Note: for the full suite of measurements from the SoundStage! Audio-Electronics Lab, click here.
The power amplifier is the tough guy of the audio world. A good power amp is quiet, solid, and powerful. There are no moving parts in an amplifier. It does one thing only, and, if it’s a good one, it does that with grace, strength, and purpose. My martial-arts teacher, a quiet, solid, powerful Korean gentleman who’s now in his early 80s, says that while you can’t always tell who is tough by looks alone, it’s pretty damn easy to determine who isn’t tough.
Chin position is a good indicator, he once said. The tough animals in nature keep their chins down, tucked in and out of the way. The eagle. The tiger. These animals keep their heads down, eyes locked forward, saying nothing. Now consider a small dog. It strains against its leash, with its chin up, yapping away—utterly ineffectual.
Point being, if you’re approached by a loud-mouthed, chin-up, chest-out assailant, it’s probably all bluster. Now, I’m looking at Balanced Audio Technology’s REX 300 sitting in front of me, between my speakers. It’s solid, dark, and powerful; it does its job without fuss or drama. It’s heavy, inert, and purposeful.
Carry the weight
The REX 300 ($15,000, all prices in USD), the latest amplifier from US-based BAT, is a midsized powerhouse: a smaller version of the company’s top-of-the-line, solid-state REX 500 ($25,000). While BAT broke into the audio scene in 1995 as a manufacturer of tube amplifiers, it has been making solid-state amps since 1996, and the company’s lineup features nearly as many solid-state products as it does tube-based components.
BAT specifies that the REX 300 will output 200Wpc into 8 ohms or 400Wpc into 4 ohms. The ability to double the power by halving the impedance suggests that this guy is likely stable into even lower impedances. The REX 500 has more than twice the output of the REX 300, but this reviewer thinks that the little bro is more than powerful enough for any sane use. The REX 300 can be converted at the factory to a mono amplifier, so you could always add another REX 300 if you’re feeling the need.
There’s much of note going on in the REX 300. The business end of the amp comprises ten 300W n-channel MOSFETs. Backing up these devices is BAT’s signature SuperPak power supply. The single 800VA transformer is filtered by a large number of high-quality capacitors, which BAT cofounder Steve Bednarski describes thusly:
The fourth-generation SuperPak uses the concept of a bypass capacitor to improve the performance of the power supply but goes far beyond the traditional implementation of a bypass cap. Put simply, a high-quality bypass cap is commonly placed in parallel with capacitors (such as electrolytic power supply caps) to provide a “path of least resistance” for power delivery. Most often, you will see small, red, Chiclet-style poly caps used for this application. Such poly caps are very inexpensive. The REX 300 amplifier uses four stages of total filtration—or three levels of bypass beyond the first level of filtration provided by the electrolytic capacitors. Here, BAT uses some of the most expensive capacitors to tune the power supply for best performance. For example, the silver-foil-in-oil capacitors used in the REX 300 SuperPak are just such a cap.
Of note here is the REX 300’s SuperPak Quattro. This new version of the SuperPak is—as of now—exclusive to the REX 300.
The REX 300’s build quality is very good. The top panel is admirably thick (but not ridiculously so) and well damped, and the venting, front panel, and heatsinks are all stylishly machined. The power button is located in the middle of the front panel, and is easily accessed via a sock-covered big toe. Powering up the REX 300 is anticlimactic—there’s a very short delay, maybe five seconds, after which there’s music. During my time with the REX 300, the amp did not so much as burp. Music played when it was switched on and was accompanied by no other noises.
There’s a big, rounded handle at the rear, which is nice, but without any other handholds, it’s limited in its usefulness. Visually, this amplifier doesn’t break any new ground. It’s nicely finished, but won’t look good anywhere but in a dedicated stereo system—not that the last point is a bad thing.
Speaker connections are via nicely turned brass binding posts on opposite sides of the rear panel. While there is one external slow-blow fuse for overall safety’s sake, the REX 300 is safeguarded by a fuseless protection circuit. Should you ham-fist a short while messing with the speaker cables, each channel can be individually reset via reset buttons next to the binding posts. I did not test this feature.
Over my time with the REX 300, I used three different pairs of speakers. First up were the DALI Epikore 9s, which I wrote about last month. After the DALIs moved on to their next destination, I inserted my own Aurelia XO Cerica XLs, which I’m still greatly enjoying. Toward the end of my time with the REX 300, I dropped in the Bowers & Wilkins 805 D4 Signatures (review forthcoming), running full range but augmented at the bottom end by a pair of Bowers & Wilkins DB2D subwoofers. Speaker cables throughout this time were Crystal Cable Art Series Monets.
Hookup was as simple as you’d expect. At 70 pounds, the REX 300 is a chunky little guy, but not unmanageable by me alone. Of note are the inputs. This is—obviously—balanced-input territory. There are no RCA inputs, and if you want to use a single-ended preamp, you’ll need to source RCA-to-XLR adapters. But really, the Balanced Audio Technology philosophy is predicated on balanced signals—hence the name. I don’t think this amp is right for you if you’re using a single-ended preamp.
I used two different preamplifiers with the REX 300: a Simaudio Moon Evolution 740P and a Hegel P30A. These are both fully balanced, and I connected them to the REX 300 via Nordost Tyr 2 balanced interconnects. My sources—a EMM Labs DS-EQ1 optical phono equalizer and Meitner Audio MA3 streaming DAC—were also connected via XLR interconnects, so we were balanced all the way, baby.
The REX 300 ran hot. It warmed up from cold right quick, and while listening at reasonable levels, I registered 122°F at the hottest part of the heatsink. While driving the DALIs during one particularly sprightly listening session, I managed to get the amp up to 127°F. I queried Bednarski about this, asking him how far into class A the REX 300 was biased. He responded pithily:
The REX 300 is designed as a heavily biased class AB design. This allows the output devices to work at their best set point for peak performance. As such, the unit will run somewhat hot. In this regard, note that 127 degrees Fahrenheit is not “hot” by electronics standards. For example, premium capacitors are rated to 85 degrees Centigrade, such that the 50 degree to 55 degree Centigrade temperature of the REX 300 is well below such a rating. I have hiked down the Grand Canyon with the heat radiating off the rocks at a temperature of about the same. Silicon is far more tolerant of such heat.
Nipping over to the REX 300’s web page, I discovered that its power consumption is specified as 400W at idle and an impressive 3000W at full chat. Needless to say, I powered off the REX 300 at the end of my listening sessions. One evening I forgot to do so, and next morning I winced as I imagined the little dial on my electric meter spinning wildly for the whole night. I was surprised to note that the REX 300 didn’t need much warm-up time before its auditory performance steadied out. Ten minutes or so was all it took to stabilize.
Toasty
The REX 300 is a harmonically complete amplifier. While it’s (obviously) got muscle, it’s kind to the music’s inner details. And this is where we will start: All those tiny hints of information, the dust motes that float through the air as the sun shines through the window. Music’s Brownian motion. It’s all here inside the world that the REX 300 creates.
There’s a whole world of small happenings inside Talk Talk’s music. I’ve recently been re-exploring Talk Talk’s first real album—where the band found its voice and broke out into the world. I was 21 when It’s My Life (LP, EMI ST17113) was released, and I recall how it struck me, bouncing to the title track in a huge dance club, and later while lost in the rest of the album via headphones as I fell into Talk Talk’s ethereal world. “Tomorrow Started” projects an immersive soundscape, with Paul Webb’s fretless bass underpinning all the other comings and goings. With the REX 300 in the signal chain, I found myself drawn in, more able to contrast the programmed drum track to Morris Pert’s tasteful percussion. Through the BAT, the brief trumpet break sizzled with juicy overtones, and the sprinkled piano notes stood out in three-dimensional space.
The textural density of the REX 300 is a result of its harmonic purity. Over the years, I’ve noted that much of the music played at hi-fi shows tends toward the sparse end of things. One or two instruments, or a quartet at most. Exhibitors don’t favor thrashy, busy music as it often doesn’t bring out the best in a system. Busy music is difficult, I think, for both the systems and the listeners.
I don’t want to lay the issue of complex music being hard to reproduce solely at the feet of the amplifier. A speaker, by its very nature, has to do a whole bunch of things at once, playing many tones at the same time. On the face of it, this task seems nearly impossible—but it works! Still, I think different amplifiers handle complicated music in different ways. Some work at the macro level, giving scale and power, while others dig deeper and unearth details that might otherwise be missed.
And of course, there are degrees here. A single-ended 300B tube amp is at one end of the equation—it’s all inner detail and not much on the grand scale. My Hegel H30A amplifier is all the way at the other end. It’s a huge, powerful amp that portrays music with power and grace.
If you put that 300B amp over at the far left of my little scale—let’s say at -10—and the Hegel way over on the right at +10, the REX 300 sits somewhere around +7, I’d say. This doesn’t mean the Hegel is better than the BAT. No, sir—it’s just different. The REX 300 has tons of scale and horsepower, it still slams, but it trades off just a smidge of scale for a sense of delicacy in how it portrays those small details, those flourishes.
Four-Calendar Café (16-bit/44.1kHz FLAC, Capitol–EMI / Tidal), by Cocteau Twins, is full of little baroque flourishes. “Bluebeard” finds Elizabeth Fraser’s voice rising and falling, with chirping birdlike accents above and below her main melody, weaving a vocal tapestry that’s utterly magical. “Are you toxic for me? / Will you betray my confidence?” she muses. Through the REX 300, I found my attention jumping between the different versions of her overdubbed voice, each layer rendered through the midrange with clarity and harmonic completeness.
Being a large solid-state amplifier, you’d expect the bass to be solid, quick, and tight. There were no surprises here. Solid, quick, and tight along with just a lick of that textural detail, this was a very satisfying amplifier when playing bass-heavy music. Massive Attack’s Protection (LP, Wild Bunch 7243 8 39883 1 0) is bass-heavy music. The title track doesn’t go down so very low, but it crept out from the REX 300 like a heavier-than-air gas, suffusing the room with a weight that pressed down on my chest and made it hard to breathe. Via the BAT, I got that weight, with just the tiniest extra sense of definition within the harmonic that surrounds the fundamental. That textural subtlety with the midrange and treble added just a hint of slinky tunefulness to the bass.
I heard that bass flavor, that swagger, in Gord Sinclair’s playing on the Tragically Hip’s Fully Completely (LP, MCA 0254704109). Sinclair isn’t a virtuoso; he’s no Geddy Lee. No, he’s a tasteful player. You can hear this on “Pigeon Camera,” where his playing complements what everyone else is doing. He’s not trying to make himself heard, but, my stars, does he get the job done! I usually don’t focus on Sinclair’s bass lines, but here, through the REX 300, I could pick out his playing with more clarity than usual. Not because of a level difference, and not because the bass was any quicker or tighter than I’m used to. And on the occasions when Sinclair lights it up, as he does in the title track, the REX 300 gave me a touch more focus on the roundness of his loping, giddy-up backbeat.
Up top, the REX 300 managed that balancing trick of sounding both detailed and sweet in the highs, with—I hope I’m not boring you here—excellent resolution of textures and harmonics. Flipping over to another Hip album, Road Apples (LP, MCA 3844804), Johnny Fay’s cymbals—both hi-hat and ride—are beautifully recorded. On “Little Bones,” I was drawn into the mix, bouncing off each instrument in turn. Those cymbals were prominent and juicy, and I could fall into them or let them recede back in my focus at will. I could also turn up the system really, really loud without any ear strain. On the contrary, the REX 300’s silky highs, redolent with crisp clarity in the fundamental and burnished richness in the harmonics, seemed to make loud listening sessions—especially to a magnificent album like Road Apples—a true pleasure.
As I have mentioned, I drove three different sets of speakers with the REX 300, and (cop-out incoming) it sounded terrific with each of them. The amp’s unique, textural beauty, the deep sense of purity, came clearly through with each of them, and I could live happily with the resultant sound no matter which speaker it was driving.
But if I had to choose, the best pairing of the three was with the Bowers & Wilkins 805 D4 Signature. You might be forgiven for thinking that an amplifier that emphasizes texture and detail might not be the best match for a speaker that also emphasizes texture and detail. My review of the 805 is forthcoming, but it’s no surprise, and I don’t think I’m giving anything away if I tell you right now, that the 805 has a fair amount of similarity to the 801 D4 Signature, which I reviewed a couple of months back. Both speakers—big brother and little brother—lit up the music as if they were powered by the sun. And the combination of the B&W 805 D4 and the REX 300 was so engaging that it took my breath away.
The REX 300 also sounded great through the Epikore 9s. Same thing here—I could easily identify the harmonic purity of the BAT, its tonal beauty. At anything short of full-throttle volumes, the BAT could spank the DALIs right hard, but there came a point where it felt like the amp was starting to harden up. The 50%-more-powerful Hegel Music Systems H30A amplifier didn’t seem to hit the same wall. Keep in mind that we’re talking about serious, neighbor-hating volumes here, played via a large, complex speaker. It’s no slight on the REX 300 that it had a bit of trouble here. If you’re really that much of a headbanger, BAT offers the REX 500, or you could go baller and spring for two REX 300s, which, via the Epikore 9s, could likely fuse hydrogen atoms. One last option is to listen at sensible, adult levels and never encounter this issue.
My own Aurelias? The Cerica XL is a pushover and sounds pretty damn good with any amp. The REX 300 blended wonderfully, giving just a hint of that extra inner light to the Aurelia’s holy-shit 3D imaging.
The short hairs
I guess we’re down to the short hairs of this review. After I sent the REX 300 off to our SoundStage! measurements lab, I reinserted my Hegel H30A and continued listening. The H30A is a wonderful amp: it’s neutral from bottom to top; it’s clean, clean, clean. That said, the Hegel is never bright or aggressive. No matter what speaker I use with it, no matter what music I’m playing, the H30A never imposes its own character. It’s the perfect reviewer’s tool.
The REX 300 is also tonally neutral. It doesn’t highlight any area of the frequency spectrum. However, it does add in the smallest amount of sweetness in the highs. Or takes out some of the almost-inaudible, residual harshness. This is a delightful trait that allows an amplifier that could be an excellent reviewer’s vehicle to take a slight veer over into the music lover’s lane.
Don’t bother wrapping it
I could easily live with this amp. Throughout this review, I’ve resisted making any allusions to Balanced Audio Technology’s tube-based origins, as a component—such as this one—should stand alone without referencing other products in the company’s line.
However, as I finish this review, I’m listening to “Nisroc” from Koby Israelite’s Orobas: Book of Angels, Volume 4 (16/44.1 FLAC, Tzadik Records / Tidal), which is ostensibly a John Zorn composition. The overriding instrument in this song is a gently brushed ride cymbal, and it’s accompanied by a full house of other instruments playing in the same frequency range. There’s a sense of sparkle, a delicacy, an ingrained juiciness that is often the hallmark of the best tube amplifiers, and seldom translates to solid state.
No, the REX 300 doesn’t sound like a tube amp. What it sounds like is an excellent solid-state amplifier that’s been designed and built by a tube-amplifier company. It’s a lovely component and deserves my highest recommendation.
. . . Jason Thorpe
jasont@soundstagenetwork.com
Note: for the full suite of measurements from the SoundStage! Audio-Electronics Lab, click here.
Associated Equipment
- Analog sources: VPI Prime Signature turntable; European Audio Team Fortissimo S turntable; European Audio Team Jo N°8, DS Audio DS 003 cartridges
- Digital sources: Logitech Squeezebox Touch, Meitner Audio MA3
- Phono preamplifiers: Aqvox Phono 2 CI, Hegel Music Systems V10, EMM Labs DS-EQ1, Meitner Audio DS-EQ2
- Preamplifiers: Hegel Music Systems P30A, Meitner Audio PRE, Simaudio Moon Evolution 740P
- Power amplifier: Hegel Music Systems H30A
- Integrated amplifiers: Hegel Music Systems H120, Eico HF-81
- Speakers: Focus Audio FP60 BE, Aurelia Cerica XL, Totem Acoustic Sky Towers, DALI Epikore 9, Bowers & Wilkins 805 D4 Signature
- Speaker cables: Audience Au24 SX, Nordost Tyr 2, Crystal Cable Art Series Monet
- Interconnects: Audience Au24 SX, Furutech Ag-16, Nordost Tyr 2, Crystal Cable Diamond Series 2
- Power cords: Audience FrontRow, Nordost Vishnu
- Power conditioner: Quantum QBase QB8 Mk II
- Accessories: Little Fwend tonearm lift, VPI Cyclone record-cleaning machine
Balanced Audio Technology REX 300 stereo amplifier
Price: $15,000
Warranty: Five years, parts and labor
Balanced Audio Technology
1300 First State Blvd., Suite A
Wilmington, DE 19804
United States
Phone: (302) 999-8855
Website: balancedaudio.net
