Over the years, quite a few theremin designs have been drawn. Their quality varies from toy or gadget devices via hobby theremins to carefully designed instruments. I've tried to put each circuit diagram in the appropriate category. A special category is that of the vintage theremins, like the RCA theremin. And then there are, some even modern, vacuum tube theremin designs.
You can use these schematic diagrams to build your own theremin or for reference when you wish to design or modify one. However, if you're not experienced in electronics you are probably better off with a theremin kit.
Analog theremin, Univ. of Glasgow
circuit diagram (gif 35k)
For this analogue theremin they used a transistor oscillator which follows a design originally developed by Colpitts. There are four oscillators in total, arranged in two pairs. Each pair forms a beat-frequency oscillator the outputs of which are modulated by the effect of a player's hand capacitance near each antenna. This is how the pitch and volume of the instrument are controlled.
Digital theremin, Univ. of Glasgow
circuit diagram (gif 30k)
revised pitch-circuit diagram (GIF 17k)
The digital theremin uses CMOS oscillators and logic gates to produce two DC Levels. One DC Level varies with the proximity of the player's hands from the pitch antenna, and the other DC Level varies when the volume antenna is approached. This design of circuit is advantageous because it pretty much depends on the imagination of the constructer, what he/she wants to do with these DC Levels. Obviously, a basic instrument would have the DC Levels controlling a voltage-controlled oscillator (VCO) and voltage-controlled amplifier (VCA). However, such a DC Level could also control a voltage-controlled filter (VCF). There are numerous designs of such voltage-controlled circuit elements. In this circuit which you can download, it shows a VCO and VCA block based on commonly available commerical integrated circuits. Each block is controlled by a CMOS oscillator/logic gate stage, of which there are two (one for each antenna). The design has proven very successful in recording, where the signal-to-noise is of HI-FI quality, and also in playability, since the tuning and volume offset is easily trimmed by adjustable knobs on the front panel. The pitch control circuit has been revised and can easily replace the original circuit. (Designed and built by Lindsay Reid and Brendan Dougan for a final year project ) There is now a FAQ about this project at theremin world.
Electronics World (Moog) 1961 theremin a.k.a. Moog Melodia
page 1 (288k jpg)
page 2 (472k jpg)
page 3 (400k jpg)
page 4 (342k jpg)
page 5 (135k jpg)
Diagram + partlist (112k gif)
In 1961 Dr. Robert Moog published one of the first transistorized theremin designs. It was a popular design, as he sold over 1000 kits. Today this still is a nice design for 'your first theremin'. You may need to consult a store, specialized in radio components, for suitable coil replacements. Page 1-5 is the full article, with interesting info on the circuit and on making the coils. If you don't want to download all the large files, you could just download the diagram with partlist. (All files taken from PDF files, send to me by Ted Rosenberg -thanks :)
Popular Electronics 1967 theremin
schematic diagram (18k gif)
article (20k pdf)
diagram (35k pdf)
printed circuit board (78k pdf)
This is the design from Popular Electronics 1967. The PDF files (Acrobat reader) contain the full article, circuitboard and diagram + partlist. Its the predecessor of the 1974 or SWTP #142 theremin. It's not wise to build this one since the #142 theremin has some usefull corrections and modifications.
Popular Electronics 1974 / SWTP #142 Theremin
original circuit diagram (gif 25k)
Same design but different diagrams (©1999 by Athur Harrison), which are easier to read:
part 1: volume section (gif 7k)
part 2: amplifier section (gif 7k)
part 3: pitch section (gif 8k)
This used to be a kit from Southwest Technical Products Corp. back in '74, called kit #142, a.k.a. the TECI Hybrid Theremin. It was published in Popular Electronics in that year. The design has some corrections and improvements over the '67 model. This theremin is fairly easy to build, however, placement of the components is a bit critical. Look at Art's Theremin page for more info and construction details.
#144 Theremin
part 1: volume section (gif 9k)
part 2: amplifier section (gif 11k)
part 3: pitch section (gif 9k)
Some improvements were made over the #142 theremin. The result is, considering its simplicity, a good instrument, with a clean sound. Today it's still a design worth building. However, since RF technology is involved (like with all theremins) component placement is somewhat critical. More info and construction details can be found at Art's Theremin page. Diagrams are ©1999 by Arthur Harrison.
#145 Theremin
diagram (gif 39k)
#144.5 theremin (prototype of the #145) (png 23k)
In nov. 2000 Athur Harrison supprised us with a new redesign of the #144 theremin. This new design promisses to be more stable thanks to a new oscillator design (differential paired instead of Colpitts). And changes have been made to the oscillator levels, reducing non-linear distortion. The result is a consistent sound troughout the entire volume range. Also, there is less rf noise on the audio output thanks to an added filter. A full description of the circuit and detailed construction instructions can be found at Art's theremin page. Second diagram is of the prototype of the #145 theremin, called #144.5. This one is added for comparison purpose only. These diagrams are ©2000 by Arthur Harrison.
PAiA Theremax kit
Electronics Now feb/mar 1996
circuit diagram (gif 47k)
circuit board (gif 76k)
component placement (gif 280k)
PAiA Electronics, Inc. offers a kit for this theremin, which seems to me the best way to build this theremin. The circuitry is rather complex, transistor based. You can find info on their site on changing the sound, as well as a detailed description on the circuitry. It's a very sensitive instrument (large pitch range) and has several outputs to drive an analog synth. The pitch and velocity CV outputs are not very good. Fred Nachbauer made some mods to solve these problems.
