Hi. First post here and first theremin build. I have some fundamental questions before starting on it. I've appreciated the theremin and its concept for some time but rather passively. Recently I was at this concert which revived my interest and made me want to build my own
http://www.theatredelarchipel.org/fr-show-730.html I'm going to build something based on the etherwave, perhaps with a bit of improvisation as I go along.
I have a background in physics and I'm not too bad with electronics so I'm not too daunted by the build but I do have some very basic questions.
First, the case: What happens if you use a metal case? I appreciate that this seems a rather basic question for someone who purports to understand the principle of operation but, assuming the casing is earthed then we'd have a fixed field between antenna and base. The player's hand would interrupt this field but I'm guessing that the physical size and shape of this field would make playing difficult. Is that right? Exactly the same applies if I use a metal base only (and the rest of the case in wood). How far from the case would I need to place the antennae in order to have a reasonable playing space? Would placing the antennae on booms say 2ft in front of a metal case be enough? And, if it weren't for the issue of a field between antenna and earthed box, surely encasing the electronics in a metal box is a good thing to do. Any thoughts?
I've referred a fair bit to https://www.element14.com/community/docs/DOC-16794/l/thereminamjphysexcellentpdf . If you look at fig. 8, you can see that in this build, each module is contained in a metal box for screening (and connected by screened cable). That screening appeals to me as good practice, as does the idea of each circuit on a separate board. In this case, with all those earthed metal boxes in there, surely it's the same as a metal casing from the pitch antenna field point of view.
I also want to make my theremin dual voltage so that it can run on a 220v ac supply or 12v dc. If the latter then it will need earthing so a connection from metal case to ground seems like a good idea.
Can you guide me and let me know if I'm getting things really wrong here. Will the antenna be ok mounted on an insulator 10cm above a metal casing or do I need more distance? And is a metal casing simply a bad idea?
Thanks in advance for your help.