I suspect my title is cryptically obtuse so here's the bigger story. I need to sense when a particular audio jack has been plugged into but I don't have an isolated switch to use. The jack has only "shunting" switches that connect to the pins that actually carry the audio signal. I think I can trigger a GPIO pin using some load resistors that won't affect my incoming signals adversely but I'm curious about the possibility of this GPIO pin contributing noise or other artifacts if it is actually connected to the incoming signal path. Any thoughts or suggestions?