I have a cheap S/PDIF to RCA converter, powered by DC from micro USB connector. You can definitely hear distortions and background hum with some USB chargers.
But if you're spending $2500 on a headphone amp instead of $250 on a professional quality audio interface, or $1500 on jewel encrusted RCA cables instead of $30 on balanced XLR cables, or you think 192kHz sounds better than 48kHz because you have superhuman hearing and can somehow hear ultrasound, you're wasting your money and you have no idea what you're doing when it comes to audio quality.