Posted: 3/16/2011 10:34:02 AM

Joined: 3/16/2011

well u see, im doing my senior exit project on theremin. i kinda understand how it works,but can someone like explain it to me in laymans terms how it works. Im afraid that my classmates wouldnt understand me. PLEASE need help XD. also if u prefer email >>> <<< if u want to help me
Posted: 3/16/2011 11:24:35 PM

From: Eastleigh, Hampshire, U.K. ................................... Fred Mundell. ................................... Electronics Engineer. (Primarily Analogue) .. CV Synths 1974-1980 .. Theremin developer 2007 to present .. soon to be Developing / Trading as . ...................................

Joined: 12/7/2007

"Can someone help me"?

- Probably not! ;-)

There are many 'layman' descriptions of how the theremin works all over the web.. everywhere from Wiki through the many theremin sites.. a few minutes with Google and you will find 'layman' descriptions for every level..

If you want help, be specific about what you are having a problem with - if there is something particular you need help on, we might be able to give this ... But if you want someone to do your homework for you, well - it ain't me babe! ;-)

Posted: 3/16/2011 11:40:03 PM
Jeff S

From: N.E. Ohio

Joined: 2/14/2005

This happens every year. It never ceases to amaze me how many people make posts like this.

"I've decided to design and build a theremin for my final project. I don't know anything about them. I've got two weeks to finish. Can someone help me?!!!"

What ya gonna do?
Posted: 3/17/2011 2:05:54 AM

From: Eastleigh, Hampshire, U.K. ................................... Fred Mundell. ................................... Electronics Engineer. (Primarily Analogue) .. CV Synths 1974-1980 .. Theremin developer 2007 to present .. soon to be Developing / Trading as . ...................................

Joined: 12/7/2007

ok - Jeff, you are right! but what can I say.. I feel compelled to write! ;-)

The theremin consists of two seperate circuits - one provides an audio tone (the pitch section) the other provides a control voltage or current to control the volume.. Each of these circuits is connected to a seperate 'antenna'.

The "antennas" are in fact equivalent to one side (or plate) of a capacitor, the player forms the other 'plate' which is (due to body mass) effectively coupled to ground.. So for practical simple explanation, the antennas can be regarded as variable capacitors coupled to ground, with their capacitance being controlleed by the players proximity.

Pitch circuit:
An oscillator [VFO] is connected to the pitch antenna in such a way that its frequency drops as the player gets closer to the pitch antenna (frequency drops because capacitance 'of' this antenna increases). There is a fixed oscillator [REF] running at a constant frequency, set to the frequency that the VFO produces when the players hand is away (say 60cm) from the pitch antenna.

A mixer (heterodyning) circuit mixes the REF and VFO signals, and produces an output which is the difference of the VFO and REF frequencies.

Take an example:

REF is set to 203kHz, VFO runs at 203kHz when hand is 60cm from the antenna, and the VFO frequency drops to 200kHz when the hand is 10cm from the antenna... Over this range, audio will be output.. At 60cm, both REF and VFO will be at the same frequency, there is no frequency difference, and no audio is produced (this is also known as the null point).. As the hand aproaches the antenna, the difference frequency increases, and at 10cm, the difference frequency will be 203kHz - 200kHz so the output (audio) frequency will be 3kHz.

Volume circuit:

Rather than producing a tone, this circuit produces a voltage or current proportional to proximity.. This voltage / current is used to control the gain of a voltage controlled amplifier (VCA) - audio from the pitch circuit is fed through this VCA so that the audio volume is controlled by the volume antenna.

This is the bible (

And .. marknudz231 .. IF I have just done your homework for you, please look at Streetkids rescue ( and make a donation! ;-)

Posted: 3/18/2011 8:01:24 AM

Joined: 3/16/2011

thanks fred and im afraid im broke right now. Although most of your explanations are kinda hard to understand BUT i did learn something new. I didnt know there were 2 circuits or something

Also sorry if i wasnt specific enough. I did do some research before i posted here. I feel COMPELLED to post a topic. I want to know more and seeing that this forum is about the theremin i feel like i will learn a lot more from the very mouths of the thereminist. I mean if this is how this forum works where some people get bitchy if someone ask them something about this instrument then Whats the point of having one?
Posted: 3/18/2011 8:02:19 AM

Joined: 3/16/2011

Posted: 3/18/2011 9:44:09 AM
Jeff S

From: N.E. Ohio

Joined: 2/14/2005

marknudz231 - Since I have to assume you are referring to me...

You said...

"if this is how this forum works where some people get bitchy if someone ask them something"

I'm sorry if you misinterpreted my intent, but I was merely making an observation. Surely, you can see the irony in it. This sort of posting is as common and predictable as the blooming of flowers in Spring.

Unlike you, I've been on this forum for nearly ten years and have (tried) to help countless people. Perhaps you could take things with a grain of salt and cut people a little slack.
Posted: 3/19/2011 2:15:18 AM

From: Eastleigh, Hampshire, U.K. ................................... Fred Mundell. ................................... Electronics Engineer. (Primarily Analogue) .. CV Synths 1974-1980 .. Theremin developer 2007 to present .. soon to be Developing / Trading as . ...................................

Joined: 12/7/2007

[i]"if this is how this forum works where some people get bitchy if someone ask them something about this instrument then Whats the point of having one?"[/i]

Well - its not that anyone here has any problem giving advice.. Its just that it takes (a lot of) time to give what you are asking.. Which is fine.. Except that the 'answer' to your question is available freely at multiple locations on the web, is easy to find, and repeating the basic information *seems* like a waste of time..

To me, if someone has taken the time to look at what is available, they will A) understand the core principles at least.. b) Perhaps have some specific areas they do not understand, and can ask about these.. c) Not understand anything they have read - in which case they are probably best advised to walk away from the subject.

The "trouble" with the theremin (and other electronics projects) is that one really needs a reasonable understanding of basic physics in order to have any chance of understanding how they work.. Alas (IMO) Physics understanding in the general population is abysmal (as is knowledge of all scientific matters).. If you do not have a clue about what voltage, current, or resistance, frequency etc are / do, then you have no hope .. You really need reasonable understanding of capacitance, inductance and AC theory to make any comprehension of a high frequency system like a theremin..

Without this core understanding, it will not matter how many pages anyone writes for you - you will not get a full understanding - and therefore you will not be able to explain to anyone else how a theremin works.

In order to explain to you, comprehensively, how a theremin works, I would need to know what level of understanding (regarding physics / electronics) you are at - and then tutor you in any missing aspects before we actually started discussing the theremin.

Nothing in my prior posting is "heavy" (I deliberately kept it at low level)..

And I think this is where the frustration expressed when postings like your original one appear.. It is not that we dont want to help - but we have been here before (many times).

The fault, I believe, does not rest soley on your (the student) "inability" .. IMO it is probably more about the appalling education that today's students are getting. Everything has been watered down - made "easy" -

When I was 13, I took an ICS correspondence course in electronics.. this was their 'starter' course - but it took me through physics and maths to a level equivalent to what people doing their 2nd year Bsc courses today are doing.. This was before electronics is even started [i](which I found extremely frustrating at the time - I almost gave up, I wanted to do electronics, not maths and physics!)[/i]... Then the electronics started with in-depth course notes covering circuit theory (DC and AC) physics of semiconductors, transistors etc..

There are no equivalent courses available today - this "starter" course from ICS was actually more comprehensive than what todays students obtain when graduating with a Bsc ... Back then, you were lucky if completing this course even got you entrance to a university Bsc course.[i](I was lucky - I got into university based on this course, despite having dropped out of school at 14)[/i]

If you do not have good understanding of physics, I advise you to get this - or abandon engineering as a career choice.

It is 'ok' for a thereminist to have a 'sketchy' understanding of the physics / electronics of the theremin... But IMO, if you are doing this project within the context of an engineering qualification, it is not 'ok'.

And this is probably also a factor in how 'we' treat people who make posings like you did..

Posted: 3/20/2011 12:48:32 AM

Joined: 3/16/2011

Well your right that schools today sucks. I mean they all focus on sports than science or math. Well i kinda understand how it works. I did some research and asked some famous thereminist. But its kinda hard to explain it to the other students. Some of them did not take physics or is not eligible. But if someone can give me an example and try to connect that on how the inside of the theremin works, it would be awesome. I know that there are oscillators and a detector. But how does one thing work? i mean is it like a metal detector? that when my hands are in the range in the electromagnetic field, the disruption of it makes the system produce sounds?
Posted: 3/20/2011 7:17:23 AM

From: Croxley Green, Hertfordshire, UK

Joined: 10/5/2005

OK - examples...

Do you have a portable AM radio or TV? You know how tricky it is to tune one because when you go near the antenna it knocks it out of tune.

This is the same effect as with a theremin. The antenna and your body form a capacitor which is attached to an oscillator. Moving closer to or further from the antenna changes the capacitance of the body/antenna capacitor and that changes the frequency at which the oscillator oscillates.

Next example - check with your physics or music lab to see if they have a thing to demonstrate "beat frequencies" - it's two identical tuning forks on top of an open ended box. If you tap one tuning fork the other rings too because they are identical so the second one resonates.

Now stick a lump of blu-tak on one of the tines of one of the forks, so that it oscillates at a very slightly different frequency to the other one. Now when you tap the tuning forks you will hear a note that varies in volume going from loud to soft to loud to soft. This is called "beating" or a beat frequency.

Now imagine that the notes produced by the tuning forks were so high frequency that you could not hear them, and the beating was so fast that it was an audible note. Now we're into theremin territory...

The two oscillators in a theremin pitch circuit operate at radio frequencies - way too high to hear. Approaching the antenna is like blu-taking one of the oscillators. The other one does not change. The circuit that makes the audible beat frequency between the two radio frequencies is called a heterodyne circuit. It is the radio frequency equivalent of an amplitude modulator or ring modulator.



Any help there? Yes? - OK, go click on Fred's Streetkids link!

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