Audio Note UK IO Limited field-coil cartridge system Review

There are lots of cartridges out there, a handful of manufacturers being responsible for the vast majority of the technologies and shapes of them. Swapping cartridges in and out of the system to enjoy a slightly different flavor of one’s favorite music is part of the charm of the analog experience. That said, when one begins to spend more money on progressively more-sensitive cartridges, tonearms, turntables, and phono cables, not to mention the rest of the system downstream, the experience becomes more unreal. One begins to hear things on a daily basis fewer and fewer audiophiles will. Accuracy becomes the focal point in increasing intensity and things can begin to get absolutely mental. Limited is the profound experience where accuracy equates to musicality.

The $16,500 Top Wing Suzaku coreless straight-flux cartridge that I reviewed in July 2020 was the most detailed cartridge I had heard, with a finely balanced suite of strengths in dynamic contrasts, dimensionality and tonal vividness. The trajectory from that experience was a search for cartridges that can either do even more, albeit at a higher price, or that can do most of it at a much lower price. I ventured into cartridges at lower price points to find one encompassing the virtues of the TW sans the price. The first to impress me was the $12,500 Van den Hul The Colibri XGW Master Signature in July 2021. It came close when used with the companion $20,000 The Grail SE phono stage. Keeping in mind that the $48,000 Pass Laboratories Xs Phono was amplifying the Top Wing, the Van den Hul experience spoke volumes. Then came Japanese cartridge veteran manufacturer Miyajima Laboratory’s $7,600 Destiny moving-coil from U.S. importer Robin Wyatt of Robyatt Audio. It flaunted a very nicely balanced suite of attributes no sub-$10,000 cartridges that I auditioned by then could match. The one Robin sent me was a brand new one, and even the physicality of it was quite a beauty to behold.

In that juncture of time and space, a handful of designs on the costlier end of the price spectrum than the Top Wing remained on my audition list, but such review samples are far and few between. Then, the Audio Note UK IO Limited waiting list I was on since first quarter of 2022 finally got to my order, and after eight months of waiting, the cartridge arrived.

Quite a few cartridges out there are alleged as “top” designs by their manufacturers, but different designers understand the concept of ultimacy differently. When one company puts forth a $16,500 cartridge as its supreme effort and another proclaims its $5,000 cartridge as the fruit of years of research, representing the sum of all the company’s knowledge, it’s clear that neither the design teams, production priorities nor the production models are equals. Then came the $20,000 Audio Note IO LTD field-coil six-pin cartridge system, the subject of this review, with the outboard power supply for the cartridge’s field-coil generator, and the attendant $13,000 AN-1S-SOGON six-wire, ten-inch tonearm with its captive, 50-strand 99.99% pure silver litz wiring.  This uber expensive Audio Note UK cartridge features magnetism generated not by even the strongest permanent magnet but a live, flowing DC charge, which is, in turn, electrified by an external power supply unit.

Audio Note UK engineer Andy Grove will discuss the creation and concept of the IO Ltd in a Commentary article to be published next.

The Audio Note UK IO Ltd cartridge system comprises the cartridge itself, an outboard full-sized power supply unit for the cartridge’s field coil generator, and the AN-1S six-wire tonearm. There is no magnet but an iron core in its place. In addition to the four pins at the back of the cartridge for left positive/negative and right positive/negative, there are two additional positive and negative pins for transmitting a voltage for the purpose of energizing the iron core. When energized, the pure iron coil inside the cartridge body produces a magnetic field of low-loss hysteresis loop that is lower than even the most powerful permanent magnet in existence. The result is superior linearity and less noise.

To ensure the purest in transmission of signal, Audio Note UK fitted the cartridge with the company’s own 99.99% pure silver wire from the coil to the terminals without break. The wires are about the same thickness as a hair at 0.05 mm, all wound by hand. Per Peter Qvortrup, company owner, “As there is no machine that can do this, it is a major reason our cartridges are so much better than anything else.”

The IO Ltd’s cantilever is made of “extra thick walled, slightly tapered” long titanium tube, tapered both on the outside and inside for highest rigidity. The cantilever’s length means reduced movement, enabling superior tracking ability over complex, highly modulated grooves, as well as reduction in the non-linearity of the magnetic field, and a highly controlled stylus movement.

The stylus is a solid diamond cut and polished into a “perfect, natural octagon to a level of the best surgical instruments used for eye and other fine surgery, on a diamond less than half the size of the closest, readily available option.” The company claims this diamond is the finest in use on any cartridge to this day, and describes its efforts of developing the process of cutting such a diamond as “heroic.” I don’t disbelieve it.

The final mounting procedure includes an initial pinching of the diamond into the cantilever before being glued with a proprietary epoxy resin and then baked for three hours to harden.

The body of the cartridge is the topic of mystery, for the company will not divulge materials used. Still, the company claims the long body is to minimize vibration and energy storage for translating the signal accurately. Rigidity is further enhanced, supposedly, using six mounting bolts to secure the cartridge inside the body. In fact, this enclosure design is bequeathed to all IO cartridges.

The cartridge and the Power Supply are such delicate equipment that in order to prolong their operational lifespans, AN-UK instructs the user to switch off the unit if not used for more than a few days. Throughout the owner’s manual, this instruction is mentioned several times, one of them especially noteworthy for its all-upper-case font and concluding exclamation mark. Of course, I just needed to hear from Peter if he had further to add, and he did: “Switch the cartridge power off if not being played for over fifteen minutes, and turn the Power Supply’s main power off if not used for more than several hours. Before turning the cartridge on for the first time, users are urged to break out a voltmeter and measure the voltage off the cartridge’s pins. The voltage/current should be set to around 1.2 volt at 0.4 – 0.5 amperes measured at the terminals on the cartridge, using an accurate and calibrated meter. This is to make sure that the energizing coil has the ideal voltage and current.” An electrician friend of mine stopped by and confirmed the measurement in exchange for a collector LP that he’s been lusting after.