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Reviewer: Edgar Kramer
Source Digital: Sony XA-5ES as transport; Bel Canto Design DAC 2
Source Analogue: Pro-ject 6.1 turntable with Pro-ject arm and Goldring cartridge
Preamp/Integrated: Supratek Sauvignon with NOS RCA and Sylvania tubes
Amplifier: Pass Labs X 250.5
Speakers: Wilson Audio WATT/Puppy System 6
Cables: Harmonic Technology Magic Digital; Harmonic Technology Magic and Truthlink Silver; DanA Digital Reference Silver; Eichmann eXpress 6 Series 2; Bocchino Audio Morning Glory interconnect cable [on loan]); Harmonic Technology PRO-9+ loudspeaker cable; Harmonic Technology Fantasy AC; Shunyata Research Diamondback power cords, Eichmann eXpress AC power cable
Stands: Lush 4-tier, partly sand filled
Powerline conditioning: PS Audio P-300 Power Plant (digital equipment only), dedicated 20 amp circuit
Sundry accessories: Bright Star Audio IsoRock Reference 3, Bright Star Audio IsoRock 4 isolation platforms and BSA IsoNode feet; Black Diamond Racing cones; Stillpoints ERS paper in strategic positions around DAC, Shakti On Lines; Densen CD demagnetizer; Auric Illuminator CD Treatment; ASC Tube Traps
Room size: 16' w x 21' d x 10'/11' h [stepped ceiling] in short wall setup, opens to adjoining office room
Review component retail: $3,995/pair

An honest Rogue
Those of you who have followed my previous writing would be familiar with my habit to start a review with some sort of theme or pertinent lead into the review proper though sometimes, I can rave on. Not this time, however. This review will right away reflect my impressions of the subject at hand, the Rogue Audio M150 monoblock valve amplifiers. Matter of fact. To the point!

And that's just how some audio manufacturers present themselves and their equipment. No bullshit, just straightforward honest gear that often surprises the auditioner or potential buyer with tier-defying sonic quality and value for money. More often than not, such gear conceals its merit underneath the covers, as though the hidden parts quality and astute engineering were blushing with pre-nuptial innocence and modesty.

Rogue Audio strike me as one of these modest yet quietly achieving brands that strive to provide well-designed value-for-money products commensurate with audiophiles' stringent sonic demands.

The M150s are second from the top of the company's range of quality valve amplification. Below the M150s sits the more modest Stereo 90 and above, the pride and joy Zeus 225-watt mono monster flagship.

Aesthetically the M150s present an almost conventional, nicely rounded-over, solid aluminum and flat fascia with the company's name deeply etched into it. The look is very "solid-state amplifier". Beyond the fascia and past the "ultra high bandwidth custom wound" transformer's enclosure, the more traditional valve amplifier look takes over - a flat steel panel upon which are mounted four KT88s in push-pull configuration outputting 150 watts. Input valves consist of the reliable and easily attainable 12AX7 for phase inversion and two 12AU7 mu-followers to drive the output valves.

The driver circuit design claims excellent signal transfer and ultra quiet operation, something I can vouch for in my high-gain system. A bias meter sits atop for convenient adjustments once the easily removed protective metal grill is lifted off and the hatch cover has been removed [left].

Further, this unit sports separate 8 and 4 ohm taps on good quality terminals -- I used the 4 ohm taps with my demanding WATT/Puppies -- RCA and XLR inputs, a triode/ultra-linear external switch (more on this little feature later) and a soft start circuit to extend valve life. The tubes are biased at 40mA. While on the subject of valve life, Mark O'Brien -- designer and company principal – estimates output valve life to be between 2,000 - 3,000 hours and input valve expectancy up to a maximum of 10,000 hours. Not bad.

Dastardly Deeds
No matter how objective we say we are when approaching reviews, we are at the very least only kidding ourselves. We come with baggage, preconceptions, misconceptions and biases. We hold views and attitudes that are the product of hundreds of self-important reviews, bull-headed opinions, myths and indoctrinations. One of the most aged and clichéd notions is that valve amplification can't do good bass. The claim is that valve bass is slow or ill-defined, boomy or virtually non-existent.

Well, what struck me about the Rogues on first listen was the quality of the bass. In my room, the M150s made great boogie bass - tight, detailed and with a wholesome bloom, a combination that was startling. Brian Bromberg's wonderfully produced Wood [A440 Music Group, 2002] is one of the great tests for bass-reproducing ability. In the Beatles cover "Come Together", Brian strokes, plucks, picks and pulls at the bass strings. He plays fast, then paces himself, then throws a googly and spans the frequency range of his instrument exploring tones and colors that paint a sonic picture of gut, skin, nail and wood. How'd the Rogues do? They passed with flying colors. Bass notes had a fast and detailed leading edge followed by the note proper full of body, effortless dynamics and resonance, then decayed with superb harmonic content.

I must add that my newly updated and tweaked-up Supratek Sauvignon valve preamplifier played a major role in further contradicting the "valves equals mediocre bass" myth. In the crucial preamplifier and amplifier football match, the two made a formidable team. The Sauvignon handled the ball with great dexterity and skill to side-step boom, then long-passed to the Rogues for the touch-down at the spiked feet of the Wilsons.

The other most striking feature of the M150s was their overall sense of balance. If the rest of the system permits, the Rogues' wire walk over a precipice is so precise and well tuned that if something in the audible band is out of whack, I would feel confident in blaming another component for plunging the Rogues into the abyss below.

The piano is one of the few instruments that can scope out the frequency range from twinkling highs to rumbling lows. An unbalanced component will accentuate or diminish a certain frequency range to only affect particular notes. Such anomalies result in notes jumping out from the mix or seeming muted in contrast to the preceding or following notes. I've experienced this phenomenon both with treble-happy speakers and lean, forward-sounding amplifiers. Rachmaninoff's 3rd piano concerto as played by Martha Argerich [Philips 446 673-2, 1995] clearly displayed that sense of balance I refer to. The piano sounded clear, tonally full, harmonically accurate and even. There was also a true sense of the instrument's location within the soundstage.

And yes, for those whose opinion of the WATT/Puppy is that it's tipped up in the mid/high transitional range, the M150s neither compounded nor subtracted from such an alleged inherent character.

This same balancing act was consistent on numerous CDs I tested, from large orchestral works through to male and female vocal, rock and blues - the works. In other words, any expectations about tube-induced frequency domain squiggles found themselves relegated to the trash can labeled "myths".

I was not surprised but indeed pleased that another HiFi publication listed Patty Larkin's Re-Grooving the Dream [Vanguard Records 79552-2, 2000] as one of the best sounding contemporary music CDs. "Then", the 12th track, has superbly recorded drums, cymbal work and acoustic guitar. The M150s play it punchy, play it true and play it powerfully, the gut-pounding impact not reduced nor stunted when compared to my reference Pass Labs amplifier. When Patty's vocal comes in late in the piece, her voice is clearly defined with its own solid image and in surprising relief even against the tidal wave of instrumentation that occurs around her.

The above serves to exemplify again what I mean by balance. When mixes get busy, the Rogues are never confused nor do they homogenize the music into a flustered mash. Instrumental strands always remain clearly discernable regardless of complexity of the mix and playback level. While there's no lack of detail -- the M150s are able to resolve maximum recorded nuances -- they never sound harsh or bright. No matter what, music remains smooth and listenable and most importantly, enjoyable.

Ani Di Franco's Up, up, up, up [Righteous Babe Music, 1999] is highly regarded for its
production values. Ani's vocals on "'tis of thee" came across with a realistic sense of "lung-air-through-throat" friction with that in your room thing again. Also very challenging for any audio system is the way in which Ani hammers her guitar. A dynamically challenged component in the chain will result in loss of power and punch on the vigorously pounding strums. The Rogues did the transient attack very well as also proven on the previous musical material. Dynamically, they also performed very well here but fell just short when compared to the best SET brethren or good solid-state cousins, the best examples of the latter seemingly more effortless in their dynamic envelope.

Two modes of transport
The above sonic quality was ascertained with the amplifiers set to triode as recommended by the Australian importer. I indeed recall reading numerous reviews of amplifiers with this feature where the reviewers prefer triode over ultralinear. Be that as it may, I'd perform my own investigations, thank you very much.

Flicking over to higher-power push-pull operation on the fly rendered some subtle changes. Going back to all the earlier pieces of music, I found push-pull to have a little more clarity on vocals and perhaps a little more sense of air to the high notes. I however much preferred triode mode for its superior stage width and depth, image body and overall sense of ease to the entire presentation. Triode mode has an inherent smoothness without loss of detail that I really enjoyed.

Going back to my Pass Labs X250.5 for cross-referencing, I discovered a couple of very small fissures in the Rogues' armor. Dynamically both in the micro and macro domains, the Pass amp bested the Rogues. Massive dynamic contrasts were marginally stunted by the M150s and the microdynamic shadings of for example finger-picking sounds on guitar strings were slightly veiled and less resolved. To put this in perspective however, these minor issues were only noticed once comparing the Rogues to a rival in a higher price bracket and of different applied technology. These changes were indeed quite subtle and prior to the comparison, really non-issues.

All in all, the Rogues were very impressive. $3,995 buys you a pair of handsome, well-built mono- amplifiers with a full set of features, considerable valve power, conservative operation and very impressive sonic skills. The M150s perform all the audiophile prerequisites of soundstaging, imaging, tonality very well. Exceptional however is the way in which the Rogues reproduce bass frequencies - and their tonal and frequency balance is truly superb.

These Rogues thus lived up to their rascallian appellative by performing a short con on me: Deceptively simple in appearance yet capable of outstanding sonics. These amps are a ripper. Highly recommended.
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