Balanced Audio Technologies VK-90 and REX 500

REVIEW
Buzz Hughes
Apr 03, 2025

The Balanced Audio Technologies VK-90 preamp and REX 500 power amplification combination is a warhorse. Like you would expect when describing a warhorse. The combo is physically imposing and designed to have everyone who takes it in nod with respect. When the 19kg VK-90 and the nearly 26cm tall, 63kg REX 500 were set up side by side on my credenza, it made the rest of my reference system look like little toys.

This warhorse effect is precisely what Victor Khomenko, BAT’s chief designer, had in mind when his REX 500 was designed. It can power any speaker on the planet by producing 500watts/channel into eight ohms and 1000 watts/channel into four ohms. The list prices for the VK-90 and REX 500 fall somewhere between ‘ultra-hobbyist’ and ‘high-ender’. So, is the VK-90 and REX 500 combo one of the highest-performing combos out there? What happens when these warhorses go to war?

BAT_VK_90_Preamplifier

The VK-90 is a fully balanced zero feedback tubed preamplifier with only one gain stage. The preamp uses eight 6H30 custom BAT supertubes (known for low distortion and minimal microphonic noise) in a ‘unistage’ circuit. This circuit is an ideal model of straight signal integrity. It amplifies the incoming signal only once without any other global feedback. The simpler and shorter the gain stage, the less chance a design will lose micro detail or gain any noise. Also notable in the VK-90 is the custom-designed Superpak energy storage power supply. The Superpak is on its 3rd generation of refinement and skilfully constructs two capacitors brought together into a single low resonance shell with internal silver/oil hybrid construction.

Sure to Impress

When it comes to tactile and visual impressions, the VK-90 also is sure to impress. The brushed aluminium case is simple and understated but has a very intriguing front face etching that suggests to my mind that this preamp is positioned to look into the future without presenting itself aesthetically as too far “out there,” a pitfall other equipment in the price range plunges into far too often.

The all-important volume knob for the VK-90 is a delightful feeling shunt volume attenuator that is a CPU-controlled analogue resistor ladder through which BAT has ensured that the signal will remain completely analogue. I found the sound of the VK-90 to be extraordinarily stable and neutral.

Tubes?

Hearing this preamp blind, I would never have guessed that it was a tube-based sound. To my ears, it erred on the side of being clean and precise rather than soft and romantic. The VK-90 did an excellent job of getting out of the way and remaining an impactful yet discreet part of the signal chain.

However, BAT’s flagship REX 500 Power amp does not have the same luxury of remaining so discreet. This massive 19″ x 10’’ x 24’’ stallion of a power amp is not going to be able to hide anywhere in your rack. Why is it so big? Well, BAT engineers would tell you that a bigger box allows for adding a bigger power supply. BAT asserts that cubic inches matter and takes it to be the most fundamental design principle of the REX 500. The immense non-regulated power supply in the Superpak is decoupled from the primary energy storage. It contains 800µF of energy storage with the help of sixteen high-quality hybrid silver foil oil capacitors. The more power capacity offered, the more the music can untether itself from your speakers and immerse you in a more genuinely open, three-dimensional space.

The BAT Pak

Previous BAT power amps have used the BAT-Pak technology as well. Still, the significantly higher-rated REX necessitated that the BAT-Pak be redesigned. This reworking provides a more fluid delivery instead of acting as merely an onboard energy extension. The REX Superpak is designed with a two-stage signal path and an authentic dual-mono design; the second signal path is designed with on-board power rectifiers, making it capable of adding power to the output stage. BAT designs are known to balance gain stages to achieve zero feedback, which also applies to the REX 500. The company strongly believes a well-designed power supply needs power-line frequency ripple reduction. BAT achieves this goal in the REX design by using active filter supply C-multiplier circuits, which can handle the fine nuances linked to higher frequency components.

In the product literature, BAT states that its goal with this amplification combo was to find new levels of open and spacious sound. This was one of the noticeable effects of my listening experience with the equipment.

Sell the sizzle

To augment the open quality, I also heard added slam and sizzling hot detail pushed obscenely far out into the perimeters of my regular listening environment. The descriptor ‘sizzling’ is deliberate because, listening through my Totem Metals V2s, I have never been treated to this kind of tactile bubbling energy so far away from my speakers. Chalk that up to the Balanced Audio Technologies VK-90 and REX 500.

I never thought I had any issue filling up my wide room with sound before this audition, but now, with the VK-90 and REX 500 pushing the envelope, details, textures, nuance, and visceral power were heard so far away from the speakers it was almost as if someone had set up an adjacent two-channel system on both sides of my speakers. I must admit that I had become used to the idea that any soundstage would melt away the further you got away from your pair of speakers’ sweet spot. Still, this BAT equipment completely changed my notion; that the correct effect is a strong picture frame with weight and punch in the outermost reaches.

Out of the Cool

To illustrate this picture frame effect, I’ll reference the ‘Stratusphunk’ track from the Acoustic Sounds Series LP reissue of Gil Evans Out of the Cool [Impluse]. Right around 1:58 seconds into the cut, drums crash in from the left and the trombones and trumpets crash in from the right channel. If you’re listening on the VK-90 and the REX 500 you had better be ready because the crash at the perimeter picture frame is so far away and yet so real and so powerful that the effect is as shocking as if someone snuck into your house and obliterated a vast pane of glass in the next room, it pulled me out of the cool indeed and then out of my seat. Bravo Gil!

Another indelible mark made by this equipment combo is the freaky three-dimensionality this preamp and power amp could summon throughout diverse genres of music. To make my point here, I will reference the marvellous and completely underappreciated English rock record; Jimmy Campell’s Half Baked [Vertigo]. The front to back space between acoustic guitar phrasing on the title track ‘Half Baked’ became almost a visual experience rather than an auditory one. So much so that I admit it was slightly disorienting at first.

Touching shapes

I won’t beat a dead (war)horse, but this is the first amplification combo in my system that had me restraining myself from trying to touch the shapes as one would imagine at a 3D movie premiere. Without straining, I could hear around and behind the violins and floating acoustic guitars to discover new pockets of space. I have listened to Half Baked at least 25 times, but these discoveries were important; they were of the “how can this record be so good” type and made me love the music all the more.

There is one drawback to the VK-90 / REX 500 combo that I could not outrun. This amplification is a brutal revealer of bad recordings. I had the experience multiple times that LPS and CDs in my collection that I used to think sounded great had severe and crippling limitations. It can be a bit hollowing to realise a pet favourite is not all you thought, and it was hard not to associate these feelings with the BAT equipment as the ‘cop’ policing what sounds good or not so good. But if you think about it, that kind of look into reality is what you are after in your system. Once I got over some of those small personal losses, the upside of the experience was that it was rich and nuanced with worthy recordings that balanced out in some cosmic way.

Oompa Loompa BATtadee dee

I’ll leave you with one final anecdote. My daughter’s ‘end of the 5th term musical’ was Charlie and the Chocolate Factory… and she played a no-talent-needed Oompa Loompa; thank you for asking. We must have watched the classic Wonka movie four times in preparation. An incredible scene comes to mind at the film’s end when Willy Wonka asks Charlie not to forget the cautionary tale of the man who suddenly got everything he ever wanted… punchline: he lived happily ever after. The VK-90 and REX 500 enabled my equipment and the best of my recordings to sound better than I ever thought possible.

It’s a whole lot better. Not inches, miles. Some were so new and endowed with fresh magic when played on the Balanced Audio Technologies VK-90 and REX 500. I know I won’t be able to pull them back out until I can hear them again in BAT’s glow. That notion will not work out well for me when I have to give the review samples back. The point is, if the VK-90 and REX 500 were the last pairing I ever had the opportunity to audition, mark me down as a yes. I could live with them happily ever after without ever having a second thought.