Jeff Rowland Design Group Corus Linestage and 725 Monoblock Amplifier

From the Inside Out

Equipment report
Categories:
Solid-state power amplifiers
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Products:
Jeff Rowland Design 725 Monoblock,
Jeff Rowland Design Corus
Jeff Rowland Design Group Corus Linestage and 725 Monoblock Amplifier

The Jeff Rowland Corus linestage and 725 power amplifiers are the most beautiful, and beautifully made, electronics I’ve had in my home. They are visually stunning, with a unique diamond-cut front- panel adorning a chassis hewn from solid aluminum blocks.

I’ve seen many lavishly made audio products but these Rowland electronics give off a different vibe. While many “luxury” audio components seem to have superficial “bling” added later to foster their appearance, the Corus’ and 725’s outward beauty appear to be a manifestation of their inner beauty. By inner beauty I don’t just mean the fabulous build-quality visible under the top panel, but rather the obvious care and dedication that went into their design and construction. The quality flows from the inside out rather than being tacked on after the fact.

The Corus linestage is not only gorgeous to look at, it’s also an ergonomic delight. Using it on a daily basis is simply a joy. Take the display, for instance. On many preamplifiers the display

is either big and garish (but functional) or small and unreadable from across the room. The Corus features a vacuum fluorescent display that is at once subtle and useful. It can be easily read from the listening seat, yet never calls attention to itself. The soft blue color, the size and shape of the letters and numbers, and the brightness could not be improved upon. It’s elegant in a way that most audio-component displays are not. This is no accident; the display’s standard character-generator was abandoned in favor of Rowland-designed alphanumeric characters, symbols, and icons. Even the display’s light-blue color was customized for the Corus. Moreover, the display can be set to one of four brightness levels, and two timer-based modes automatically turn it off (it will still illuminates briefly when a command is received).

And then there’s the volume control that changes its ballistics in response to hand movement. Turn the knob quickly to get up to a specific volume range and the volume changes quickly. As your hand naturally slows down as you approach the ideal level, the volume-change speed slows commensurately. This process is transparent to the user; you just do what comes naturally and the Corus adapts. The result is an ability to quickly and precisely set the perfect playback level for any recording or situation.

I’ve gone into this detail about the display and volume control because they exemplify the fact that every aspect of these products has been carefully considered and optimized. I don’t know that I’ve reviewed a preamplifier that has had this much thought put into its visual appearance and the user experience. The designers obviously care deeply about their customers. The Corus reminded me of an observation in Robert Pirsig’s Zen and the Art of Motorcycle Maintenance: “Care and Quality are internal and external aspects of the same thing.”

The Corus is also highly capable, with four balanced inputs, two unbalanced inputs, four main outputs (two balanced, two unbalanced), and two record outputs. Any input can be set to “theater pass-through” mode for integrating the Corus into a multichannel system. A gain-offset feature memorizes different gain settings for each input, allowing you to switch among sources without large jumps in playback volume. In addition, the secondary main output has a programmable gain offset with 0.5dB resolution, a useful feature when bi-amping with two amplifiers of different gains. One of the record outputs features an independent gain-adjustable signal path for driving a second zone in a multi-room installation. The inputs can be named, although I found that the pre-programmed input names (DAC, Phono, etc.) worked just fine. Another nice touch is the inclusion of a balance control, although you must enter the menu system to access it.

The small outboard power supply connects to the Corus via left and right-channel umbilicals. A third cord runs between the Corus and the remote IR sensor. This latter feature allows you to position the Corus without maintaining a line-of-sight to the listening position. Naturally, the power-supply chassis and remote sensor are machined from aluminum billet.

The 725 power amplifier is just as beautifully built as the Corus but, being an amplifier, isn’t distinguished by the Corus’ array of functional and ergonomic refinements. The chassis is quite compact for an amplifier of this power—330W into 8 ohms, 650 into 4 ohms. In fact, in density it is a solid monolithic block. That’s not surprising given that each chassis and its integral heatsinks are machined from a solid block of non-resonant aircraft-grade aluminum. Removing the top cover and looking inside conjured up an image of a bank vault. In a further indication of the level of thought and detail that went into these products, the holes that form the heat sinks are not of uniform size or position so that the chassis is less supportive of resonances. The chassis dimensions are also based on the Golden Ratio, again for resonance suppression.

This high output power from such a small chassis is made possible by the 725’s switching power supply. All the audio circuitry, including the output stage, are linear (non-switching) circuits. But the power supply that converts AC from the wall into DC to supply the circuits is realized with switching technology. (Incidentally, Linn’s spectacularly great CD12 CD player featured a switching supply, not for compactness or weight, but because Linn thought it sounded better than a linear supply.)

The 725’s front panel features the distinctive vertical striations that have been characteristic of Rowland products for more than 20 years. A small round power button gently lights up when the amplifier is powered on. The metal-work is as good as it gets. (See the sidebar for more technical details on both products.)

Listening

I auditioned the Corus and 725 with three different loudspeakers, the Venture Ultimate Reference, the Lansche No.7, and the Magico Q7. With each of these very different loudspeakers the electronics’ essential qualities remained consistent. The first, and overriding, quality is the Corus’ and 725’s transparency to sources. They have very little in the way of a personality or distinctive character. They get out of the way, providing a clean window back to the original musical event. Their sound is not one that calls attention to itself as “spectacular” hi-fi, but rather one that subtly conveys musical expression. The result was a presentation that fosters an immediate and deep musical involvement.

A large part of the Corus’ and 725’s musicality can be credited to their smoothness and absence of grain. The treble had a refinement, resolution, and delicacy that lacked any hint of transistor hardness. I wouldn’t characterize the treble as either forward or laid-back (which is easy to do with most amplifiers), but rather as an organic and wholly integrated aspect of the sound that defies conventional descriptors. Some electronics draw your attention to the treble as a detached component riding on top of the music—like a tweeter that sticks out. With the Rowland, the treble had a full measure of energy and life, yet at the same time was subtle and refined. In addition, the treble had a crystalline clarity coupled with a sense of top-end extension and openness. The delicate cymbal and brush work on Jimmy Cobb’s Jazz in the Key of Blue [Chesky, hybrid SACD] were reproduced with tremendous clarity and resolution without a trace of etch. In addition, the Rowland electronics resolved the cymbals’ fine decays into the very lowest levels, adding to the sense of realism.

The exemplary treble performance extended down into the midrange, where the Rowland electronics exhibited a gorgeous rendering of instrumental timbre. The sound was simultaneously lush and highly resolved—an extremely compelling combination. By lush I don’t mean overly romantic like many tubed amplifiers, but rather densely saturated in tone color and complete lacking grain and electronic artifacts. The wonderfully recorded brass and woodwinds on Count Basie’s 88 Basie Street [JVC XRCD] fairly jumped to life from the loudspeakers with a totally natural quality. String sound was also well served by the Rowland’s clean, but never dry or sterile, midrange and treble. Again, the combination of lushness and resolution is a powerful one; the lushness invites physical involvement by allowing your ears to more fully “open up,” and the resolution invites intellectual involvement. That is, the lack of hardness and grain put me in a more receptive state to the music’s meaning and expression.

Rowland amplifiers are known for their solid bottom end, but this description doesn’t do justice to the 725’s bass reproduction. I heard not just tremendous weight and authority, but a natural warmth, richness, and fullness that made many other solid-state amplifiers sound a bit bleached and threadbare by comparison. The bass and midbass were densely textured and rich, but never thick, bloated, or lacking articulation. The richness of tone color through the bass and midbass contributed to the overall feeling of relaxing into the music rather than being held at arm’s length as a detached observer. The Rowland’s reproduction of acoustic bass was outstanding. Check out Edgar Meyer’s virtuoso playing on Hop, Skip & Wobble; the Rowland conveyed every nuance of the instrument’s color, dynamics, and size as well as Meyer’s expression. The Rowland was completely unfazed by any pitch or playback level, including the subterranean Hammond B3 pedals on organist Joey DeFrancesco’s Part III. The 725 had plenty of power in reserve judging from the way that kick drum cut through the mix dynamically rather than sounding soft and mushy at high playback levels. I got the impression that the 725 had an iron-fisted grip on the loudspeaker’s woofers; such was the sense of control and precision. The sound was totally effortless and composed no matter how dense and complex the music, and at any playback level.

The Corus and 725 are also very fast and clean, reproducing transient detail with tremendous clarity. In addition to conveying a sense of “suddenness” on transient attacks, the decays between attacks are characterized by a deep silence, a combination that adds to the impression of hearing an instrument hanging in space between the loudspeakers. Paco De Lucia’s rapid-fire flamenco guitar work and the multiple handclaps and foot stomps on his 1993 recording Live in America highlighted the Rowland’s dynamic agility. What impressed me as much as the Rowland’s transient fidelity was the lack of etch or “skeletal” sound that often accompanies such a highly detailed and resolved presentation. Despite the Rowland’s speed and articulation, it never crossed the line into the clinical.

I evaluated the Corus independently by performing the bypass test by listening to a DAC’s output driving the power amplifiers directly and then putting the Corus in the signal path. The Corus was surprisingly transparent, shaving off just a bit of air and vividness but otherwise introducing no thickness or opacity to the soundstage. The Corus was also extremely clean-sounding, adding very little sonic signature. No preamplifier is completely transparent in the bypass test (which also adds a pair of interconnects to the signal path), but the Corus is far better than most.

As much as I enjoyed and admired the Corus and 725 with the Venture and Lansche loudspeakers, it took the astonishing Magico Q7 to reveal the extent of the Rowland’s greatness. The Rowland electronics and Q7 share many fundamental goals, particularly in the area of resonance control, resolution of micro-dynamics, reduction of stored energy, and the general removal of sources of signal contamination. The Q7 is so transparent and resolving that it immediately exposes any amplifier or source shortcomings. But the Roland was easily up for the task. With the Q7 I could hear way, way down into the finest details of music’s microdynamic structure, the subtlest inner details of instrumental timbre, and what must be miniscule spatial cues that conjure up the impression of sitting in the original acoustic space. I was repeatedly floored by this combination’s ability to paint a vast panorama of acoustic space populated by tangible instruments. One of the most vivid examples is the Analogue Productions’ 45rpm reissue of Muddy Waters’ Folk Singer. I have never felt a stronger impression of being transported across space and time to a musical performance. The Q7 also showed me the Corus’ and 725’s stunningly quiet background, superb ability to reach way down into the lowest levels of timbral and spatial information, amazing transient speed, and bass grip and extension.

Conclusion

The Jeff Rowland Corus linestage and 725 power amplifiers are world-class electronics in every sense of the phrase. They are stunningly gorgeous to look at, a delight to use on a daily basis courtesy of their exemplary user interface, and intensely musical. Moreover, they are backed by an American company with a 26-year track record. Frankly, considering the build-quality, the technology, and musical performance, they are a great value. Although $13,600 for a linestage and $29,800 for a pair of amplifiers is hardly inexpensive, many other companies routinely charge more for less. These electronics were perfectly at home in the context of the $165,000 Magico Q7 and $54,000 Basis Inspiration turntable.

Beyond the specific sonic characteristics I’ve described, the Corus and 725 were unfailingly musical. They’re the kind of electronics that seem to disappear from the signal path rather than make you constantly aware of their presence. At the end of the day a good yardstick for audio component quality is how quickly and how deeply they immerse you in the musical expression. By those fundamental criteria, the Corus and 725 are a home run.

The Corus and 725 are so visually appealing that you might be tempted to think of them as boutique products—all frills and little substance. But they are at their heart serious pieces of engineering that represent Jeff Rowland’s more than 40 years of experience in amplifier design. The Corus and 725 are truly examples of beauty flowing from the inside out.

Specs & Pricing

CORUS LINESTAGE

Inputs: Four balanced, two unbalanced, programmable gain offset on all inputs
Outputs: Four main, two record (one of which has independent gain adjustment)
Gain: 7dB (+/-20dB gain programmable on each input)
Gain resolution: 0.5dB over entire 99.5dB range
Input impedance: 40k ohms (balanced or unbalanced)
Output impedance: 60 ohms (balanced or unbalanced)
Power consumption: 15W
Dimensions: 15.5" x 3.9" x 12.3" (linestage chassis); 4.7" x 2.9" x 11" (power supply)
Weight: 22 lbs. (linestage); 6 lbs. (power supply)
Price: $13,600

725 MONOBLOCK POWER AMPLIFIER

Output power: 330W into 8 ohms, 650W into 4 ohms
Input impedance: 40k ohms
Damping factor: >200
Gain: 27dB
Inputs: Balanced XLR 
Power consumption: 1W (standby); 85W idle
Dimensions: 15.5" x 5.75" x 16.25"
Weight: 54 lbs. each
Price: $29,800 per pair

JEFF ROWLAND DESIGN GROUP

2911 N. Prospect
Colorado Springs, CO 80907
(719) 473-1181
jeffrowland.com

ASSOCIATED COMPONENTS

Venture Ultimate Reference, Lansche No.7, and Magico Q7 loudspeakers; Jeff Rowland Design Group Aeris DAC; Berkeley Audio Design Alpha DAC Series 2; iMac server with Berkeley Alpha USB interface; Basis Inspiration turntable with Basis Vector 4 tonearm, Air Tight PC-1 Supreme Cartridge; Aesthetix Rhea Signature phonostage; Simaudio Moon 810LP phonostage; Shunyata Triton and Talos AC conditioners, Audience aR6TS power conditioner; Shunyata CX-series and Zitron Anaconda AC cords; Audience Au24 and PowerChord AC cords; Shunyata Anaconda interconnects and loudspeaker cables; AudioQuest Diamond USB digital cable; AudioQuest WEL Signature interconnects, Transparent XL Reference interconnects; Transparent XL Reference loudspeaker cables; Stillpoints SS equipment racks, Stillpoints Ultra SS and Ultra 5 isolation, ASC 16" Full-Round Tube Traps. VPI 16.5 record-cleaning machine; Mobile Fidelity record brush, cleaning fluid, stylus cleaner