The 203 Theremin


Posted on Feb 5, 2014

The 203 Theremin utilizes Wien-bridge oscillators in a heterodyne configuration to produce an audible tone that corresponds to hand position. The instrument provides the convenience and safety of 9-volt battery operation, in a compact enclosure. It is a pitch-only theremin, primarily intended for use with an external amplifier and speaker, although it has sufficient output power to drive headphones directly.


The 203 Theremin
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A jack on the top of the unit accepts the antenna assembly that consists of a support rod and a 6-inch-square metal plate. An on-off switch and a pitch zero control are located on the top panel, and a 1/8th-inch monophonic phone jack for the output is located on the side. A note regarding external interference: The 203 Theremin is prone to interference from sources such as power lines, fluorescent lighting fixtures, incandescent lamp dimmers, and computers. Such sources will cause modulation of the instrument`s output tone that may render it unsuitable for certain applications where high fidelity is required. In some cases, effects from interfering sources may be remedied by moving the theremin to a different area. Where absolute assurance of fidelity is not an issue, the 203 Theremin is highly suitable as a practice and demonstration instrument, due to its portability, excellent stability, and pleasing tone quality. The MP3 sound sample below was recorded under typical conditions. Your results may vary. The following graph illustrates the approximate relationship of pitch and hand distance for a 203 theremin, when constructed and calibrated as specified in




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