Theremin controller

[LektroiD]

Hi, I've been thinking about buying a Theremin, but they are extremely expensive, especially the ones with CV/Gate. So, I'm wondering if it would be easy to build a controller; I won't need a VCO or VCA, just something to convert the antennas into CV, preferably with a range control.

As a side note, I am not interested in making a cheap LDR controller. It must be a classic Theremin with 2 antennas.

Has anyone built something similar, could maybe give me a few pointers, schematics etc?

[Taylor]

Have you seen this?

http://paia.com/theremax.asp
http://paia.com/ProdArticles/theresch.htm

[LektroiD]

[gwaidan]

If you want something to make noise with get the Paia (lots of CV sources including a velocity detector). If you want to play chromatic music get the Moog Etherwave Plus-it ain't cheap but is very well made and performs very well.

Pretty much any two-antenna theremin, even the cheapies, can be modified to give you a single CV out as all theremins use a VCA circuit for volume control.

[LektroiD]

[Taylor]

What about the Paia is no good? It seems a pretty straightforward transistor version of the original theremin concept - 2 high freq oscillators heterodyning, one is variable in pitch. The lower sideband folds down into the audio range, giving you a sine wave. This particular unit then uses that to create a square. I'm sure the Moog is different, but similar - no super special mojo in there.

BTW, I suspect that building even the most complex theremin will be easier than learning to play one well... So don't let difficulty be an obstacle - if it is, you'd be playing autoharp.

[gwaidan]

I didn't mean to say the Paia was no good so sorry if I gave that impression-it's just that the extra $$$ for the Etherwave Plus does get some features that make it easier to use.

The Moog has an equalisation coil on both antennas to "linearise" the pitch response so that the space between notes wlll be relatively predictable throughout the range, rather than with the low pitches spread out and the high pitches cramped together near the antenna. This makes it easier to make fast pitch "jumps" between notes as the interval distance will be much the same whether near the antenna or away from it.

Also, the Etherwave has a temperature compensated log converter so that its CV output is 1V/Octave, plus its frequency to CV converter is Bob Moog's peak picker circuit which won't give sluggish response-the Paia has a conventional Hz/V converter that sends a pulse train into a 1uF capacitor.

Then again, all the above may not be important for what you want it for. And of course a CV output can be put thru external log converters and shaped by distortion circuitry to give a linear response without the help of an equalisation coil-apparently this was the technique used in Moog's own Etherwave Pro! As well a non-linear response can be really good for getting started playing theremin because of the finer pitch control it gives you away from the antenna.

Main thing is to just go for it, whichever one you choose. My first real one was one of the $60 jaycar kits and I still use it, even after getting the Etherwave. And yep, they're all really simple to build but devils to learn to play!!!!

[j.dilisio]

MOOG provides a schematic and circuit description for their Etherwave in a freely available pdf entitled UNDERSTANDING, CUSTOMIZING, AND HOT-RODDING YOUR ETHERWAVE THEREMIN

It doesn't look too complex. I'm planning on building one someday but first things first, what are those weird bumpy symbols labeled mH and uH?
Coils maybe?

http://www.moogmusic.com/manuals/HotRodEtherwav.pdf

[Taylor]

Inductors - uH is really μH and means microhenries. mH is millihenries.

It appears to use some variable inductors. I think those will be pretty hard to find and expensive.