Car­tridge Type EMM or MC)

NOVO - - INTROTOPHONOSTAGES -

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.

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