Teensy 4.1 MQS noise.

[albnys]

I'm building a teensy 4.1 based synth and trying to use the MQS (medium quality sound) as the output.
The sound quality is good, but I get a constant background noise/buzz from the output, even when I'm not playing any sounds.
Doer anyone have an idea how to solve this?

[PaulStoffregen]

As a first troubleshooting step, try running Teensy from a battery or "floating" power supply. Make sure the USB cable is unplugged and no other wires apart from the MQS output connect it to any grounds on other things.

Ground loops are the most common problem, so try this first.

You could also have power supply noise feeding through to the output. That sort of problem is harder to test but easier to solve (by adding some circuitry).