Koetsu Rosewood Signature Moving-Coil Phono Cartridge

Classic Musicality

Equipment report
Koetsu Rosewood Signature Moving-Coil Phono Cartridge

Yoshiaki Sugano (1907–2002) is truly an iconic figure, whose place in high-end audio’s hall of fame is most secure. His legacy is that of a consummate artisan, whose masterwork moving-coil cartridge designs propelled the art to a pinnacle not previously known in its day. Their magic has assuredly not faded over the years. He founded Koetsu in the 1970s and chose a company name to honor a distant ancestor—the famous Japanese craftsman, potter, and calligrapher, Honami Koetsu (1558–1637). Sugano greatly admired Koetsu and throughout his life faithfully practiced the master’s credo, that “nothing so exquisite exists in this world as an object made by the human hand.” Sugano-san was a true renaissance man, with a deep knowledge of Japanese samurai swords, painting, and calligraphy. In his youth, he was even a boxer for several years before settling down for a long and successful career at the Toyota motor company. He had the good sense to retire at age 60 so he could devote more time to his passions of audio and art. From its early inception, Koetsu was and has remained a family business. In particular, Sugano apprenticed his eldest son, Fumihiko, who then took over production in the early 1990s when physical constraints made it impossible for Sugano to continue. Limited production means limited availability. Distribution has been spotty over the years, but we can all thank the current U.S. distributor, MoFi Distribution, for keeping the supply line open.

Originally, Sugano studied and modified commercial cartridges before finally embarking on a full-fledged business venture to hand-build no-compromise mc cartridges. He realized from the start that the path to good sound begins with exceptional materials and components. He solicited research labs and specialty craftsmen to create the necessary components for his mc’s. Coils were initially wound using 4-nine pure copper, though today 6-nine pure copper is used exclusively. During early production, the magnetic field in which the moving coils are immersed used Alnico magnets and pure-iron plate formers. Alnico was eventually replaced by samarium-cobalt magnets in the entry-level, aluminum-bodied Black Goldline, as well as in the Rosewood Standard and Rosewood Signature models. Wood-bodied models with urushi lacquer use permendur magnets. All the stone-bodied models, as well as the Rosewood Signature Platinum, use platinum-iron magnets. Special attention was focused on the cantilever’s rubber suspension, parts being sourced under license from a rubber damper manufacturer and pre-aged for consistency. According to Koetsu, the stylus tip is a line-contact type, which is not specifically mentioned in the basic specs. In typical Koetsu fashion, the cartridge arrives packaged in a wooden box with no documentation whatsoever. I suppose this is Sugano’s way of informing the end user to use his or her ears and enjoy the music instead of obsessing over measurements.

The essential design elements of the Koetsu line have not changed over the years, and aside from internal differences in magnets and wire, the most obvious distinguishing feature is the cartridge body. The entry-level Black’s body is aluminum, and above it sits the Rosewood and its tighter tolerance Signature version. Then come the urushi-lacquered rosewood models which are stiffer than the stock body, and finally the culmination of the line, several semiprecious-stone-bodied models. It’s clear that Sugano purposely sought desired colorations via the tonality of various cartridge bodies since each body imposes its own unique resonant frequency onto the output signal. Wood and even the lacquered wood bodies would be expected to be more acoustically inert than stone. Thus, simply on the basis of the cartridge body one would expect a subtle sonic difference between each model, along a scale of color saturation, with the stone bodies perhaps being the most flamboyant or Technicolored of the lot. This shouldn’t be surprising since a stylus is adept at picking up minute vibrational energy much like a seismometer, a fact that was brought home many years ago when I happened to place a turntable on a hollow wooden box. If you’re into a thick and fat lower midrange, this is one way to get it without having to resort to an equalizer.

For years I’ve set up cartridge offset angle and overhang using a template based on the Löfgren A alignment, which actually gives identical results to the Baerwald and Stevenson B alignments. In all of these cases, the weighted tracking error, that is the tracking error divided by the groove radius, is minimized across the surface of the record. That makes perfect sense since distortion increases as the stylus approaches the inner grooves. As with other cartridges, the Rosewood also benefits from precise VTA adjustment, an easy task with my Kuzma tonearm which allows me to adjust VTA during play. I simply insert my ears into the process and tweak the VTA until image outlines snap into focus. A vertical tracking force of 1.9 gram, right in the middle of the recommended range of 1.8 to 2.0 gram, proved to be perfectly adequate to keep the stylus in contact with the groove at all times. As far as cartridge loading, I experimented with a number of settings over the range of 30 to 300 ohms. At least in the context of my system, I found a 50-ohm loading to sound best.

My first sonic impressions were attained via River Road (Opus 3, 8017), recorded by Bo Hansson on a two-tack analog tape recorder using a single Neumann SM 69 stereo microphone with modified electronics. The SM 69 was Neumann’s first large-diaphragm stereo microphone. Both capsules could be set to a variety of single-point stereo pickup patterns, and Opus 3 always used the Blumlein configuration for its live recordings. It’s clear that Hansson had found just the right venue and mic placement, accounting for this purist recording’s superb tonal balance and spectacular you-are-there spatial perspective. And the conviction with which the spatial illusion unfolds has proven to be an excellent marker for a phono cartridge’s soundstaging ability. The Rosewood was able to position Eric Bibb and Bert Deivert, that is their image outlines, with insane precision and focus, highlighting the mic’s pickup pattern within an airy soundstage. In my experience, its performance in this regard is second to none.

My long-time reference mc has been the Clearaudio da Vinci V2. Over the years I’ve had the chance to compare it extensively with two similarly priced mc cartridges, the Dynavector XV-1s ($5450) and Shelter’s Harmony Carbon Fiber ($5495). In this grouping, the Dynavector was clearly the most dynamic-sounding with a killer bass range that is bound to impress short term. On the minus side, texturally it wasn’t the smoothest performer and sounded a bit mechanical, especially relative to the Shelter Harmony, whose unique ability is to be one with the music. The da Vinci V2 approaches the natural textural character of the Shelter Harmony but with a greater sense of speed and focus. Enter the Rosewood Signature. It exceeded the Shelter Harmony’s strong suits, but relative to the da Vinci, it appeared to trade a bit of transient speed for textural smoothness. But who could possibly complain about its incredibly velvety textures that were so complimentary to soprano voice and violin overtones?

The Rosewood’s calling card has always been and remains the midrange. The old production (pre-1992) Rosewood was said to be warm-sounding. I didn’t find the new Rosewood to stray far from tonal neutrality. What it did deliver so gloriously was what I like to refer to as a “big sky” midrange, combining see-through transparency, a tuneful full-bodied lower midrange, 3-D spatiality, and what felt like unbounded dynamics. And it didn’t stop there. It weaved an organic wholosity, to borrow a concept from the late Harvey Rosenberg, with no obvious discontinuity across the tonal spectrum. It was detailed without calling attention to itself. Surface noise was not emphasized. It tracked well, and it sang with emotional intensity while avoiding upper-midrange emphasis or treble brightness. The bass range was tightly defined and well-integrated with the lower midrange. You might say that the Rosewood Signature epitomizes my ideal notion of the Goldilocks mc.

Listening to the Rosewood Signature was an addictive experience. It became difficult to curtail a listening session as there was always one more album I had to spin. It’s the cartridge I could happily live with for years to come. This is one of the easiest recommendations I’ve ever made, in essence a gift for the music lover who would like to kick back at the end of a long day and just enjoy the music. I think this is what Sugano-san had in mind all along.

Specs & Pricing

Type: Moving-coil
Nominal output: 0.4mV 
Body: Natural rosewood
Coil: 6N copper wire
Magnet type: Samarium cobalt
Cantilever: Boron
Weight: 8.9 grams 
Recommended tracking force: 1.8–2.0 gram
Recommended loading: 80–1000 ohms
Price: $4995

MoFi Distribution (U.S. Distributor)

Associated Equipment
Speakers: Analysis Audio Omega
Power amplifier: VTL Manley Reference 200/100, D-Sonic M3a-1500M, and Wyred 4 Sound monoblocks
Preamplifier: Lamm Audio L2.1, Blue Velvet (DIY), Supratek Chardonnay line preamps, Experience Music AVC
Analog source: Kuzma Reference turntable and Stogi Reference 313 VTA tonearm
Cables: FMS Nexus-2 & Kimber KCAG interconnects, Acoustic Zen Hologram II and Wireworld speaker cable

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