Just built Etherwave doesn't work

"Could you suggest me a good heterodyne theremin scheme using the higher frequency for future building." - Ubermann

There really isnt much out there if one doesnt have good electronics skills and equipment.. personally I would stay with the EM / EW design, or look at the Silicon Chip / Jaycar designs which are higher frequency, simpler, cheaper and dont have the dual resonator (no antenna inductors) topology.

The Jaycar theremins are supplied in kits with PCB and components for about $60. But if you are after "good" I certainly think  EW is better than the Jaycar - although I personally much prefer playing the Jaycar to the EW (but I havent ever liked the EW's feel and am not qualified to comment as I am not a musician - most people play EWs).

The Enkelaar theremin is a variant of the Silicon Chip design (built using a Silicon Chip board) and has been praised by some thereminists - its no more linear than any other of this type of design, but has better sounds:

http://www.element14.com/community/docs/DOC-23047/l/enkelaar-theremin-schematic

I have several documents on Element 14 related to this instrument (photos, layouts etc) on this and the preceding page.. Also loads of other theremin documents - but beware.. this is not a hobby site - these documents are not posted with the intent that home constructors pick them up and build them, they are their to inform and as a resource to theremin developers - you are free to do what you want with them, but its entirely at your own risk and has high hazard if you arent competent!

Fred.

Guys, I have a new problem.

The Etherwave is completely built now and works fine excluding pitch antenna.

I tuned the theremin according to instruction from "Build the EM theremin" document from 1996. So when I touch the pitch antenna it sounds on about 3KHz frequency (~3,5 octave above middle C; i.e. middle of seventh octave). I checked the tone using a synthizer. And when I retract my hand away the sound frequency becomes lower and lower and mutes (zero beats) on distance about 1 meter from pitch antenna. So it looks like the pitch antenna is tuned ok.

 

But there is a problem of pitch antenna sensitivity. As we can see on video

http://www.youtube.com/watch?v=v0d4GHK04zc

or http://www.youtube.com/watch?v=zPaljdE6o2w

pitch changes more or less uniformly from 5cm to 1m out of antenna. But on my device the pitch changes just within 4-5 half-tones on distance 5cm to 60cm from pitch antenna. And much more on distance 1mm to 5cm. And when I touch the pitch antenna the pitch jumps to 3KHz (from may be about 2 KHz).

Why sensitivity is so bad? I know about nonlinearity effect when such L1-L4 coils geometry is used but it's much bigger than I expected. And it's quite difficult to play something on theremin with so short pitch range.

All experiments I performed in a center of my room where all metallic stuffs are far from antennas. I also tried to remove a screw nut of pitch antenna socket to check possible case if it's electrically isolated and affects antenna sevsitivity. But result was the same.

As you can see from photos above I use 3/8 copper non-chromed tubes as antennas. Can it affect the linearity by oxide film availbale or something like that? Is there a critical difference between using chromed and non-chromed copper tube?

What do you think?

 

 

How long is your pitch antenna?

62cm.

make it shorter... 40 to 43cm. Actually the static antenna capacitance is ways too high which makes that the linearization circuitry cannot work.

Yeah!

It works cool now! Thank you, Thierry!

In my case the best pitch antenna length was 30cm. It looks funny but works great.:)

"Yes, the wires are МГТФ and the PCB was made by "laser iron technique". But is it important here?" -- Ubermann

Just looked at the photos and found that the wires from antennas to PCB are "MGTF" type. 
Generally, it is not very good, because this brand is so flexible that can change the shape and location into cabinet when the instrument is shaken or simply leans over.

Needs to be fixed by glue or be replaced by solid and thicker.

Think I may have shorted something, because the volume antenna doesnt respond and the actual volume is really low.

 

 

 

My amp doesn't have an earth and the power adapter from M00g doesn't have the earth connected. When I was trying to tune L11, I think something must of happened as the ammount of crackle you got from touching the volume antenna nearly poped my amp speaker out.

 

 

 

So, I've rigged up a temporary earth from the earth lug on the audio jack, into a plug to provide earthing. This has got rid of the crackling and popping, so I'm well grounded, but still no real response from the volume antenna.

 

 

 

So I replaced U3 and pin 12 gives -11v and when I short out C28 get 0v

 

 

 

And the volume IS REALLY LOUD!

 

 

 

I replaced D1 as I didn't get any -v reading on the negative side and that's where I am so far.

 

 

 

 

 

I tuned L11 into 450MHz and L5 into 285MHz and have adjusted L6 for zero beat and get a correct range over the pitch antenna but still no volume.

 

 

 

When tuning L11 you eventually get very distorted notes and turning the Volume CCW across to CW gives real distortion across the pitches – I don't think that's normal.

 

 

 

Latest volt readings are;

 

 

 

Antenna side

 

L9 4.8v 3.5v

 

L8 3.6v 3.3v

 

L7 3.1v - 011.7mv

 

D1 3.0v 043.6mv

 

C12 042.3mv -012.9mv

 

 

 

Top Middle Bottom

 

Q6 11.5v - 170.1mv 141.8mv

 

Q7 12.6v - 010.5mv 141.1mv

 

 

 

Please advise as what I could try next.

 

myesol,

 

Sorry for the delay with answer. If it's still actual now, I think you have the same problem of shifted resonant frequency of L7-L10 series. According to Thierry's advise I firstly replaced L10 with a short wire. But that didn't give the required result. Then I also replaced L8 with a short wire. And then my theremin become workable fine (adjustments of L11 allows me to catch the resonant frequency). Try to do the same.

Of course if you sure your volume oscillator works fine (you checked the signal on oscilloscope)...

 

About your ground to 0V, nice idea. However that as better as dissipation surface bigger. It's one of factors affect sound quality. Hope your ground is enough to make the sound clean from noise and crackling when you gound pin 12 of U3.

 

Greetings to all!

What type of coils L1-L4, L7-L8, L9-L10 is used in Etherwave? Theremin already assembled, it remains only to find these coils.
Did anyone know an online store where you could buy these coils with shipping to Russia?

Regards, Alex.