. (The self-adjusting air bearing sometimes needs...adjusting!)
I relied on the Jadis JA 200s and the Forsell Statement for amplification, these wired up with a long run of Decade (both single-ended and balanced). Decade also did the deed between the amps and the Avalon Ascents. I also spent time with the P10 wired up to both the Graaf 13.5B line-level preamp and the YBA 6 Chassis; through the latter, I could listen to the P10 and compare it to the YBA's own phono stage.
I tickled the best sound out of the VK-P10 by putting it and the VK-5i up on Shun Mook Diamond Resonators. I set a pair of Shakti Stones on end and pushed them close (but not touching) the case of the BAT units near the front-mounted vertical transformers. (Shakti earmuffs!) I also experimented—and had good results—with Shakti On-Lines. These little black thingies snuggle up against interconnects, secured with Velcro ties. More on these little guys later.—Jonathan Scull
NEXT: Victor Khomenko Interview »
Balanced Audio Technology VK-P10 phono preamplifier Victor Khomenko Interview
Sidebar 2: J-10 talks with BAT's Victor Khomenko
Jonathan Scull: Victor, why balanced circuits, if you please?
Victor Khomenko: I remember reading an article that said balanced topology is inherently much more complicated than single-ended. They felt it was a cumbersome way of building circuits. And they provided proof in the form of a very ugly circuit representing "balanced" configuration.
Now, of course, a balanced circuit can be ugly. But that doesn't mean that every balanced circuit has to be like that. On the contrary, when properly implemented, a balanced circuit is inherently one of the most beautiful creations in electronics. I remember the first time I learned about the nature of differential balanced circuits from one of my tutors. He showed me that nothing in electronics was more elegant than a simple differential pair of transistors.
Look at the circuitry used in some classic 1950s McIntosh components, for example. If you take some of their monoblock designs from that period and cut off the input connector, you're left with, essentially, a balanced circuit.
Scull: The question begs to be asked: Why didn't they use a balanced input?
Khomenko: Sure, because at that time the marketplace hadn't accepted balanced as the right way of doing things. So they provided a single-ended RCA connector, and the signal was converted to balanced internally.
Scull: This happened often?
Khomenko: Exactly. And I can understand why. There are many reasons why I believe balanced is better inherently from an electrical perspective—as well as, how shall I say, from the philosophical point of view, in the sense of being more symmetrical. So balanced naturally becomes the choice of many designers.
Once you've accepted this, it's a shame not to use the full potential of the balanced topology. But what you often find, as with the McIntosh, is an RCA single-ended connector attached to one input of a differential pair, the other side grounded. In this way the distinction between balanced and single-ended becomes very blurred. It's almost nonexistent in many designs.
Scull: There seems to be a misconception regarding balanced equipment and its suitability for use in single-ended systems.
Khomenko: All our equipment—and I mean all our equipment—is fully compatible with other single-ended components. Which is to say, you can take the VK-5 or VK-5i and connect any mix of single-ended and balanced sources to it, and you won't lose much performance as a result.
Scull: You provide the best-sounding XLR-to-RCA adapters I've ever heard...
Khomenko: Well, even with the adapters, we feel there is some degradation when going from balanced to single-ended configuration. But you understand that,in all our models, the signal processing is always differential balanced.
Scull: And other benefits accrue from that?
Khomenko: Yes. One big advantage is in the way balanced circuitry interacts with the power supply. When you look at the interaction between a single-ended circuit and its power supply, it's always a current-on-demand situation. The power supply has to struggle to keep up with the instantaneous demand.
Scull: Especially when heavily regulated?
Khomenko: Yes, exactly.
Scull: You don't regulate your power supplies at all, just filter them heavily?
Khomenko: Correct, because when you're talking about regulation, you're talking about feedback. That can result in delay and slew-rate limitations. Balanced circuitry, by virtue of its symmetrical in-and-out of phase operation, does not have this problem. Basically, the power supply maintains DC to the power rail, and this is traditionally accomplished with regulators. But in our experience, the value of the DC rail in and of itself does not determine the sound quality to any great degree.
Scull: And what about the AC side, so to speak?
Khomenko: That relates to how the power supply absorbs and provides instantaneous current changes. And that's a much more difficult aspect of design because of feedback implications and AC fluctuations.
Scull: So the power supply has an easier time of it when it's symmetrical?
Khomenko: Yes. Once you remove this major demand from the power supply by doing circuits in differential topology, the power supply starts breathing easier. It becomes unshackled. It runs freely. It becomes what it really wants to be—a circuit by itself.
Scull: Victor, what was the design brief behind the VK-P10 phono stage?
Khomenko: First of all, it had to be extremely versatile. There's a switch-selectable configuration for any type of cartridge out there. And I'm talking about an output voltage range anywhere from well under 0.1 all the way up to 4 or more millivolts.
Scull: And you even included step-up transformers in your design.
Khomenko: Right; it's an additional way of providing flexibility to the user. We're not saying that you must use the transformers in every case. One can try and see what works best for one's cartridge and system. It's another tool for the owner to use.
Scull: Victor, how about some specifics of the circuit? I suppose it's not very typical?
Khomenko: Of course, nothing we introduce is just another me-too product. [laughs] We wanted our phono stage to be different from essentially everything else on the market. And there are several areas in which we address this. First—and I would say it's our trademark—we don't use any cathode followers or buffers in the signal path. All circuits are typically plate-loaded triodes throughout.
Scull: And I suppose that means no feedback?
Khomenko: Right, the phono stage doesn't have any global feedback.
Scull: There are three amplification stages in the VK-P10?
Khomenko: Yes. There are many ways of implementing high-gain circuitry, of course, but the one we take is a three-stage design: very crisp, very simple, with no buffers. And, of course, we rely on totally passive RIAA equalization. Except it has a twist—we call it "Flying Passive RIAA." To our knowledge it's a unique topology, and we have a patent application in process.
Scull: I gather you won't be giving too many details of it during the interview!
Khomenko: [laughs] Right! I guess it's enough to say that it allows us to simplify the RIAA equalization circuit tremendously. That impacts cost to some degree, and makes the unit more manufacturable, so to speak.
Scull: Poking around inside, I see you use a pair of toroidal transformers...are those Plitrons?
Khomenko: That's right.
Scull: And you use Russian 6922s, which are also known as 6DJ8s?
Khomenko: Yes. It was also called the 6H23 in Russia. It's a wonderful low-impedance tube that was designed for cascode circuit applications. In fact, we don't use cascodes; I don't like the sound.
Scull: And then there's a pair of 6SN7s...
Khomenko: Yes. If you look at the basic configuration of a differential gain stage, it always requires some type of current source. This can be supplied by a simple resistor, a solid-state device, or vacuum tubes. Most of the time I try to use vacuum tube-based current sources.
Scull: Why is that?
Khomenko: Oh, maybe for the sense of purity. When you build a "classic" tube phono stage, it naturally pops into your mind to use a vacuum-tube current source. My own inclination is always to try to use tubes, unless I run into practical or other difficulties. Out of the three stages in the VK-P10, two use resistors as a current source and one uses tubes. It's a tradeoff. You want to make the product practical and have it come in at a particular price point.
Scull: Thanks for the lowdown, Victor!
Khomenko: My pleasure...
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