A Wealth of Riches: Comparing the Audio Research Reference 10, VTL TL-7.5 Series III Reference and Conrad-Johnson GAT Series 2 Preamps

by Roy Gregory | November 19, 2016

while ago I wrote a blog entitled "Strange Bedfellows," about the way in which the review schedule and the inevitable changes, disappointments and no-shows introduce unintended combinations of equipment with surprising and occasionally startling results. There is a flipside to this: occasionally and by happy coincidence you end up having two or more pieces of similar equipment that, under normal circumstances, you’d rarely if ever find under the same roof, let alone in the same system. Imagine, for instance, having the opportunity to listen to the flagship preamps from Audio Research, VTL and Conrad-Johnson, those three premiere tube-based US manufacturers. It’s exactly the sort of comparison that readers and consumers so often cry out for, exactly the comparison I’m in a position to make, and exactly the kind of comparison that manufacturers often go out of their way to avoid -- with good reason.

Why? Because, on the face of it, although such direct comparisons should deliver a simple, slam-dunk, first-past-the-post answer regarding relative performance, the reality is anything but simple. So yes, this is too good an opportunity to miss, both to experience these three stellar units side-by-side -- but also to appreciate the problems of such an approach and the limitations it suffers.

On the most basic level, you can start by asking what system you’d use these units in. Clearly, one needs to be aware of possible synergy between preamp and power amp tilting the playing field (itself a point that calls any such comparison into question), so using a VTL, C-J or Audio Research power amp is out of the question. This is a problem, as I have both VTL and Audio Research amps in-house and there’s only so much room. Whatever amp I use is also going to have to accept both single-ended and balanced input without fear or favor, as the C-J preamp only offers RCA connection, which further complicates things.

Talking of room, I also need to have the space to accommodate all three units simultaneously, which is no small matter. Not only do you need to house the GAT Series 2 ($24,000), but the twin-chassis VTL TL-7.5 Series 2 ($25,000) and Audio Research Reference 10 ($30,000), with their separate power supplies. And it’s not enough to just "accommodate" them; I also need to provide identical (or equivalent) support under each -- quite possibly while I have other ongoing commitments that also need to be accommodated. In a perfect world, I’d optimize support for each individual chassis, but believe me, with five boxes and different racks and different positioning within those racks to contend with, in that way lies madness.

I’ll also need to be aware of relative levels, meaning that I’ll need an SPL meter to match levels between the three units in order to assess relative performance, as well as carry out separate listening at each unit’s preferred level, a setting influenced by spectral balance and dynamic range. Finally, I’ll also need to be aware of the impact of overall spectral balance on speaker positioning and the reality that such a fundamental change as swapping the preamp in a system will also require a compensatory shifting of the speakers. All of which raises the questions, How do you actually set about performing such a comparison, but what question are you actually answering? It’s easy to compare three such units, but am I really discovering which sounds best, which best suits the system being used or simply which I happen to prefer -- and under what circumstances?

You can begin to understand why manufacturers run shy of simplistic, comparative reviews. After all, not so long ago, reviews and reviewers (especially those working with the most expensive units) had the power to kill a product with a single indifferent review. Fortunately, those days have -- for the most part -- passed. I say "fortunately" because these days, the age of the omniscient reviewer is long gone. There’s simply too much equipment out there for any one individual to be properly familiar with even a fraction of it, despite the self-delusional attitudes of some.

But there’s also a deeper, methodological objection to the simple comparative approach. Let’s use athletics as an analogy and the question of who is the fastest runner in the world. On the face of it that’s simple to decide: line up the contenders, fire the gun, and first past the post wins. But in reality all that tells you is who was fastest on the day -- at that precise moment in time. It doesn’t take account of condition (when in an individual athlete’s training cycle that race occurs), freedom from injury, or specific conditions (for instance, some runners are better at handling a headwind). Then there’s questions of distance. One might assume that the race would be run over 100 meters, but why not 60 -- or 200? Or even 150 yards? In a straight line or round a bend? Finally, there’s the possibility of accident or circumstance. Maybe a runner gets a bad start or his blocks slip, his pet dog died the night before or he has a stomach ache or a cold. Perhaps he just slept badly. All of these things can, do and have happened. So perhaps we need an alternative measure. That’s easy: we’ll just use times. But even here strict comparison is almost impossible. The wind direction and speed, the track itself and the circumstances of the race can all influence the times run.

Now consider our three-way preamp comparison and factor in the variables, and you can appreciate the problem. First, I set up a dedicated second system with a common source (in fact, I used two -- the Aesthetix Romulus and Audio Research Reference 9 CD players, flirting with inappropriate synergy in the case of the latter, although in practice the musical results stayed consistent between sources). I chose CD for its consistency and repeatability (issues with file replay) and because it eliminated the further variable of the phono stage required for a record player. I accommodated the units in adjacent racks, the three preamps in one, all sharing the same supports/couplers, the power supplies and source in a second, again with common supports and couplers (although it wasn’t possible to have identical support under all elements, across both racks). I could have achieved completely consistent support if I’d dismantled the main system, but that would have interrupted work. Not only is it necessary to get reviews completed, but the crossover period when all three preamps would be present was only a week, and allowing them to stabilize and warm up properly imposed its own time constraints. Besides which, identical support is itself a compromise. It removes a variable, but introduces an intangible: what if the chosen supports/couplers favor one unit over the others?

Power amps were my Berning Quadrature Zs (happy running single-ended or balanced and neutral in every sense of that word), and I hooked those up to a pair of Focal Sopra No.2s, one of that crop of new, affordable, compact floorstanders that have appeared recently, redefining price/performance expectations along the way. Cabling was Nordost Odin 2, another choice that risks favoring one unit over another -- but there’s a limit to just how many variables one can cover in the time available.

Hopefully by now you are beginning to appreciate the magnitude and sheer complexity of this particular problem. Still, with the preparations made and the system installed and well warmed through, it was time to take a listen. Which brings me slap up against the issue of running order.

With two devices to test, the ABA/BAB protocol is well established. Introduce a third and things start to get tricky: ABA/CAB/CBAC is the ideal running order -- one that I ran in full twice with different material. Beyond that, having established baseline performance characteristics, I reverted to ABACA or simple binary comparisons on the grounds of time and efficiency. The process itself was further complicated by the need to switch between single-ended and balanced connections, reverse absolute phase at the speakers for the phase-inverting C-J preamp and ensure that levels, once established, were properly adhered to. If you think reading this laundry list is tedious, you should try doing the listening -- especially as any misstep means starting over -- but it does underline just how involved any such comparison is (or should be) and the limitations of its conclusions.

alking of conclusions, I guess it’s time to talk sonic turkey. How did the three units sound and was one clearly superior to the others? The short answer to the last question is no. Preference would depend on the listeners, their priorities. However, what was interesting was how big the musical differences of these units were: certainly big enough to develop clear preferences. That and just how large a part the rest of the system played in defining those differences/preferences.

When I started listening to establish relative levels between the different units on various material, it quickly became apparent that the Reference 10 sounded significantly louder than the other two, even with matched peak levels. It was the averaged levels that told the story, with the Reference 10 registering around 2dB higher on average for the same peak reading. It also sounded big, muscle-bound and musically clumsy, which wasn’t a great start. Shifting the speakers forward around a centimeter certainly helped, but didn’t cure the issue of its overly boisterous output. However, the Berning amps offer a three-position feedback switch. With the Sopra 2s, this was preferred at the minimum setting for both the VTL and C-J preamps; however, switching it to the middle setting (and adjusting level accordingly) transformed the performance with the Audio Research, introducing stability, focus and grip to proceedings. Shifting the speakers and adjusting the feedback elevated the Audio Research onto the same level as the other units, but without either of these measures it was an also-ran, a salutary lesson in terms of system matching and how changing the system context can dramatically impact the performance of any DUT.

With the various settings finally established, comparative listening could start in earnest, quickly revealing the basic strengths and characteristics of each design. Of the three, the Reference 10 was the biggest-boned and boldest performer, delivering a sound with tremendous scale and presence. Its music never lacked for body or momentum -- just as long as you paid attention to the niceties of speaker positioning and amp matching. It was fuller, warmer and more rounded, due mainly to a more generous bottom end, qualities that meant it suffered in terms of immediacy compared to the extraordinarily natural tonality and textures of the GAT Series 2.

In many ways, the Conrad-Johnson was the joker in this deck, its single-chassis design and lack of physical stature putting it at an immediate visual disadvantage compared to the competition -- a disadvantage underlined by its lack of sophisticated operational niceties and balanced connection. However, what it might have lacked in parts count and facilities it more than made up for in the sheer purity of its musical delivery, the lack of additive fingerprints or subtractive influence imposed on the signal. If you want musically invisible, then this is as close as you’ll get. It lacks the sheer weight and scale of the Audio Research preamp and the bottom-end definition, utter stability and dynamic authority of the VTL, but there’s a corresponding subtlety and delicacy that can be absolutely breathtaking.

The VTL 7.5 Series III sits firmly between the extremes defined by the Audio Research and C-J, although they represent no straight line, rather the points of a triangle, each offering a contrast to the other two when it comes to different aspects of performance. The VTL’s greatest strength is its combination of rock-like stability and dynamic discrimination, qualities that allow it to capture the relative scale of instruments and weight of notes. Whereas the Audio Research tends to write the music large, the VTL scales the proportions of players and playing perfectly, while its ability to map the subtle changes in energy levels brings a natural sense of pace and purpose to playing, whether that’s the forward momentum and driving rhythms of Neil Young or the relaxed, unforced ease of Charlie Byrd, the samba beat of Getz and Gilberto or the rigid discipline and carefully measured exuberance of La Petite Bande playing a Corelli Concerto Grosso.

For each product, it’s possible to pick a track or album with which it excels, both demonstrating its essential character and its specific strengths. So, as impressive as the VTL was with Harvest [Reprise 9362-494975], it can’t match the solid drive and almost physical presence of the Reference 10. The Audio Research might roll instruments together, allowing them to expand into the space, but there’s no ignoring the infectious sense of attitude in its holistic presentation. Neil Young’s voice is bigger and more forward, rounder and smoothed off but offering a more engaging balance and more weight to the lyrics. It might lack that last ounce of nasal roughness that makes Young so instantly recognizable, but there’s no denying just how engaging and entertaining it is. The VTL does a good job on the patterns and instrumentation and certainly captures Young’s distinctive voice, but ultimately lacks the sheer bloodiness to give this music the necessary spark. The C-J simply sounds detached. I’m not sure if electronics can express that mild approbation so redolent of British butlers in period drama, but that’s what this sounded like.

On the other hand, the unimpeded honesty of the C-J GAT Series 2 also has its place. Play "Strike The Viol" from Christine Pluhar and L’Arpeggiata, Music For A While [Erato/Warner Classics 463375 0 7], one of a series of modern interpretations of Purcell songs played by an early-music consort with added clarinet and acoustic or electric guitar, and it captures the jazz rhythms, acoustic instrumentation and space between the notes beautifully. But what really stands out is soprano Raquel Andueza’s singing. Her remarkable articulation and technique coupled to the natural tonality, immediacy and transparency with which they’re presented make her an almost ghostly presence in the room. You will seldom hear a voice reproduced with such recognizable and intelligible timbre and diction -- and we all know what voices sound like. There is a humanity and lack of grain or artifice that make the C-J’s presentation very special indeed. In comparison, the Audio Research preamp is smoothed off and lacking both delicacy and intimacy. The VTL gets way closer, arguably doing a better job with the complex rhythms in the instrumentation, but lacking the unforced immediacy of the C-J. Of course, part of that may well be down to the lack of really deep bass weight from both the recording and the GAT Series 2. Restore the balance in the source material and the overall balance of virtues shifts yet again.

When it comes to the VTL TL-7.5 Series III, it’s tempting to reach for something big and complex to show off its unflappable musical and dynamic security. It’s tempting to reach for something involving piano, another area in which the VTL excels, effortlessly capturing the weight, complexity and power of the instrument as well as the strange combination of delicacy and explosive energy required to make it sing. But instead I’ll take that Corelli disc (Kuijken/La Petite Bande [Deutsche Harmonia Mundi Box 8887503750-14]), with the rigid, ornate structures and embellishments of the Concerti Grossi, the tonal challenge of the period instruments and the harpsichord, all combined with La Petite Bande’s energetic style and emphatic phrasing. It requires a perfectly judged grip on proceedings, a hold that’s firm enough to preserve the structure in the music, deft enough to allow the verve in the playing and the harmonic intricacies captured by the recording to emerge.

The TL-7.5 III sets up a naturally proportioned soundstage and populates it with believable players playing believable instruments. Their energy is clearly apparent -- as is the power of their ensemble playing. But it is the harpsichord that really impresses. Few systems (or recordings, for that matter) ever manage to fully realize the shiny, sparkled, layered complexity and boxy body of this instrument, but the VTL does a superb job here. The strings provide that uncanny combination of restraint and vigor, against which is poised the tinkling, quicksilver attack of the keyboard, in turn underpinned by the life and vibrational layers of what is quite literally a box full of strings. Never are those strings divorced from the box, and never is the continuo separate or incidental to the rest of the orchestra. It’s a perfect example of the VTL’s ability to both control and express, to keep things separate but at the same time present the whole.

Turn instead to a single disc and concentrate on differences between these three units and the picture remains clear. Using Harnoncourt’s reading of the Mozart Requiem from the same Deutsche Harmonia Mundi box (with the Concentus Musicus Wien and Arnold Schoenberg Chor), each preamp stamps its character on proceedings. The Audio Research’s presentation is big and bold, with a huge acoustic space, filled with music and drama. The Confutatis is delivered with real power and contrast, a warmth and sweetness that are impressive and beguiling. The VTL presents a less clearly defined overall acoustic, but the locations of instruments and voice within it as well as the spaces between them are more clearly defined. The bass arpeggios of the Confutatis have more texture and rigor, a darker, more threatening aspect that is ultimately more in keeping with the sense and structure of the piece, the disposition of the choir and orchestra is more tangible and more convincing. The C-J can’t rival the scale or dimensionality of the other two, but play the Benedictus and its ability to separate the soloists, capture the character of their individual voices and the interplay between them, is truly beautiful.

here does that leave us? All three of these preamps are exceptional performers, but each will find favor with a different listener and quite possibly in different systems. I know that both the Reference 10 and the TL-7.5 III excel in the company of their own amplifiers, and past experiences with C-J suggests that the GAT Series 2 will be no different. All I can report on is their relative virtues in this system; the degree of difference and even those differences themselves may well vary with different partnering equipment, just as they may appear different to a different set of ears -- and that’s the root of the problem. I’ve spent a considerable amount of time listening to these three units, both in isolation and in direct comparison. I can tell you how I think that they sound, but what I can’t tell you is which one would be best for you or your situation. I can’t even tell you which one I think is best, because as I’ve hopefully shown, that depends on the nature of the music being played. I can get a great performance out of any of these units; let me play with the system constituents and I can take that a whole lot further.

At the end of the day, I can offer pointers, a character sketch and suggest possible pitfalls (the C-J’s phase inversion and the Audio Research’s sensitivity to damping factor are examples) that you need to take into consideration -- but that’s as good as it gets. Despite an almost obsessive level of care, it’s simply not possible to define an overall winner, or even to eliminate the major variables -- the most major of all being the individual listener.

Ultimately, the song remains the same: you pays your money and you takes your choice. What’s important is that it is your choice -- not mine. I can shine a light on relative merits, but I can’t rank the contenders.

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