Open Theremin v3 - bad sound

Posted: 8/27/2020 9:53:28 AM

From: Colmar, France

Joined: 12/31/2007

There are thoughts to add more CPU power. A STM32F4 would probably be an overkill, though. The current thoughts are going towards a very affordable and easily maintainable 32bit 48MHz Cortex M0+ solution which would have roughly 12+ times the power of an Arduino UNO. 

Backwards compatibility with the V3 shield is probably not on the list since the oscillators should gain in robustness and stability at the same time and 3V3 compatibility is an important topic.

Can't tell more for the moment, due to a "No vaporware" policy...

Posted: 9/8/2020 9:07:42 PM

Joined: 7/31/2020

Hi, i have built 5 ones by assembling jlcpcb execpt bb914 , 102J, 8mhz and 7.32 mhz oscillators which they didnt have in stock. 
The first two shields pitch didnt worked. Last 3 ones were ok and worked perfectly. I figure it out that i soldered Bb914 badly kind of cold solder and to much solder around its leg. I removed and soldered again. Likely i saved both unworking shields.  Just check out your self soldering work. Or measure the antennas be sure all are under 50 cm including jack and wire if you housed it in to a box and built antennas as wire+ female banana + male banana + antenna. Be sure that no electronic devices around during calibrating. I got these sounds if my antenna touchs something around or if i touch by my finger.

Posted: 1/4/2021 2:27:33 PM

Joined: 1/4/2021

And about the arduino itself, is it an original one or a clone? There is something about arduino clone in the FAQ :"Q:  Why do I have strange tone vibration on low frequencies (like buzzing flies, around note E).You may be using a Arduino clone with a cheap ceramic resonator instead of a quartz crystal. Replace your Arduino with an original Arduino. Or then try to replace the oscillator yourself as shown here. (Thanks to Sergey Anokhin for figuring this out.)"

Hi Guys,

I'm in the deal again. A few years ago we discussed with Urs issue called "buzzing flies", so finally I couldn't get good sound on Arduino clone from Aliexpress. I tried to repace ceramic resonator with quartz crystal, also I made some changes around boot loader. Professional guys skilled in development of electrical circuits recommened to try to change "fuses" (see datasheets for Atmega) (sorry I'm mistaken, it was a few years ago, so I forgot this already). I saw that in this topic exist real Arduino skilled guys, so I'll be happy to give any feedbacks...

I played around with something like these parameters, but didn't get any good results. Also I tried battery power 9V.

Also, skilled guys said:
the jitter effect grow up from unstable Arduino frequency. Sometimes, China's arduino have 12Mhz, but programmed on 16Mhz. Also, guys recommended me to replace ceramic resonator and capacitors near, but looks like I didn't get the success.

Finally, I bouhgt original Arduino UNO and the sound became much-much better, but the problem from the first topicaster's video is actual, but I'm linking the problem with "dirty ground" or with high the interference level. I'm using steel waterpipes as groung wire, I suspect that it's not a good solution, but it's better then without ground.
I have to try OpenTheremin in "clear" studio, with clear ground and with clear power.

Of course, there are a lot of articles from the Internet about replacement ceramic resonators in 100% original Arduino.
People make it for projects with clock critical accuracy.
What you think, will it make sence to try to replace ceramic resonator to quartz crystal for OpenTheremin in 100% original Arduino Uno?
Something like this:

About the second topicaster's video, looks like it's distortion/limitting the signal. Looks like an amplifier input is overloaded.
BWT, what about output impedance of OpenTheremin? Can you remind me this? In the theory, it can make distore the sound in case of wrong pluging scheme.

PS Today, I updated the firmware to 3.1 so I have to learn to play once again a little

PPS Let's share videos and measurenments! It would be very interesting.


Posted: 1/4/2021 2:41:04 PM

Joined: 1/4/2021

with Arduino clone:

with Original Arduino:

The second is not ideal but more better. These old videos with 3.0 firmware.

Posted: 1/4/2021 4:42:47 PM

Joined: 1/4/2021

Helpful video about fuses and resonators:

Posted: 1/5/2021 8:42:30 AM

Joined: 1/4/2021

Hi All,

Of course, I can't say exactly on 100% that is real frequency jittering. I used grounded OpenTheremin with a static steel thing near the pitch antenna. Of cource, it can be a measurement error. However, there is a little jitter at the bottom of frequency range by the hear.

It would be great to see real measurenments from the clean studio (clean ground/clean power/ high quality audio devices)

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