Etherwave Circuit Questions

Hi, 

I'm thinking about playing around with an old Etherwave Standard to learn about analog circuits and I just had a few questions. Apologies if they've already been answered somewhere. Do you guys know if the front aluminum panel is important to the circuit? Is there any capacitive coupling there and would replacing it with wood or plastic improve it, or at least not change it? 

Also I noticed there are metal screws that connect the theremin cabinet. I'm assuming there's some coupling there as well. Do you think changing those to plastic inserts and plastic bolts would improve it?

I've been reading on these boards about adding bulbs for esd protection. Has anyone tried this? And could this extra capacitance be offset by changing something as simple as the screws or aluminum plate?

Thanks! 

The EWS is the finest commercially available theremin out there. Nothing you mention will add any improvement or affect the performance of the instrument. The EWS in general does not have a static discharge issue. Keep exploring you will have fun. I write more of my experiences on this webpage.

Christopher

Hi Christopher

Thanks for putting up all that info online. I think I'll definitely have to clean the pots if I ever want to try to play the thing (It's my Dad's old instrument and nearly 20 years old) I'm still a bit confused though, especially with the front metal plate. Why doesn't the line connecting the antenna to the coils interfere with the grounded plate? Isn't it similar to your hand near the antenna? Sorry if this is all really obvious but I'm new at this :)

Thanks again

Hello sitaras,

It is not obvious to most what's going on. The front metal plate has little mass so it has very little affect. There is also capacitive coupling to grounded surfaces but also very little if not nearby. Keep exploring these are very good questions.

Some people think they can make their car a theremin but that has too much mass to work!

Christopher

The wire towards the pitch antenna above the grounded foil adds (like the screws in the wood and the front panel) to the static capacitance seen by the pitch antenna, which is needed to maintain stable operation. All these capacitances have been taken into account during the circuit design. Removing or replacing them will affect and most times degrade the pitch range and/or the linearity of the instrument.

Perhaps its time for an article in the technical repository here at TW that deals with grounding and capacitance - An article that starts simply, so that non technical readers can understand it, but perhaps goes deeper for those who are interested.

It seems to me that many of the questions here at TW relate to this matter - it would be nice IMO to have a link that can be pasted whenever one of these comes up, rather than needing to go over the same ground again and again, and get the same dumb arguments posted again and again by those who don't understand but perhaps think they do.

I would be happy to write such an article - but think my doing so would be like a red rag to a bull, so would prefer the article to be vetted and "approved" by some technically competent TW members before its "sanctified" by inclusion on TW.. In my view, such "vetting" needs to be done regardless of who the author is.

In my view, there are some basics of theremin operation which are 99.999% "confirmed" - they are not "factoids" they are facts - in the same way that the laws of thermodynamics are 'facts' - Even accepting that the precision of these facts are not 'absolute' they are facts for all practical purposes.

Without understanding how the player capacitively interacts with ground and the theremin, or understanding that it is "plate" area, not mass, which defines capacitive coupling inside and outside of the theremin, players and constructors cannot understand how things work or why they work, and are lost when things dont work.

I feel that its time TW took its roll in educating people and dispelling the needless mystery some seem intent on cultivating.

Fred.