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- Written by Vade Forrester Vade Forrester
- Category: Full-Length Equipment Reviews Full-Length Equipment Reviews
- Created: 01 March 2017 01 March 2017
The LS28 tubed line-stage preamplifier is part of Audio Research’s new Foundation series. Other models in the series include the DAC9 digital-to-analog converter, PH9 phono preamplifier, and VT80 power amplifier, most of which the SoundStage! Network will eventually review. While the Foundations are now ARC’s least expensive models, they’re hardly cheap -- the LS28, DAC9, and PH9 each cost $7500 USD, the VT80 $8000.
All Foundation models share similar styling and look like smaller versions of the pricier Reference models, while retaining some features of past ARC products -- for example, they all have rack handles reminiscent of the LS1, introduced in 1989, though none of them will ever see a rack. While the LS28 still has two knobs, they’re much larger than traditional ARC knobs, are round instead of oval, they actually rotate, and are two-toned: the center is polished silver, the outer edge and rim are black. I understand that it’s a challenge to anodize two-tone metal knobs.
In another departure from ARC tradition going back to the LS1, the LS28’s right knob is its Volume control, and the left knob is the Input selector. There’s still a row of pushbuttons -- Power, Menu, Enter, Mono, Invert, Mute -- below the display, which is still not a touchscreen, or even a full-color screen, as on some ARC models. The vacuum-fluorescent display is surrounded by black glass, McIntosh Laboratory style, and looks very stylish. The styling groove with rounded edges, previously enclosed by the handles, has been moved outside them to the very edge of the faceplate, whose back edges are beveled and fairly thin. While I’m sure some purists will mourn any change in ARC’s traditional styling, I think the new look is handsome, and far more attractive in person than in pictures. I’d even call it elegant.
Having owned the LS28’s predecessors, the LS26 and LS27, I was curious to see first-hand what other changes the new model includes. One of the most obvious is the rear panel. Like many ARC line stages and preamps, the LS26 and LS27 had balanced and unbalanced jacks for every input and output; using the front-panel controls, you had to specify whether an input was balanced or unbalanced, which was confusing. With the LS28, you needn’t specify -- it provides eight inputs, four each balanced and unbalanced, labeled separately on the rear panel and on the display. There are three outputs, two main and one Record, each with both balanced and unbalanced jacks. The input impedance is 100k ohms balanced or 50k ohms unbalanced; the output impedance is 600 ohms balanced or 300 ohms unbalanced, with a recommended minimum resistive load of 20k ohms and maximum capacitance of 2000pF. That’s a pretty high minimum-load recommendation, and may be incompatible with some solid-state amps; e.g., the one in my JL Audio subwoofer.
The LS28 measures 19”W x 6.5”H x 13.7”D and weighs 15.9 pounds. The single circuit board that fills its interior is fitted with half power supply, half audio circuit, and the biggest changes are in the latter: the LS28 uses four 6H30P tubes instead of the LS27’s two. The circuit is still a hybrid design, using JFETs as well as tubes. As in the LS27, the power supply is solid-state, but the LS28 has a bigger transformer and more capacitance. A 103-step volume control is used; the LS27 had a 104-step volume control, but ARC claims that the new model sounds better, which is what matters. The three-year warranty on parts and labor seems appropriate for a $7500 component.
Setup and use
The first thing I did was read the manual, which was easy -- it’s printed in a large font (in recognition of an aging customer base?). It told me to remove the LS28’s top panel to install the four tubes, which are shipped in their own cardboard box lined with soft foam. Audio Research even provides an Xcelite Phillips screwdriver with which to remove the cover -- and, for the first time in my experience, extra screws in case one or more should go missing. Each tube was marked to indicate which socket it was to be inserted in. The manual also told me that the expected life of the tubes is about 4000 hours -- the LS28’s built-in timer lets you know how long the current tubes have been in use. Sovtek or Electro-Harmonix 6H30P tubes can be purchased from most tube suppliers, but I prefer getting replacements from ARC -- it’s a pain to install new tubes and find that one or more is defective, and ARC rigorously tests theirs.
I placed the LS28 on a shelf in my equipment rack and plugged it directly into the wall using the stock power cord. ARC takes pains to provide good-sounding power cords, and expects reviewers to use them. That’s reasonable -- if you let reviewers pick their own cords, who knows what the result will sound like? The same consideration would apply to any other modification by a reviewer -- swapping out tubes for favorite new old stock (NOS) types, or using power conditioners, or aftermarket footers. Doing any of those things turns the review sample into a one-of-a-kind device that won’t necessarily sound like the other production units. So what’s the point of the review?
Since my power amplifier has only an unbalanced input, I connected it to the LS28 using High Fidelity Cables CT-1 unbalanced interconnects; to the DAC with Audience Au24 SX balanced interconnects; and to the subwoofers with CablePro Freedom unbalanced interconnects. That done, I set the LS28’s front-panel display to label the inputs, so that I’d know at a glance what was connected to each active input. The small font of the display was barely readable from my listening seat, about 10’ away; however, the most important information, the numeric volume setting, is displayed in much larger digits. Using the Input knob on the front panel, I could select inputs by cycling through all of them -- or I could use the remote control, on which each input has its own button. I preferred the latter, which gave me direct access to all inputs.
In addition to its eight Input buttons, the remote has buttons for controlling almost all functions of the LS28. Though encased in textured, silver-colored metal, this remote handset is not one of those massive ingots that requires a reinforced coffee table; it’s just a practical remote whose appearance won’t embarrass you by looking like the remote for a $99 DVD player. And its edges are rounded, which you’ll appreciate when you drop it on your coffee table. The cover of the battery bay is held in place by a Phillips screw, solving a problem in the plastic remotes of earlier LS-series preamps -- their battery-bay latches tended to break or loosen. I remember having to secure one remote’s bay with cellophane tape -- something else that’s unlikely to impress your friends.
ARC recommends that the LS28 be broken in for 600 hours -- which is precisely 25 days, 24/7. The first 175 hours of break-in give the most improvement, with further, more gradual improvement after that. I occasionally get love notes from readers who tell me I’m a fool for breaking in equipment. Sorry, folks -- I believe that responsible reviewers observe manufacturers’ break-in recommendations, however inconvenient.
A feature new in the LS28 is automatic cutoff, which turns it off after a specified period -- the default setting is two hours. This is a great feature in coffee-makers; in preamps, not so much. Fortunately, using the menu, you can pick a longer period of time for the LS28 to remain on -- or, my favorite, you can turn off automatic cutoff entirely. You can also name each input so that, in addition to the physical input, the display reads CD or DAC or Phono. So instead of reading BAL1 (for Balanced Input 1), you might set it to read BAL1 CD. But when you scroll through the menu of inputs, you’d better be quick; the choices are visible for only a few seconds before the menu turns off. This feature will be used only occasionally; the choices should stay on longer.
My source component was ARC’s DAC9, fed by a Toshiba Satellite laptop computer running JRiver Media Center 22 under Windows 10. I connected the DAC to the LS28 with Audience Au24 SX balanced interconnects. I also had a Mytek HiFi Brooklyn DAC in for review (forthcoming), and couldn’t resist trying it with the LS28, using the same Toshiba laptop as the source.
A recent change in my system was the replacement of my JL Audio Fathom f110 subwoofer with two Syzygy Acoustics SLF870 wireless subs. With two 12” subs replacing one 10” unit, I now enjoy deeper, considerably more powerful bass, and I can control the Syzygys with my iPhone or iPad. Fortunately, the Syzygys’ wireless transmitter box has an input impedance of 20k ohms -- the lowest impedance recommended by Audio Research for use with the LS28.
If you’ve ever turned off your preamp before turning off your amp, your speakers may have produced a big thump! That won’t happen with the LS28, because its mute circuit is automatically engaged before the LS28 turns off -- classy. Also, when you turn the LS28 on, the volume level on each individual input is reset to zero and the mute circuit is engaged -- you won’t hear any turn-on transients from the LS28. The mute circuit stays on until you turn it off, but if, like me, you’re impatient, you can manually turn it off any time -- it will then remain engaged for another 45 seconds before turning itself off. You can also advance the volume to whatever level you’re comfortable with before the mute circuit turns off.
Mytek HiFi’s Brooklyn DAC is one of the first non-Meridian DACs that will fully decode Master Quality Authenticated (MQA) files. The LS28 proved a valuable tool in comparing different formats of high-resolution files -- it was extremely transparent to source components. I could easily tell that MQA-encoded files had little or none of the digital glare or edge that, to some extent, afflict all other digitally encoded files in my collection. The DSD version of the Oslo String Quartet’s recording of Schubert’s String Quartet No.14 in d, D.810, “Death and the Maiden,” from The Schubert Connection (DSD128/DFF, 2L), sounded a little aggressive, with some digital bite. When I switched to the MQA version (24-bit/352.8kHz FLAC, 2L), the strings sounded sweeter and less edgy. With Tidal now streaming hi-rez MQA files, it’s easier than ever to enjoy hi-rez sound, especially with an MQA-equipped DAC.
Audio Research’s DAC9 was able to play a maximum of “only” DXD and DSD128 files, but that wasn’t giving up much -- and certainly not when I listened to a favorite track, “Folia Rodrigo Martinez,” from La Folia 1490-1701, performed by Jordi Savall and his band of renaissance specialists (16/44.1 AIFF, Alia Vox). The LS28 rendered the opening strokes on the cascabels (sleigh bells) with enough detail for me to easily distinguish between the various whacks; with most components, it’s harder to tell them apart. The ARC reproduced bass powerfully and deeply, reaching this recording’s mid-20Hz limit, yet with plenty of impact and detail. With powerful subwoofers, it’s easy to crank up the bass to whatever level you want -- but I took great care to match my subs to the main speakers, and the subwoofer software automatically equalized the subs for flat response in my room. Savall’s viola da gamba, a fretted, cello-like instrument popular in the renaissance and baroque eras, was portrayed with startling timbral accuracy as it carried the melody above the clatter of percussion. Sometimes those percussion instruments smear into a background haze, but the LS28 kept each distinct and audible at all times. The highs were bright and extended, with no peakiness, which can emerge at a couple spots in this track. This was a candidate for the best reproduction of “Folia Rodrigo Martinez” I’ve heard.
Every review should include at least one recording of a woman’s voice. I picked another fave, Shelby Lynne’s Just a Little Lovin’ (DSD64/DSF, Lost Highway/Analogue Productions). In the title track, the opening bass note literally shook the room and sounded like a believable part of the performance. The growling bass guitar provides a strong underpinning for this song, as it does for the entire album. Instrumental parts were reproduced with such delicate, detailed precision that they sounded quite real, and the textures of Lynne’s voice were reproduced with plenty of expression and feeling. About 2:45 into this track, the drummer very lightly taps a cymbal -- the LS28 reproduced it with exquisite detail.
I then turned to an instrumental solo: guitarist Alex de Grassi playing “Shenandoah,” from Special Event 19 (DSD64/DFF, Blue Coast). Engineered by DSD recording guru Cookie Marenco, this recording achieves a near-ideal balance of the amounts of musical detail and guitar-and-player noise captured. The LS28 superbly reproduced the microdynamic changes of de Grassi’s phrasing, and his guitar harmonics were realistic. The unusual drone effect de Grassi achieves was eerie. The recording favors string tone over body tone, but the LS28 also well captured body effects. This is one of the most enjoyable guitar recordings in my collection, and it was enhanced by the LS28’s melodic expressiveness.
Allegri’s Miserere is a work for unaccompanied voices. In the recording by the Tallis Scholars that pairs it with works by Palestrina (24/96 FLAC, Gimell 41), the main chorus is at the front of the soundstage, with a solo tenor at the center and a second, smaller chorus some distance behind the main group. The LS28 captured the opening phrases with none of the slight hardness that can creep into this passage. The soundstage was huge, extending from speaker to speaker. I could distinguish the individual voices in the main group, which usually blend together. When the solo tenor entered, I could make out the finest details of his voice, including his very slight vibrato. The small group at the rear of the space then entered, revealing a breadth and depth of soundstage that was cavernous, yet the reverberant echo never smeared or blurred the sound. I could even distinguish individual singers in the distant group, something I’d never heard before. Scary.
What could I tell from these listening sessions? The LS28 is, in my experience, unmatched in its soundstaging precision -- the sound was wide open. Everything I played through it exhibited a harmonic veracity that was not overdone, just musically accurate. Both ends of the audioband were extended, but the bass was special, especially for a tubed line stage: it had both slam and detail, yet merged smoothly into the midrange. I encountered no operational glitches; everything worked flawlessly (once I’d disabled the automatic turn-off feature) and all the controls, especially those massive knobs, felt great to the touch. Faults? A larger font in some parts of the display would have made it easier to read. Pretty trivial.
What better candidate for comparison for the LS28 than its predecessor, the LS27 ($6995)? The LS27 was the last line stage in Audio Research’s traditional styling, with oval knobs that turn a few degrees but don’t actually fully rotate, a smaller display, and my favorite feature, complete duplication of balanced and unbalanced jacks for every input and output. The LS27, too, had a hybrid circuit that combined JFETs and tubes, but without the increased transconductance afforded by the LS28’s four output tubes.
It was a challenging comparison: both units are ARC line stages, and both have the ARC house sound. But that’s why they pay me the big bucks. The LS27 had a plastic remote -- in itself sufficient reason to upgrade to the LS28. (Just kidding!)
Through the LS27, “Folia Rodrigo Martinez” sounded a bit less organic and more mechanical, as if I were listening to a hi-fi rather than the musical performance. The bass was deep, perhaps with a bit less impact than through the LS28, but still sounded amply detailed. The highs were a smidgen less smooth, and percussion instruments were less distinct above the background noise. These were very small differences.
Allegri’s Miserere at first sounded very much as it had through the LS28, but as I listened closely, I realized that the LS28 had sounded more luminous, less mechanical. The LS27’s soundstage was slightly smaller, especially in depth, and the distant choral group sounded slightly more congested.
With Alex de Grassi’s recording of “Shenandoah,” it was very close -- I’m not sure I could reliably tell a difference. Both line stages were very expressive and detailed.
When I began reviewing audio gear, it wasn’t rare to hear tubed components that were a bit noisy: hum, hiss, tube rush, and buzzing were things we almost expected from tubes. No longer -- today’s tubed gear is expected to be almost as quiet as solid-state. Today, noise is usually manifested only in how much detail a component obscures. And, oh yeah, by the “black” backgrounds “audible” in moments of silence. That faint cymbal stroke in “Just a Little Lovin’” was indeed faint through the LS27 -- almost inaudible. Although the two ARCs sport similarly -- and incredibly -- low noise specifications, I think it was a lower noise level that let more detail emerge from the LS28. But this was not a difference I could hear except in direct comparisons. And with both models, the bass whomped forth lustily in successful transition from subwoofers to mains.
Overall, the LS27 is still a terrific line stage capable of producing beautiful, realistic sound. The LS28 didn’t blow it away in any single area, instead seeming to be just slightly better across the board. But those slight improvements added up -- regardless of what I played, the LS28 had an open, lit-from-within tonal quality that made its sound more relaxing, more natural, more organic than the LS27’s.
When I switched from Audio Research’s LS26 to their LS27, I thought the improvements in sound were modest. I was prepared to hear the same degree of improvement between the LS27 and LS28. Instead, I found that the LS28 exhibited better detail, lower noise, and a more spacious sound. And not only did the LS28 sound better, to my eye it was hands-down more attractive than the LS27. Does that matter? Well, if I spend big bucks on an audio component, I want to take pride in its appearance.
I think that, for most audiophiles, there’s a point of diminishing returns at which buying a more expensive component doesn’t bring a commensurate gain in listening pleasure. I’ll bet they’re humdingers (that’s Texan for real good), but I’ll probably never hear Audio Research’s Reference 6 ($14,000) or Reference 10 ($30,000) line stages. For me, the point of diminishing returns is the LS28. If your budget can swing it, I strongly recommend that you audition the LS28. You might like it as much as I did.
. . . Vade Forrester
- Speakers -- Affirm Audio Lumination, Syzygy SLF-870 subwoofers (2)
- Amplifier -- Berning ZH-230
- Preamplifier -- Audio Research LS27
- Digital sources -- Toshiba Satellite laptop computer (i7 processor, 16GB RAM, 1TB hard drive) running 64-bit Windows 10 Home, JRiver Media Center 22, Roon 1.3 music-server software; QNAP TS-251 NAS; all servers and digital players connected to a PS Audio DirectStream DAC; Audio Research DAC9 DAC (in for review); Mytek HiFi Brooklyn DAC (in for review)
- Interconnects -- Audience Au24 SX (balanced, unbalanced), CablePro Freedom (unbalanced), Crystal Cable Piccolo (unbalanced)
- Speaker cables -- Crimson RM Music Link
- Power cords -- Audience Au24 SE LP powerChord and powerChord e, Clarity Cables Vortex, Purist Audio Design Venustas
- Digital link -- Audience Au24 SE (USB)
- Power conditioner-distributor -- Audience aR6-T
Audio Research Foundation LS28 Preamplifier
Price: $7500 USD.
Warranty: Three years parts and labor; 90 days, tubes.
Audio Research Corporation
3900 Annapolis Lane N.
Plymouth, MN 55447-5447
Phone: (763) 577-9700