Pre/Power Amplifiers

Balanced Audio Technology, otherwise known as BAT, doesn’t beat about the bush when it comes to its audio philosophy. The main page on the US manufacturer’s website lists core principles, all of which have an engineering bent: ‘balanced is best’, ‘dual-mono construction maximises performance’, and ‘zero global feedback achieves natural sound’. All three of these are at play in the company’s VK-90 preamp.

Priced £14,995 and offered in BAT’s usual choice of silver or black anodising, this is the company’s flagship single-chassis preamplifier, ranged below the £30,000 REX 3, which has separate control (audio) and power (PSU) enclosures, but more on that later. Filling out the roster of preamps are the VK-80, ticketed at £9995, and the new VK-85, for £12,500. The latter is a solid-state design, while the others are valve-based, employing the 6H30 ‘SuperTubes’ long-favoured by BAT’s chief designer/co-founder Victor Khomenko.

Tube to tango

Giving its customers tube and solid-state options isn’t new for BAT – its range of power amplifiers reflects the same flexible thinking. This means there’s no definitive ‘partner’ amp for the VK-90, the catalogue instead encouraging mixing and matching of the two technologies. Want all tubes? Check out the REX 3, BAT’s heftiest (6C33C-B triode-based) tube amplifier, rated at 2x80W/8ohm and selling for £20,000, or the VK-80t (2x60W/8ohm), for £9995. Or maybe you want to follow the lead of BAT’s VK-3500i tube/solid-state hybrid integrated [HFN Sep ’21] by pairing the VK-90 with the 500W-per-channel £22,500 REX 500 [see boxout] or £15,000 REX 300 (which despite the name claims 200W per side). All are fully differential, dual mono amplifiers and configurable, by way of upgrade, as higher-power, single-channel monoblocks.

That the VK-90 is a tube preamp is not obvious from the outside, as the eight 6H30 bottles, four per channel, are mounted within its 483x146x394mm (whd) chassis. Their ‘high current, low impedance’ characteristics are key to the amp’s ‘Unistage’ circuit design, which features a single gain stage to minimise component count and maintain signal integrity. Also claiming performance benefits are transformer-coupled outputs, with Cardas copper windings and mu-metal shielding, and a third-generation of BAT’s SuperPak PSU. This includes ‘hybrid’ capacitors, one being a silver-in-oil type, that are combined within a low-resonance shell. Silver and gold-in-oil bypass capacitors are deployed in the high capacity, low ESR supply too.

Flare and function

Meanwhile, those six tubes are just visible through a perforated top panel that flares out at the front to meet the VK-90’s milled aluminium fascia. This is smartly designed, with a large ‘BAT’ logo in the centre above an easy-to-read alphanumeric display, and the model number engraved on a strip on the left-hand side. Small buttons either side of the display handle standby/on/off, mute, absolute phase inversion, mono mode, and access to the menus, while the numbered row below is for source selection.

Above: BAT’s Gen3 ‘SuperPak’ PSU has silver-in-oil caps with silver and gold bypass caps potted into [orange] cylinders. Four 6H30 ‘SuperTube’ triodes [left and right] are used in a single gain stage per channel with Cardas OFC-wired, mu-metal screened, output transformers [top, left/right]

This preamp offers a total of five analogue line inputs, plus two main outputs and a tape out, on a neatly arranged back panel. All use balanced XLR connections, whereas the VK-80 and VK-85 include RCA options. The reason, explains BAT co-founder Steve Bednarski, is that the VK-90 is identical to the ‘control module’ of the two-box REX 3 flagship – and ‘BAT has always maintained all balanced connections for our reference models’.

Moreover, the company offers a REX 3 upgrade path for VK-90 owners. Here, the amp is returned to the brand’s facility in Wilmington, Delaware to be fitted with additional sockets to accommodate a set of umbilical cables. BAT then adds the ten-tube external power supply that brings it to REX 3 status. Note, though, that the local PSU in the VK-90/control unit remains in use, supporting one phase of the supply while the external PSU supports the other.

Operating the VK-90 is largely a breeze, although renaming inputs (to a maximum of four characters) using the supplied VK-R5 remote, or the front-panel buttons and volume control, is a bit long-winded (and they will of course still be numbered on the handset). Other features include balance adjust, plus max/fixed volume settings for each input. Meanwhile, BAT’s ‘electronic shunt volume attenuator’ allows your preferred level to be set with precision [see PM's Lab Report].

Hart and soul
Allied to the REX 500 power amplifier, the VK-90 – despite its tube gain stage – doesn’t call undue attention to itself. Certainly, its sound has an element of warmth and lushness, but not to the level that might cause a die-hard tube-lover to go weak at the knees. I’ve no doubt a more ‘hot-bottle sound’ could be achieved running the VK-90 with BAT’s REX 3 amp, just as I’d imagine the wholesome flavour of our VK-90/REX 500 combination could be largely replicated by employing the more affordable REX 300 model.

Anyway, back to the preamplifier, and a performance that’s noteworthy for not just its tonal richness, but its depth, weight and attack. Listening to Beth Hart’s ‘Baddest Blues’, from her 2012 set Bang Bang Boom Boom [Provogue PRD 7393 2], the vocals sounded full of character and body, as did the piano and gentle drums of the introduction. Then – pow! – the track erupts with distorted guitars and a powerful, crashing delivery, and the VK-90 brought it all out while making sure Hart remained the focal point.

It was an exhilarating rendition, full of energy and immediacy, and this sense of liveliness was also present during the Steve Miller Band’s ‘Sugar Babe’ [The Joker; Capitol Records, 96kHz/24-bit], at least in Gerald Johnson’s driving bassline and Miller’s guitar riffs. On the other hand, cymbal crashes erred a little on the soft side, and the sound overall had more of an ‘analogue’ vibe. But don’t confuse that with the VK-90 adding too much of its own seasoning – from the same album, the title track sounded big, open and dynamic through Rockport’s Orion floorstanders [HFN May ’25], both in terms of the drums and bass, but also the vocal and acoustic guitar.

Above: Five balanced inputs, one line/tape monitor output and two preamplifier outputs – all on XLR connections. Sources and systems with single-ended/RCA sockets will need adapters for use with BAT’s VK-90

Indeed, the bassline on ‘The Joker’ song was beautifully etched, each note distinct and fulsome, setting the foundation for the rest of the band. Less tuneful are the low-end electronic washes of Daisy Gray’s ‘Wicked Game’ [self-released download], but these have an important role to play, giving her take on Chris Isaak’s ballad an ethereal feel.

The VK-90 took this modern production in its stride, letting the system as a whole dig into the low octaves while Gray’s tremulous vocals took flight.

Concert clarity

It was the Antonio Forcione Quartet’s In Concert live set [Naim Label, 44.1kHz/24-bit] that really sold me on BAT’s preamp. This album encourages a close listen, as the guitarist – accompanied by cello, percussion, bass and flute – explores various textures and rhythms within the acoustic of Tunbridge Wells’ Trinity Theatre. The VK-90 appeared to sweep nothing under the carpet in terms of detail, shining a light on Forcione’s slick guitar playing in the languid ‘Heart Beat’, and conveying the force of Adriano Adewale’s snare drum hits in the jazzier ‘Attempo’.

These pieces sounded effortlessly musical, aided by a spacious soundstage. Yet when Rebecca Pidgeon’s ‘Underwater Boys’, from Sudden Exposure To Light [Toy Canteen Records], required the opposite, being music with a tightly focused image, BAT’s VK-90 followed suit. Here was a precise, punchy presentation, with Pidgeon’s vocals, complete with odd ‘underwater’ effect, pushed forward of insouciant-sounding piano and keyboards.

Above: BAT’s all-alloy VK-R5 remote provides access to input selection, volume, mute, mono, absolute phase and display brightness

The partnering REX 500 power amp clearly acts in synergy with the VK-90 in delivering the overall system sound, so those interested in this preamp should audition it with both that unit (or the REX 300), and the tube-based REX 3. Either way, this preamp retains an ability to fully immerse you in the music, revealing vocal inflections and instrument timbres, and matching its slightly romantic air with swagger and slam.

Grit to glory

The Rolling Stones’ ‘Live By The Sword’ [Hackney Diamonds; Polydor, 96kHz/24-bit] features Mick Jagger belting out rhyming couplets and a first-take-of-the-night groove, down to the handclaps and Elton John hammering away at the piano. The VK-90 sounded lithe and loose here, before ramping up the scale and grandeur for ‘Sweet Sounds Of Heaven’, where the venerable rock stars slip into gospel mode.

This is a big-hearted composition, with the juxtaposed vocals of Jagger and Lady Gaga sat atop a deep, rich bass. There are moments of blackness, the track flitting in and out of darkness, where the VK-90’s silent background pays very real dividends. For a band in its sixth decade to be delivering music this fresh is quite remarkable. While BAT is 25 years young, the same might also be said of its VK-90 preamp. Sweet sounds, indeed…

Hi-Fi News Verdict

At half the price of BAT’s REX 3 reference preamp but leveraging much the same technology and all of the features and connections, the VK-90 is an easy recommendation. Its tube gain stage yields a detailed, smooth and open performance that gets to the heart of the music at hand. Add one of the brand’s solid-state amps for a ‘best of both worlds’ pre/power combo, or keep it all tubes. The choice is yours.

Sound Quality: 89%