Cartridges — Koetsu Rhodonite

The Rhodonite is a Koetsu moving-coil cartridge for vinyl playback, part of the stone body family that the Japanese maker places at the top of its cartridge design. Each body is machined from a block of rhodonite, a pink mineral, and every block is selected for its natural grain before being polished to a fine finish, a process the maker applies to every stone housing. Alongside the Blue Onyx, it is described as the rarest of the stone-bodied Koetsu cartridges. The price is EUR 11,500.

Key specs that matter

Output is 0.3 mV, the figure shared by every stone model in the current catalogue, compared with 0.4 mV for most rosewood and lacquered versions. Recommended load runs from 75 to 500 ohms. At 13.5 g net the Rhodonite is the heaviest of the stone models, ahead of the Onyx Platinum, Tigereye Platinum and Blue Lace at 12.5 g and the Azule at 13 g. Koetsu lists one tracking force window of 1.8 to 2.0 g for its whole range.

Engineering and use context

Inside the stone housing sit coils of silver-plated copper wire, precisely matched to each other, together with a platinum magnet. Koetsu reserves platinum magnets for its stone cartridges and the Rosewood Signature Platinum, while other wooden and lacquered models use samarium cobalt or Permendur magnets. The cantilever is boron, a material the brand fits to every cartridge it builds. Koetsu organises its catalogue into three families. The rosewood line covers the Black Goldline, Rosewood, Rosewood Signature and Rosewood Signature Platinum. The Urushi family uses traditional lacquer finishes in Black, Wajima, Sky Blue, Vermilion and Tsugaru versions, weighing between 9 and 9.37 g. The stone family currently lists the Onyx Platinum, Azule, Rhodonite, Tigereye Platinum and Blue Lace, while the Jade Platinum and Coralstone were retired in 2022 at 13 g and 12 g respectively. A version with a diamond cantilever upgrade in place of the standard boron part has also been offered for the Rhodonite.

Pairing

This output level needs a moving-coil phono input with loading adjustable within the recommended window. The heavy body and the tracking force window guide the choice of tonearm and its effective mass.

Alternatives

The Koetsu Tigereye Platinum is another stone-bodied model with the same output and a slightly lighter body.