Moving Magnet vs. Moving Coil phono cartridges

Moving Magnet vs. Moving Coil phono cartridges

 Two types

There are 2 dominant phono cartridge (Cart) topologies. These are Moving Magnet (MM) and Moving Coil (MC) (there are also induced, variable reluctance, strain gauge and moving iron systems).  At a basic level, internally to the cartridge, an MM design features a stylus cantilever connected fixed magnet, which moves back and forth inside a fixed coil in sympathy with groove indentations. The MM design is of comparatively high mass and generates its output by exciting a large coil fixed inside the cartridge body.  An MC design differs from MM in that it is comparatively a low mass design with 2 miniscule coils affixed to the stylus cantilever, generating a far lower output in conjunction with fixed magnets inside the cartridge.

MM vs. MC

Advantages of Moving Magnet designs

Simpler design and therefore cheaper to manufacture and costs less than its MC equivalent. This is primarily on account of the reason that you don't have the complexity of attaching a coil of wire from the cantilever to the cartridge body as an MC design.

It is easy to replace the stylus (needle). Since the magnet is not attached to anything in the body of the cartridge, it's simple to replace.  You simply can't do this with an MC stylus, as the internal coil is attached to the cantilever, which is then attached to the cartridge body. If you pulled it out, it would break the wire and destroy the entire cartridge.

Nearly all tone arms are designed to accommodate MM cartridges.

MM cartridges are more robust

MM designs have far greater voltage outputs, often negating the requirements for high quality phono preamps in favour of lower cost equivalents.

On account of the higher output voltages generated, and lower gain levels of pre amplification required, there is usually less system hiss/hum to contend with.

Disadvantages

The increased weight of MM cartridges tend to inhibit the ability of the stylus/cantilever to move with record groove vibrations, some of which are in the order of millionth of a millimetre. This greater mass value generally means that the stylus can't move as quickly over the record, which inhibits its ability to track the subtle changes within the groove's surface. This can add up to less detail, accuracy, and distortion of the original recording.

The long and large coil design inside the MM body tends to act as a filter, cutting off high frequencies.

A small magnet needs a large coil and it is possible to have coil inductance issues. This can result on a harsh or distorted sound.

 Advantages of Moving Coil designs

The whole concept of the MC design is around the huge advantage its reduced mass can be brought into play. Rather than put a relatively heavy magnet on the stylus cantilever, the MC system uses a light coil of wire, which is far more nimble and more responsive to subtle groove vibrations. The MC concept uses a small coil of wire on the cantilever, which makes it light and importantly, nimble, and then put a relatively larger magnet in the cartridge body in order to generate sufficient electrical signal. It's better to have the relatively heavy magnet in the cartridge than on the cantilever, although you still don't want it too big and heavy in the cartridge either.

The small coil in an MC cartridge implies greatly reduced high frequency filtering will take place.

And you have the other advantage of adding less weight to the tone arm cantilever.

MC designs tend to track better due to lower mass and therefore tend to be more revealing, with improved accuracy, and less distortion of sound.

Disadvantages

Serious money often needs to be invested to get a low output MC setup (stylus/cartridge/tone arm and depending on pre amplifier a transformer, phono pre amplifier) working to its optimal levels.

Moving coil designs are more delicate and susceptible to handling misuse.

Your tone arm needs to be able to accommodate MC designs on account of the reason that the moving part of an MC cartridge is heavier than its MM equivalent. This high tracking requirement of most MC cartridges is around 2 grams, on average, where most MM's top out in the 1.5 gram range.

The stylus on the moving coil design is not user replaceable. This implies that in the event that the stylus is worn or broken, it will need to be sent away to a specialist to repair or replace it. In a refurbishment situation, the stylus can be re-tipped, but MC repairs and replacements are always expensive.

On account of the miniscule length of coil attached to the stylus cantilever, the corresponding output voltage is also very low. A low output voltage implies that a high quality phono pre amplifier or well matched step up transformer will need to be employed in your system. See Perreaux Audiant VP3

On account of the low output of an MC design, it needs far more gain, which means it is also far more susceptible to system hiss/hum issues. Because the MC cartridge has such a small signal, due to the coil being so small, the more likely it is to be overwhelmed by hiss, or by the noise floor of your other components. Although the MC is more sensitive to record vibrations, it follows that it is also more sensitive to other noise as well.

Although MC cartridges can offer a significant upgrade in performance, the rest of your system must also be up to the task, or you've wasted your money.

High and Low output MC cartridges

As can be seen, each topology comes with its advantages and disadvantages which amounts to a series of tradeoffs having to be made. More powerful magnets and finer control over the winding process have resulted in higher output MC cartridges. This is an attempt to combine the best of both topologies into one. The high output MC design uses a larger coil, however a downside is increased weight equating to reduced dynamics and increased high frequency filtering. In life everything is a trade off and the high output MC design perfectly embodies this concept. One big advantage is that you can often input a high gain MC cartridge directly into the MM phono input. See Perreaux VP3 Phono Pre amplifier.

That said, there is a feeling in the audio community that high output MC designs are a step in the wrong direction and come with all the same inherent limitations of MM designs that low output MC designs neatly avoid.

Characteristic sounds (words of MC and MM users)

MM cartridges more easily give a solid performance when compared to lower priced MC equivalents.

The extra high frequencies obtainable from MC cartridges provide an enhanced sense of airiness and openness.

An MC combined with a good preamp or step-up transformer provides a lot more audible bandwidth and for want of a better term, transient 'snap' - on everything you play.

For classical music I prefer MC

Harpsichords and pianos work best with MC

MM midrange excellence is perfect for jazz. And female vocals – absolutely beautiful.

Conclusions

Whichever phono cartridge topology you settle for, the Perreaux VP3 phono preamplifier is capable of bringing out the very best in whichever type you select. For more information on the Perreaux VP3 please click on the link attached.

 

Perreaux VP3 MM/MC Phono preamplifier

Perreaux Products