Cartridges — Accuphase AC-6

The AC-6 is an MC phono pickup designed by Accuphase of Yokohama, Japan, launched in 2018. It continues a series of Accuphase MC designs that includes the earlier AC-1, AC-2, AC-3 and AC-5, and combines a titanium base, an aluminium body and a solid boron cantilever with a semi line contact stylus.

Key specs that matter

Rated output is 0.4 mV at 1 kHz, and coil DC resistance is 1.8 ohm. Channel separation is 30 dB or better at 1 kHz, and compliance is 8 x 10-6 cm/dyne at 100 Hz. Accuphase quotes a frequency response of 10 Hz to 50 kHz. Recommended tracking force spans 1.9 to 2.2 g, with 2.0 g given as the optimum. The cartridge weighs 13.5 g. The stylus tip has a semi line contact profile measuring 3 by 30 micrometres, and the solid boron cantilever is 0.3 mm in diameter. Its coils use OFC wire with a 50 micrometre gauge, and the output terminals are rhodium plated.

Engineering and use context

Accuphase chose boron because vibration travels through it at 16,200 m/s, faster than the 12,870 m/s of beryllium and close to the 18,350 m/s of diamond, so stylus motion reaches the generator with little delay. Accuphase describes this as a way to transmit even minute vibrations from the groove faithfully to the magnetic circuit. The semi line contact tip presents a long contact area in the vertical direction of the groove while staying narrow along its length, which lowers tracking distortion caused by the pinching effect. The magnetic circuit uses a grade N50 neodymium permanent magnet and is mounted on a base of stiff extruded titanium that is further hardened by gold ion plating. The outer body is extruded aluminium finished with a gold-coloured alumite coating, giving a rigid structure around the generator.

Pairing

With its low output and very low coil resistance, the AC-6 calls for an MC input with plenty of gain. Accuphase itself has made the C-7, a head amplifier that raises the signal of low output MC cartridges to a level suited to an MM phono stage, which then applies gain and RIAA equalisation. The medium compliance figure fits tonearms of moderate effective mass. The fairly heavy body points to a tonearm whose counterweight has enough range to balance it.

Alternatives

The Accuphase AC-5 is an earlier MC cartridge in the same Accuphase series, released before the AC-6 arrived.