Rogue Audio Sphinx

The Absolute Sound 10/2013

Ron Doering

Rogue Audio Sphinx Tube Hybrid Integrated Amplifier
Class D With A Difference

Rogue is one of those lovely, elastic words that give so much lyricism and color to the English language. Five hundred years ago a “rogue” would have been a low-level thief or beggar. And now? Well, Nissan certainly didn’t have that meaning in mind when it named its little crossover. Like many other words whose meanings have evolved over the years, “rogue” now could mean a slightly dishonest person, but more commonly someone who has a bit of a devilish (but not harmful) side. And there are those who may normally act under orders but then “go rogue” and do their own thing.

This last connotation is what Rogue’s owner and designer Mark O’Brien had in mind when he started the company 17 years ago, and all Rogue products reflect the moniker, especially in their refreshing design approach, price, and value. The Sphinx integrated amplifier, subject of this review, may be the most roguish of the lot. Tubes? One hundred watts per channel? U.S. design and manufacture? For $1300? Come on!

’Tis true. And nothing, as far as I can tell, is obviously traded away in build- and parts-quality. I’m still scratching my head over how Mark can do it. Throw in the facts that each and every Rogue component is hand-built or that Rogue calls Pennsylvania home and not Rick Perry’s business-friendly Texas—or China, for that matter—and the company seems all the more amazing. Like the bumblebee that the experts say should not be able to fly, perhaps Mark just doesn’t know any better. Or maybe he’s a bloody genius. After visiting Rogue’s facilities in Brodheadsville, I have to say my money’s on the latter.

Equally well known for affordable all-tube components, Rogue also offers a growing line of hybrid power and integrated amplifiers, which meld tubes and Class D outputs. The Sphinx is one of the latter. I’ve come to respect Class D for its efficiency but, thus far, cannot say it has equaled a good conventional transistor, much less all-tube, design in sonics. What Rogue has achieved, judging from the very affordable Sphinx, is not only demonstrably world-class sound, but the strongest argument I’ve yet come across for Class D topology.

Yes, the Sphinx is by nature energy-efficient, so I really was not surprised that it ran cool (barely warm to the touch even on the hottest summer days). More to the point for us audiophiles is that this is one ballsy amplifier. With 100 watts on tap into 8 ohms and 200 watts into half that impedance, this thing is powerful and can swing current. And with a damping factor of greater than 1000, woofers will love it. Damping factor is a specification which seems to have gone out of fashion over the years, but this doesn’t diminish its importance. In simplest terms, as the ratio of a connected speaker’s impedance to the amplifier’s output impedance, it’s an indication of control. The higher the damping factor, the more control the amplifier is projecting on the loudspeaker driver(s), especially the woofer(s). This control translates into bass accuracy and speed, sometimes described as “slam,” a quality which the Sphinx easily demonstrated in my auditioning.

Still, I get the sense that Mark O’Brien is not yet convinced that the perfectionist audio world is completely ready to speak of “Class D” in the same breath as “tubes” or “Class A”; the circuit topology used isn’t mentioned at all in the sales materials I’ve seen or in the owner’s manual. I sympathize, but this only reflects the less-than-fully realized promise of the circuit in the designs of others. In my experience Rogue is the first to bring Class D to a world-class performance level, but I think Mark knows

he is going to have to do a lot of convincing.

Use and Listening

I’ll be honest. I don’t have a clue why the Sphinx sounds as good as it does. The obvious non-answer is good design and carefully chosen if not super-premium parts. Mark uses a pair of JJ Electronic 12AU7 tubes in the preamp section and Hypex UCD180 Class D modules for the output stage. Important to making this all work well is the power supply, according to Mark, who uses a fairly hefty toroidal transformer from Avel Lindberg. The headphone circuit has its own discrete amplifier section and is the same one used in Rogue’s more expensive preamps.

While there are none of the sometimes very steep tradeoffs I’ve learned to accept if I want cheap and good sound, the need to make some accommodations with respect to the user interface is still present. The materials and fit-and-finish of the Sphinx’s faceplate and controls are competitive for this price sector, but anyone who has had even the briefest experience with, say, a McIntosh or Accuphase control amplifier will be reminded of the massive engineering effort that can be devoted to issues that have nothing to do with sound.

 

So soft-touch controls and microprocessors are absent. Instead, the stand-by power switch is a hefty spring-loaded affair, while the source-selector feels both stiff and a bit spongy due to the long torque tube spanning the deep 17" chassis. Sorry, there is no tape loop, but the Sphinx does accept up to three line sources and has a moving-magnet phono input. A balance control is welcome, as is the optional motorized volume control ($100), which quite commendably worked without overshoot. With this option, the all-metal dedicated remote volume control is large, heavy, and all business. Drop it on your big toe and you’ll know it!

The EIC power socket, the main power switch, widely separated three-way binding posts, and surface-mount RCA connectors on the back panel make good use of the plentiful acreage found there. Nearby is a pair of fixed and variable line-level outputs suitable for processors, subwoofers, external headphone amplifiers, or power amplifiers. Speaking of headphones, I found the built-in headphone circuit to be sweet sounding and very refined, yet I could have used a little more gain to better suit my power-hungry Sennheiser HD 600s.

Some operational notes before I get into the sound. Mark designed the Sphinx to be energized in stand-by mode, but that doesn’t apply to the two input tubes, which only see current when you throw the front-panel “power” switch, and are then slowly ramped up to full power—a process that takes about 20 seconds. It might not be the craziest thing to buy the Sphinx for its phonostage alone, for it really is that good. Dynamic, spacious, quiet, possessing very good resolving power, it is a simplified version of the circuit used in Rogue’s solid-state Triton phono preamp, and it made for a splendid fit with either of my moving- magnet cartridges.

Be forewarned, though, as you may find some of your old vinyl favorites no longer listenable. I had to chuck up the dough for a fresh pressing of Dark Side of the Moon [Harvest SHVL 804] thanks to the Sphinx’s ability to demonstrate just how noisy my three-decade-old edition had become. Annoying, but I can’t shoot the messenger. So how does the Rogue sound on the new record? Well, DSM is, of course, a creation of studio wizardry but its fame as the hi-fi demo record for the last 40 years is justified. Floor shaking heartbeats? Jet airplanes leaving the tarmac? A cacophony of alarm clock bells? Gorgeous female vocals? They were all there, fresh as the day I first heard this masterpiece of 1970s pop-art. The Sphinx also found a way to make my mono soundtrack of Porgy and Bess [Columbia] sound fresh, vibrant, and vital, even after 54 years. Adele Addison’s performance of “I Loves You, Porgy” (her voice was used to dub that of the film’s star Dorothy Dandridge) is brief but oh so devastatingly lovely.

If you have no use for a phonostage, the Sphinx would still be a bargain for the price. (Mark might even change out the phono circuitry for an extra line-level input if you ask him nicely.)

On CD and high-resolution computer audio, this amp, for a lot less money, reminded me in many ways of the very good Musical Fidelity M6, even though the two amplifiers are about as different in concept and execution as you can find. Sonically though, if not twins, they share an ease in presenting dynamics, both micro and macro, which I have found to be the cornerstone to realistic and/or involving audio reproduction. Vanishingly low distortion? Ultra-high resolving power? Wide bandwidth? I’ll take ’em all—as long as the life and excitement is not sucked out of the sound, which can be the case when these attributes are pursued with a little too much zeal.

I don’t have the instruments to measure such things so I really don’t know if the Sphinx is meeting its claimed THD or frequency- response specifications. What I do know is that I thoroughly enjoyed the added blast of loose and “rangy” bass, drums, and guitar at the beginning of “Black” from Ten [Epic], Pearl Jam’s first studio album. This is big sound music that is believable only if the supporting electronics are both quick and powerful.

I was as impressed with that performance as I was with the delicacy that the Sphinx brought to Glenn Gould’s almost superhuman rendering of the Goldberg Variations. Where is the separation between human (Gould) and machine (piano)? Sony’s beautifully packaged A State of Wonder [S3K 87703] explores this question using a singularly brilliant score and its greatest interpreter—first as a 22-year-old musical wunderkind, and then a seasoned middle-aged master, just days before the stroke that would take his life. Over a quarter of a century separates these recordings (1955–1981) and the differences are both expected (mono versus stereo) and unexpected (the later recording is over 12 1/2 minutes longer). But comparing Gould youthful and mature is not what makes this recording meaningful for me. The later (possibly last) recording of Gould is my favorite; full of the craft, technique, and eccentricity that made this artist so special. Gould was one of the best at finding the beauty in Bach, and the Sphinx did not betray him.

Conclusion

To put it simply, I think the Sphinx has the goods and is worthy of all the positive buzz generated since its debut at the 2013 Consumer Electronics Show. One of the few amplifiers that can claim to be both “green” and “good” in the audiophile sense of the word, I’m all over this thing. Recommended, and I’ve purchased the review sample. So there!