Popping and Humming noise from my audio system?
Ground Loop Isolators are nice, but if you want truly crystal clear sound, you will need to run a common ground. All electronics will need to be run close to the amp, as more than about 3 feet of ground wire from the amp can cause sound issues. When I ran my common ground, I connected my radio and satellite together, and ran one sigle ground wire to the backseat of my car, where the amp grounds are located. This will optimize the clarity of the sound coming through the speakers. For the popping sound in the speakers when the car is powered on or off, you need to see if the radio itself has a wire to power the remote connection on the amp. Most of the time, they will, and this is the wire you will use to turn on the amp itself, as it delays each item powering on and reduces the chance of popping in the speakers. DO NOT run the remote wire from the amp to the accessory wire of the radio, as this will cause the popping sound you are hearing. If the radio does not have an Amp Turn-on wire, then you may need to improvise by using an accessory wire in another location, but even this is may cause popping as well. The pop comes from multiple things turning on at once, so the Amp Turn-on wire delays the amps for just a moment, preventing the pops.