Popular Electronics Magazine, April 1955

When I spotted this April, 1955 issue of Popular Electronics magazine at a swap meet, I practically left burning rubber on the floor as I rushed over to grab it. Theremins have always interested me, and I had been seeking this issue for a long time after spotting one (ovepriced!) in an online auction.

The cover depicts a dreamy-looking gent playing his homebuilt Theremin. Theremins were among the very earliest electronic musical instruments. Invented in the 1920s by a Russian, Leon Theremin, this namesake instrument is played without any physical contact between the musician and the device! You merely move your hands in the air near two antennas to control the Theremin's pitch and volume.

Theremin Plans

The magazine contains complete plans for building this Theremin. Using five tubes (5Y3GT, 6AU6, 6AT6, 6BE6, 6C4), the device uses a transformer-type power supply and and is constructed using a standard 1950s amplifier chassis and housing.

Most Theremin antennas take the shape of simple loops or poles. In this design, the antennas are terminated with large sheet-metal letters, T for tone and V for volume. Below is the schematic and basic technical description.

In operation, the signals from a variable frequency RF oscillator (the 6C4 stage) are combined with the signals from a fixed frequency RF oscillator in the mixer stage (6BE6). The difference frequency output, an audio frequency, is fed through a filter circuit to remove any RF signals that might remain and then to a variable gain amplifier (6AU6). The amount of amplification given by the 6AU6 stage depends on its grid bias and this, in turn, depends on the output of a third high frequency oscillator (6AT6).

One antenna permits the operator to vary the frequency of the 6C4 oscillator ("T" or tone control antenna) and hence the pitch of the note produced. Another antenna permits the operator to vary the output of the 6AT6 oscillator ("V" or volume control antenna) and hence the loudness of the note. By moving his hands closer to and away from the two antennas, the musician changes capacities to ground in the two oscillators, and can play any note desired.

The full plans are too large to publish on this web page. If you would like a copy at nominal cost, send me some email.

Many other Theremin designs were published in the 1950s and 1960s. The January, 1961 issue of Electronics Illustrated has plans for a five-tube Theremin similar to the one shown here. The August, 1962 issue of Popular Electronics shows how to convert an inexpensive five-tube radio into a Theremin. The January, 1966 issue of Popular Electronics shows plans for a solid-state version dubbed the Lumemin, which substitutes photocells for the antennas.

Theremin History and Resources

The greatest Theremin artist was Clara Rockmore, who trained with Leon Theremin and performed around the world. A Theremin is fiendishly hard to play and few people other than Rockmore ever mastered it sufficiently to play at the concert level. I tried playing a restored RCA Theremin at the American Museum of Radio and Electricity in Bellingham, Washington, and I can testify to the difficulty. With nothing to guide or rest your hands on, it's tricky even to hold a simple, clear note!

Theremin music figured prominently in the sound tracks of films, including The Day the Earth Stood Still, starring Michael Rennie, and Spellbound, starring Ingrid Bergman and Gregory Peck and featuring a score by Miklos Rosza.

Interest in the Theremin has grown during the last decade. The 1990s documentary film, Theremin: An Electronic Odyssey, told the story of Leon Theremin. You can also buy CD collections of Theremin music. The Art of the Theremin, released by Delos, contains twelve performances by Clara Rockmore herself. You can even buy the complete soundtrack of The Day the Earth Stood Still. All of these items are available from amazon.com and other retailers.

Modern Theremin kits are also available, notably from PAIA Electronics.

You will find many websites devoted to Theremins. One of the best is Theremin World.