Hello evryone !
I'm facing some issues with my Open Theremin V3 build. As you can hear, there's a whining sound when I lower my hand near the volume antenna at a specific height — very close to touching it.
In the attached audio file, I tried to demonstrate this by holding my hand steady near the pitch antenna while only modulating the volume.
I should mention that I modified the V3 board by adding an additional 33pF capacitor to C7. Without this modification, the theremin wouldn't function properly and couldn't even complete the calibration process.
Could this added capacitor be causing the issue, or should I be looking elsewhere?
Thanks in advance for your help.
I'm using an arduino R3 (looks legit), the box is made out of metal and is connected to ground (The defect exists even outside of that box). I also have been running the device on a grounded 5v supply.
Antenna calibration output with added cap.:
PITCH CALIBRATION
Arudino Freq: 15985765.00
Pitch Set Frequency: 499745
Frequency tuning range: 492645 to 531544
DAC value L: 0 Freq L: -7072
DAC value H: 4095 Freq H: 31836
DAC value L: 4095 Freq L: 31845
DAC value H: 745 Freq H: -4207
DAC value L: 745 Freq L: -4211
DAC value H: 1135 Freq H: -1128
DAC value L: 1135 Freq L: -1124
DAC value H: 1277 Freq H: 946
DAC value L: 1277 Freq L: 947
DAC value H: 1213 Freq H: -52
DAC value L: 1213 Freq L: -45
DAC value H: 1216 Freq H: 7
DAC value L: 1216 Freq L: 5
DAC value H: 1216 Freq H: 7
VOLUME CALIBRATION
Volume Set Frequency: 460475
Frequency tuning range: 457620 to 487456
DAC value L: 0 Freq L: -2794
DAC value H: 4095 Freq H: 26867
DAC value L: 4095 Freq L: 26935
DAC value H: 386 Freq H: -1855
DAC value L: 386 Freq L: -1826
DAC value H: 624 Freq H: -1162
DAC value L: 624 Freq L: -1172
DAC value H: 1040 Freq H: -81
DAC value L: 1040 Freq L: -60
DAC value H: 1070 Freq H: 28
DAC value L: 1070 Freq L: 25
DAC value H: 1061 Freq H: -28
DAC value L: 1061 Freq L: -13
DAC value H: 1065 Freq H: 7
DAC value L: 1065 Freq L: 24
DAC value H: 1064 Freq H: 36
CALIBRATION COMPLETED