Koetsu Onyx “Long Body” Review

The Koetsu Onyx “Long Body” is a rare, early production moving-coil cartridge from the Yoshiaki Sugano era (roughly late 1970s to early 1980s). It belongs to the first generation of Koetsu stone-bodied designs and is distinct from the modern Onyx Platinum. The elongated body was necessary to house the larger Alnico magnets used at the time; weaker magnetic materials required greater volume, resulting in the characteristic “long body” form that collectors prize today.

These cartridges are handmade, low-output MCs that embody the classic Sugano house sound—warm, lush, and highly musical—rather than the more refined, higher-resolution character of later Platinum-series models.

Design & Specifications

• Body: Natural onyx stone (hand-selected and finished), longer overall length than modern Koetsu stone bodies.
• Magnet: Large Alnico (the primary reason for the extended body).
• Coils: Typically copper (some rare variants reportedly used silver).
• Cantilever: Usually boron or boron-coated aluminum in period examples.
• Stylus: Proprietary fine-line or elliptical diamond (original tips are now scarce; many surviving examples have been retipped).
• Output: Generally in the 0.4–0.6 mV range (higher than modern Platinum models).
• Weight: Typically around 11–13 g depending on exact example.
• Compliance: Medium, suited to medium-to-higher mass tonearms of the period.
• Recommended tracking force: Usually in the 1.8–2.2 g range (exact figures vary by sample and condition).

Because these are decades-old, handmade cartridges, individual examples can differ, and originality (stylus, suspension, cantilever, and magnet integrity) strongly affects both performance and value.

Sound Quality

The Long Body Onyx delivers the romantic, full-bodied Koetsu character that established the brand’s reputation. Listeners and owners frequently describe:

• A rich, lush midrange with exceptional body and harmonic density on voices and acoustic instruments.
• Deep, weighty, and atmospheric bass with a sense of bloom and three-dimensionality.
• A large, immersive soundstage that feels expansive and layered.
• Smooth, non-fatiguing highs that favor tonal beauty over maximum air or etched detail.
• Strong emotional engagement and a “you-are-there” quality on well-recorded acoustic, jazz, and classical material.

Compared with modern Koetsu Onyx Platinum (platinum magnets, silver-plated coils, tighter tolerances), the vintage Long Body is generally warmer, denser, and more romantic, with less ultimate resolution and transient speed. Many enthusiasts who prefer the original Sugano sound consider the early long-body stone models among the most beguiling Koetsus ever made. Tracking ability and noise performance depend heavily on the condition of the stylus and suspension; a well-preserved or expertly retipped example can still perform at a very high level.

Practical Considerations

These cartridges require careful setup in a compatible medium-to-high mass tonearm and a high-quality phono stage or step-up transformer capable of handling low-output MCs. Because surviving original-stylus examples are scarce, many on the market have been retipped (often by specialists familiar with Koetsu geometry). Originality and documentation significantly affect collectible value.

Strengths

• Classic, highly musical Sugano-era Koetsu sound
• Lush midrange, rich bass, and immersive soundstaging
• Unique long-body aesthetic and historical significance
• Strong emotional engagement with acoustic and vocal recordings

Limitations

• Rare and expensive on the secondary market
• Condition varies widely; original styli are scarce
• Warmer, less resolving presentation than modern high-end MCs (including current Koetsu Platinum models)
• Demands careful matching of arm, loading, and gain

Verdict

The Koetsu Onyx Long Body is a collector’s and connoisseur’s cartridge that captures the original romantic magic of Yoshiaki Sugano’s designs. It prioritizes tonal beauty, midrange presence, and musical flow over forensic detail or modern neutrality. For listeners who value the classic Koetsu character—and who can find a well-preserved or expertly restored example—it remains one of the most characterful and emotionally rewarding vintage moving-coil cartridges available.

It is not the most practical or resolving choice for every system, but for those seeking the authentic early Koetsu experience in a rare stone-bodied form, the Long Body Onyx holds a special place. As with all vintage high-end cartridges, thorough evaluation of condition and, ideally, an audition are essential before purchase.