Build an Electro-Theremin or Tannerin

The only implementation of a volts-per-octave oscillator (that I know of) is to implement a linear-to-exponential converter.

Jeff once sent me a picture of his tannerin. It does not use a ribbon controller -- instead, it has a roller that connects to what appears to be a telescoping antenna -- as such I think the linear movement of the roller causes an exponential change in the length of the telescoping rod/antenna within the tannerin's case. Perhaps Jeff could jump into this thread -- I've only seen pictures, haven't seen the schematics.

Anyway, since the frequency doubles with each upward octave, you would need some means to convert linear motion on your ribbon controller to exponential changes in the frequency.

Exponential convertion.. interesting, but I must protect it from any interference or feedback, or it will fry in a second..

I think only Op-Amps can do such an operation.. (i'm not very glad of this..)

The Tannerin Kevin mentioned is the Electro-Theremin I posted about several days ago.

Obviously, I cannot post pictures of the interior of this device on the internet without exposing myself to possible legal action. But, that doesn't mean I can't comment on it.

My take on it is that the telescoping antenna is simply the mechanical linkage between the external slider and an internal potentiometer that controls the frequency. I'm sure it also plays a role in accounting for any nonlinearity so that something reasonably close to a keyboard (graphic) can be used as a guide to find the correct notes while playing.

Could you post a drawing of this system? I'm not sure to understand it all (especially about the telescopic antenna)

Thanky you

Personally, I've designed and built my own Tannerin. I don't know if it can be called a true Tannerin, but it works on the same principle. It has a slide that is connected to a pontentiometer via a ball chain, and that controls the pitch from the tone generator. If anyone would like to know anything else, please let me know! I will be more than happy to upload schematics and/or pictures.

ValveMan,
I, think I speak for a great number of Theremin, Electro-Theremin and Tannerin enthusiasts, in saying that we would love if you would post anything you know about the aforementioned items! Please!

Good Luck!

teslatheremin

Here's the schematic. I must say that the tone is actually digital, though the control is analog. It works on the same principle that an mp3 player does. It won't make a completely perfect sine wave, but I can program up to eight different waveforms into it, and it still behaves just like a Tannerin. If you are interested in building this circuit, let me know. I can you a programmed chip with whatever waveforms you desire. I can't upload the schematic straight into the forum apparently, so here's a link to my LiveJournal page that has the schematic.

http://valveman.livejournal.com/

I'll upload pictures of the actual instrument, including all the mechanical workings, as soon as I can get hold of a digital camera.

To come back on earlier questions: There are potentiometers with a linear change of resistance and there are others with a logarithmic behaviour. This could perhaps help...

A logarithmic potentiometer would most certainly provide better linearity, but in my design, I used a multi-turn pot to keep the cabinet as small as possible. That way, I didn't have to use a seven inch pulley! However, I have never been able to find a multi-turn logarithmic pot, so I'm stuck.

Would this website (http://www.musicfromouterspace.com/analogsynth/vco.html) be helpful for you?