Ever built a theremin?

[Tractorfan]

Any of you lads & lasses out there in olde worlde wireless land ever had a go at building one of these instruments?? It's something I've fancied having a go at for a while & I've got a couple of schematics for said instrument using valves (naturally, what else?) but I'm stuck for ideas for coils for the tuned circuits. I thought of using IFT's from a scrap radio set but I'm not sure what RF frequency theremins use. Would 470Khz or so be OK or am I likely to play havoc with all the AM sets in the village? One article says their theremin operates "well below the broadcast band" but doesn't say where. If I remember correctly one of its coils only had 150 turns (tapped at 50 turns) which would surely put it ABOVE the broadcast band? The article was in an American magazine from 1949. D'you think I'll need to wind the coils? and if so how do I find out how many turns of what wire on which sized core resonates at what frequency? I haven't got access to a grid dip meter, sorry. Any suggestions gratefully received. I should have most of the other bits in me junkbox.
BTW, in said article some capacitor values were given in uufd's (micro micro farads). How do they relate to modern new fangled nano & picothingies?
PS Can anyone out there actually play a theremin?

[Alan Stepney]

A pal of mine has several of them, but then he has a wide variety of electronic music as repairing and building that sort of stuff is his job.

If you dont get answers here, I can ask him whatever you need to know.

[Tom_I]

Originally Posted by Tractorfan

BTW, in said article some capacitor values were given in uufd's (micro micro farads). How do they relate to modern new fangled nano & picothingies?

One micro microfarad (i.e. one million millionth) = one picofarad.

[stuie319]

Hi there

Some years back (now it could be *some* years but i'll hazard early 90's) ISTR a theramin article in one of the electronics mags probably ETI. From memory it was quite in depth in terms of the instruments history, with a project to build. Now it would of course been solid state, but nevertheless it might be worth a search in this direction?

Regards
Stu

[evingar]

I built a moog type a few years ago - It works well, but needed to be in a wooden box with a carefully screened linear PSU. It was silicn (transistors) though.

This might be of interest to folks wanting to have a go at a valve version :-

http://www.thereminworld.com/moog1954.asp

[KeithsTV]

There was a solid state Theremin in the October 2004 Everyday Practical Electronics.

Keith

[Mike Phelan]

There is a Theremin circuit using four NPN transistors in p108 of the Electronic Musical Instrument Manual by Alan Douglas (not our forum member) ISBN 0 273 361937. It also describes the Trautonium. Well worth buying if you have any interest in this sort of thing.

Now, what you really want to build is one of these - the Ondes Martenot.

[Alan Stepney]

Whilst on the subject of music and the unusual, I wonder if anyone has ever constructed a Poulson Singing Arc.?

Just the thing to have in your sitting room!

[CanonMan]

Originally Posted by KeithsTV

There was a solid state Theremin in the October 2004 Everyday Practical Electronics.

Keith

There's also yet another one in last month's and this month's issues.

It's one of the many projects they now buy in from Silicon Chip magazine in Australia

[arjoll]

Jaycar do the SC one from 2000 as a kit - http://www.jaycarelectronics.co.uk/p....asp?ID=KC5295 - and it looks like you guys get it cheaper than NZ (GBP15 = NZ$40 or so, compared to NZ$72 on their NZ website!). They also had two different versions with MIDI in their 2007 print catalogue but it looks like they've been discontinued.

[Tractorfan]

Thanks everyone for the useful info and apologies to the mods for having to move it, sorry.
I think I found a schematic on the 'net that mentioned 455Khz so IFT's seem feasible without the hassle of winding coils. Thinking about it I don't reckon the frequency is too important anyway so long as I use adequate screening. I don't really fancy using transistors or chips as they "blow" far too easily if I make even the tiniest wiring error or slip of the meter prod. Very few solid state projects I've ever built have worked properly, if at all. Valves are much more forgiving in my view and I'm (painfully) aware of the mains & HT hazards. Thanks once again.
Cheers de Pete.

[dominicbeesley]

Only just spotted this, is funny as I've been playing the theremin tonight trying to get my prototype superhet comms receiver working. I have to move my hand around near the oscillator coil to get it spot-on when trying to tune in an ssb signal.

I had one going recently with 2 IFT's out of a broken '50s transistor radio running as oscillators driven by two halves of a double triode, the two signals added together at the grid of an af amplifier. One oscillator nicely screened the other with a length of 1mm copper wire sticking straight up.

It worked but it wasn't exactly musical if I recall right it was a bit too sensitive so I think you'd probably want to swamp the coils with a bit more capacitance than normal (and so reduce the frequency a bit).

This gave various howls but there was no real way to control the volume. I then got distracted by other things....

Dom

[umberto60]

Hi there,
if you want to practise your Italian ....here is a full project to build a theremin

http://www.leradiodisophie.it/Downlo...elle_radio.pdf

And if you want to have a look at the web site, here are some notes written in English:

http://www.leradiodisophie.it/english_notes.htm

Cheers,
Umberto

[espidog]

I have a circuit diagram of a 1929 RCA Theremin in PDF form that might be of interest. The image quality is a bit smudgy, but OK.

To download it, right-click the following link and select "Save target as..." (Windows) or "Download linked file" (Mac OSX).

Theremin circuit diagram

[mastermanx2001]

Sorry, could not resist this:

http://www.youtube.com/watch?v=hUmJ2Wg_hR4

There is also a video of building a Theremin and plenty of videos of very capable Thereminists.

[Top Cap]

Good one here if you scroll through the magazine

http://www.radio-portal.ru/book/%C6%...20-2004-10.pdf

[mastermanx2001]

There seem to be a lot of chips in that design, I wonder why.

[Tractorfan]

Thanks again for the info & links to circuits & stuff. I've dug out some SP61's together with their M.O. valve holders and a kaput radio that's about to donate its IFT's. Don't worry, it's nothing collectible and it's beyond reasonable repair anyway (side contact valveholders anyone?) Thanks, Top Cap for the link to the E.P.E. theremin, a good read but far too "chippy" for me!
Cheers de Pete.

[dave walsh]

I'm sure that there have been a couple of other Theremin threads on here.
I remember digging out and mentioning an article in [I think] Radio Bygones that included the original valve circuit and one from a US electronics mag. People certainly build these things professionally and there used to be a kit at around £600!
Interest in this device never goes away with the likes of Radiohead using one. Last weeks Guardian 23/5 had an article "Ghost In the Machine" re the Theremin and the ondes Martenot, although I've not come across anyone building the latter. There was good documentary on Ch4 a few years back re Mr Theremin as a celebrity in New York during the thirties when his device had them packing theatres [until the Russian secret Service took him back home]. His daughter played a Theremin concert at Southampton in 1996. I rang up to ask if there would be a radio broadcast as I was too ill to get there and the next week the manager sent me a private recording. It's amazing how helpfull people can be. Dave W

[Boom]

I fell in love with the Theremin when I heard Emerson Lake and Palmer play 'Lucky Man' in the 60's.

Google 'virtual Theremin' on Google and you will find several if you don't want to actually build one. Here's one that uses a webcam to get the 'players' movements from.

http://homepages.ihug.com.au/~squires/vt/