It's possible -- depending on the setup -- to get a bit of LED scanning noise when using a lot of overdrive/distortion. This is fairly common with tuners and nothing unique to the PolyTune. However, there are a couple of possible solutions:
- Don't use overdrive/distortion while tuning;
- Use an isolated output from your power supply power supply to PolyTune (and ONLY the PolyTune);
- Use a battery to power the PolyTune instead of a power supply.