Tuning issue - my theremins is way too high

Hi there, firtst of all, I'm vere glad to see there's such a cool community out there:)

Well, I've got my first etherwave standard one month ago, and since than I had the feeling that somenthing was worng with tuning: I always kept the tuning knob almost on the extreme clockwise position. Today it's very clear that even setted to the lowest note possible it seems to procuce very high notes, I can't reach the zero beat zone, even moving far away from the theremin. In other words, the lowest note I can play atm is king of a G string on a standard guitar :(

any ideas?

ps:
sorry for my english, I'm italian :) (and the prime minister is not speaking in my name, btw)

Welcome to Theremin World, neurocelso.

Your English is fine, and I am not happy that my Prime Minister has [i]my[/i] name! :-)

While we wait for our electronics experts to wake up, here are some simple things to occupy your time.

First of all, let's rule out environmental factors. Nearby conductive masses can adversely affect your theremin, so if it is possible to take it outside then try your theremin in the garden. If not, then in the centre of your largest room. (Conductive masses include wooden tables and steel girders hidden inside walls and floors.)

Next, did you keep the small plastic two-headed screwdriver that came with your etherwave? (It is about 13cm long and probably red.) You will need that to make internal adjustments to your etherwave. [i]Do not use a metal screwdriver instead. You could easily damage your instrument.[/i]

You will find Moog's instructions for tuning the pitch circuits here (http://www.moogmusic.com/faq/?content_id=26&cat_id=4).

Moog's instructions are good, but a simpler adjustment may be sufficient to correct your problem.

Remove the lid of the theremin (4 screws, 2 at the front, 2 at the back) and plug your theremin in. DO NOT TOUCH ANYTHING INSIDE THE THEREMIN WHILE IT IS POWERED. (I know you understand that, and that you understand why I must say it anyway.)

Put the pitch knob to the centre position - pointing straight up. Now put the lid of the theremin upside-down on top of the body and listen to the lowest note you can play.

The couple of times times that I needed to adjust the pitch field of my theremin I found that a small adjustment to the inductor L5 was sufficient. Put the red tool in the top and turn it a small amount one way, then put the lid back and see if the lowest note is now lower or higher. If it is lower, make another small adjustment i the same direction. If it is higher, turn it the other way. Repeat this until you have the zero-beat in about the right position.

The inductor should be easy to adjust. If you feel any increase in it's resistance to turning do not try to make it turn forcibly - you have reached the end and applying more torque will damage it. It is delicate.

(You can also adjust the field by flexing the rigid wire connecting the circuit board to the pitch antenna, so that it is a little further away from the metal sheet underneath it. This will make the field smaller as required, but the danger is that you could fracture the solder joints at either end of the wire.)

Now put the lid back on properly. If you can achieve a satisfactory pitch field by turning the pitch knob, then I suggest that you do no more at present.

As you gain more experience in playing the theremin you will become more aware of the behaviour of the pitch field and may want to make more adjustments to improve the range and linearity of the instrument, but after only a month of playing I would be surprised if your field awareness is sufficiently acute to justify that.

I see no need for me to wake up since Gordon has already said all which I also would have said...


...out of: Don't touch L5 but use L6 for adjustment. Changes of L5 have an important impact on linearity.

Oops!

Yes. L6.

Thanks for the kind, fast and I hope effective replies :)

As soon as I can (I'm travelling atm) I'll open my theremin and hope I can fix it :)

well guys, believe it or not, the only thing I can say for sure is that the theremin is scared of medical doctors, neuroscientists, and/or homeopats (I'm all the three :D )

Long story short, now it's working perfectly, but I've just opened it (and now it's still opened) and ... voià, it worked :D

Now I'm gonna close it again.... suspence..... stay tuned :D

And if you will close it, the capacitance of the 8 big screws in the cover will once more trouble your pitch field. The art is to adjust L6 when the cover is open so that the pitch field is correct after you close the cover...

The alternative, as practised by the Moog engineers (*), is to drill small holes in the lid and perform keyhole surgery.






(*) They keep a spare lid for that purpose - they do not damage etherwaves returned for repair.

lol ok, it seeemed so very strange, I was thinking that maybe the only othe variable (disconnecting and reconnecting the power source) coul affect the pitch, but now with the cover on it' the same as before :)

well as a scientis I go on ste by step, tomorrow I'm gonna re-open it (controlled variable) act on l6 (or l5 I can't remember right now I'm almost sleeping) and tell you about the (I hope predictable) effects :)

mmmm so you say a small hole in the right place could solve the "art" problem? :D well i'm gonna try without it for now ;)

thanks again to you all for all the help!!!

It is L6! Here a small hint from a practitioner: When the cover is open, you may adjust L6 so that the zero beat is with your hand about 5cm away from the pitch rod. Try this and close the cover... ;-)