ther-force one...NEW DUAL THEREMIN

Posted: 12/3/2008 4:27:58 PM

Joined: 10/31/2008

i am a drummer and got a crazy idea to incorporate two theremins into my drumset. i have put two art harrison theremins in a small enclosure.

i would like to get some advice on antennas, however. i am running a two to three foot wire from the antenna solder hole on the circuit board. the wire is insulated but not shielded. i can't get an antenna working. the wire does act as an antenna, but, i would like to have a metal disc or plate antenna like suggested by art harrison.

any ideas as to how i can get this working? i think that i would like to use pie plates as the antenna...
Posted: 12/3/2008 5:41:56 PM

Joined: 10/31/2008

just another quick question.

i have read on art harrison's website that the antenna lead should be 8 inches or shorter. do you think that there is anyway to increase the distance between the antenna and the antenna lead without losing sensitivity?

Posted: 12/3/2008 6:49:50 PM

From: Croxley Green, Hertfordshire, UK

Joined: 10/5/2005

[i]i have put two art harrison theremins in a small enclosure.[/i]

I can't help you with the antennas, but I can mention that putting two theremins operating on the same frequencies close to one another will change their behaviour. Whether it will cause them stop working entirely or become erratic and unpredictable, as it does with etherwaves, I cannot predict.

I think better to have two separate instruments with integral antennas than a conjoined pair with remote antennas.

Mmm. Pie.
Posted: 12/4/2008 3:53:34 PM

From: Escondido, CA

Joined: 2/6/2008

Ok, I am at a loss as to what you want to do with those 2 theremins. Playing theremin requires a steady hand and very slight finger movements ... a far cry from the motion of drum rolls and high-hat hits!

If you want to use hits on the toms to trigger sounds, you would have more luck adapting triggers from electronic drum kits. They are ready-made for this purpose.

Posted: 12/4/2008 4:21:44 PM

Joined: 10/31/2008

i realize that it takes a steady hand to play the theremin, however, i won't be "playing" the theremin in its purist sense. i will be using them as texture devices. basically when i crash a cymbal, i want to move my hand past the antenna quickly so i get quick pitch slides to which i will apply reverb and delay to get neat spacey effects. if i want to solo on the theremin, it won't be while i am simultaneously playing the drums.

i still need help for the antenna! does anyone know how i can make a good one?
Posted: 12/4/2008 5:16:49 PM

From: Eastleigh, Hampshire, U.K. ................................... Fred Mundell. ................................... Electronics Engineer. (Primarily Analogue) .. CV Synths 1974-1980 .. Theremin developer 2007 to present .. soon to be Developing / Trading as . ...................................

Joined: 12/7/2007

I presume these are pitch-only Theremins..
1.) You will need to detune the Theremins from each other, to frequencies which no not interact.
2a.) The length of the antennas is critical for tuning - a longer antenna has higher capacitance which results in lower pitch oscillator frequency - the reference oscillator must be correctly tuned to match the pitch oscillator frequency.
2b.) Increasing antenna capacitance also impacts on sensitivity in many ways - large 'background' capacitance with respect to player capacitance reduces sensitivity.
3.)Any shape antenna is possible provided the above issues are taken into account.
4.)the wire connecting to the antenna 'object' IS part of the antenna, making connecting wires 'insensitive' is not simple.. screening the wire adds huge capacitance to the total antenna.
5.) It IS possible to screen an antenna connecting wire, but not simple.. one needs to have a high bandwidth buffer amplifier input connected to the antenna input point on the board, and take the output of this amplifier to the screen - unless done with great care and attention, this will cause all sorts of instability - but with a carefully designed amplifier at slightly less than unity gain, one can produce a capacitance 'invisibility' screen.
Posted: 12/4/2008 7:58:36 PM

From: Croxley Green, Hertfordshire, UK

Joined: 10/5/2005

[i]i want to move my hand past the antenna quickly so i get quick pitch slides to which i will apply reverb and delay to get neat spacey effects[/i]

If you have an old pair of sticks you can happily modify, (1) insulate their butts and (2) run a strip of conductive tape along their shafts to the shoulders so that you can tap one end with your finger.

Moving your finger on and off the strip while the other end is in the pitch field should cause the pitch to step up and down.

I just tried with an extra long screwdriver, an etherwave, delay and reverb. I like it. YMMV :-)
Posted: 12/4/2008 8:15:57 PM

From: Bristol, United Kingdom

Joined: 12/30/2006

My bandmate used to have a tiny synth with a clip for attaching it to a drum. You hit the drum, it picks up the vibration and triggers the oscillator.

Isn't that better suited to what you're after?
Posted: 12/4/2008 9:07:28 PM

Joined: 10/31/2008

well that might be better suited, but i don't have a synth, but i have two minimum theremins in a box.

i was thinking of using an old drumstick. can i just coil the wire around it, or do you think the conductive tape will be more sensitive?
Posted: 12/5/2008 10:45:33 AM

From: Croxley Green, Hertfordshire, UK

Joined: 10/5/2005

Not sure if one would be better than the other. The wooden stick offers a certain amount of conductivity (hence the insulation) but my test with the handle of a wooden spoon suggested it was not enough by itself.

I should think that the wire will work fine. Try it and compare it to something all metal. (If you have a pair of metal practice sticks, for instance...)

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