As a proportion of the total mass of a record player, the cartridge is a tiny percentage. Even the largest and heaviest examples of the breed will rarely tip the scales at much more than twenty grams and will be no larger than the end of an adult thumb. Despite their tiny size, cartridges perform a vital task, turning the groove of a record into an electrical signal. As this role is so crucial to the overall actions of the player, they have an enormous influence on the sound that your turntable will produce.
If you have had need to look at buying a cartridge for a new turntable or are looking for a replacement one- or indeed you’ve simply made killing time at work an art form--you will know that cartridges start at around $30 but from there, prices climb steadily, ultimately heading into figures that can secure you a brand new, warrantied and well specified car. If you’ve dug down further into this information, you’ll also note that the more expensive cartridges are generally listed as moving coil designs. More terrestrially priced cartridges tend to be moving magnet type designs-- so what is a moving coil cartridge and why should you even consider shelling out for one?
The role of a cartridge is to turn the groove of a record into an electrical signal. To do this a moving magnet cartridge has a tiny permanent magnet mounted at the end of the cantilever. This moves between a pair of coils mounted in the cartridge body and generates an electrical signal. The system works extremely well and has the benefit of being something that can be assembled relatively cost effectively but at the same time, benefit from a little refinement to the process too. This means that as well as improvements to the stylus profile, better magnets, larger coils with more windings and greater attention to the chassis in which they are mounted will all help boost performance.
A moving coil cartridge effectively reverses this principle. A small coil is mounted at the end of the cantilever and this is suspended in a magnetic field. The movement of the coil within this field generates the electrical signal which goes on to be the actual audio output of the turntable. The immediate benefit of doing this is the reduction in the mass at the end of the cantilever. Because the coil can be significantly smaller than the magnet, the inertial weight on the cantilever is reduced and the performance of the cartridge improved. It is worth pointing out that advances in engineering- particularly machine winding- over the last few years has eroded this advantage somewhat.
The flipside to this reduced mass is that the coil on the end of the cantilever is tiny and this means that the voltage that a normal moving coil cartridge can produce is correspondingly very small. If we take the typical output of a moving magnet cartridge to be about 0.4V (that is to say the sort of voltage that is comfortably lower than a potato is capable of creating), a moving coil design can be as low as 0.2mV, an order of magnitude less. This is because the number of windings that can be worked into the small coil is limited. Once again relatively recent innovations in the construction of cartridges has created moving coil cartridges that have an output more in keeping with a moving magnet design although these remain fairly rare.
This signal, small or otherwise, does have some other advantages. The inductance and impedance of the signal from a moving coil cartridge is much lower than a moving magnet one so you will have less problem with capacitance- the storing of electrical charge rather than it dissipating. In modern electronics, this is less important than it was but it is fair to say that a moving coil cartridge is closer to a notional ideal than a moving magnet design.
That’s the on-paper take on the differences but what do they mean for you? If you are shopping for a cartridge, should you take the plunge and go moving coil or should you stick with what you know? The first thing to consider with a ‘normal’ low output moving coil cartridge is that they need dedicated hardware to function. That low output needs a phono preamp that is capable of delivering the required levels of gain to be audible. A conventional moving magnet phono cartridge is not going to be able to do this without a step up transformer- a passive device that boosts the voltage of a moving coil signal to one that can be used by a moving magnet phono circuit. This is neither a cheap nor entirely straightforward way of doing things (although done correctly, it can sound superb) so a dedicated moving coil phono preamp is likely to be a better bet. These go from a $100 and up but as noted in an earlier piece, the function they perform means that you can generally hear the benefits of going further up the ladder. These costs need to be taken into account.
Those hidden numbers don’t end there either. When most moving magnet cartridges wear out, you have a choice of replacing the stylus and keeping going. Once a moving coil stylus wears out however, their design means that unless the cartridge is largely rebuilt, it is scrap. With some seriously expensive examples of the breed, this means that the running costs of the cartridge alone can run to the order of a dollar (or more) a side which is something to take into account.
There’s also the indisputable fact that in the last few years, some staggeringly good moving magnet cartridges have been released. Companies like Ortofon, Goldring, Clearaudio and Nagaoka have pushed the engineering of moving magnet cartridges to new heights and the performance of some of their high specification designs are competitive with good moving coil designs all the way up to $1,000 or so- which is a huge amount of money for a phono cartridge.
So, taking all this on board, when is a moving coil cartridge suitable and should be something you should actively be looking for? First and foremost, I think the cutoff point below which moving coil designs offer few benefits with all of their downsides is $500. Until you reach this point, there is nothing that a moving coil design offers that a comparably priced moving magnet doesn’t with the benefit of lower running costs and the ability to use a simpler phono stage. Above this price though, the benefits of moving coil carts- a speed of response and an effortlessness in terms of scale and effects placement start to make sense and they pull out an advantage over moving magnet models.
If you are feeling flush though, once you are over and above the $1,000 mark, there are cartridges that- used in suitably capable supporting systems- can do some deeply impressive things. The manner in which some designs can produce music with no sense of mechanical interface at all is something that has to be experienced. In an absolute sense, it shouldn’t matter but there is a jewel like quality to some of these designs that is hard not to be impressed by. If you are the pragmatic sort, the enclosed bodies of Ortofon and Shelter designs might appeal while those who like to have their engineering on show might be more interested in Lyra or Dynavector designs. Finally, if you want something entirely spectacular, a Koetsu might be more your thing.
Ultimately, moving coil cartridges can offer staggering performance. Used with the right supporting equipment, they offer a jump in performance that can leave you grinning like an idiot. They are however not the only path to great sound and you should go into ownership aware of the potential pitfalls. Get the supporting equipment right though and you’ll be able to experience some seriously impressive vinyl playback.
Ed is a UK based journalist and consultant in the HiFi industry. He has an unhealthy obsession with nineties electronica and is skilled at removing plastic toys from speakers.