I think emg and most (not all) ceramic pickups to be sterile. So for more on this lets go to kinman
It is a fact that Ferrite (Ceramic) magnets play absolutely no part in tone shaping of a guitar pickup simply because they are non-conductive, non-metal magnets and do not influence the electrical behaviour of the coil, and exchanging these with Samarium Cobalt magnets has similar sonic results; in other words these magnets are completely toneless / soundless (ie they play no part in tone shaping). On the other hand we have Alnico, the magical magnet. Alnico is unique because it imparts a TONE flavour and certain dersirable performance characteristics into the sound. It does this because it is metallic and conductive and does influence the electrical behaviour of the coil. There are those that will tell you that a clever designer of Samarium Cobalt or Ferrite magnet pickup can somehow, miraculously, compensate for the missing Alnico by clever magnetic circuit design, this is simply not so. Magnetism is just magnetism, but 'coil core' material is a whole different story. Core material and behaviour is one of the BIG subjects that old time Electrical Engineers (not the modern electronic variety of engineer) had to study during their education. You have probably heard about Inductance (measured in Henrys), it's one of the most important and revealing specifications that a guitar pickup possesses. Did you know that Inductance is primarily derived from the core material? Steel had high inductance, Alnico has low inductance, about 1/4 that of steel. Fender sound demands just the right amount of inductance derived from the core.
