Audio Research LS17 Preamp Reviewed

Audio Research LS17 Preamp Reviewed

Audio Research's $6000 line-only preamp delivers consummate performance with its 104-step volume control, two 6H30 twin triode tubes and hybrid JFET/tube output stage. With nearly all the detail retrieval and openness of the REF 3, the LS17 is a surefire winner.

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Given that Audio Research managed to provide a frisson of REF sound in their entry-level PH5 phono stage, is it too much to hope that the same benediction might apply to a new entry-level LS-series preamplifier? Imagine: an affordable preamp with a goodly slice of REF3 magic. 

Clearly, the LS26, which nestles smack in the middle of the range, exhibits much of the REF3's capability, but that unit costs £5300. You'd not merely expect top-flight performance at that price, you'd demand it. The LS17's price tag, though, brings us that much closer to Earth. It costs a more attainable £3099/$6000.

Additional Resources
• Read more stereo preamp reviews from HomeTheaterReview.com.
• Find a pair a speakers that work well with the LS17.

Which is not to say that it lacks for anything beyond an elevated price, and I would not deduct a single point for the absence of a phono stage: this was designed from the get-go as a line-level-only preamp. Besides, it begs for the partnering PH5 phono stage, should vinyl be among your most-used sources.

Audio Research has been making line-only stages from some time, and this one clearly respects the brilliance of its predecessor, the delightful LS16, by tampering only slightly with the recipe. Like its forebear, the LS17's ingress and egress include two balanced and five single-ended inputs, plus two balanced and one single-ended output, while a tape deck is served by a dedicated monitor input and record output. The seven inputs are labeled BAL2 and BAL1 for the XLR-equipped balanced inputs, while the phono-socketed single-ended inputs are tagged AUX, Tuner, CD, Proc (for the insertion of a processor) and Monitor.

Where the '17 departs from the '16, while resisting the full-on light show of the REF3, is the fitting of a rather classy, newly-commissioned linear LED display. Its main function is a 20-lamp horizontal sequence for visual determination of where you've set the 104-step volume control - very tasty. It also contains indicators for the selected input and muting, and it's about as sensible and legible as one could want in this day of preamp/processors with miniature LCD TV screens onboard.

So hair-shirt it is not. Two rotaries control volume and source selection, while push buttons access power, tape monitor, the unity-gain processor loop and mute; these functions are also found on the supplied handheld remote. The company has also addressed custom installations, so all of the LS17's functions are individually addressable by discrete codes for integration with external controllers. Despite such modern touches, the LS17, especially in silver, is unmistakably an ARC product, thanks to its lab look, complete with black handles fitted as standard.

Under the hood, the LS17 employs two 6H30 twin triodes in its hybrid JFET/tube audio stage. The 480 x 134 x 305mm (WHD) chassis houses a larger power transformer, redesigned power supply with line regulation better than 0.01 percent and new parts, including proprietary output coupling caps. The power supplies are electronically-regulated, low and high voltage types. The circuitry provides an automatic 50-second warm-up time, which places the LS17 into mute mode after switch-on, thus precluding any nasty power-on thumps. 

Around back, a host of XLRs stared me in the face, so it was all but mandatory that I first savored the difference between single-ended and balanced usage. Regular readers will know that I prefer the latter, and the LS17 did nothing to change my mind. If you have balanced-output sources and balanced input amplifiers, invest in some balanced-XLR-terminated cables and enjoy the added coherence, tighter bass and everything else that studio types will tell you do not exist merely by going to balanced operation. But, as I learned, those single-ended outputs came in handy when I stumbled upon a match made in Heaven. Of which, more anon.

Sources included balanced-output PS Audio and Sim Moon phono stages (with SME 30/SME V turntable and Koetsu Urushi cartridge) and the balanced output of the Marantz CD12/DA12 CD player. Power amps included the McIntosh MC2102 and Krell Evolution 600, driving Sonus faber Guarneris and Rogers 15-ohm LS3/5As. Speaker wiring came from Yter, and contained a mix of Transparent and Kimber balanced and single-ended interconnects.

For some inexplicable, if not quite perverse, reason, I've been masochistically over-indulging in singer-songwriter works of late, much of it like cod liver oil: you know it's supposed to be good for you, even if it tastes like something from the crankcase of a 1947 Hudson. So, too, is the music of Joni Mitchell, something everyone with taste is supposed to love, despite a voice like fingernails across a chalkboard. Bob Lind of "Elusive Butterfly" fame, the supremely over-rated, tuneless Tim Buckley - whatever is music's equivalent of luvvies. Maybe I did it for, well, enlightenment. Or to understand why I worship the Ramones.

Read more about the LS17 on Page 2.

audio-research-ls17-new.jpgBut what these "poets" all share are breathtaking recordings, masterful backing musicians and vocals with character. Feeding them through a system with the LS17 at its heart enables the listener to tap directly into their angst, which surely is the raison d'etre of their whining. Where it shines most is in its ability to sound devoid of coloration, especially ssss-artifice, while somehow conveying all the humanity of a voice without resorting to euphonic tube enhancement. That's the trickiest part of all to explain: the LS17 is undeniably a valve preamp, yet it keeps the euphony in check. Vintage-sounding it most certainly is not.

And that's because the LS17 has nearly all the detail retrieval and openness of the REF3, even if the portrayal is somewhat less majestic in dimensional terms. If there's arc with "warm" to one side and "cool" to the other, with perfection in the middle, the REF3 is a mere degree or two toward warm, while Krell's Evolution 600 is a hair toward cool. The LS17? A teensy bit warmer than the REF3, but still close enough to dead-center to qualify as a reference (with a small "r") device.

Enhancing this experience, a midband so lifelike as to beg a diet of unplugged material, are rapid transients and deep, rich bass able to flatter the hard, tight lower octaves of modern funk, as well as acoustic bass and percussion. Wilko Johnson's guitar fusillade on the remastered edition of Dr. Feelgood's Down by The Jetty borders on the vicious, with all the attack that his chopping style should embody. In the
same tracks, the late Lee Brilleaux's harp both punctuates and challenges the guitar, and the bass/drum rhythm section has such sheer mass that the mono disc sounds almost as visceral as the fuller stereo bonus CD. 

Shifting from Essex R&B to twee folk and back, from the wry delivery of Long John Baldry's Anglicized blues to the intricate harmonies of the Four Seasons, the LS17 proved as versatile with material as it is with source handling. But all of that was in an ideal situation: balanced mode, feeding 6k's worth of amp and another 6k's worth of speakers. I wanted to have some real-world fun with it.

So out came the Quad II Classic power amp. And although it's single-ended, it presented one of the nicest surprises of the review sessions. I was messing around in the listening room, organizing my CD library, doing the annual turf-out and clean up, and I suddenly got the urge to hook up the LS3/5As and the Quad II Classics - why, I'm not sure. Still using the aforementioned vinyl and silver disc sources, I heard a system few would imagine assembling even in full-on "Fantasy Hi-Fi" mode, but, by gum, it worked.

Both its immediate and net effects were revelatory, as if each component was allowed to shine and perform of its best - like tasting every ingredient in a fine sauce, while they still blended into a whole. There was the trademark LS3/5A midband, used to great effect on the new collection of Dusty Springfield at the BBC sessions. All the requisite textures were maintained, while the Quads inserted a tingle of warmth, a hint of lushness. Meanwhile, the LS17 simply did as it was told, commanding the sources components and feeding the amps.

It sounded so good that I even broke the rules by hooking the Guarneris to the Quads - a no-no because the Sonus fabers like more power. But at normal levels, with not-too-strenuous material, I was still able to hear the LS17 sounding almost as wide open as with the bigger amps, while it revealed a subtlety that complemented the small BBC monitors. Acoustic guitars - some Eric Bibb, some Rory Block - possessed a deliciously authentic woodiness. Bottleneck? Slippery and suitably metallic.

Far be it from me to suggest that this preamp negates the need for an LS26 or a REF3. But it is, undeniably, the best value of the trio, and a product so impossible to fault that I've ordered one for myself. Perhaps it's because my PH5 was feeling a bit lonely.

When Audio Research brings out new models, they always demonstrate the best of the "trickle-down" theory. A salesperson could say with a straight face that the LS17 offers, for around 3000, what would have cost 6000 five years ago. So, yes, it flaunts an indecent amount of the 9000 REF 3's prowess. Yes, it sounds simply delicious. And, yes, I'm buying one.

Additional Resources
• Read more stereo preamp reviews from HomeTheaterReview.com.
• Find a pair a speakers that work well with the LS17.

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