The Theremin Stretch

[bertus]

Hello,

The schematic in post #3 calls for a 4 - 22 pF.
You could try the 8 - 40 pF:
https://secure.sayal.com/STORE2/View_SHOP.php?SKU=218582

If you can get hold of them, I would use some higher quality variable capacitors, like the ones I have here:



Bertus

 

[SparkyCal]

Hi Bertus- I am following the breadboarded version on the video, as I already built it. It calls for a 4-50pf I believe.

 

[bertus]

Hello,

I see that the breadboarded version uses the 4 to 50 pF.



You can still try the 8 to 40 pF capacitor.
When it has a to low value, you can put a 15 pF fixed capacitor in parallel.

Here I found a video that explains the use of a "real" (commercial) theremin:

Bertus

 

[SparkyCal]

Hi...I bought the J110's and popped them in, as well as the 8-40pF capacitor. I am still not getting any sound. However, the new capacitor has three pins and i am not sure I hooked it up correctly. I hooked one of the pins to one side of the 1mH inductor , and the other to ground. I'm not sure what the third pin is for, or whether I hooked up the other two correctly.

 

[bertus]

Hello,

The two side pins are connected together, the other pin is the other side of the capacitor:



Bertus

 

[SparkyCal]

Hello,

The two side pins are connected together, the other pin is the other side of the capacitor:

View attachment 49089

Bertus

Thanks. Will try this latter tonight and report back

 

[SparkyCal]

Hello,

I see that the breadboarded version uses the 4 to 50 pF.

View attachment 49088

You can still try the 8 to 40 pF capacitor.
When it has a to low value, you can put a 15 pF fixed capacitor in parallel.

Here I found a video that explains the use of a "real" (commercial) theremin:

Bertus

Very cool. Makes me want to buy one

 

[SparkyCal]

Funny- still no sound.

R 12 and R 42 continue to show zero volts. Is there anyway of breaking this down and testing voltages at certain junctures to determine where the breakdown is?

 

[bertus]

Hello,

Did you use the correct pin-out?



Bertus

 

[SparkyCal]

Hello,

I see that the breadboarded version uses the 4 to 50 pF.
I did because the previous jfet I used had a different pin mapping which coincides with the j110s mapping. So I basically just had to swap out the jfets with the new j110s because the components had already been adjusted.
View attachment 49088

You can still try the 8 to 40 pF capacitor.
When it has a to low value, you can put a 15 pF fixed capacitor in parallel.

Here I found a video that explains the use of a "real" (commercial) theremin:

Bertus

 

[SparkyCal]

Hello,

Did you use the correct pin-out?

View attachment 49091

Bertus

I believe I have because the previous ones I used have the same pin out mapping as the j110s. As I already had adjusted the components to comply, I just had to swap them out

 

[Audioguru]

In the video, I liked the bubbles playing sounds and the pedal making chords.

The woman with the severe English accent was talking in a room that had severe echoes. She has a speech problem that causes every sentence to fade away like she was running out of breathing air.

 

[SparkyCal]

Hey guys...as mentioned, I will be leaving soon and back Sept 7th. I don';t think i will have time to trouble shoot the theremin. between now and then, but plan to get back to it, when i return. Bertus- I also plan to read about theremin design, when i am away. I figure, if I can better understand how they are built, it can't hurt with the trouble shooting.,

 

[bertus]

Hello,

if you want to "study" on a real theremin, have a look at the theremin from Bob Moog:



There is a full description based on the given schematic in this PDF:
https://www.cs.nmsu.edu/~rth/EMTheremin.pdf

Bertus