Crystal Radio Earphone

A crystal earpiece, also known as an earphone or high impedance earpiece consists of a piezoelectric crystal. This crystal expands and contracts according to the electrical current flowing through it. When an audio signal passes through it, it vibrates accordingly; hence, it can convert an electrical audio signal into an audible form.

The piezoelectric crystal mounts on a rigid plastic or metal structure, so that when the crystal vibrates, the surrounding structure that it is fixed to vibrates also and resonates, consequently this makes the sound louder.

An earphone such as this is typically in the style of granny's hearing aid, and therefore sometimes called as such. They tend to be skin brown and have a tube, which carries the sound. These types of earphones are also high-impedance, making them very sensitive to very small electrical currents. The impedance is typically in the region of 2 MΩ. A serious crystal radio fanatic will often have a couple of these for testing out their radio experiments.

This red coloured earphone is a vintage one from the 70s. They no longer make these, however it is a useful tool for comparison purposes with modern earpieces. This one uses a slightly different crystal material and is more sensitive and louder than the modern ones.

This particular one terminates with metal clips to provide a good electrical contact. The modern ones usually terminate with a 3.5 mm mono jack plug.

The sound quality of these older ones is very good. They are louder, and the sound is clearer.

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