I do not want the distorted sound. please help!

I just recieved a new Moog standard Theremin.
The first weekend it worked out very well, but the other night when I tried to play the tone was fine the first 30 sec and then it became more and more distorted and somehow darker, and after a while it is a completely different sound (not a´the pure "sinus tone" at all!). I tried again yesterday and today and the same thing happened. I also tried to play on it in different rooms/places to see if there was a disturbing radio nearby, but this seems not to be the case. The range of pitch is also much smaller than before. This makes me vary sad. What should I do?

Take out your cell phone and your keychain of your pocket...

Had the same phenomenon some days ago. Moving the theremin around in the house, including one level higher I discovered that the new xmas illumination in the street in front of the house did these negative effects (perhaps a switching power supply).

On the higher level all worked fine.

Out of that, the Etherwave never produces a pure sine wave...

Frankjulie: [i]not the pure "sinus tone" at all[/i]

Thierry: [i]the Etherwave never produces a pure sine wave[/i]

It has a rather nasal tone.

I am puzzled that it takes half a minute to become distorted. It suggests to me that some problem is manifesting itself as the circuitry warms up. A dodgy component or iffy solder joint?

(Just to rule out the obvious - it isn't that you became more confident and played louder, overloading your guitar amp, is it?)

Anyway, please don't be sad, Frankjulie. Here's some good advice about what to do when feeling glum...

http://www.youtube.com/watch?v=WlBiLNN1NhQ

That sounds like a problem with a coupling capacitor somewhere in the circuit. This is the sort of failure mode that occurs when an electrolytic capacitor is going bad.

If you are brave enough to dive inside of your theremin, you can look for the aluminum electrolytic capacitors and try changing them one-by-one. Just be sure to get the same or higher voltage rating and to align the + side with the + marking on the board. (I'm guessing you don't have an oscilloscope to go poking about in the circuit to determine which one might be bad).


Don

just gunna state the obvious: did you accidently rub against the brightness knob? that kinda makes the sound more buzzy.