Analog Theremin

How to build a real analog Theremin that produces sine waves instead of digital square waves?

Can someone please help me with the design of a fully analog Theremin (producing sine waves instead of digital square waves) using coils that can be bought easily or made easily out of parts that are commonly available? There are many Theremin schematics available online but I can't find one with clear & detailed explanations of how to wind the coils or make the antennas or where to get the parts. Please understand that I am not an electronics expert. Any help would be greatly apprectiated.

Project Elements

https://youtu.be/ajM4vYCZMZk

Discussion (13 comments)

Guy Peeters 5 months ago

i can help............

ElektorLabs 4 months ago

Thank you very much for your kind offer. However, it would be much more helpful if you post your information here, so anyone can profit from it. If you only want to email it, please email it to labs _@_ elektor _dot_ com and we'll see how to proceed from there.

1 Comment(s)

Guy Peeters 5 months ago

i have a massive lot of info about the theremin and most of all the schematics articles on different magazines from old to new.by interesed i can email it .......

legalhesap 1 day ago

Hello. letsgolocation@gmail.com. Send me please

1 Comment(s)

JPALLEMAND 4 years ago

Hi,
In the number 95 (june of 2007) of "Electronique et Loisirs" (you can dowload it here : https://archive.org/details/Electronique_et_Loisirs ), there is a project of Theremin who use standard coil (455 kHz IF transformer like this one : http://www.elecdif-pro.com/product_info.php?cPath=105_1010_1021&products_id=39049
I have it in project, (in 2021, not before)
Jean-Pierre

CerealKiller 8 months ago

... a lot for the link, JP!

1 Comment(s)

electrostat 6 years ago

Hi,

sometimes an Internet search can be helpful - have a look here:

http://www.swtpc.com/mholley/PopularElectronics/Nov1967/PE_Nov1967.htm

I built this one years ago, it worked fine and the coils were simply wound on standard coil formers with iron cores. I figured out the number of windings experimentally but I don´t have the data anymore. As far as I remember I started with about 100 windings - but in these modern times multimeters for Henrys are available for under $ 20.

More details here:

http://www.theremin.us/144/144.htm

An earlier tube version you find here:

http://www.swtpc.com/mholley/PopularElectronics/Apr1955/PE_Apr1955.htm

or here updated:

https://www.antiqueradio.org/BuildingATubeTheremin.htm

...and another one here:

http://www.thereminworld.com/schematics

Good luck!

0 Comment(s)

Jean.Noel 6 years ago

I found this on the Web:
https://pdfs.semanticscholar.org/159b/8f7ab33083fc1b8de584ec338b0ee2f6fd7b.pdf

Physics of the Theremin (1605kb)

purple-bobby 4 years ago

From Google translate
"no the oscillator is digital on an arduino type Due with analog outputs.
the sinusoid is managed by integration of a second order differential equation.
one parameter for frequency the other for damping, adjustable by the 2 antenna wires on 2 analog inputs."

Well done on getting it to work.

f4dui 4 years ago

non l'oscillateur est numérique sur un arduino type Due avec sorties analogiques.
la sinusoide est gérée par intégration d'une équation différentielle du 2ème ordre.
un paramètre pour la fréquence l'autre pour l'amortissement, réglables par les 2 fils antennes sur 2 entrées analogiques.

Ulrich Dreher 4 years ago

f4dui wrote:
"On the arduino analog inputs I put 30 cm long wires and when approaching wires the values changed which can modulate what we want
(attenuation, amplitude, frequency ....)"

It's not 50 Hz - f4dui is just describing the effect of change of capacitance.
Might be there is some picking up of 50 Hz, but considering that the Theremin's oscillators work in the multi-kHz / MHz bands, 50/60 Hz shouldn't disturb as it is way out of band.

(Considering the small changes in capacitance, you need a quite high frequency oscillator so that these small changes effect a large-enough frequency change. We're talking about base frequencies of 500 kHz and alike. (Ref.: the article from "Electronique et Loisirs".)

purple-bobby 4 years ago

I think f4dui said
On the Arduino analogue input, I have 30cm long filaments mis and on approach of filaments, the values change which it modulate peut what it the on wish
(reduce/level frequency amplitude)

Is this 50Hz? Your body picks up voltage (typically 5V in to 1M ohm) from the domestic 220V AC.

Indoors / Inside you could use the amplitude of this 50Hz hum to modulate pitch or amplitude.

Outdoors / Outside, if you made an oscillator (or use Arduino analogue/PWM output) of 2200 Hz at 5V and attach it to yourself. By change in capacitance more or less of this signal would reach the analogue input.

f4dui 4 years ago

sur les entrées analogiques arduino j'avais mis des fils de 30 cm de long et en approchant des fils les valeurs changeaient ce qui peut moduler ce que l'on veut
(fréquence amplitude amortissement ....)
f4dui gerard

1 Attachment(s) 5 Comment(s)

Jean.Noel 6 years ago

I think this ca help: https://www.element14.com/community/docs/DOC-50631/l/build-the-em-theremin1pdf

sans-titre-20180615094022.png (720kb)

Charlie Lamm 6 years ago

Paia Theremax.
https://www.paia.com/proddetail.asp?prod=9505KC

1 Attachment(s) 1 Comment(s)

purple-bobby 6 years ago

From <http://info.ee.surrey.ac.uk/Workshop/advice/coils/air_coils.html> a plastic, glass or paper former, say 20 mm radius and 80 mm windings length. Rearrange the single layer winding formula L = 0.001 N² r² / (228 r + 254 l) gives N² = L (228 r + 254 l) 1000 / r² ; therefore N² = L 62,200,000.
For L = 75uH would require N = 68 turns; these evenly spaced along the 80 mm length.

Resonance frequency
(2 pi f)² = 1/LC rearange LC = 1/(2 pi f)²

For 500kHz, LC = 100E-15 with L = 75uH C would be 1.3nF (a bit large).

Approximate capacitance between hand and aerial/antenna, assume the area of closed hand is 20 mm times 100 mm and open hand 150 mm times 100 mm, the distance of hand to aerial is between 50 mm and 200 mm. Assume the aerial is a large sheet, not a rod. C = e_0 A / d ; e_0 = 8.85 pF/m, A is area of the plates in m² and d is distance between plates in m.

Closed hand at 200 mm 8.85fF virtually nothing.
Closed hand at 50 mm 0.35pF
Open hand at 200 mm 0.7pF
Open hand at 50 mm 2.6pF.

Two oscillators, one fixed and one variable by hand capacitance, if the pitch is the beat frequency (the frequency difference between them) this will be in the range 260 Hz to 8 kHz. The fixed oscillator at 510kHz and the variable between 502,000 and 509,740 Hz (so the nearer your hand the higher pitch). 1.3nF in parallel with 2.6pF gives 1.3026nF => f = 509,195 Hz difference of 805 Hz - this is not enough.
Try 130pF with 75uH => 1.611,825MHz ; 130+2.6pF with 75uH => 1.595,944MHz ; difference 15,881 Hz ; 130+0.7pF with 75uH => 1.607,503MHz, difference 4,322 Hz ; this is kind of the right sort of range - we can add a (variable) capacitor to the fixed oscillator and lower its frequency by say 4kHz, then the beat frequency would range from 322 Hz at 200 mm to 11,881 Hz at 50 mm.

0 Comment(s)

purple-bobby 6 years ago

I was going to design one, but found this <https://www.moogmusic.com/products/etherwave-theremins/etherwave-theremin-kit#info-tab> there is an IC on the PCB, but the PCB looks like an analogue radio circuit; sadly out of stock.

I would imagine the water content of your body verses the air surrounding the loop aerial and rod aerial affects the inductance (loop) or capacitance (rod). Any oscillator using a capacitor inductor for its frequency reference, can have its frequency adjusted by a variable inductor or capacitor.

I think you would need three oscillators:
Either a fixed frequency oscillator and variable low-pass filter, or vis-versa; and use this change in filter or frequency to control volume.
The tone could be the difference in frequency of two oscillators, one fixed and one variable.

Alternatively, measure the inductance of the loop aerial and use this to control the volume; measure the capacitance of the rod aerial and use this to control the frequency.

Another control might be the timbre/distortion, the dual oscillator beat frequency is more likely to have a spacey timbre.

Since radio frequencies are being generated you probably need to use a scientific frequency, may be 13.56 MHz.

Modern touch screens use capacitance which increases as you bring your finger nearer to the invisible electrodes printed on the back of the glass screen.

Correction:
An oscillator is typically an amplifier with positive feedback an a certain frequency and a gain reducing (negative) feedback so the output does not clip. A capacitor and inductor in series will have low impedance (resistance) at its resonance frequency.

Steven Greenfield 6 years ago

That IC is just a transconductance Op Amp being used as a VCA (voltage controlled amplifier) for volume control.

Theory of operation, schematics, etc. are available here:
http://manuals.fdiskc.com/flat/BigBriar%20Etherwave%20Service%20Manual.pdf

The LM13600 Transconductance Op Amp is still available, under $3 each from Futurelec.
https://www.futurlec.com/Linear/LM13600Npr.shtml

Steven Greenfield 6 years ago

"A capacitor and inductor in parallel will have low impedance (resistance) at its resonance frequency."

That is incorrect. A capacitor and inductor in parallel with have high impedance at the resonant frequency.

A capacitor and inductor in series will have low impedance at the resonant frequency.

It isn't the water content of your body, it is the fact that you are a large conductive object.

purple-bobby 6 years ago

https://www.youtube.com/watch?v=_FytVf5hH88

3 Comment(s)

Frankrudolf 6 years ago

Hey, just two dayws ago i built a Theremin with a preconditioned PCB of FRANZIS, it comes with a booklet and some part you have to solder - a variable capacitor, a potentiometer and two coils.
I built it for my grandchildren.
You can see it with the following URL:
https://www.franzis.de/maker/bausaetze/das-franzis-bauset-theremin-selber-bauen-bausatz?gclid=EAIaIQobChMI2avnuJaz2wIVUhgbCh1BHgkXEAAYASAAEgIJL_D_BwE

Good luck

Frank

0 Comment(s)

Gottfried Karenovics 6 years ago

To be correct: Led Zeppelin did not use a Theremin but a Tannerin. This invention by Paul Tanner uses a shift potentiometer for pitch control instead of an antenna.

I have listened the song "Whole lotta love" and was slightly disappointed because the Tannerin sound was nearly unheard by the average sound and noise level.

Yours

Gottfried

Steven Greenfield 6 years ago

I think you are confusing songs. The Beach Boys used a Tannerin on Good Vibrations, I watched a show about them and they even showed the Tannerin and demo'd playing that bit of the song.

Jimmy Page did in fact use a pitch-only Theremin. I've seen concert footage.

1 Comment(s)

kimbal summers 6 years ago

You can easily build a Theremin from two old transistor radios. Have one as the base oscillator and the second as the pitch oscillator. Fit a loop on one - the base oscillator which controls the dynamics and volume - with the second radio having the aerial for the pitch osc.
Have them both hetrodyne with a bit of tweeking of each oscilator coils and then feed their difference signal output into a detector and then an audio amplifier. In reality it may be a bit more complex than i've described, but that's the basic gist of it. Digital stuff is unsuitale with this old technology - in that its not able to drift. The shift has to be analogue not digital. You want the oscillators to drift with a shift in capitance of your body. Valves work "better" in that they carry space charge - which semiconductors lack. Two old valve radios would be even better than two transistor sets in my opinion. If you want to see theremin work, look at Led Zeppelin's "Whole Lotta Love" in ":The song remains the same" concert (1973). Jimmy Page uses one on stage and its fantastic. I think Pink Floyd also used one in their music tracks on later albums.
Here are some samples of such in use >
https://www.youtube.com/watch?v=4kujH0ScAi0
https://www.youtube.com/watch?v=K6KbEnGnymk
https://www.youtube.com/watch?v=KPhXm-UPfEU
https://www.youtube.com/watch?v=xwu7b0jiNOQ
https://www.youtube.com/watch?v=dWyYj5EE4CU

0 Comment(s)

Ulrich Dreher 6 years ago

The following "pitch only" design is great for its simplicity:
http://thereminworld.com/Forums/T/29231/my-new-year-gift-to-tw

Duplicate this for volume control (maybe with a differing fixed inductance value), mix the two outputs and add "downstream" whatever "gimmicks" you'd love to have.

0 Comment(s)

Johannes Zink 11 years ago

There was a Theremin Schematic on Elektor (February 1974)

Yours

Johannes

Electron35 12 years ago

Hello, I have realised one "Theremin" a few years ago. it's work very well for the moment. je would like post the picture the next week. best regards, Christian sorry for my "english".

breedj 12 years ago

HI, I found this article some time ago. Its written by Robert Moog. The guy of the Moog synthesizer. So it might be a good schematics. He also explaines the antennas in detail. You can download the pdf document by clicking the link 'View download'. http://www.element14.com/community/docs/DOC-16870/l/build-the-em-thereminpdf Kind regards, Joost Breed

Klaus Schricker 12 years ago

At NUOVA ELETTRONICA Giugno-Luglio 2011 a Theremin was published very detailed, a complete kit is available. I could copy the article (in italian of course) for some Euros or you can buy the issue at: NUOVA ELETTRONICA via Cracovia 19 40139 BOLOGNA Italy (for 5 Euro without mail) yours K. Schricker

Klaus Schönhoff 12 years ago

I'm in doubt if a classic radio frequency theremin will work satisfactory with all these mobile phones, smart phones, WLANs around. I#d expect a lot of audible noise. Maybe a non-RF approach might be better, measuring distance from "antenna" to hands with ultrasonic airwaves or light pulses time-of-flight?

Johannes Zink 12 years ago

I don't know if this is possible because it might be copyrighted material. But you find the schematic when you search "Theremin Schematic" on google. Yours Johannes

ENSEA92 12 years ago

I did not know the Theremin, so I have made a search and I find this site : http://www.theremin.info/-/viewpub/tid/8/pid/2 and http://en.wikipedia.org/wiki/Theremin You can find the schematic of the Elektor's Theremin (december 1973 page 66) here : http://www.theremin.info/index.php?module=-&type=file&func=get&tid=15&fid=image&pid=47