If you download Visual Analyzer from here,
and connect a microphone to your PC sound card, you can use the Spectrum Analyzer to see what frequency the hum is at.
If it's ~490 Hz, that is likely the PWM. If it's something else, find the culprit.
If you download Visual Analyzer from here,
and connect a microphone to your PC sound card, you can use the Spectrum Analyzer to see what frequency the hum is at.
If it's ~490 Hz, that is likely the PWM. If it's something else, find the culprit.