February 2006

Rogue Audio Atlas Stereo Amplifier

by David Millman

Review Summary Sound The Atlas "is a tube amp free of bloat and possessed of nimbleness and agility. However, I'm glad to say that it retains its tube soul. There is a slight dark tilt to its sound, but nothing would I call grossly colored." "The Atlas delivers plenty of air, shimmer and vibrancy -- in short, musical life." Features Push-pull, 55Wpc stereo amp that uses "eight tubes: four KT77 output tubes (EL34s can also be used) along with two 12AX7 and two 12AU7 input tubes." " One of the keys to the Atlas's design is the output transformer, which O'Brien described as being far more expensive than he planned to use. In fact, it is the same transformer as that used in the Rogue 90 amplifier." Use "Tubes are biased individually, which gives an accurate reading of each tube rather than a generalization of many (with some amps, the bias is actually an average of several tubes). In practice, adjusting the Atlas's bias was a snap, and very little fussing was required over the course of several months." Value "Accuracy and musicality are bedrocks of good audio design, and they are embedded in the Rogue Audio Atlas, which, at $1395, is a rock-'solid' success."

Solid. Once upon a time, "solid" was a badge of honor. Solid science, solid circuit design, solid measurements, solid performance. I suspect that after the audio industry began to grow up, and as engineering departments ceded space to marketing departments within a company's corridors, "solid" didn't have quite the ring needed to sell units.

If ever one could reduce an entire audio product down to one word, that product would be the Rogue Audio Atlas amplifier and that word would be "solid." Engineering, build quality, value, pricing, aesthetics, sound -- all are decidedly "solid." "Excellent" comes to mind, too, but "solid" is what kept coming back to me throughout my time with this 50-pound, 55Wpc, vacuum-tube delight.

The making of a Rogue

The story of Rogue Audio is a good one. Three refugees from Lucent Technologies formed the company in 1994. Chief designer Mark O'Brien is a fan of classic engineering, and he incorporates radical concepts like reliability into all of his work. In the world of audio, where exotica is often held in higher esteem than common sense, it takes guts to eschew flash for substance, but that's Rogue Audio. And, in an audio world that regularly sees the price of statement products soaring well into the five-figure range, Rogue Audio's behemoth Zeus amplifier is relatively affordable at $7495. If that's not enough, one can certainly appreciate the fact that every other product in the Rogue Audio lineup shoehorns in between $800 and $4000. The company has no time limit on how long a particular product will remain in production (i.e., no planned obsolescence), and the company's latest emphasis is on bringing strong thinking to gear priced in the $1000-$1800 range.

That new series, released under the Titan banner, comprises three products: the Atlas amplifier under review here ($1395 USD), the Metis preamp ($995; $1095 with remote control), and the Cronus integrated amplifier ($1795). All are hand built in the US, which makes their price points somewhat more remarkable, and all are fully tested, burned in and auditioned before shipping. The Atlas, like all Rogue Audio amp designs, operates in push-pull configuration. Rogue uses printed circuit boards with point-to-point wiring as necessary. This is said to give the amps better control and the ease of manufacturing necessary for maintaining high quality. The company uses all high-precision components, such as Mundorf caps, in critical positions.

Overall, the Titan series is, in some ways, a return to the company's roots. Rogue's debut products, the 66 preamplifier and the 88 power amplifier, were introduced as high-value propositions. Over time, Rogue has moved into higher price ranges, but Mark O'Brien felt that with everything his company had learned in the last ten years, there was room in the product line and need in the marketplace for products at the entry-level price point. Audiophiles love the trickle-down effect, and O'Brien thinks the Atlas is a perfect example. Finally, as more and more manufacturing moves to China, Rogue wanted to show that it's possible to make excellent, affordable audio products in the US.

The making of an Atlas

Upon unpacking the Atlas, one immediately sees that the layout is thoughtful, and elegant in the old-fashion sense of the word. At 18" wide, 17" deep but only 5 1/2" tall, the Atlas has a robust but sleek profile. On the thick, silver front panel there is a single button -- for power on/off -- and a blue power-indicator LED. A black faceplate is an option, as is a protective tube cage.

One of the keys to the Atlas's design is the output transformer, which O'Brien described as being far more expensive than he planned to use. In fact, it is the same transformer as that used in the Rogue 90 amplifier. O'Brien is counting on the increased volume of orders between the 90 and the Atlas to bring enough economy of scale to bear to justify the extra cost.

Looking down from above, one sees the large power transformer and those two sizeable output transformers, all of which are hand-wound in Chicago for the company. Dead center is an American-made '50s-style bias meter. A small plate can be unscrewed to allow access to the biasing toggles, and the requisite biasing tool is attached behind the power transformer for safekeeping. Tubes are biased individually, which gives an accurate reading of each tube rather than a generalization of many (with some amps, the bias is actually an average of several tubes). In practice, adjusting the Atlas's bias was a snap, and very little fussing was required over the course of several months.

There are eight tubes: four KT77 output tubes (EL34s can also be used) along with two 12AX7 and two 12AU7 input tubes. All KT77s are stamped with the Rogue Audio logo and the word "approved," indicating that Rogue has tested and matched each. For output tubes, the company recommends that customers stay with what's provided, but owners are free to experiment with input tubes as they see fit. For the purposes of this review, I decided against tube rolling. Tube sockets are all ceramic.

On the back, there is an IEC inlet, allowing the use of the power cord of one's choice. In general, the company doesn't make power-cord suggestions (or any kind of cable recommendations, for that matter), despite feedback from customers about particularly successful combinations, because it can't guarantee that all cables will perform well in all rigs.

Completing the rear-panel tour, there are two sets of high-quality speaker binding posts, one set of RCA input jacks, and a fuse holder. You can choose between 8- and 4-ohm taps. To change, one must remove the cover and then swap the taps at the binding post. Both sets of taps are already prepped for connection. Given that my Vandersteen speakers have a nominal impedance of 6 ohms, I never varied from the 8-ohm taps.

Review system

My review system continues to give me joy, so I haven't felt the itch to upgrade or change for quite a while. For digital playback, I use a Pioneer DVD-434 DVD player (ModWright modified) as a CD transport, Perpetual Technologies P-3A DAC (with ModWright Level II mods) and a Jena Labs Digi-Link digital cable. I also use a prototype ModWright tube preamp, a PS Audio HCA-2 amplifier (with ModWright mods), and Vandersteen 1C speakers. Interconnects are Jena Labs Trios, with Mapleshade Clearview speaker cables also used. A Shunyata Research Hydra Model-6 feeds all electronics; it reaches the wall via a Shunyata Copperhead power cord.

Powering up the Atlas is a simple pleasure. The tubes begin to glow, making a happy, crackling sound as they warm up. Though you can enjoy music after only a minute or so, I found that listening was far more engaging after 30 minutes. As the amp arrives already burned-in, I didn't expect there to be much change after a few months, and indeed there wasn't.

A mighty sound

In recent years, there has been an attempt to make tube amps sound more like solid-state amps in terms of speed, neutrality and bass heft, and there has been an attempt to make solid-state amps sound more tube-like, with better imaging and greater overall musicality. The Atlas is of this crossover school. It is a tube amp free of bloat and possessed of nimbleness and agility. However, I'm glad to say that it retains its tube soul. There is a slight dark tilt to its sound, but nothing would I call grossly colored.

On a recording such as the icy, Nordic classic Changing Places [ECM 1834-2] from the Tord Gustavsen Trio, the Atlas lays out the piano, bass and drums on a clear, human-sized soundstage. The highs are present, not etched or rolled off. The midrange and bass are taut, not stuffed with anything extra. Drummer Jarle Vespestad's pensive brushwork is given front positioning, and the Atlas makes the most of the rich detail that's been recorded. Lovely.

Lately I've spent a lot of time listening to the Broken Flowers soundtrack [Decca 5150-02], which is a testament to director Jim Jarmusch's ability to weave interesting, offbeat music into his films in a profound way. In this case, he has chosen various tracks, most of which have a lo-fi flavor, to help carry the action. The thematic "There Is An End," by the Greenhornes with singer Holly Golightly, sounds like it was recorded in one take in a small studio about 35 years ago. And that's the point. A fundamentally honest amp like the Atlas presents the recording's vibrant intentions, rather than cleans up the sound. Other cuts, notably those by Ethiopian legend Mulatu Astatke (which are used in the film as interludes), have life and fire, but are clearly of their budget. Thus, drums sound cheap and snappy, the farfisa-esque organ is mildly distorted, and horns are stretching to stay in tune. The effect is cool, in the same way that early Jamaican recordings have a shotgun-shack authenticity that is part and parcel of the overall message. Astatke's music has been described as having a hypnotic, snake-charmer character to it, and that's certainly true. Via the Atlas, I felt like I was in the pit.

The one real departure on Broken Flowers is Fauré's Requiem, op.48, performed by Oxford Camerata. The Atlas does a fine job of arranging the parts on the soundstage. Lisa Beckley's vocal solo sits back in the soundstage, about two feet behind the speakers, while the delicate strings mass in front, in a sweet, provocative way. Colm Carey's pipe organ dives below and is reserved and somewhat distant, an accent rather than a main ingredient, but clearly present.

It has been 12 years since Kate Bush's last record, so the fact that her new work, Aerial [Columbia 97772-2], is a double-disc event makes it all the more welcome. Now, as much as I love Kate Bush, I often find that her recordings are sonically compromised, as if they've been run through an effects machine one too many times. That's true here, and the Atlas doesn't hide any of the shortcomings. A track like "Bertie," a beautiful song from mother to son drawn in quasi-Elizabethan folk tones, seems held back by the lack of air and transparency. On the album's first single, "King of the Mountain," a lilting reggae guitar sitting low in the mix helps move the tune along, but the deep bass seems muted and rough.

How does one know it's the recording and not the amp? The minute I popped in the new Nine Horses CD Snow Borne Sorrow [samadhisound 006], a collaboration among David Sylvian, Steve Jansen, and Burnt Friedman, I could hear clearly what a well-recorded work sounds like via the Atlas. Sylvian's rich voice is abundant with complex overtones and shadings navigating the emotionally difficult material. Jansen's drumming, a model of restraint, balances a good trap set with electronic embellishments, leaving room for Friedman's treatments. The Atlas delivers plenty of air, shimmer and vibrancy -- in short, musical life.

And this remained true through many hours of listening -- from Nick Drake to reggae to Van Morrison to opera. Whatever the recording quality, it was revealed, for better and for worse, through the Atlas, amidst its touch of duskiness. This turned out to be an imposing combination.

By comparison

I've been using a slightly modified PS Audio HCA-2 digital amp ($1695 when still available) to great effect over the last couple years. Though no longer in production, the HCA-2 is exactly the kind of amp one would consider alongside the Titan when shopping in the sub-$2000 price category. Given the HCA-2's acknowledged strengths (clarity through the entire frequency range; deep, taut bass; excellent soundstaging; ample muscle), I was surprised by how similar the Rogue Atlas sounded in many respects. I think this goes back to my earlier observation that the Atlas is designed by engineers to capture some of solid state's virtues.

But, and this is a big but, I spent two months listening to the Atlas, and then put the HCA-2 back in. This was a brutal reminder of how much I love a good tube design. There is that oft-praised magic: the three-dimensionality, the heightened musicality, the extra sensuality of the music -- much of which disappeared immediately with the HCA-2. I know I'll go back to being happy with my PS Audio amp when the time comes to return the Atlas, but, side by side, I'm going to choose the Atlas every time. No, the Rogue Audio amp isn't better in every category. You'll still want the 150Wpc HCA-2 for those nights when you need to rock the whole block, or even when you want to play some music with extra thump, but for anything more delicate, particularly small jazz and classical ensembles, the Atlas is my clear favorite.

Conclusion

Rogue Audio started with a plan to produce an affordable push-pull tube amp of medium power with a reach into true high-end sound. The result is the Atlas, an amp I especially liked because it embodies so much of what makes tubes fun to listen to without completely abandoning the drive and honesty of solid-state designs. One could spend a whole lot more money on an amp that doesn't sound nearly as good. Accuracy and musicality are bedrocks of good audio design, and they are embedded in the Rogue Audio Atlas, which, at $1395, is a rock-"solid" success.

...David Millman
davidm@soundstage.com

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