My New Year gift to TW: A new theremin circuit

Posted: 12/14/2020 1:46:51 PM

Joined: 12/9/2020

Thank you so much guys, I am trying hard to build this and to understand all the circuit.
I will follow your instructions, and when i get some results I'll be here again to share with you!

Posted: 12/21/2020 3:13:02 PM

From: Russia

Joined: 9/8/2016

Dear Thierry. Is it possible to determine from these parameters whether copies of 2N5484 transistors should be selected in a smaller or larger denomination of these values?
Excuse me. I am not an electronics engineer and I need to choose the transistors that are best suited for such a circuit in terms of parameters.

(photo of measurement with transistor tester)

Posted: 12/21/2020 4:22:21 PM

From: Theremin Motherland

Joined: 11/13/2005

Дорогой Тьерри, скажите мне, в каком направлении эти параметры 2N5484 лучше подходят для работы такой схемы?Более или менее?(photo of measurement by transistor tester)

Это шутка такая?

Ты по ошибке составил исходный вопрос на английском, а потом перевёл его гуглом  на русский и вставил сюда?

In any case welcome back!

Posted: 12/21/2020 4:54:03 PM

From: Theremin Motherland

Joined: 11/13/2005

I assume Martel asks about the most appropriate (best for performance) characteristics of 2N5484.

Posted: 12/21/2020 5:04:40 PM

From: Theremin Motherland

Joined: 11/13/2005

did you buy a hundred of ones on aliexpress?

Posted: 12/21/2020 5:58:01 PM

From: Russia

Joined: 9/8/2016

Sorry, my browser commands auto-translation and apparently these posts are an annoying technical misunderstanding (in terms of the language of the text.).

О, приветствую , Илья. Рад видеть))

Я написал на русском, перевел на английский и создал пост. Я старался. А что не так?
Я написал (исходник не сохранился) "Уважаемый Тьерри. Можно ли по этим параметрам определить, в меньший или бОльший номинал этих значений надо выбирать экземпляры 2N5484 транзисторов?"

Нет, я когда-то покупал с десяток и там нашлось три-четыре хороших пары.

Я что, допустил какой-то глупый технический вопрос? :-)
Извините. Я не электронщик и мне надо выбрать транзисторы наилучше подходящие для такой схемы.
Ааа..наверное у меня сглючил автопереводчик. Браузер сам включает автоперевод. 
Спасибо за указание)

Excuse me. I am not an electronics engineer and I need to choose the best transistors for this circuit.
Ahh .. probably my auto-translator got it wrong. The browser itself enables auto-translation.

Posted: 12/21/2020 10:18:43 PM

From: Colmar, France

Joined: 12/31/2007

The required DC parameters for the FET is a pinch-off voltage of -1.5 to -3.0V (That’s the Ugs which one must apply to full cut drain current) and a Idss (drain current when Ugs=0V) of 2 to 6mA.

Posted: 12/22/2020 8:17:44 PM

From: Theremin Motherland

Joined: 11/13/2005

your transistor tester shows something myth parameters (not Ugs and Idss), 
so you could try dewster approach

(твой транзистор-тестер показывает какие то непонятные параметры, так что лучше попробовать способ dewster-а):

Posted: 12/23/2020 6:23:17 AM

From: Russia

Joined: 9/8/2016

ваш транзисторный тестер показывает что-то мифическое (не Ugs и Idss),

I'm sorry. I was hoping that these parameters are somehow related and correlated with the parameters indicated by Thierry, and I was hoping that he would explain it, but apparently not. I put the connectors on the board to test various transistors and try to select them this way, primitively :-)
I put together this schematic with minor modifications.

Russian transistors KP303, I soldered a zener diode to protect Q41. And I added one trimmer capacitor from the antenna to the ground. And an amplifier on LM386.
Everything works well )

Posted: 5/15/2021 8:01:08 AM

Joined: 5/15/2021

Hi Thierry, 

I've built your simple pitch-only theremin, seems that is working using exactly the components you choose and I'm amplifying the audio with this circuit found in a youtube videos that uses your circuit: 

The output is very very low in volume, what am I doing wrong ?

Thank you very much.


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