The predawn of pick-ups

摘要

What do photodiodes, miniature capacitor microphones and slivers of semiconductor have to do with vinyl disc replay? Not much, you may think - but you'd be wrong. In fact they all feature in weird and wacky designs of pick-up cartridge which, down the decades, have tried to persuade audiophiles - with little real success - that they represent a better way of extracting the signal from a record groove. EXOTIC ALTERNATIVES Today the vast majority of hi-fi pick-up cartridges operate on the principle of electromagnetic induction, discovered by Michael Faraday in 1833 (narrowly beating its independent discovery by Joseph Henry in the US). Hans Christian Oersted had already discovered, 13 years earlier, that a wire carrying an electric current sets up a magnetic field. What Faraday demonstrated was the corollary, that relative motion between a magnet and an electrical conductor, such that moving lines of magnetic force 'cut' the conductor, results in an electric current being induced within it.