There was a period in the 1970s when many pop ballads that should have had understated arrangements instead turned grandiose and even maudlin. Take Gilbert O’Sullivan’s sensational single “Nothing Rhymed” (a track that went deep for a pop hit, referencing famine, duty, and morality). Soon after the start, O’Sullivan’s piano is overshadowed by a loud, saccharine string section.
Another example is “Lotte,” German singer Stephan Sulke’s portrayal of a dying love affair. The devastatingly wistful chanson is burdened by a mawkish orchestral track—the equivalent of glitterbombing an Edward Hopper painting.
Contrast this with Roberta Flack’s definitive version of Ewan MacColl’s “The First Time Ever I Saw Your Face.” Apart from Flack’s voice and her emotional delivery, the gently strummed guitar and quiet piano do all the heavy lifting. An unhurried double bass and a couple of minimally bowed string instruments leave swaths of negative space, helping to give her interpretation its hushed, reverent character.
I reflected on all this after spending several months with Balanced Audio Technology’s REX 500 solid state power amplifier ($25,000), which has more in common with the Roberta Flack track than with the bombast of “Nothing Rhymed.” I don’t mean to say that the REX’s sonics are understated—that might imply shyness, and it definitely isn’t a shy-sounding product, but it’s a far cry from the amplifier equivalent of O’Sullivan’s bombast. But enough about this for now: more after you’ve met the amplifier in question.
Attack of the forklift
You’ll need help moving and unboxing this beast, which is deeper (23.5″) than it is wide (19″) and weighs a grueling 140lb. I experienced its bulk and weight more than once because the first time I received the REX 500, it had to go back for repair. What seemed at first like an inconsequential tear in the shipping box was, upon closer scrutiny, the likely result of a forklift blade punching through the cardboard and ramming the REX’s right side. The bend in the casework looked like it was part of the swooping design of the flanks, and the damage to the heatsink was invisible except when the top cover was removed. What was easily noticed was a loud hum from the speakers. Hours of troubleshooting got me nowhere. The buzz was impervious to different outlets, power conditioners, interconnects, power cables, and assorted sources. It did go away when I substituted either my Krell or Anthem amplifiers. At that point, I knew that the REX needed a bench check, so back it went to the Wilmington, Delaware, BAT cave.
The company determined that a hard impact had dislodged one of the SuperPak capacitors and broken some solder joints. (The build quality of the REX 500—all aluminum except for a thick steel bottom plate that supports the supersized transformers—is sterling (footnote 1), but in a deathmatch with a carelessly driven 9000lb forklift, it lost.)
About 10 days later, I took possession of a replacement Rex 500. Other than my poor back, after that, all was well.
Visually, the REX means business. Forty-eight heatsink fins adorn each side, hidden behind the fascia when you view it straight-on. The front of the amplifier is almost but not perfectly symmetrical: On the left edge is a 1″-wide vertical billeted-aluminum strip, mounted at about a 20° angle toward the rear, milled to read “Rex 500″ with a swoopy, vaguely art deco–style R. Positioned in the middle of the front plate is a springy, narrow, 2”-tall power switch. The blue LED just to its right, slightly off-center, has a simple function: It merely indicates whether the power is off or on—it doesn’t flash during the roughly eight-second turn-on sequence or turn red when the protection circuit kicks in. Protruding from the back panel is a curved metal handle that’s intended to assist in lifting the REX—but it’s not enough by itself. BAT advises using a rope or cloth sling tied around the front so that two people can lift the REX from the box and move it into place.
Also on the back, you’ll find loudspeaker binding posts, a pair of XLR inputs, and two each—one per channel—IEC connectors and fuse holders.
BAT makes a point of avoiding fuses inside its amplifiers: “The best-sounding fuse is no fuse at all,” the company says. BAT’s auto-protection circuit does away with the need to replace internal fuses. The absence of internal fuses has the secondary benefit of allowing the REX to handle higher currents without crippling the circuit’s operation.
Those fuse holders you see? They’re in line with the AC, to protect the whole amplifier from external power surges. Why two? Because the REX 500 has separate left and right power cords and power transformers.
Speaking of protection circuits, if your speaker cables are terminated with spade lugs, as my AudioQuest Thunderbird Zeros are, I’d advise caution. The posts are close enough together that large spades are only separated by a millimeter or two. Once, with the amp turned on and everything connected, I decided to tidy up the speaker cables a bit. As I moved the first one, its positive and negative lugs torqued around the binding post stem … and touched.
The only anomaly I experienced during my time with the REX involved the auto-protection circuit, which kicked in seemingly at random three or four times over a few months. The puzzled BAT team asked if it shared the AC line with another piece of equipment with a large power draw, such as a refrigerator. It didn’t. In fact, my listening room has a dedicated line for audio, with a pair of 20A circuits. Perhaps, we speculated, intermittent voltage drops or surges caused the cutouts.
Then again, since I began using the new room more than a year ago, no other straight-to-the-wall amplifier seemed affected by voltage irregularities.
None of this is worth obsessing over considering that the BAT’s better-safe-than-sorry protection circuit activated infrequently and that getting the amp back to normal was always a quick affair (footnote 2).
To preamp or not to preamp
Because my equipment console is only 15″ deep—about 8″ too short for the REX—I used an impressively beefy Finite Elemente Pagode HD-10 amplifier stand, centered on the floor between the speakers. Atop the amplifier, separated from it by a 4″-tall Townshend Seismic Podium that allowed for good separation, I placed the REX’s preamplifier brethren, the tubed VK-90. BAT had sent the VK-90 along with the REX 500 in the expectation that it would prove an ideal pairing.
I decided to evaluate the amp in three ways. First, I went without a preamp, using the volume control of my main source, an Aurender A20 digital transport and server. Then I listened to the REX with the Aurender connected via the line stage of my Benchmark HPA4. Finally, I pressed the VK-90 into service, again using the A20 as a source.
While I did indeed prefer the sound with the BAT preamp in the chain by a small margin, I spent the least amount of time with that combination because I wanted to home in on the sonics of the REX without the wild card the VK-90 presented.
BAT co-founder Steve Bednarski told me he’s keen on listening with a preamp in the system. I asked him why: What’s the downside to feeding a power amp the output stage of a DAC or other digital source? “A well-designed active line stage will provide greater current delivery from its output stage than almost any source omponent,” Bednarski emailed back. “Current delivery gives a sense of liveliness and joie de vivre to the reproduction of music. For instance, a CD player that uses an op-amp–based output stage will provide weak current delivery. When such an output stage is connected directly to an amplifier, the music can sound flat and uninvolving.” (footnote 3)
Bednarski wanted me to experience the REX with a tubed line stage like the VK-90 because he feels that combining a valve preamp with a solid state amplifier can better flesh out colors and textures. This regard for tubes goes back to the company’s very beginning, in 1995. For almost three decades, BAT has built high-end valve and solid state components, the latter culminating (for now) with the REX 500, BAT’s flagship power amp.
Footnote 1: Damage aside, removing the top cover reveals this to be a very handsome amplifier on the inside—at least as attractive as its outside. That assumes, though, that it hasn’t been rammed by a forklift.
Footnote 2: I swear that right as I was typing that sentence, the amp’s protection circuit kicked in. An all-day storm is raging outside, with 65mph coastal winds that tax my state’s antediluvian power grid.
Footnote 3: There are other arguments in favor of using an active preamplifier. For one of the more convincing, see the post by Benchmark Media’s John Siau at benchmarkmedia.com/blogs/ application_notes/benchmarks-256-step-relay-controlled-attenuator. Scroll down and start reading at the subhead, “The ‘Fully Passive’ Myth.”—Jim Austin
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DE 19804
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