For the past few months I’ve been evaluating two products from Balanced Audio Technology: the VK-53SE preamplifier and the subject of this review, the VK-255SE stereo power amplifier. The VK-255SE presents attractive measures of size, mass, gain, and power output for its asking price of $8995 USD, but would its impressive specifications result in equally impressive sound quality? I couldn’t wait to find out.
A high-end audio product should be assessed on the basis of not only its sound quality but its architecture, the quality of materials used and the care with which they’ve been assembled, its warranty, and how much fun it is to own and operate. When I reviewed Simaudio’s Moon Evolution 760A amplifier ($8000), I was charmed before I’d unpacked it -- it arrived double boxed, secured on all sides by robust, form-fitting foam inserts, and cocooned in a Simaudio bag. Under the amp was a secondary insert containing a box with its own inner foam inserts, the latter shaped to hold the 760A’s power cord, trigger cable, feet, and instruction manual. Before I’d put plug to socket, the 760A felt special.
The VK-255SE’s packaging was considerably simpler. I needed to open only one box to reveal the amp, wrapped in a clear plastic bag and cushioned by a foam insert on each side. Beneath the amp, a heavy-duty ziplock bag contained the power cord, spare fuse, Allen key, and manual.
While the VK-255SE’s packaging may have been disappointing, the amp itself drips with quality. It measures 19”W x 6.5”H x 16”D and weighs 75 pounds. The faceplate, heatsinks, and top panel are all CNC milled from aluminum; the chassis is of thick, stamped steel. The front panel comprises four pieces: a subpanel that spans the amp’s full width, left and right cheeks, and a small plate bearing BAT’s logo, all subtly fastened together. The faceplate is vertically bisected by a thin aluminum bar that can be pressed to toggle the amp between On and Standby modes. To the right of this bar are blue and green LEDs: blue for On, Green for standby. At far right, the model name is silk-screened vertically and bordered by a CNC-routed groove.
Toward the top of the rear panel is a large handle. In the top left and right corners are the balanced Neutrik (XLR) input connectors, and below them are three-way Cardas speaker binding posts of solid brass. Unlike the Simaudio 760A or the Constellation Audio Inspiration Stereo 1.0 ($11,000), which I’ve also reviewed, the BAT VK-255SE has no single-ended inputs. Running along the bottom of the rear panel, from left to right, are an IEC power inlet, a fuse bay, and 12V trigger In and Out jacks. The finish options are all silver or all black.
The VK-255SE is a fully balanced, zero-feedback, solid-state design, and can be configured at the factory for use as a monoblock or stereo amp. Should you begin with a single two-channel VK-255SE and later buy a second unit, to use the pair as monoblocks, BAT will reconfigure them for $200. A stereo VK-255SE is specified to output 150Wpc into 8 ohms or 300Wpc into 4 ohms. The monoblock version can pump out 200W or 400W into those respective impedances.
Inside, the VK-255SE reminded me more of the Simaudio 760A than of the Constellation Audio Inspiration Stereo 1.0: BAT has done a commendable job of cleanly and efficiently using the amp’s internal volume to pack in a lot of large, high-quality parts. Virtually all wiring is neatly hidden under a large, shielded compartment spanning the amp’s depth and much of its width. This not only helps keep things tidy but, more important, helps minimize the induction of noise from the VK-255SE’s robust power supply, which is mounted atop the shield. All visible wires are tightly wrapped, sheathed, and routed for the shortest possible signal path. Because most of the circuitry is hidden, or mounted directly on the heatsinks that constitute the side panel, I asked the VK-255SE’s designer, Victor Khomenko, to tell me about it. Clearly a patient man, Khomenko brought me up to speed on a few of the VK-255SE’s key design parameters.
First, the VK-255SE was designed to be an evolutionary improvement over its predecessor, the VK-250SE, most of the changes having been made in the gain stage and the power supply. Signal paths, optimized to be even shorter than before, now comprise only the gain stage followed directly by the output stage. The VK-255SE’s gain stage is purely symmetrical, but unique in deriving its drive from only two gain blocks, configured to use only high-bias current. The advantage of this, Khomenko told me, is that it “enables the gain stages to work in the most linear area of their devices’ characteristics, thus reducing distortion.” He went on to say that the input and output stages have been improved by using only N-channel MOSFET devices, which are generally of higher quality, to ensure a perfectly balanced signal.
With a total of nine separate supplies drawing power from the single, large, 1000VA toroidal transformer, the circuitry of the VK-255SEs’ new power supply is elaborate, to say the least. The most notable upgrade here is the use of BAT’s latest Super-Pak of oil-filled capacitors, which BAT claims offer over ten times the energy storage of those used in the VK-250SE. This new Super-Pak has been lifted directly from BAT’s much more costly REX II preamplifier, and, according to Khomenko, enables the VK-255SE to better control demanding loudspeakers while vastly improving dynamic drive. He also mentioned that these capacitors play a big part in improving the way the power supply handles higher frequencies while maintaining a low noise floor, and a measured total harmonic distortion of 0.2% at full tilt.
Installing the VK-255SE was a snap. I replaced my reference monoblocks, Simaudio Moon Evolution W-7Ms, with the VK-255SE, while leaving in place my Simaudio Moon Evolution P-8 preamplifier, PS Audio DirectStream DAC, PS Audio P10 power conditioner, and reference Rockport Technologies Atria loudspeakers. Clarus Crimson balanced interconnects, speaker cables, and power cords tethered everything together.
Within seconds of first hearing the VK-255SE, I was presented with a curious problem: the volume level was considerably lower than what I’m used to hearing from my Simaudio gear. After checking all connections, and reviewing the specifications of my own gear and the VK-255SE, I traced the problem to the Simaudio P-8, which provides only 9dB of gain. This is no problem when the P-8 feeds the W-7Ms, which produce a whopping 33dB of gain, but the VK-255SE provides a more normal 26dB -- to produce the same level of output as the W-7Ms, it requires a higher-volume input. Luckily, the Moon Evolution P-8 generates very little self-noise -- I heard no detrimental effects when driving the VK-255SE to my preferred levels.
Within moments of beginning to critically listen to the VK-255SE, I was reminded of the slogan that recurs throughout BAT’s website: “warmth of tubes, dynamics of solid-state.” Those ten syllables sum up this amp’s sonic character, particularly as compared to that of my more neutral-sounding Simaudio W-7M monoblocks. For example, as I listened to Patricia Barber’s “What a Shame,” from her Café Blue (16-bit/44.1kHz FLAC, Premonition), Barber was presented with such ease and fluidity that I found it difficult to stay focused on analyzing the sound -- the temptation was great to lose myself in the music. A crisp three-dimensional image of Barber’s voice hung front and center in the soundstage, with enough body, texture, and scale that it seemed possible to reach out and touch her. But there was something not quite right about Mark Walker’s bongos. Placed about a foot behind the right speaker, somehow Walker’s drums sounded as if they were much farther back on the stage. As I listened more closely, I realized that I was hearing a slight reduction in scale rather than an exaggeration of depth. When I focused on John McLean’s expertly manipulated electric guitar, I heard something similar -- notes seemed to lack that last iota of bite and transient definition, yet were replete with expected levels of density and dynamic inflection. Conversely, Michael Arnopol’s double bass was arresting in its power and solidity, anchoring the track like a block of iron. Each note was easy to hear, deeply extended, and tonally accurate.
Clearly, I had more listening to do -- the VK-255SE’s reproductions of McLean’s guitar and Walker’s drums just weren’t fitting the mold. I dug into my Dire Straits collection and cued up the title track of Brothers in Arms (16/44.1 FLAC, Mercury), a recording I’m very familiar with that’s chock full of prominent electric guitar. This was more like it: Mark Knopfler’s electric guitar had enough bite or attack to draw me into the music, though I still missed that last iota of textural detail I hear from the Simaudio 760A and the Constellation Inspiration. John Illsley’s bass, as he lays down a thoroughly satisfying bass line, had balls, wonderfully contrasting with the restrained taps of drummer Terry Williams’s cymbals and the various background synth effects.
After repeated playings of this and other tracks from this and other albums, from Diana Krall’s Turn Up the Quiet (16/44.1 FLAC, Verve/Tidal) to the Tragically Hip’s Fully Completely (16/44.1 FLAC, MCA), I began to understand that what I was missing was the conveyance of ambience -- the space or air between and around instruments. In her cover of Rodgers and Hart’s “Isn’t It Romantic?,” Krall’s voice was chiseled at center stage, clear as day, and the liquidity and tonal color of her piano notes floating in my room could have fooled all but the most discerning that they were listening to tubes, not transistors. But as inviting as this was, the overall sound suffered a bit -- those same instruments occupied a stage that was slightly smaller in all three dimensions. The VK-255SE’s reproduction of whatever music I played consistently fell just a hair short of coming fully alive in my room.
When I received the VK-255SE, it arrived accompanied by its natural counterpart, BAT’s VK-53SE tubed preamplifier. My initial impression of the VK-53SE’s sound was that it was rather open and airy, and considerably warmer than that of my Simaudio Moon Evolution P-8 preamp. So I swapped out the P-8 for the VK-53SE, in hopes that a pre- and a power amp made by the same company would better complement each other sonically.
For the most part, they did. The first thing I noticed was that the volume problem I’d had with the P-8 and VK-255SE was gone. I was also immediately aware of just how quiet the VK-53SE was -- I heard little to no additional artifacts through the already discreet VK-255SE. The remaining changes, while subtle, were an added bloom that, whether due solely to the VK-53SE or to pairing it with the VK-255SE, translated into a marginally more open, airy sound. With good recordings, it sounded as if all the instruments had been separated by another 6”.
Also on hand for review were pairs of two very different speakers: Sonus Faber’s Amati Tradition, and Tidal Audio’s Piano Diacera G2. As the Tidals sounded surprisingly similar to my Rockport Atrias, I experienced much the same smooth, warm, vigorously robust sound from BAT’s dynamic duo driving the Tidals as I did with my Rockports -- but when I swapped in the Amati Traditions, it was like tightly stretching a previously painted canvas over a marginally larger frame: everything was slightly bigger, particularly the spaces between objects.
As indicated in my review of the Amati Traditions, published in mid-November, I found them to be different animals from their predecessors. The Amati Traditions sound more pronounced in the highs, and with the BATs they produced musical magic. The warmth of the VK-255SE expertly complemented the hints of hotness otherwise heard in my room from the Amatis, while generating a midrange so natural, so communicative, that such terms as rightness, neutrality, and vividness came to mind. Equally appealing was how well the VK-255SE was able to lock on to and drive each Amati’s twin 8.7” woofers. In my review of the Amatis, I described what I heard when listening to “Royals,” from Lorde’s Pure Heroine (16/44.1 FLAC, Universal): “Lorde’s voice was vividly etched center stage against a thunderous bass line and room-encompassing backing vocals. The transients of the hi-hat cymbal were fast, controlled, and well defined.” I went on to say that “the bass was not quite as deep as what I heard when I reviewed Paradigm’s Persona 7F speaker ($25,000/pair),” but that was more a reflection of the speaker, not the amp.
I pitted the VK-255SE against the only other amplifiers I had on hand: my reference Simaudio Moon Evolution W-7M monoblocks. To be sure, the comparison was unfair -- the W-7Ms are vastly more powerful and, at $25,000/pair, cost almost three times as much as the BAT. On the other hand, the VK-255SE had already pushed far beyond what I might have expected for $8995 in terms of control, dynamics, and bass authority. To level the playing field, I focused more on how accurately recordings were being reproduced by both amps in terms of tonality, dimension, and detail -- I fully expected the VK-255SE to hold its own dynamically. I further leveled the playing field by putting my Simaudio P-8 back in the system: I know it to be a relentlessly neutral and revealing preamplifier, and wanted to ensure that I was hearing, as much as possible, only the VK-255SE. The P-8’s dual outputs also meant I could perform direct A/B comparisons between amplifiers simply by swapping speaker cables.
I began by revisiting “Brothers in Arms.” Immediately, I heard obvious differences. The Simaudio amps threw a much vaster soundstage, on which I was able to more clearly hear the detail, definition, and dimension of the crackling thunder. It was as if the storm were above and around my room, whereas the BAT confined the storm within my room. The synth’s sound was grander through the Simaudios, extending far beyond the outer side panels of my Atrias -- through the BAT, the synth seemed smaller, and a wisp less articulately defined. As the track continued, the BAT presented Mark Knopfler’s electric guitar with more grit and weight, which I found compelling. The Simaudios, on the other hand, excelled at defining the guitar in space, imaging it dead center, with a smoother texture; I could also more easily hear Knopfler’s pick on the strings.
The Simaudio and BAT amps locked Knopfler’s voice chiseled in space at center stage, with comparable levels of texture and scale. But every time I swapped back in the Simaudios, I couldn’t ignore the longer decay of each crack of the wood blocks, and the added space and shimmer around each tapped cymbal. Not surprisingly, the BAT did an admirable job of reproducing the deep, punchy bass line this song demands to sound right. Knopfler’s dynamic inflections on electric guitar were also taken in stride, surprisingly on a par with the Simaudios in volume and control, but not in size. In terms of tonal coloration, these amplifiers were quite different: the Simaudios are pretty much dead neutral, while the BAT leaned toward the warmer side by a few degrees, and sounded a shade darker.
The VK-255SE was a pleasure to use -- its power toggle is cleverly hidden, its rear handle makes installation a breeze, and its high-quality connectors easily accommodate just about any spade- or banana-terminated speaker cable now made. Inside, the VK-255SE’s overall design and execution are exemplary, with short signal paths, a unique dual-gain-stage design, a proprietary power-supply architecture, and an abundance of high-quality parts. Outside, it looks great and is built exceedingly well. However, the VK-255SE ran hot, whether idling or in use -- it will need good ventilation, somewhere a child can’t touch it.
My impressions of its sound were mixed. The smooth-talking VK-255SE proved masterful at reproducing dynamic inflections, was fully capable of producing mesmeric levels of bottom-end fortitude and control, and its midrange was purer than that of almost any other solid-state power amplifier I’ve heard. However, the VK-255SE’s ability to produce a realistic sense of ambience or air, or to squeeze out that last iota of inner detail, notably trailed those of Constellation Audio’s Inspiration Stereo 1.0, Simaudio’s Moon Evolution 760A, and my considerably more expensive Simaudio Moon Evolution W-7Ms. The sound of BAT’s VK-255SE is therefore not quite my cup of tea -- but if tube-like warmth, buttery textures, and arresting dynamics are what you find most inviting, then this amplifier deserves to be on your audition list.
. . . Aron Garrecht
- Speakers -- Rockport Technologies Atria, Sonus Faber Amati Tradition, Tidal Piano Diacera G2
- Subwoofers -- JL Audio Fathom f112 (2)
- Amplifiers -- Parasound Halo A 51 (five-channel), Simaudio Moon Evolution W-7M (monoblocks)
- Preamplifiers -- Anthem AVM 60, Balanced Audio Technology VK-53SE, Simaudio Moon Evolution P-8
- Sources -- Oppo Digital BDP-103 universal BD player, Dell E7440 Ultrabook laptop computer running Windows 10, JRiver Media Center 20
- Digital-to-analog converter -- PS Audio DirectStream
- Cables -- Clarus Crimson S/PDIF, USB, balanced interconnects, speaker cables, and power cords
- Power conditioner -- PS Audio P10
Balanced Audio Technology VK-255SE Stereo Amplifier
Price: $8995 USD.
Warranty: Five years parts and labor.
Balanced Audio Technology Inc.
1300 First State Boulevard, Suite A
Wilmington, DE 19804
Phone: (302) 999-8855
Fax: (302) 999-8818