Analog Corner

Forty years ago, moving-coil cartridges were exotic. Now they're mainstream. The main advantage of MCs is obvious: rather than the system used in moving-magnet cartridges, in which relatively heavy magnets attached to the stylus's cantilever are moved past a stationary coil-and-armory assembly to create the electrical signal, moving coils, as the name implies, move the relatively lightweight coil and armature past the magnets. The lower the cantilever assembly's moving mass, the lower the system's response time. The lower the response time, the faster and more detailed the reproduction of the music. And MCs' electrical characteristics mean that they have greater bandwidth.

Those aren't the only two types of phono cartridge, of course. There are the moving-iron systems used by Grado and Soundsmith, as well as strain-gauge types and the new optical cartridge from DS Audio.

Given the proliferation of MCs, particularly at the top of the sonic pecking order, it's reasonable to argue that, compared to the 1970s, MC and MM cartridges have reversed places in terms of popularity—much to the consternation of those who argue that MMs have considerable advantages over MCs, despite the latter's lower moving mass.

MM cartridges' fixed coils comprise far more turns of wire than do the coils in MCs, which means that MMs output far more voltage—on average, 10 times more. Thus they don't require head amps, or step-up transformers, or an extra gain stage, any of which, unless carefully designed and built, can add noise. MMs tend to have greater compliance or flexibility (think: softer springs on a car suspension) than MCs, and can therefore accurately track and trace an LP's groove with a lower vertical tracking force (VTF). In the late 1960s, the peak of MM design, cartridges from Shure, Pickering, Empire, and other manufacturers were able to work with VTFs as low as 1–1.5gm. These MM cartridges of low VTF and high compliance in turn required low-mass tonearms to keep the resonant frequency of the arm and cartridge below the lowest audible notes of music (16Hz), but above the level where warp and wow kick in (below 8Hz). Today, designers tend to come up with tonearms of medium to high mass that are better suited to the higher mass, lower compliance, and greater VTFs required by MCs.

I can hear you newly arrived vinyl fans: "Why would you give up lighter VTFs and higher output? What do you gain?" The best answer is to listen to a properly configured and amplified MC cartridge. Speed kills, both literally and in the word's more positive colloquial definition.

As for the alleged record wear caused by higher VTFs (today's MCs average 1.75–2.4gm), the evidence suggests that reducing or preventing wear is more a matter of tracking accuracy than of lower VTF—though it could be argued that the least amount of wear should be produced by a combination of the lowest possible VTF and the most accurate tracking.

That said, based on decades of experience, I can report with 100% certainty that heavier VTFs do not cause audible groove wear or shave off high frequencies. In fact, the only audibly damaged records I have are those from the days of my light-tracking fetish in the late '60s, when I bought my first Shure V-15. Shure claimed that model could track at 0.75–1.5gm, so I figured lighter was better—and it might have been, had I had a top-quality arm. But while my Dual 1009SK turntable's arm was good for a record changer, it wasn't good enough for the Shure to track well at 0.75gm. I wasn't aware of that as I played records—at least, not at first—but eventually I began to hear a constant, low-level crackling noise. I came to realize that this was wear created by the stylus bouncing around in the groove, ricocheting off the groove walls.

Today, using various MC cartridges with VTFs of 1.72–2.8gm, I hear no wear, and the highs are all still there. I love playing, for MC skeptics, an original pink-label pressing of Jethro Tull's Stand Up (Island ILPS 9103) that I bought in 1969 and have played dozens, if not a hundred times, and having them compare it to their CD edition. In terms of cymbal shimmer and flute air, there's no comparison. The LP kills the CD—and not because I've incorrectly loaded the cartridge to produce a high-frequency resonant peak. The HF etchings on that record remain intact—perhaps more than does the magnetic flux on the almost half-century–old master tape!

MC and MM cartridges are both resonant systems that produce electrical peaks in need of taming, using the loading provided by the input impedance of the phono preamplifier. In the case of MMs, loading is primarily in the form of shunt capacitance, while MCs require resistive loading. Let's steer clear of the "whys" in this review. If you want to learn more about all this, read Jim Hagerman's excellent tutorial on the subject: www.hagtech.com/loading.html.

To optimally shorten an MC's response time while producing reasonably high voltage output, designers use powerful fixed magnets and fewer turns of wire in the coils. Modern magnet and coil technology can produce greater outputs (up to 0.5mV) from fewer turns than was possible a few years ago, when fewer turns (and faster response) meant outputs as low as 0.1mV—and higher outputs meant more turns of wire, thus more mass, and higher internal impedances. Today's MCs produce outputs of 0.2–0.5mV while maintaining low internal impedances of 2–8 ohms. The fewer turns of wire in a coil, the closer the circuit is to a short, and the lower its impedance and inductance.

In any case, when you see a low-output MC with a relatively generous output (ca 0.5mV) and a relatively high internal impedance (ca 30 ohms or more), the odds are good that its designer has wound many more turns of wire on the coil and used weaker magnets. The result is a "slower," warmer sound that some listeners prefer.

If an MC has a very low output (0.2mV or less) and low internal impedance (2–8 ohms), that's been achieved with fewer turns of wire, to keep the mass down, and with stronger magnets. Fewer and fewer such cartridges are made today—there's no advantage to ultralow output. But from the late 1970s through the '80s, to achieve the lowest possible mass and the greatest speed and detail, designers such as A.J. van den Hul and Transfiguration's Seiji Yoshioka made MCs of ultralow moving mass and ultralow output because the magnets of that era still couldn't generate enough flux to produce a higher output. At the time, these ultralow-output cartridges became popular among analog "speed freaks" who had money to burn because, in addition to the high cost of the exotic cartridge, the buyer had to spend another small fortune to greatly and accurately increase the low output voltages to levels of 4–4.5mV, to properly drive the MM phono stages found in most preamplifiers of that time. Exotic transformers with coils of pure silver wire, like the one made by Mitchell Cotter at the end of the 1970s, could cost more than the cartridge itself. Even today, a used Cotter transformer can cost almost $1000.

First-time buyers of exotic MCs back then also had to leave their comfort zone of styli that could be easily removed and replaced—virtually no MC cartridge is equipped with a user-replaceable stylus. In the slide-out design of most MMs, the cantilever, with tiny magnets attached, terminates in a square, hollow metal rod that the user inserts in a hole in the cartridge body. But a variety of factors, including the width of the coil assembly, make replaceable MC styli all but unfeasible (though Audio-Technica managed one in the 1980s). (You can read more about how MC cartridges are built in my review of the Lyra Clavis Da Capo, originally published in the April 1996 issue.)

Clearaudio Maestro V2 moving-magnet cartridge
I also wrote about the Clearaudio Maestro V2 moving-magnet cartridge in the April 2015 Analog Corner. You can find that review here.