Kreuzer elektor theremin

Posted: 1/7/2007 1:23:42 PM

From: chicago

Joined: 1/7/2007

I'm in the process of building one of Albert Kreuzer's elektor theremins... and halfway through populating the pcb I realized that I don't know what k1 is. Is that a standard electronic component and I just don't recognize the symbol?

I was also wondering why there are three leads (a,b,c) for output... but I was thinking that was just for making output that would work with headphones or instrument cables.

Any assistance would be much obliged. I figured I would try here before bothering him directly.


Posted: 1/7/2007 2:22:16 PM

From: Croxley Green, Hertfordshire, UK

Joined: 10/5/2005

Not an expert, but I would hazard a guess that k1 is a jack socket.

Posted: 1/7/2007 8:29:56 PM

From: chicago

Joined: 1/7/2007

k1 one looks like a relay i think. A, b and C are ... output and a lead for the antennae? Does anyone have the original elektor schematic/writeup?
Posted: 1/8/2007 6:37:02 AM
Charlie D

From: England

Joined: 2/28/2005

This might help:
Posted: 3/18/2012 6:36:50 PM

Joined: 3/18/2012

I'm building elektor theremin too and i have got the same problem. Here's schematic:

Isn't the K1 the jack out for amp?

What the **** is A, B and C? How to connect it with the antenna? This theremin has got only one, pitch, antenna.



Posted: 3/18/2012 6:49:36 PM

From: Northern NJ, USA

Joined: 2/17/2012

K1 is audio out jack.

Connect pitch antenna to A.

B & C are variable and fixed (respectively) oscillator outputs pre-mixer.  Perhaps these are test points to make sure both oscillators are really oscillating?

This is an RC Theremin so I imagine it doesn't work very well (i.e. non-linear and picks up interference)?  I'm curious as to what one gets in the way of maximum playing range (max usable hand distance) with it because I have no direct experience with RC Theremins.

Posted: 3/18/2012 8:05:54 PM

From: Colmar, France

Joined: 12/31/2007

A very interesting circuit! 

One could use the B and C outputs and send them through separate /2 frequency dividers (D-Flipflops) or even twice in order to obtain /4 before using the remaining XNOR gates of IC3 in order to mix these signals and obtain additional outputs where the audio signal is lowered exactly by 1 and by 2 octaves.

Sending the original signal and both new ones to a mixing table will allow to do additive wave synthesis with the faders.

RC theremins must not be bad at all. With a well calculated choice of the pitch rod's static capcitance (depends on lenghth an diameter, for example about 8.5pF for the Etherwave's pitch rod when installed near the grounded aluminum foil in the cabinet and the cover containing those big metal screws closed) and the capacitance variation through the player's hand (depends mostly on the diameter and less on the length, for example about 1,5pF for the Etherwave's pitch rod) in relation to the oscillator's capacitance (82pF plus some pF for stray capacitance) it should be possible to get an non-linear but playable range of about 5 octaves.

Posted: 3/18/2012 8:28:07 PM
RS Theremin

From: 60 mi. N of San Diego CA

Joined: 2/15/2005

And the Wheel begins to spin again...this could be a good thing?

Thierry said: possible to get an non-linear but playable range of about 5 octaves

 but forgot to say probably within 6" from the antenna. That's about 15 cm.

Here is the proper link Elektor Theremin

Don't build any theremin circuit that does not furnish a sound sample!!!!

There is a reason the author does not want you to hear his results.

Gentlemen, RS Theremin fibbed a little bit in another thread on his Bass sample. On my RS Theremin circuit board graphic the left side has a terminal B. This is for a 6" short wire open end loose coupling. I made the same connection in my EWS to improve the bass. Everything depends upon where you place the open end. Non technical types will have no clue of what I am talking about, so I will leave it there.

It is so rare to have constructive theremin talk a TW, we all have pumped up chests!   Musicians included!!!!

Posted: 3/18/2012 8:51:31 PM

From: Colmar, France

Joined: 12/31/2007

Christopher, if that happens within 6" or a wider range depends on many factors. That's not an invariant and absolute value as far as I know. Or can you show me the formula and the computations which give you that result?

I've already played commercial theremins with RC oscillators which had their 5 octave pitch range within a field of 16" = 40cm...

One single example which proves that your statement cannot be correct under all circumstances.

It's all a question of the df/dC curve of the antenna/oscillator system.

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