Hi Alec, You're right, I did use valves for the first one I built - EF80s if I remember correctly and two telescopic aerials recovered from scrap portable radios - as you say - one for pitch control and the other for volume control. I revisited the project, in the late 70s, at the request of a friend, but used transistors and ICs on that occasion. I've lost touch with him, so can't determine if it's still alive
If you fancy a bit of fun with a simulated version, follow the 'bbc' link on my 'Theremin' post.


------------------
Willum