Audio Note UK IO Limited field-coil cartridge system Review

A cartridge with six pins requires special tonearms, preferably one with six wires. The $13,000 Audio Note UK AN-1S SOGON ten-inch, then, is mandatory. It is hardwired with the company’s highly regarded 50 strands, 99.99% pure silver wire in litz configuration and RCA termination.

It was obvious right from the first moment I put the Audio Note UK IO Ltd cartridge into the system that it was not for the uninitiated. For one, the cartridge exposed certain inadequacies in my turntable of choice.

The AN-1S SOGON was first installed on one of the three pillars of the belt-driven Clearaudio Master Innovation turntable in late 2022, accommodated by a custom armboard from Clearaudio. The $10,000 PS Audio P20 AC Regenerator was instrumental in generating the most perfect AC sinewave in feeding the Clearaudio so as to achieve precise rotation. The way the IO Ltd unraveled groove modulation laid bare the minutest effects of platter rotational inconsistency, which impacted my enjoyment of classical solo piano music. My NOS direct-drive Technics SP-10 Mk2A that I bought in 2008, sealed under factory blue tape upon arrival, subsequently took over the review duty. It didn’t hurt that the AN-1S tonearm fit perfectly onto one of the included armboards.

The subsequent arrival of the $30,000 Audio Note UK M6 Phono Preamplifier in late 2023 completed the analog playback system that began with the IO Ltd, followed sequentially by the AN-1S tonearm and the $25,000 AN-9L SUT, designed specifically for the IO Ltd. I say, again, to experience the highest quality in reproducing classical solo pianos, exacting platter rotation proved to be definitive and indispensable. Credit to Audio Federation of Castro Valley, CA, for supplying an earlier-generation AN-9L for a full year of auditioning before AN-UK shipped the current production model to me.

The very short body of IO Ltd makes for a rather low clearance from the record surface. The emphasis for final adjustment is on the Anti-Skate. Per Peter: “The general rule for satisfactory Anti-Skate function, but should only be regarded as a GUIDE, is to start with the control knob turned fully CLOCKWISE [on the AN-1S], and start by rotating ANTI-CLOCKWISE approximately one-third of a revolution. This position should be fine-tuned BY EAR for REAL assessment of the correct position.

“The reason for this is purely because of small variations within the final hand assembling of the IO cartridge, which makes one track at a slightly different force from another. This has no adverse effect on the sound output whatsoever. The compliances of materials and design theories found within the IO construction have been chosen to accommodate a wide range of tracking forces.

“As always, final assessment of correct alignment should be performed by listening tests. A snapshot of technical data will help you fit the AN-1S collar clamp assembly if the need arises, as there is an offset of 7.37mm from pivot to collar centering.”

Handwound field-coil generator, to be installed into the headshell.

Finally, Peter, again, “The engineer responsible for the production and engineering of the IO cartridges, development of the TT Three turntables and power supplies, belt drive CD transports and many, many other product developments, is Darko Greguras. The IO Ltd is made in-house from parts sourced from specialist suppliers, who can make the very small parts to the necessary tolerances and specification.”

The owner’s manual recommends 2.5 grams tracking force as optimal, which was amply agreeable to me, although I did find that 3 grams brought out more of the music in tonal vividness and ambience retrieval without impacting dynamic contrasting.

Being able to output a gain up to 76 dB, the Pass Labs Xs Phono assumed alternating reviewing duty without the $22,000 AN-9L SUT initially, then was switched to a mere 55 dB of gain at 47K ohm of loading with the AN-9L, in conjunction with the company’s own Xs Preamp and the Bricasti Design M20 preamp. Finally, the Audio Note UK M6 Phono tube preamplifier served sequentially in bringing out the most of the AN-9L SUT and the Xs Phono. When paired with either the Pass Labs or the Bricasti Design preamps, the Xs Phono was routed to the LINE input on the preamps. For the M6 Phono Preamp, the AN-9L step-up transformer was connected to the preamp’s moving-magnet PHONO inputs. A final arrangement of feeding the AN-9L into the Xs Phono via its 47k Ohm load setting again completed the auditioning.

Elaborate grounding schemes on the Clearaudio turntable were necessary for removing a persistent hum when used with any of the phono stages, beginning from a screw at the bottom plate of the Clearaudio turntable to the Xs Phono, and then from the AN-1S SOGON tonearm via its captive cable system to the IO Ltd power supply, and then a third wire connecting the power supply to the Xs Phono. The noise finally subsided completely when I plugged a third wire from the IO Ltd power supply into the PS Audio PowerPlant 20 AC regenerator. Most serendipitously, the Technics turntable provided no ground connection and yet it also exhibited no hum.

Further enhancement came in the form of the $399 Millennium M-LP-Mat Carbon LP Mat, which performed a decoupling of medium between the platter and the cartridge. With a velvet cushioning surface on the record side and carbon material on the platter side, the latter’s high density and low weight structure combined with the soft velvet disrupts the cantilever’s interaction with the platter, increasing the dynamic contrasting to the extent that the turntable would not perform at the same level without it. The M-LP-Mat must be used with the factory puck for proper weight; heavier record weights will exert excessive pressure on the velvet, flatten it and diminish its effectiveness.

The $25,000 Sound Lab Majestic 645 and its $55,000 sibling, the Majestic 945, alternated as main speakers, with the $20,990 PureAudioProject Quintet15 Voxativ AC-X open-baffle speakers also taking a turn. A pair of Pass Labs XA200.8 monoblocks powered the Sound Lab, while the First Watt SIT-1 monoblocks and SIT-2 stereo amplifier alternated with the PureAudioProject. Other amplifiers arrived during the tail-end of the review process and will be discussed in latter articles so as to avoid confusion in this review.

Previously, I wouldn’t consider any LP if an SACD or hi-res alternative is present, particularly in the case of recordings from the sixties and seventies. However, complex DSD remasterings are done to those half-century old deteriorating master tapes to restore the sound to its former glory while rendering them DSD format compliant before they are issued on SACD. But my experience of the Audio Note UK IO Ltd field-coil cartridge system turned my choice a hundred and eighty degrees around.