Cartridges — Audio-Technica AT33xMONO/I

The AT33xMONO/I is one of two monophonic cartridges in the AT33x family that Audio-Technica launched on 27 October 2025, a reworked AT33 line hand-built in Japan. It was listed at USD 649, which puts it above the AT33xMONO/II. Instead of a stereo coil arrangement it uses what Audio-Technica calls a True Mono dual moving-coil design, which produces an electrical signal only from horizontal stylus movement. The maker positions it as a way to play mono LPs through a stereo system.

Key specs that matter

A 0.65 mil conical nude diamond sits on a duralumin pipe cantilever. Horizontal output is 0.42 mV at 1 kHz and 5 cm/sec, output balance is 1.0 dB and vertical output sits 25 dB below horizontal output at 1 kHz. Frequency response covers 20 to 30,000 Hz. The coils show 10 ohm impedance and 10 ohm DC resistance, slightly below the 12 ohm of the stereo AT33x models, with 27 microhenry inductance at 1 kHz. Compliance is 14 x 10-6 cm/dyne static and 6 x 10-6 cm/dyne dynamic at 100 Hz. The tracking window is 2.0 to 2.4 g, with 2.2 g as the standard setting, and the vertical tracking angle is 20 degrees. Dimensions are 16.1 mm high, 16.6 mm wide and 26.1 mm deep, and the weight is 10.1 g.

Engineering and use context

Since vertical groove motion does not generate output, surface noise carried in the vertical plane is reduced. The conical profile is chosen to suit mono groove tracking. A neodymium magnet drives a permendur yoke that has been specially shaped for mono reproduction, and the coils are wound from PCOCC copper. Tracking precision comes from a newly engineered suspension that uses piano wire. Like the stereo models, the body is a composite of die-cast zinc, aluminium and high-rigidity polymer, with the zinc at the base to damp resonance and distribute it evenly. Two M2.6 threaded holes let the cartridge be bolted to a headshell without nuts. The stylus assembly is not field-replaceable, so a fee-based Moving Coil Exchange Program covers worn units.

Pairing

The rated load is 100 ohm or higher with a head amplifier, so an MC phono stage or step-up device is required. Audio-Technica lists the box contents as a non-magnetic screwdriver, a brush, two washers, six M2.6 screws in 8.0, 10.0 and 13.0 mm lengths and a stylus guard.

Alternatives

The AT33xMONO/II keeps the same 0.65 mil conical tip and duralumin pipe but uses a samarium cobalt magnet and sells for USD 449.