AverageOne-of-a-kind, California-built reference system personally overseen by Mitchell A. Cotter
Provenance
This is a unique, custom-engineered playback system built under the direct supervision of Mitchell A. Cotter, one of analog’s most respected innovators.
Cotter designed this plinth and suspension system during a two-month residency at a private home in California circa 1981–83, where he prototyped his ultimate “moving coil reference concept.”
The system was acquired directly from the widow of Cotter’s friend — the original owner at whose residence the project was conceived and built.
Every component reflects Cotter’s “spare no expense” philosophy — mechanical, electrical, and resonance isolation executed to absolute reference standards.
System Overview
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Technics SP-10MK3 motor and controller — broadcast-grade, quartz-locked, high-torque drive.
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Mitchell A. Cotter Custom Isolation Plinth — hand-built, one-off platform combining layered birch/aluminum composite with a tuned suspension system using blue compression springs housed in a black containment box to eliminate torque feedback and motor rumble.
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Fidelity Research FR-66FX tonearm with B-60 adjustable base, factory silver internal wiring, and original counterweight assembly — widely regarded as one of the finest tonearms ever built.
This configuration represents Cotter’s final integration of moving-coil isolation theory: a mechanically grounded yet dynamically decoupled system achieving sub-5 Hz resonance control.
Technical Highlights
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Blue spring suspension system inside a black wooden isolation frame — tuned to cancel SP-10MK3 motor resonance.
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Dual-layer plinth architecture with armboard precision-machined for Fidelity Research geometry.
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Separate multi-pin umbilical connector system (Cotter’s lab-standard design).
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B-60 base allows precision VTA adjustment during playback.
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Silver tonearm wiring throughout for ultra-low-impedance MC compatibility.
Condition
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Excellent overall condition — all original parts present.
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Motor holds perfect quartz lock; SP-10MK3 PSU fully functional.
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Arm bearings are tight, smooth, and noise-free.
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Minor cosmetic wear consistent with age but exceptionally preserved.
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Original Cotter wiring harness and connectors intact.
Comparable Cotter-engineered systems are museum-level rarities — most surviving Cotter bases are Type B-2 or B-3; this is a bespoke prototype from his California period.
Included
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Technics SP-10MK3 motor unit and controller
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Mitchell A. Cotter custom isolation plinth with tuned spring suspension
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Fidelity Research FR-66FX tonearm with B-60 base and silver internal wiring
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Cotter wiring harness and connectors
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Digital dossier and provenance documentation (PDF, prepared for verification or appraisal)
