Головки звукоснимателя — Air Tight Opus-1

The Opus-1 is a low-impedance moving coil phono cartridge made in Osaka, Japan, by A&M Limited under its Air Tight name. Released in 2016 for the company's thirtieth anniversary, it arrived with a fully renovated mechanical construction and power train compared with earlier Air Tight designs. The development was led by Y. Matsudaira, a moving coil designer with four decades of experience, together with Atsushi Miura, and the work centred on finding the best ratio between internal impedance and output voltage.

Key specs that matter

Output is 0.45 mV at 1 kHz from an internal impedance of 1.4 ohm DCR. The frequency range spans 10 Hz to 50,000 Hz, channel balance stays within 0.5 dB at 1 kHz and crosstalk exceeds 30 dB. A boron cantilever carries a semi-line contact stylus with a 3 x 30 micron profile. Dynamic compliance is 8 x 10 to the power of minus 6 cm per dyne, the recommended tracking force is 2.0 to 2.2 g and the cartridge weighs 12.5 g.

Engineering and use context

The magnetic circuit uses the SH-uX core material, which Air Tight says has a saturation flux density three times higher than conventional high-permeability materials. That allows fewer coil turns for a given output, which keeps the internal resistance very low. The windings themselves have a cross-section about 10 percent larger than those of the earlier PC-1 Supreme. A Neodymium #50 magnet supplies the field. Boron was chosen for the cantilever because of its physical properties as a stiff, light material. The base is machined from A7075 aluminium alloy with DLC plating, the housing is A5056 alloy with rhodium plating, and the terminal pins are rhodium plated as well. A later Opus-1 Ermitage variant replaces the boron cantilever with one of ultra-hard duralumin alloy, uses a stylus with a 0.1 mm square tip and is rated at 0.5 mV output, with a tracking force range widened to 1.9 to 2.2 g.

Pairing

This modest output from a very low coil resistance calls for either an MC phono stage offering a lot of gain together with very low input noise or a step-up transformer designed for low-impedance coils, since the tiny coil resistance lets a transformer with a high step-up ratio work effectively. The low compliance figure and the heavy body point toward medium-mass tonearms, and the arm's counterweight must be able to balance a cartridge of this weight while delivering about 2.1 g of downforce.

Alternatives

The Air Tight PC-1 Supreme is the earlier low-impedance moving coil cartridge of the brand on which the Opus-1 coil design was developed.