"This passive system," Mikey wrote in his column, "is designed to greatly reduce a broad range of high-frequency noise picked up by and created by electronics, and also noise that gets into connecting cables via radiation and into components from the AC mains. In these Wi-Fi/Bluetooth days, there can be a lot of noise." As you might expect based on the name, the Ground Control boxes concern themselves with noise on the signal ground. They do that by utilizing a component's unused inputs. Figuring out how best to utilize the various types of connecting cables required some creativity and sounded like fun.