Grounding of electrical systems is an often forgotten yet important design consideration. Issues with proper grounding can be complicated, confusing, and downright frustrating to solve. So much so that engineers can spend their entire careers specializing in grounding and bonding. [Bsilvereagle] was running into just this sort of frustrating problem while attempting to send audio from a Nintendo Switch into a PC, and documented some of the ways he attempted to fix a common problem known as a ground loop.
Ground loops occur when there are multiple paths to ground, especially in wires carrying signals. The low impedance path creates oscillations and ringing which is especially problematic for audio. When sending the Switch audio into a computer a loop like this formed. [Bsilvereagle] set about solving the issue using an isolating transformer. It took a few revisions, but eventually they settled on a circuit which improved sound quality tremendously. With that out of the way, the task of mixing the Switch audio with sources from other devices could finally proceed unimpeded.
As an investigation into a nuisance problem, this project goes into quite a bit of depth about ground loops and carrying signals over various transforming devices. It’s a great read if you’ve ever been stumped by a mysterious noise in a project. If you’ve never heard of a ground loop before, take a look at this guide to we featured a few years ago.