Clara Rockmore's black tape?

I've noticed Clara had black tape on the volume antenna of her instrument - just wondering what the reason for that was?

Some theremins have a tendancy to "chirp" when the skin touches metal. The tape (or any other covering) will help prevent that.

Hmmm I was wondering how to stop that annoying chirping - Is there something a little more elegant than black tape?

@Amethyste: Transparent heat shrink tube is more elegant.

@All: Clara's theremin didn't chirp AFAIK... that's a rather unique circuit design problem of the Etherwave Standard. So I'm awaiting other guesses...

Only a guess, the hoop was nickel plated and Clara had allergic reactions to nickel.

Black Nail Polish ;)

You don't [i]look[/i] like a Goth. :-)

I use gaffer tape because I'm the gaffer. Or possibly because I make so many gaffs.

I may not look like a Goth - but I am a nail Technician and do have black polish, it's part of the trade ;)

[i]"@All: Clara's theremin didn't chirp AFAIK... that's a rather unique circuit design problem of the Etherwave Standard. So I'm awaiting other guesses..." Thierry [/i]

My guesses (and this is all they are! ;-)

1.) Touching an antenna massively / instantaneously increaces the capacitance 'seen' by the antenna - If one imagines the player as a fixed capacitor of (say) 100pF connected to ground, and the hand<->antenna as a variable capacitor of (say) 0.1pF to 10pF, then touching the antenna is equivalent to shorting out this hand<->antenna capacitance, and the capacitance 'seen' by the antenna jumping from 10pF to 100pF instantaneously. The numbers I have given may be a bit on the extreme side - but the general idea is sound.. The antenna series capacitor will limit the extreme capacitive coupling (value is not shown on the schematic I have, but it may be as high as 100pF, resulting in a jump from say 20pF to 50pF 'actually seen' by the antenna )

Regardless of whether there is a 'chirp' or not, such a jump and the resulting oscillator change and/or effect on the oscillator may produce undesirable effects.. It may be, for example, that after touching the volume antenna, the theremin took longer to settle and allow the volume level to return to 'normal'.. Again, my lack of understanding about this schematic (I cannot see where the volume circuit couples to the mixer for example) and lack of 'feel' for tube circuits means that what I say here cannot be trusted at all! ;-)

2.) I have no idea about the amplitude of the oscillator signal on the antenna - but the tank is (as far as I can see) driven from 90V.. Is it possible that touching the antenna gave an unpleasant sensation? .. Certainly, if there was leakage via the antenna capacitor (as might be more likely with old capacitors) there could be enough potential for a low level electrick shock.

But these are only guesses..

In my view, it makes a great deal of sense to insulate theremin antennas regardless of the design. Heat shrink tubing carefully applied is good for this, as is clear epoxy paint - I see no reason why nail varnish wont work ;-) - probably easier than epoxy.. In fact, some clear plastic CD cases disolved in Acetone could make an ideal low-cost paint...?...

Fred.