The phono cartridge converts the mechanical movement of the stylus in the record groove into an electrical signal. Two main types of cartridge designs dominate the market: moving magnet (MM) and moving coil (MC). Understanding the differences between them helps you choose the right cartridge for your setup and your budget, and helps you understand why certain combinations of cartridge and phono preamp work together or do not.

How Moving Magnet Cartridges Work

In a moving magnet design, a small magnet is attached to the cantilever, the thin rod that holds the stylus tip. As the stylus vibrates in the groove, the magnet moves relative to fixed coils in the cartridge body, inducing a small electrical current. The output of an MM cartridge is relatively high, typically 3 to 5 millivolts, which means the phono preamp does not need to provide as much gain.

The practical advantages of moving magnet cartridges include wider availability, lower cost, higher output, and user-replaceable stylus assemblies. When the stylus wears out, you can purchase a replacement stylus and snap it onto the existing cartridge body, which costs far less than replacing the entire unit. The vast majority of entry-level and mid-priced cartridges are MM designs.

How Moving Coil Cartridges Work

In a moving coil design, small coils are attached to the cantilever and move relative to fixed magnets. Because coils can be made much lighter than a magnet assembly, the moving mass of the system is lower. Lower moving mass allows the cantilever to respond more quickly and accurately to high-frequency groove modulations. Many listeners and engineers believe this results in finer detail retrieval, better transient response, and a more open and extended high-frequency presentation.

The tradeoffs are significant. MC cartridges produce much lower output, typically 0.2 to 0.5 millivolts for a low-output MC design, compared to the 3 to 5 millivolts of a moving magnet. This requires either a phono preamp with a high-gain MC input or a separate step-up transformer to bring the signal up to a level the preamp can handle. Most standard phono preamps support MM only and will not work correctly with a low-output MC.

MC cartridges are also more expensive, often significantly so, and most do not have user-replaceable styli. When the stylus wears out, the cartridge is typically sent back to the manufacturer for a retip at considerable cost, or replaced entirely.

High-Output MC: A Middle Ground

Some moving coil cartridges are designed with higher output, typically 1.5 to 2.5 millivolts, by using more turns of wire in the coils. These high-output MC cartridges can work with standard MM phono inputs and offer some of the sonic character associated with MC designs at a lower price point and without the preamp compatibility issue. They represent a reasonable first step into MC territory.

Which Should You Choose?

For most beginners and intermediate listeners, a quality moving magnet cartridge is the right choice. Excellent MM cartridges from Audio-Technica, Ortofon, Nagaoka, and Grado in the $50 to $300 range are capable of genuinely good sound and are easy to live with. The replaceable stylus is a significant practical advantage.

Moving coil cartridges become worth considering when you have a high-quality turntable and tonearm capable of resolving the differences they offer, a phono preamp with a proper MC input, and a budget for both the initial cost and eventual retipping. Jumping to a mid-priced MC on a budget turntable with an inadequate phono stage is unlikely to be a rewarding upgrade.

Build your system methodically, get the most from your current setup, and the question of when to explore MC will answer itself naturally.