Electric gramophone phonograph pick-up. Early - make unknown.

1925 was the pivotal year in the introduction of electrical disc recording. Within a short time, it totally displaced to original mechanical ('acoustic') recording which had prevailed for over 40 years. And 1927 seems to be the year when electric pick-ups to play 78 rpm discs started to appear in large quantities. Many different configurations were used, but virtually all were of the 'moving iron' type. That is, the needle tracing the groove of the record was located in a holder, or armature, the top end of which moved 'as directed' by the needle, in the gap between the two poles of a magnet. The movement of the iron armature caused variations in the magnetic field between the poles. A coil of wire (usually many thousands of turns of very fine wire) was also near to the poles of the magnet - frequently the armature passed through a hole in the coil. The variation of the magnetic field induced a small (equally varying) current of electricity to flow in the coil. This current, when applied to an electrical load, became a voltage - and was, typically, applied to the grid of a valve (vacuum tube) amplifier driving a loudspeaker. Hence electrical reproduction of disc records was finally possible, and soon far exceeded the sound quality obtainable from most mechanical (so-called 'acoustic') gramophones (phonographs). However, the principle of changing a mechanical action into a corresponding electrical current dated back at least as far as 1876, when it was employed by Alexander Graham Bell in the first practical telephone. This video deals with an unusual variant on the customary lay-out of a moving iron pick-up. It probably dates from the late 1920s, but the maker's name is missing. Its coil was open circuit, but a make-shift was contrived, and sort-of worked, but a severe problem was encountered when it was tried out!

Видео Electric gramophone phonograph pick-up. Early - make unknown. канала Norman Field