Open Theremin v3 - bad sound

1. 3. and 4. most probably show that your problems come from your theremin not being grounded.

Thanks again, I'll send logs and photos of my theremin a bit later. My wife dreams of playing the theremin, this is for her )))

1. 3. and 4. most probably show that your problems come from your theremin not being grounded.

   Hello. I'm sorry for taking so long to answer. I made a grounding for the theremin. My two problems are still present.

   I have made 3 attempts at calibration logs. With an old quartz resonator and 3 with a new one. In order to see possible frequency deviations of the resonators from attempt to attempt. The calibration conditions have not changed.

   I also took a photo of my theremin and attached a video immediately after calibration and 8-10 minutes after being idle in sleep mode. The video shows an example of a rattling sound and the appearance of two ranges after downtime.

   I will follow all recommendations. I attached all the material to Google Drive so as not to clog up the topic.

   All media

Looking at the audio spectra of your video I see strong mains hum intermodulation:

There are clear peaks at 50Hz, 100Hz, 150Hz, etc.  I believe this accounts for any "growling" type timbres.  

It also seems like there is audio clipping here and there in the signal chain - maybe turn your amp down?  Or if it is a guitar amp maybe it is set up to clip / distort?

Calibration logs - nothing much worrying:
Pitch calibration finds the value in 5 iteration which is normal.
Volume calibration is longer: 10 iterations (it happens sometime), probably the volume loop is less stable, but once again it finds the value at the end.
Maybe let-us know if volume loop calibration gets very long from time to time (if it seems infinite... )

Later on : your calibration is not valid anymore because of thermal deviation. It is true that open theremin is not that stable thermally.
calibrate your theremin after some heating time. Recalibrate it from time to time. Calibrate with your body at playing position but with your hams away from the antennas.

"It also seems like there is audio clipping here and there in the signal chain" - Dewster
Yes, the Open Theremin has a quite hot output (up to 5V Peak to Peak). Some amplifier may easily clip...

Curious about your box: the 2 antennas wire cross each others (theremin is upside-down and the wire are crossed to recover the right handed assignation of antennas) maybe it is not that good...

"Curious about your box: the 2 antennas wire cross each others (theremin is upside-down and the wire are crossed to recover the right handed assignation of antennas) maybe it is not that good..."  - Mr_Dham

I was wondering about that too.  The antennas and oscillators are already super close on the Open Theremin, criss-crossing the wiring could easily make this situation worse in terms of unwanted interaction.

[EDIT] Vincent, is there any reason why the Open Theremin software couldn't swap the antennas?  It might be a good option if it is possible and not already in there.

Глядя на аудиоспектр вашего видео, я вижу сильную интермодуляцию сетевого гула:Есть чёткие пики на частотах 50 Гц, 100 Гц, 150 Гц и т. д. Я считаю, что это объясняет любые «рычащие» тембры. Также кажется, что в сигнальной цепи то тут, то там возникают искажения звука — может быть, стоит уменьшить громкость усилителя? Или, если это гитарный усилитель, возможно, он настроен на искажение?

Hello, in the near future I will try to find a room with a minimum number of electrical appliances or experience a theremin outdoors. As the final amplifier, I use a JBL Extreme portable speaker. And yes, wherever I connect it, every amplifier is overloaded at the input. It doesn't bother me right now, I'm going to make a remote pedal with volume control. Thank you for the analysis.

Журналы калибровки — ничего тревожного:Калибровка высоты тона находит значение за 5 итераций, что является нормой.Калибровка громкости занимает больше времени: 10 итераций (иногда это происходит), вероятно, контур громкости менее стабилен, но в итоге он снова находит значение.Возможно, вы сообщите нам, если калибровка контура громкости будет занимать очень много времени (если она кажется бесконечной... )В дальнейшем: ваша калибровка перестанет быть актуальной из-за теплового отклонения. Действительно, открытый терменвокс не так стабилен в температурном режиме. Откалибруйте терменвокс после некоторого времени нагрева. Время от времени проводите повторную калибровку. Калибруйте терменвокс, расположив корпус в игровой позе, но отвернув локти от антенн.«Также кажется, что в сигнальной цепи то тут, то там возникают искажения звука» — ДьюстерДа, у Open Theremin довольно высокий выходной уровень (до 5 В от пика до пика). Некоторые усилители могут легко выйти из строя...Что-то не так с вашей коробкой: провода двух антенн пересекаются (терменвокс стоит вверх ногами, а провода пересекаются, чтобы восстановить правильное расположение антенн). Может, это не очень хорошо...

   Good day. There are absolutely no problems with the volume antenna. Calibration is performed fairly quickly.
   Since my last post, I have read almost all the branches of this forum, with the request "open theremin". I've seen many reports about the critical importance of good grounding and prolonged warm-up, including not turning it off at all. I'm wondering, as far as I remember, the linear level is 0.5 - 0.7 volts, roughly speaking up to 1 volt. Why is there so much - 5 volts. Or is it related to the ability to output CV across multiple octaves?
   About my box. I was thinking how to fix it and found a 1/4" photo tripod mount, but for this placement I had to flip the board over. I assumed that this could be the cause of some kind of interference. You have confirmed this. I'll try to get rid of this, although I'll have to make a new case. Or can I use a shielded antenna connection cable and cross them. I also read a message below that maybe it can be fixed programmatically. I don't understand arduino code, but if you can tell me if it's possible to do this and give me hints, it would be a very convenient option in my situation.
   I also apologize for my English, I use a translator. There are probably a lot of mistakes.

«Любопытно насчёт вашей коробки: провода двух антенн пересекаются (терменвокс перевёрнут, и провода пересекаются, чтобы восстановить правильное расположение антенн). Может, это не так уж хорошо...» — Mr_DhamЯ тоже задавался этим вопросом. Антенны и осцилляторы в Open Theremin и так расположены очень близко друг к другу, а перекрещивание проводов может усугубить ситуацию с точки зрения нежелательного взаимодействия.[РЕДАКТИРОВАТЬ] Винсент, есть ли какая-то причина, по которой программное обеспечение Open Theremin не может менять местами антенны? Это могло бы быть хорошим вариантом, если бы это было возможно и уже не было реализовано.

Good afternoon, yes it would be great if it were possible to edit the code.

I want to thank you all for being so enthusiastic about helping a stranger. I really love kind people. Hugging, shaking hands.

One more question. I used a different antenna mount. On the connectors. This is different from most fastening methods, could it somehow affect the characteristics of the theremin? I had no idea how sensitive this device was.