Note: Measurements performed by BHK Labs can be found through this link.

Every time I think I have a good handle on this audio stuff I get thrown a curveball. Last year, I reviewed NuForce’s excellent Reference 18 class-D switching monoblock amplifier ($7600 USD per pair). Going into that review, I was sure I’d hear a very detailed, clean, crisp sound that would have me switching to some of the warmer interconnects in my collection, to make the NuForces sound more natural and human (i.e., less “digital”). Well, I couldn’t have been more wrong -- the Reference 18s turned out to be two of the most musically satisfying components I’ve ever had in my system. What did I learn from that experience? Nothing.

Enter Rogue Audio’s Medusa class-D stereo amplifier ($3995), with an input stage that uses two Russian 12AU7 tubes in front of a highly modified MOSFET output stage from Hypex (a number of the Hypex module’s functions are completely bypassed). According to the folks at Rogue, the Hypex sounded better than others they tried, and gave them more flexibility in terms of which parts of the circuit could be used or excluded. Another plus was that the Hypex required only a few dB of global feedback. In developing the Medusa and Hydra two-channel amps ($2995), Rogue used their own Atlas tubed monoblock as a reference, and claim that these new digital siblings got pretty close to the Atlas’s performance, while adding maybe a skosh more detail.

On paper, it sounds like a match made in audio heaven: the detail, power, drive, and control of a class-D output stage married to the fluidity, warmth, and dimensionality of a linear, tubed input stage. I was sure I’d be awash in a lush, bloomy, expansive soundscape, courtesy those little tubes I could see glowing through the top of the Medusa.

Well, turns out my assumptions about the Rogue Medusa were as off base as my assumptions about the NuForce Reference 18. Why can’t I ever learn to stop thinking and just listen?

Description and use

I was surprised at the Medusa’s heft. I always think of “digital” amplifiers as being small, light, and cool running (there I go, thinking again), but the Medusa measures 18"W x 5.5"H x 15"D, is built like a tank, and feels as if it weighs every ounce of its 36 pounds. The amplifier is about as simple as it gets in appearance and operation -- the only control on the front panel is a simple Power button. Push it and wait a few seconds for the blue light to come on. Perfect. Why can’t everything work this way?

The only other things visible on the thick aluminum faceplate are “Rogue Audio,” engraved on the lower right, and, under the Power button at the left, “Medusa.” It’s a simple, functional look that’s just fine with me, and matches the look of my Bryston BP-6 preamplifier like a brother from another mother (turned out they share several sonic traits as well). Also like the Bryston, the Medusa is available in silver or black.

As for the performance specifications claimed by Rogue, the Medusa pumps out a healthy 200Wpc into 8 ohms and an impressive 400Wpc into 4 ohms. I guess that’s the payoff for all that weight. The frequency response is 5Hz-30kHz, +/-1dB; the total harmonic distortion is <0.1% typical, or <1.0% at rated power; and the input sensitivity is 1.0V RMS. The smaller power supplies and smaller toroidal transformer of the Medusa’s little sibling, the Hydra, yield half the power, but output aside, the amps’ circuitry is similar and, per Rogue, they sound very similar as well. Those who might not be able to afford the Medusa and can get by with “only” 100Wpc (or 200Wpc into 4 ohms) can save a grand without much penalty.

On the Medusa’s rear panel you’ll find the usual complement of connectors: XLR and RCA inputs, IEC power inlet, five-way binding posts, and the main fuse. There’s also a master on/off switch that shuts the amplifier completely off. The front-panel Power button puts the Medusa only in standby mode, in which the output electronics remain warmed up and ready to play, while the input section is turned off to preserve tube life. I think that’s a great feature -- I don’t always plan far enough ahead to start warming up the amp several hours before a listening session. And the thought of leaving depreciating tubes on all the time -- even small ones chosen for longevity, as in the Medusa -- is even more disturbing to me. I think many will appreciate this thoughtful touch, especially immigrants from SolidStateLand. From my experience with the Medusa, I could certainly see that happening. I didn’t notice any significant improvement in sound immediately after taking the Medusa out of standby mode; apparently, the input stage warms up pretty quickly and standby mode works effectively.

Throughout the review period, the Medusa operated pretty much as solidly as it felt. The only problem I had was a low-level hum that initially surfaced at turn-on. The manual says to plug the Medusa into a power strip along with the preamplifier, to avoid ground loops and such -- which I’d done, so I didn’t think that was the problem. Turned out one of the outlets in my power strip may have a spotty ground connection; once I’d slightly repositioned a couple of my power cords, the hum ceased and never returned. Apparently the Medusa is somewhat sensitive to proper grounding -- I haven’t had this problem with other amplifiers -- but no big deal; it’s just something to keep in mind.

I also noticed that, at the end of long listening sessions, the Medusa produced a hum that I couldn’t hear until I got close enough to it to switch it back into standby mode. This hum was inaudible from my listening chair, but it was there nonetheless.

The only other quibble I had was with the five-way binding posts. While these are solid, they’re a little on the small side, which made it hard to get a good, solid connection using just my fingers. Again, no big deal, especially if you’re not a reviewer, but a little more noticeable given the user-friendly thoughtfulness of the Medusa’s overall design.

Sound

I’m not sure how many hours were already on the review sample when it arrived here, but I noticed little if any change in the Medusa’s sound during my initial listening. In fact, the amplifier sounded good right out of the box, though I did let it run in for a week or so before doing any evaluations, just to be sure.

What was easily apparent from the get-go was that this was not a traditionally polite-, euphonic-, or tubey-sounding amplifier. There was abundant air, sparkle, and snap up top, which I welcomed after having expected any tubed component to sound, if anything, a little softer up there. (Stop thinking, Tim.) In the same vein, there was an openness and spaciousness in the highs that suggested a good dose of transparency to the Medusa’s sound. Indeed, listening through the Medusa, which was what I actually seemed to be doing, was like looking through a pristinely clean window on a clear spring day. Everything through that window was also very clear and distinct, with no fuzziness or cloudiness anywhere. Images were easily “visible” in their positions on and in the multi-dimensional soundstage. The whole thing just reeked of clarity and a penchant for matter-of-fact accuracy. I didn’t sense that the Medusa was trying to embellish anything anywhere -- it was simply uncovering it.

I found the Rogue’s imaging, at least as it related to the placement of individual images on and in the stage, to be fascinating. The word that pops to mind is beguiling. Soundstaging fans take heed -- you need to hear this amplifier. Frequently I found myself involuntarily shaking my head, a smile on my puss, at previously unheard amounts of spatial information, along with subtle volume shifts and the effortlessly positioned images I was clearly staring at. And this with recordings I’ve heard hundreds of times at home, as well as through several other megabuck systems. Was this a contribution of the Medusa’s tubed input stage? Could be, but credit also the rest of the component selection and the design engineering, which ensured that this wonderful wealth of information was not quashed as it passed through the output stage and beyond. The sensation was somewhat similar to adding top-flight power conditioning to a system: The removal of all noise or grunge made everything seem to pop out of a clearer space, the positions on the stage more easily identifiable.

The Medusa was a white-wine amplifier: clear, light, airy, agile, dimensional. Images had a quality of “floating in clear air” rather than sitting in a dark black silence, as I’ve heard from other high-quality gear. And those images, while seeming very complete and accurately delineated, never had an overabundance of heft -- not that they sounded at all thin. And while soundstages were appropriately large and quite deep, they didn’t have that wall-to-wall quality that can sometimes seem almost larger than life. In a related vein, individual images had very defined and distinct placements on the stage, rather than the bigger and/or more billowy images I’ve heard through other gear. It was similar to my brief experience of listening to Magneplanar speakers: The lifelike imaging, space, and “liveness” came through in an incredible way, but instruments like, say, the tenor sax didn’t have quite the density and propulsive thrust behind them that I hear from conventional cone drivers. So it was with individual images as portrayed by the Medusa: Images were tonally there, but with slightly lighter senses of weight and presence. (I’ll address a potential caveat to this assessment in a bit.) Was the Medusa’s sound subtractive, or just more honest and realistic? Dunno. I just calls ’em like I hears ’em. Suffice it to say that soundstages were big enough to be entirely believable and realistic, along with everything in them.

My first revelation with regard to the Medusa came as I listened indirectly to it while working out in my basement. I was playing Donald Fagen’s Morph the Cat (CD, Reprise 49975), one of my bass torture-test references, and realized I was hearing tonal quality in the bass riffs that had previously been hidden. There was agility and quickness that let me hear much more clearly what was actually being played. To verify this, I put on “All or Nothing at All,” from Diana Krall’s Love Scenes (CD, Impulse! 908551), which I’ve heard dozens of times through many systems, and which has a nice little double-bass solo from Christian McBride at the beginning -- sure enough, I could much more clearly hear individual notes, phrases, and tonal nuances. And again, the images had a tad less weight, heft, and bloom, but the increases in agility and tonal accuracy were palpable trade-offs.

Looking to explore familiar avenues beyond the lower octaves, I’ve listened quite a bit to David Chesky’s Area 31 (SACD/CD, Chesky SACD288) -- but when I slipped it on this time, the first movement of Chesky’s Violin Concerto, Allegro molto, with soloist Tom Chiu and Anthony Aibel conducting Area 31, which usually sounds to me a little removed and not particularly involving, was suddenly quite a bit more interesting. This didn’t have to do with tonality or anything so outwardly obvious; instead, I was able to sense so much more of what was happening within the listening window. The piano, which initially is jammed just inside and behind the right speaker, seemed to have more going on within its cramped little space. Listening more, I noticed that I was hearing finer gradations of spatial location and volume differences within what was otherwise a performance that sounded very similar to what I’m used to. The difference, though small, made the listening experience much more involving, and helped me understand more of what was actually going on in the music.

Given all that, I pulled out Steve Gadd’s Live at Voce (CD, BFM Jazz 062403), a CD I picked up because, as a drummer, I’m a fan of The Man, and hoped it would be well recorded. A first listen through my reference system told me that while it had some interesting elements, the overall sound was a little flat and blah -- kind of like a performance that had been miked from just a bit too far away to capture a live feel. “Wasted potential” was my initial assessment -- but I wanted to hear what the Medusa might have to say about it.

Right away, I was drawn into the music in a new way, because I could now more clearly “see” all the players in their respective spaces and, just as important, better hear what they were doing and how they were playing their instruments. There were lots of examples of this, but here’s one: Gadd’s cymbals appeared in dimensions and spaces heretofore unheard. When a single audio component can so revive an otherwise flat- and blah-sounding recording without resorting to trickery or embellishment (at least, none that I could hear), I consider that accomplishment pretty impressive.

In fact, whether it was rock, classical, jazz, or even electronica, my notes were consistent. Things opened up in a way that made them more interesting to listen to, almost in the way that watching a baseball game in hi-def is a lot more interesting than watching it on an old-school, lo-def, CRT TV. For instance, when I played Daboa’s From the Gekko (CD, Baby 109116), it leapt out at me in a totally new way. Yes, the subterranean bass was considerably tightened up, but I wrote in my notes that there was also an effortless dimensionality and sense of space that left other amps sounding somewhat opaque by comparison. That pretty much sums the Medusa’s sound.

Here’s that little caveat I mentioned: If you want to adjust or season the Medusa’s sound in one direction or another, you’re free to experiment with various input tubes. Rogue’s Mark O’Brien told me that he includes Russian 12AU7s because they work well and are in good supply (and, I would guess, help him hit his costs target), but he also particularly likes a new old stock (NOS) 5814, so there’s one option right there.

The interconnects I ended up using most of the time with the Medusa were my units of the original version of Acoustic Zen’s Matrix, which hadn’t seen the light of day here in quite some time. Typically, I’ll use a combination of my Stereovox Colibri-R and Acoustic Zen Silver Reference IIs, which creates a nice combination of detail and musicality, but in my system the Matrixes added a splash of rosé to the white-wine Rogue that I found appealing, with no detrimental effects. The interesting thing was that these interconnects generally sound a bit slower and warmer than the others in my stable -- but with the Medusa, and for the first time ever, they sounded neither. The irony was that the interconnects I thought I’d end up using with the NuForce amps worked with the Medusa, and vice versa. (Keep on thinkin’, Tim.) The difference between the Matrixes and the others was still there, but was much more subtle than I’ve heard with other equipment -- and I could’ve used my other interconnects and still have been very happy. Not sure why the Medusa minimized the differences, but I found it interesting.

Comparisons

The Medusa sounded quite a bit different from my trusty ol’ McCormack DNA 0.5 Rev. A power amp (around $2500 with upgrades, discontinued). The Medusa’s bass, while not sounding as full as the 0.5’s, was substantially quicker and cleaner, allowing me to hear tonal shifts that the McCormack glossed or bowled over. The DNA 0.5’s midrange lent more power, weight, and thrust to instruments and voices, which made them sound more “here” as opposed to “there.” But it couldn’t float those images as effortlessly and clearly on the stage as the Medusa. In fact, no amplifier I’ve had in my system has done so. Within the treble range, while both amps skew toward crystalline clarity and air rather than toward laid-back sweetness, the Medusa was notably cleaner up there, letting me identify with much greater specificity things like cymbals’ positions in space, and how they were being played, without crossing the line into brightness. Again, the Medusa set a new benchmark for my system in this area. Both amps’ soundstaging was very good, and roughly equivalent in size and depth. But the Medusa cleared the air within the stage much better, while the McCormack drew me several rows closer to the performers, at the expense of the overall perspective.

From my recollection of the NuForce Reference 18s I reviewed last year, in my system these two amplifiers really did sound quite different. Going back to my explanation of backgrounds of black silence vs. clear air, the NuForce is more in the former camp, the Rogue firmly in the latter. The Reference 18s also present individual images in a much more solid way, and significantly more so than my McCormack. And the soundstages produced by the NuForces were larger and more room filling -- bigger and more billowy, as opposed to the Medusa’s clear, focused stages. If the Medusa couldn’t blow out the stage to the extent that the Reference 18s could, the NuForces can’t shed as much light on what takes place on that stage. Although both were excellent in the bass and took brutal control of my speakers’ midrange-woofers, again, the NuForces yielded fuller, richer bass, while the Medusa countered with a leaner sound that trained a microscope on tonal shifts and inflections. This translated to the mid and treble ranges as well. This is the quintessential difference between “they are here” and “you are there” amplifiers, and though both models were outstanding in what they could do, which one you’ll like better will probably come down to which type of aural teleportation you prefer.

If you held me down and demanded to know which amplifier I’ve had in my system that most reminds me of the Rogue Audio Medusa, I’d say, hands down, the Bryston 2B-SST. Like the Medusa, the 2B-SST has a crystalline clarity of sound and an ability to unveil microdetails within the stage, and both exhibited the most tight-fisted iron grip on bass that I’ve heard here. I don’t recall the Bryston uncovering quite the Medusa’s level of microdynamic shifts and image specificity, but it’s been a long time. And the Bryston began to hit its limits when I really pushed it -- the Medusa never even hinted at running out of steam, no matter what I did. But the Medusa has twice the power rating of the 2B-SST, so duh. Bryston makes several significantly more powerful models that are closer in price to the Medusa and would be worth exploring if these sonic characteristics appeal to you and you want no tubes in your system.

But I’ll repeat the descriptor I used earlier. I can’t help thinking that the Medusa’s little tubes were weaving their subtle magic in somewhere, and that that’s what made the Rogue’s sound so . . . beguiling.

Conclusions

If you’re looking to tighten things up, sort things out, throw up the proverbial sash on the sonic window, and/or want a clearer overall sound, you need to hear this amp. If banishing bass bloat or getting a firmer grip on your speakers is something you need, you need to hear this amp. If you’re a solid-state guy (or gal) who’s been wondering what adding a dash of tubes to your system might bring you without significant added trouble or expense, you need to hear this amp. If you’re a tube dude looking to add more transparency and drive to your system, you need to hear this amp.

If you’re looking for an amplifier to add tonal weight and bloom to images and make things all warm and fuzzy and big and bloomy, no matter the quality of the recording, you probably do not need to hear this amp.

But, on the whole, Rogue Audio’s Medusa seems to be a great idea implemented with great insight and skill, and with outstanding results. It certainly did sedusa me on many levels. And it happened without me even thinking about it.

. . . Tim Shea
tims@soundstagenetwork.com

Associated Equipment

• Speakers -- Soliloquy 6.2
• Amplifier -- McCormack DNA 0.5 Rev.A
• Preamplifier -- Bryston BP 6 C-Series
• Digital sources -- Oppo DV-970HD universal A/V player (used as transport), Electronic Visionary Systems Millennium DAC 1 D/A converter
• Interconnects -- Acoustic Zen Silver Reference II and Matrix Reference I
• Speaker cables -- Acoustic Zen Satori shotgun biwire
• Digital cable -- Apogee Wyde-Eye

Rogue Audio Medusa Stereo Amplifier
Price: $3995 USD.
Warranty: Three years parts and labor (nontransferable); six months, tubes.

Rogue Audio
3 Marion Lane
Brodheadsville, PA 18322
Phone: (570) 992-9901

E-mail: info@rogueaudio.com
Website: www.rogueaudio.com