Audio Research • LS27 Preamplifier

by Dennis Davis | March 30, 2011

© www.theaudiobeat.com

Nothing should be simpler than comparing a new version of an existing product to its predecessor, as it makes the "all other things being equal" rule child’s play to follow. Audio Research’s LS27 line stage is just one digit removed from the extremely successful LS26, which I used in my system for two years -- until the Reference 5 took its place. I’m not adverse to easy assignments when the menu includes something as tasty as an Audio Research line stage. A component that’s pure plug-in-and-play, with no toe-in or leveling or break-in, leaves only the exercise of typing the review as a chore. With the LS27, everything preceding those keystrokes was pure pleasure.

The LS27 is Audio Research’s middle-range line stage, sitting between the $3995 LS17 and the $11,995 Reference 5. (The $24,995 Reference Anniversary is a special edition for a small number of moguls and lottery winners. It's soon to go out of production, so let’s not count that as part of the line.) At $6995, the LS27 is a serious component that a regular audiophile can aspire to owning without robbing a bank. It updates the cosmetic look of the LS26's front panel, switching out black for silver handles (though the black are still available) There is also a Darth Vader version: black in all but the buttons. The LS27 also replaces the older square-button array with a new set of round buttons, a cosmetic touch first seen on the Reference Anniversary.

Under the hood, things look very similar to the LS26, until your eyes stray to the back of the circuit board and you notice that the unit has become almost an inch and a half deeper. This is not surprising, as the LS26 was already packed full of components, and the LS27’s upgraded parts required additional breathing space. Bulk power-supply storage has been increased. A new power transformer along with new output and bypass coupling capacitors account for the added real estate. Despite these changes, the LS27 weighs in a few ounces lighter than its predecessor. The stated specifications of the LS27, except for weight and dimensions, are identical to those of the LS26.

Like the LS26, its replacement remains a pure class-A design with zero feedback. It has a fully regulated solid-state power supply and a hybrid JFET/tube audio circuit using two 6H30 dual-triodes in the analog stage. As with the LS26, it has three selectable level settings for each input, with a recommendation that the highest setting be used for best performance. I found this to be too high for any of the cartridges I use, but the lower settings adjust for any phono stage/cartridge combination.

The LS27 also sports a choice of balanced or single ended inputs and outputs, with a total of eight input choices. Unlike with most line stages, a right-left balance control, a phase inversion switch, a mono/stereo switch, and a tube-hour counter are also included. For me, a balance control is essential, and I suspect most audiophiles do not have custom-built listening rooms that need no tweaking of right-left balance.

All of these functions may be controlled with the ubiquitous Audio Research remote. The LS27 also includes a processor pass-through for home-theater use. Audio Research states that all of these functions are controlled by a new microprocessor, although I could not detect any difference in application. Indeed, with the exception of the tube-hour counter, I could control all other functions whether I was using the LS26, LS27 or Reference 5 remote. That is to say that they all worked flawlessly and intuitively.

Audio Research long ago dispensed with attached power cords, and the LS27 has a 15-amp IEC inlet. A high-quality power cord ships with the unit for those not inclined to buy an add-on power cord.

The line stage arrived from Audio Research with about 200 hours logged on. Before listening to it, I ran it in another 50 hours or so using a burn-in CD. Audio Research now packs all of its tube electronics with a notice that the device continues breaking in until somewhere around the 600-hour mark. I suspect that this varies by unit, with the more expensive models and their larger capacitors breaking in more slowly. I have listened to other Audio Research models starting from scratch and know that the biggest changes occur in the first couple hundred hours, so I felt confident that this unit was good to go at 250 hours. After the additional break-in time, I listened to a wide range of music before comparing the LS27 to its predecessor.

Audio Research line stages all share a very strong family sonic resemblance. They are also the products of one of the industry’s most consistent trickle-down programs. Each new Reference line stage is eventually followed by a new version of the LS line stage, with those advances from the top model scaled back and incorporated into the mid-level model. So those audiophiles who refrained from mortgaging their home during the real-estate bubble to spring for a Reference 3 waited for the release of the LS26. Now the LS27 holds out promise that the Reference 5 advances have trickled down to it, notching it up near the performance of the Reference 3 (there was no 4, as it is considered an unlucky number in the Far East).

Among their consistent strong points, Audio Research line stages have an uncanny ability to organize musical information into a deep, wide soundstage, especially with the best of both stereo and mono recordings. The solidity and "you are there" qualities of the instruments within that stage are equally remarkable, and they have done nothing but get better both within the Audio Research range of products and viewed over time as each new generation of a particular model appears. The LS27 is no exception to this rule. Whether it’s reproducing large-scale orchestral works such as Stravinsky’s Firebird on Mercury [Mercury SR90226] or small-scale jazz ensemble as exemplified by the stunning mono reissue of Kenny Dorham’s Afro-Cuban [Blue Note/Music Matters MMBLP-1535], the preamp will throw as large and realistic a soundstage as your cartridge and phono stage can pass on to it.

It’s the solidity and focus of images within that soundstage, however, that really separate the very expensive units, with massive power-supply parts and ultra-spendy capacitors, from more affordable line stages. The LS27 does not match what the Reference 5 achieves in this regard, nor does any other preamplifier in this price range. The very best units can cast extremely convincing three-dimensional images, in the same way that adjusting the depth of field of in a camera viewfinder will cause the image to "pop" and take on a three-dimensional quality. You can’t make as good an image with a cheap Tokina lens as you can with top Leica glasswork, and the same limitations apply to preamplification. Audio Research does not make any Tokina-level products, and the LS27 is like a good Leica lens, but not the fastest-aperture version of a particular size. It can produce very stable images within the soundstage, if not achieve the divine results that a Reference 5 can pull together. However, the LS27 gives you an awfully close approximation of what Audio Research’s much more expensive Reference line stage can do under most circumstances. On less-complex recorded material, the differences can be subtle indeed.

The LS27 performed beautifully in the frequency range of string instruments. I spent a good deal of time listening to the new Coup d’Archet set of violinist Johanna Martzy's recordings, The EMI Recordings [COUP 16-23], and the LS27 performed brilliantly. It reproduced Martzy's unique tone, which is on the cool side, without ever sounding harsh. It captured that coolness while at the same time placed enough air around the instrument to make these refurbished early EMI recordings sound almost modern. I played some of this music for a friend and didn’t tell him that he was listening to the LS27 instead of the Reference 5. He was agog at the beauty of the recording and gave no thought to the equipment.

The LS27 was also accomplished at revealing small or large changes in other equipment in the chain. It accurately captured the differences in string sound between Lyra and Koetsu cartridges, and I used it to discern and evaluate the differences between VPI’s Super Platter and standard-issue aluminum platter, and then the differences between the aluminum platter bare, with a rubber mat and with a paper mat. The LS27 did not obscure in any way the differences among these variations.

It also was a champ at reproducing the best of Rudy Van Gelder’s Blue Note recordings. The earliest of these are in mono, and an exceptional line stage can present an almost stereo-like image with none of the drawbacks of early stereo. Kenny Dorham’s Afro-Cuban sounded alarmingly real. Like the Dorham 45rpm set, Acoustic Sounds’ remake of Nat King Cole’s great mono album After Midnight [Capitol Records/Analogue Productions AAPP 782-45] also threw an incredible mono soundstage that lacked nothing with the LS27. That’s not to say that it doesn’t show up the imbalances of poor stereo. It certainly didn’t gloss over these details, and it likewise didn’t tamp them down, as some less-stellar line stages can do.

Compared to the LS26 ($5995), the LS27 is definitely a move up the spectrum, making that thousand-dollar increase in price, along with the improved power supply and more expensive parts, wholly justifiable. I expected the improvement in soundstaging solidity, but I wasn’t prepared for a jump in tonal quality and bass definition. However, within minutes of a side-by-side comparison of the two units, my listening panel was like a group of Olympic judges, declaring a clear win for the LS27 because of these improvements. Shelby Lynne’s "Just a Little Lovin’," from the CD of that name [Lost Highway 1744825], made it clear that the LS27 had tightened up the LS26's bass and refined its highs. I never considered the LS26 lacking in these areas until this comparison. Extended listening to the two units confirmed this finding, but showed it was more pronounced with some recordings, as I could not reproduce the significant differences with most material. On one of my favorite test LPs for the quality of the upper frequencies, Salvatore Accardo’s Diabolus In Musica [Deutsche Grammophon DGG 477 6492], the differences between the way in which the two units interpreted the violin, cymbals and triangle were subtle, confirming that the LS26 was no slouch in this department. But with a few modern digital recordings, such as the Shelby Lynne, the improvements in the new unit were obvious.

Similar subtle enhancements were detected in areas where the LS26 was already quite strong. Both units have a very low noise floor, and this gives rise to acute retrieval of low-level detail and notable clarity. Like the prior model, the LS27 sounded unforced and delivered an natural entrée to the flow of recorded music -- an uncommon ability for all but a few line stages in this price range. While I had the benefit of auditioning the LS27 with a much more expensive phono stage, I suspect that the LS27 along with Audio Research's new PH8 will be a match made in heaven.

So if you can’t afford to invest more money in your hi-fi system than you have tied up in your Maserati, the LS27 may well be the ideal heart of a system you can live with for the long haul. It’s an extremely versatile and musical line stage that is surely one to beat in its price range. Audio Research continues to pull one rabbit out of the hat after another.

Associated Equipment

Analog: VPI TNT-6 turntable with rim drive and SDS speed controller, VPI 12.7 tonearm, Lyra Skala and Titan Mono cartridges, Koetsu Coral cartridge, Audio Research Reference Phono 2 phono stage.

Digital: Audio Research Reference CD7 CD player.

Preamplifier: Audio Research Reference 5.

Power amplifier: Audio Research Reference 110.

Loudspeakers: Kharma 3.2 with Enigma filter and wiring upgrade.

Interconnects: Nordost Valhalla.

Speaker cables: Nordost Frey.

Power conditioners: Quantum QBase 8 and QX4.

Power cords: Nordost Valhalla.

Equipment rack, platforms and accessories: Billy Bags equipment rack modified with a 4" maple platform, Stillpoints Ultra isolators, Stillpoints Component Stands, Furutec GTX D-Rhodium AC outlet.

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