Cartridge Type EMM or MC)
Along with the key aspects of boosting and equalization that a phono stage provides, the type of cartridge used with the turntable must be considered. Magnetic pick-up cartridges are by far the predominant class of cartridge used today and they come in two main varieties: moving magnet (MM) and moving coil (MC), with MM being the more prevalent. Within a MM cartridge, a magnet moves inside a fixed coil, while within a MC cartridge quite the opposite happens, the coil actually moves around a fixed magnet. Due to this fundamental difference in design, MM and MC cartridges provide significantly different output characteristics. MM cartridges generally provide between 2 - 10 mV and MC cartridges about ten times less, in the neighbourhood of just 0.2 - 1.0 mV. Though there area a few high-output MC cartridges that can provide an output voltage similar to that of a MM. In addition to the dramatic differences in voltage output, there are also significant differences in output impendence and the resulting load that MM and MC cartridges present to the phono stage. A typical MM cartridge will have an output impendence of around 47,000 ohms, whereas, an average MC cartridge has an output impendence of somewhere between 10 and 1,000 ohms.
What do these differences in MM and MC cartridges mean, when it comes to the phono stage? Well, it means that MC cartridges demand more signal boost given their lower output and will demand that the phono stage works harder to maintain control of the output, given the low output impendence. To address these more demanding needs of a MC cartridge, a MC compatible phono stage must provide an additional level of boost to the output signal from the turntable. This additional step-up in voltage is accomplished by way of a pre-prepreamplifier stage (yes, that’s prepre- pre and it’s still not a stutter). It should also be noted that to perform well, a MC cartridge will also need a phono stage that has a lower noise floor than one, which might happily work with a MM cartridge. Given these fundamental and substantial differences in output, there exist today, phono stages that are designed for MM cartridges, others that work only with MC cartridges and yet others that are purported to work with both MM or MC cartridges. In the case of the latter, purists will claim that there are always compromises, so phono stages designed to handle both MM and MC cartridges will favour either MM or MC and not perform equally well with both types.