[sdiy] More Theremin - WHY??

[Paul Maddox]

Harry,

> I'm playing with the U. Glasgow 'digital theremin'.

So, I've been reading..

> I added an RF choke at the suggestion of Grant Richter... it helps quite
> a bit. Put the thing in a metal box... that makes it a lot more stable.

yep, I built a PAiA theremax, worked ok on my bench, once it was in a box,
100% improvment..
that said, it needs a *good* ground, dodgy earth pins really screw it up.

> For a detector, I'm using a 4013 a'la "thereminvision.com"   The range
> of this thing is in the very high audio / ultrasonic. I plan to get a CV
> from it (eventually).

Hmmm...
Got any URLs?

> Listening to the audio output, there is MASSIVE noise at very low
> frequencies...
> its possible that it is getting some FM interference. As I move my hand
> closer the noise (jitter) decreases.   But WHY ???

Check your earth.

> Here's a good idea (from the Etherwave)... make the oscillator without
> the antenna
> the variable one... this way you can tweak the pot without screwing up
> the variable osc.

neat.

> In a finished product, I think you would need a remote variable
> resistance... tough trick at 20pF   :^P

hehe..

> Trying to make a multi-axis theremin controller by using multiplexed
> detectors... might
> be pretty hard.   ThereminVision uses the LMC555 which might be more
> stable than the CD4093 I'm using... but 4093 is in stock :^P

Thats what I was planning, adding a Y axis to the left hand side (volume).
Getting it to generate some waveform and using the extra axis for filter
control.

Let me know how you get on.

Paul