The Audio Research LS17 Preamplifier and the Grand Unified Theory

The Audio Research LS17 Preamplifier and the Grand Unified Theory


December 2007

Things tend toward integration; physics and chemistry; gravity and quantum theory; and perhaps more valuably for you and me, tubes and transistors. While tube-ophiles and transistor-ophiles argue ardently for the relative merits of these two technologies, the technologies themselves have gotten along famously under the hoods of such storied pieces as the Counterpoint SA-12/SA-100 and more recently, the Moscode 401HR amplifier. 

The former was my very first high-end amplifier and to the best of my recollection, was a marvelous symbiosis – marrying a midrange slightly honeyed by a couple of 6DJ8s to the potent, weighty bass of a solid-state bruiser. 

The Counterpoint SA-100, the Moscode 401HR, and now the Audio Research LS17 pre-amplifier. Yup, she’s a hybrid, and a beautiful one at that; a lovely blend of JFETs and 6H30 super tubes designed to capitalize on the best properties of both. While word count and training (intellect?), limit me to a brief description of the technicalities of such a fusion, a JFET or Junction Field Effect Transistor has particular objective advantages in certain applications over, say, its bipolar transistor cousin in that it offers a very high input impedance (which makes for a good input stage) and is less noisy/more linear than bipolar transistors to boot. Some people, not the least of whom are employed at the Audio Research facility, apparently feel JFETs have subjective advantages as well!

The 6H30 tube too, in the view of such industry luminaries as BAT, and now Audio Research themselves, offers gains over a 12AX7 or a 6DJ8 (more standard preamp fare) including improved linearity and significantly extended tube life; up to 5000 hours in the case of the LS17 preamplifier. 

Downsides? In a manner of speaking, that “increased linearity” that looks so sexy on an engineer’s oscilloscope, could translate, for some, into less of that sexy tube sound. Solid-state fans call this “neutrality” and tube fans call this “if I wanted a solid-state preamp –  I would have bought one!”

Meet and Greet
The star of this show arrived well-packed and intact – just the way I like ‘em. As a matter of fact, the source of my LS17 informed me they have not had an issue with significant shipping damage involving an Audio Research product in roughly a decade! Either that’s some amazing luck or testament to the security of ARC’s packing. 

Having just hefted my trusty ModWright 9.0 SE (now tube-rectified) off its perch on the Apollo equipment rack, plucking the LS17 from its Styrofoam cocoon, I noted immediately the sharp contrast in weight of the two units. The ModWright was considerably chunkier feeling and made the ARC feel like a Technics receiver or a “My First Sony” if you like. 

Must be a case of the ‘hybrids’ I thought; the ModWright being a tube unit through and through (with a mighty toroid power supply to boot). I popped the top on the 17 to inspect and install the 6H30s and noted a sleek interior layout utilizing AR’s proprietary capacitors. I carefully installed the 6H30s with the supplied tube dampers– two per side- and closed her up. 

The LS17 entered a system comprising at various times, a Lector CDP 7TL Mk. 3 CD player, a Lector CDP 0.6T mk. 2 CD player, a Parts Connection Level 2 Mod Raysonic CD128 player and depending upon my mood, an ARC 100.2 solid-state amplifier or a VTL ST-150. Speakers were my usual Proac Response 2.5s and my room is treated with Eighth Nerve Response Series products. The system is wired with JPS Labs cables, including bi-wire Superconductor+ Petite speaker cables and the remarkable Superconductor 3 interconnects. The terrific value-for-money Stereovox Firebird and Audio Art cables get subbed in from time to time as well.

A word about these new JPS ICs– they are remarkable musical conduits, leaving vanishingly small fingerprints on the signals they touch. I’d love to review ’em- but to do that, you gotta be able to describe what they sound like. Good luck with that one– damned if I can hear much of anything so far but the often times starkly distinct signatures of my other components and that‘s as it should be. Truly a laudable achievement, Joe! 

The Pudding
Once settled into my system, the LS17 proved remarkably reliable and easy to use. By way of comparison with my ModWright pre, the 17 has remote power on/off and a much more precise and finely-graded 104 step volume attenuator. This degree of precision with regard to remote volume adjustment allows you easily to dial in from the comfort of your listening perch the exact level at which a particular recording sounds most ‘live’. The coarseness of the attenuation steps in using the ModWright’s remote volume control (no issue with manual operation of same) was one of my few gripes with this otherwise wonderful pre and I understand Dan’s more upscale unit, the 36.5 (which uses 6H30 tubes… hmmm), addresses this issue handily. An upgraded volume control is apparently available for the 9.0SE as well.

Since I had just finished breaking the LS17 in for approx. 150 to 200 hours, and since it was a sunny Sunday morning and since a certain highly anticipated used Sony boxed set had recently arrived from, I decided to listen to Murray Perahia playing some Mozart piano concertos – a lot of them! I immediately noticed an increase in ‘ping’ and ‘hammer on string’ in the upper registers of the piano, along with a increase in the hall sound. The LS17 had just turned on a few more lights in the venue in which Perahia was performing. 

Stage width and depth were roughly equivalent to the ModWright player, though there seemed a slight diminishment in terms of dynamic fortitude – particularly microdynamic. In other words, my initial impressions of the ARC LS17 were that it portrayed more detail than my ModWright pre, though was a bit more delicate- a bit more reserved dynamically. 

As I listened more widely over the next few weeks, to everything from John Lee Hooker, to ‘We Three’ [Prestige/New Jazz PRCD-30162], a new Prestige re-master, the differences in the ARC and the ModWright sound came to be patently apparent. Essentially, the ModWright sounded more like you’d expect an excellent tubedpreamp to sound and the ARC sounded more akin to some of the excellent solid-state preamps I‘ve heard in the past. 

In almost all of the recordings I listened to where a concert hall was the recording venue, the ARC pre lit up more of the hall itself. The placement of singers within that space was more precise than via the ModWright and instrumental outlines were sharper. I could more easily place the locations of singers involved in duets and quartets etc. 

The ARC showed me that the ModWright does make some attempt to please its owner by warming up the mids/midbass a bit. Comparatively, the ModWright also slightly blurs the focus – but just slightly – as compared with both the excellent solid-state preamps I’ve heard and more germanely, as compared with the LS17. Mind you, I make no value judgment in terms of these perceived differences. I am certainly not of the “accuracy is best” school. I am in fact increasingly of the “the sound that most appeals to me is best” school and try to recruit members all of the time for same. 

Continuing, while the ModWright seemed to have more midbass weight and thereby could be more ‘dramatic’ with certain symphonic works etc, it seemed to have perhaps a slightly softer or at least somewhat less prominent and defined lower bass than the LS17. The very lowest bars on the stringed bass in Bill Evans’ “Sunday at the Village Vanguard” for example, seemed to shake things around the room a bit more via the LS17 than via the ModWright. 

The ModWright on the other hand, seemed to have, as previously noted, the edge if not in macro dynamics, then in microdynamics. String quartets such as the Emerson’s playing of Schubert’s work [DG 289 459 151-2] seemed more dynamically nuanced via the ModWright. It was the same with the Mozart’s piano concertos. They seemed a little more ‘lively’ via the ModWright. 

The SWL9.0SE though has achieved its well-deserved following due in no small measure to its superb dynamics and gusto, so I kind of expected this. In fact I haven’t really heard too many preamps surpass or even equal my ModWright dynamically and that includes the delightful, though less weighty and punchy Shindo Aurieges L I heard recently. 

Viva La Difference
During my time with the ARC LS17, it served as the nerve center for systems comprising both a solid-state amp and a tube amp along with three different CD players. Changes among components were quite apparent via the ModWright. They were even more starkly so via the ARC. This preamplifier is quite revealing of sonic differences among ancillaries, immediately revealing the tonal and spatial differences between my assorted amps, wires and CD players. 

I gradually began to feel that, like a good therapist, the LS17 seemed not to want to tell me too much how to live or what to do, but rather to let my system be more or less itself and speak with its own voice. 

Along these lines, the LS17 made recordings sound more drastically different from one another than I’m used to. For example, Mitsuko Uchida’s rendition of the Beethoven Emperor piano concerto under the baton of Kurt Sanderling [Philips 289 462 586-2] was revealed to be notably worse than I thought! Via the ModWright it was reasonable – not great – but reasonable. Via the LS17 – well, it was uninteresting at best; un-dynamic, flat and poorly balanced; an unmistakable mistake. Uchida’s touch is wonderful in it too (if a shade too delicate for my tastes as compared with say, Eugene Istomin); a shame. 

On the flip side, it wasn’t until I heard it via the LS17/VTL combo that I realized what a great re-master of the 1952 performance of the Beethoven ’Eroica’ with Furtwangler at the helm [EMI 7243 5 67490 2 3] was– terrific instrumental texture with absolutely no edge! 

And on it went, with John Mayer’s Continuum [Aware/Columbia 8287 679019-2] sounding more human and reach-out-and-touch-it than I’d ever heard it before and Menuhin’s older violin concertos sounding more brittle than I’d ever heard them before. Two edges to this sword… 

Colors of the Wind
The Audio Research LS17 is certainly among the finest pieces of gear I’ve heard in terms of disappearing into a system. It does not have the crystalline clarity of say, the Sonic Euphoria PLC preamp (now discontinued) I heard a few months ago, but then again in my system, the LS17 is more dynamic than that unit was and makes for a more involving listen. By the way, a lack of dynamic punch is in my book subtractive – preventing me from calling something like the PLC, with as much detail as it portrays, entirely transparent to the source.

In broad terms, the ARC did not sound quite as warm as my tube-rectified ModWright SWL 9.0 SE, and lacked just a bit by comparison in terms of drama and perhaps even scale at times. It countered though, with noticeably greater focus, detail and instrumental separation, along with perhaps a touch more low bass and better definition thereof. 

The ModWright imposed more of itself on the sound and as such, with say my VTL amp and a Lector player in the system, could therefore contribute to a touch too much warmth at times. Similarly, albeit to perhaps a lesser degree, the ARC in combination with the solid-state amp and the more detailed Raysonic player could be a bit over the top up top with certain recordings. 

Trouble is – I was shamelessly and inexcusably not invited to any of the recording sessions depicted by my CD collection, and therefore can’t for the life of me tell you how any of them arereally supposed to sound – just how they‘ve sounded on various systems I‘ve heard through the years. 

The fact that the ModWright and pieces like the Sonic Euphoria do some things better than the LS17 prevent me from using overused phrases like ’totally transparent’ and ‘nothing between you and the music.’ In absolute terms then – I know there is yet more on my recordings.

However, I suppose the ARC LS17 is the kind of piece that had me trying somewhat hard to describe its specific sonic signature- particularly as it relates to tone – from the get go. In this sense, I did not find it emotional or colorful or what have you. 

Rather, I found it a well built, suavely functional box that had an above-average knack for telling me how colorful or emotional the rest of my boxes were. If this is the essence of what a preamp is supposed to do, then the ARC LS17 does it beautifully.

As always, I bid you peace.



Frequency response +0-3dB, 0.5Hz to 160kHz at rated output (Balanced, 200k ohms load)
Distortion (THD) Less than .01% at 2V RMS BAL output.
Noise & hum 2.2uV RMS residual IHF weighted balanced equivalent input noise with volume at 1 (101 dB below 2V RMS output).
Gain Main output: 18dB Balanced output (12dB SE output).
Record output: 0dB (Processor input: 0dB SE).
Input impedance 120K ohms Balanced, 60K ohms SE.
Output impedance 700 ohms Balanced, 350 ohms SE Main (2). 20K ohms minimum load and 2000pF maximum capacitance.
Output polarity Non-inverting.
Maximum inputs 24V RMS BAL.
Rated outputs 2V RMS 1Hz to 100kHz into 200K ohm balanced load (maximum balanced output capability is 15V RMS at less than 0.5% THD at 1kHz)
Power supplies Electronically regulated low and high voltage supplies. Automatic 50 sec. warm-up/brown-out mute. Line regulation better than .01%.
Tube complement (2) 6H30 dual triode. (Hybrid JFET/tube audio circuit, solid-state power supply).
Power requirements 105-130VAC 60Hz (210-260VAC 50/60Hz) 50 watts maximum.
Other Rotary volume selector (104 steps, 20 LED indicators) and rotary input selector.
Push buttons: Power, Monitor, Proc, Mute. Also remote buttons: Bal 1, Bal 2, Aux, Tuner, CD.
Dimensions 19″ (48 cm) W x 5.25″(13.4 cm) H (standard rack panel) x 12″(30.5 cm) D. Handles extend 1.50″ (3.8 cm) forward of the front panel.
Weight 13 lbs. (5.9 kg) Net; 23 lbs. (11.5 kg) Shipping.

Price: $3995.00

Audio Research Corporation
3900 Annapolis Lane North
Plymouth, Minnesota 55447
Phone: (763) 577-9700
Fax: (763) 577-0323


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