Sound when osc=none & flickering values & reboot


First, thank you for making such a nice project.

My new built Shruthi has some strange issues:

1/ Values are flickering on the screen, value of the pot #2 seems to be changing continuously, especially when turned all the way clockwise or so

2/ Press button 1 > osc1 properties, then press again > osc2 properties, then press again > freeze or instant reboot; sometimes I can access the osc mix page.

3/ There is sound, even if I set osc1 & osc2 to “none”, like a saw-wave maybe. I need to trigger a midi note to get this behaviour. The pitch doesn’t change with midi-note, but the frequency of the filter changes accordingly. The sound is correctly affected by cutoff & resonance parameters. So, I have a “ghost oscillator”, so to speak.

  • I have access to a DSO nano oscilloscope, I see 39.21 KHz on vca & osc pins of the digital board.
  • The volume of the sound is shaped by envelope2
  • If I remove the pole-selection jumper, the sound is still there but attenuated.
  • Voltage values are good

I don’t understand where is my mistake, could you please give me a direction ?



The 39kHz waveform you see on the signal output pins is normal – this is the PWM carrier.

Have you tried with another power supply? The whine must come from somewhere, and it might be in the power supply rails - which would explain the erratic behavior you observe.

Another test: connect the two boards with all cables except the “OSC” one. Is the whine still present? I’d like to know if it specifically comes from the MCU or is just present everywhere - possibly as power rail noise not being rejected.

Thank you (fast you are)

Problem solved, you were absolutly right about de power supply thing. I swapped it for antother one and it totally solved the issue.
Now, thanks to you, my Shruthi and I will be

Thanks again :slight_smile: