How a Phono Cartridge Generates a Signal
A phono cartridge is the transducer at the front end of any analogue playback chain. A tiny diamond stylus sits in the groove of a spinning record and vibrates in response to the modulations cut into the vinyl during mastering. The cartridge converts that mechanical motion into a small electrical voltage, which is then amplified by a phono stage, passed to a preamplifier, and eventually sent to your speakers.
The two dominant approaches to this conversion — moving magnet and moving coil — each achieve the same result by different means, with different trade-offs in output level, sonic character, and running costs.
Moving Magnet (MM): How It Works
In a moving magnet cartridge, a small permanent magnet is attached to the cantilever — the thin rod that connects the stylus tip to the cartridge body. As the stylus moves in the groove, the magnet moves with it inside a fixed pair of coils. The changing magnetic field induces a voltage in those coils: this is the audio signal.
The practical consequences of this design are significant. The output voltage is relatively high — typically between 2.5 mV and 5 mV — because the coils can be wound with many turns without adding moving mass. This output level is compatible with any standard MM phono stage.
When the stylus wears out — typically after 500 to 1,000 hours — the stylus assembly on most MM cartridges can be replaced by the user, at a fraction of the cost of the full cartridge. This makes long-term ownership costs much more predictable.
Moving Coil (MC): How It Works
A moving coil cartridge inverts the arrangement: tiny coils are wound directly onto the cantilever and move with it, while the magnets are fixed in the cartridge body. Because the coils are lighter than a magnet assembly, the total moving mass of the cantilever is reduced — often dramatically.
Lower moving mass allows the stylus to track groove modulations more accurately at high frequencies, respond faster to transients, and generally retrieve more detail from the groove. These are the properties that make MC cartridges desirable on resolving systems.
The trade-off is output voltage. MC cartridges typically produce between 0.2 mV and 0.6 mV — far lower than an MM design. This demands either a dedicated MC phono stage (providing 60 dB or more of gain) or a step-up transformer (SUT) placed between the cartridge and a standard MM stage. Both add cost. MC cartridges are also generally more expensive to retip, often requiring the unit to be returned to the manufacturer or a specialist.
A third cartridge type — moving iron — exists and shares characteristics of both. A fixed iron armature moves between fixed coils and magnets, offering higher output than many MCs while keeping moving mass low. Grado and Nagaoka are the most prominent manufacturers. Moving iron cartridges are compatible with standard MM phono stages.
Practical Differences at a Glance
| Feature | Moving Magnet (MM) | Moving Coil (MC) |
|---|---|---|
| Output voltage | 2.5–5 mV (high output) | 0.2–0.6 mV (low output) |
| Phono stage required | Standard MM stage (~40 dB gain) | MC stage (~60 dB+) or SUT + MM stage |
| Moving mass | Higher (magnet on cantilever) | Lower (coils on cantilever) |
| Stylus replacement | User-replaceable on most models | Manufacturer retip required |
| Typical price range | $60–$1,000 | $200–$5,000+ |
| Well-known examples | Ortofon 2M Blue, Audio-Technica VM540ML, Nagaoka MP-200 | Hana SL, Ortofon Cadenza, Lyra Delos |
Which Phono Stage Does Each Type Need?
A standard MM phono stage applies around 40 dB of gain to bring the cartridge signal up to line level. This is sufficient for all MM cartridges and for high-output MC cartridges — those producing 1.5 mV or above, such as the Denon DL-110 or Ortofon 2M Black LVB.
A true low-output MC cartridge — producing 0.2–0.6 mV — needs approximately 60 dB of gain to reach usable line level. A dedicated MC phono stage provides this internally. Alternatively, a step-up transformer boosts the cartridge signal passively before it enters a standard MM stage; SUTs introduce no active circuitry and are preferred by some listeners for their neutrality and lack of added noise.
Before purchasing an MC cartridge, confirm that your existing phono stage has a genuine MC input with appropriate gain and impedance loading — not just a label switch that adds a few dB.
Which Type Should You Choose?
For most turntable setups below $1,200, a well-chosen MM cartridge is almost certainly the right choice. The Ortofon 2M Blue, Audio-Technica VM540ML, and Nagaoka MP-200 each offer exceptional performance at moderate prices, user-replaceable styli, and compatibility with any phono stage.
Move to MC when you have a phono stage with genuine, well-implemented MC support; a turntable and tonearm of sufficient quality to resolve what an MC offers (a mid-range arm with controlled bearings and reliable azimuth adjustment); and a willingness to budget for retipping as part of long-term ownership.
Fitting an expensive MC cartridge to an entry-level turntable is one of the most frequent and most wasteful mistakes in vinyl replay. A cartridge cannot perform to its potential if the tonearm cannot hold it in steady, controlled contact with the groove. The tonearm is the more important upgrade at the entry level.
Compare Phono Cartridges Side by Side
Use AudioScope to compare MM and MC cartridges directly — output voltage, compliance, stylus profile, loading requirements, and more.
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