We want to keep the signal path as simple as possible to minimize the distortion that's added to it.
Unfortunately, sometimes you have little choice in the matter. For example, when connecting (audio) equipment components powered by different grounded circuits (e.g., your Mac and your stereo) there is the distinct possibility of introducing hum because of a
ground loop. That's a particularly annoying problem when you’re recording, but it can be eliminated by inserting a ground loop isolator into the signal line. Such ‘inline’ isolators are available at places like
(Radio)Shack.
