Hello I had until recently extreme whistling in my car. Now I have simply connected the mass of the chinch to the housing of the radio and it is almost no longer heard. My blue point Paris RCM 104 has 2 preamp outputs (4 channel, front/rear out). I am currently using only the front out and have simply connected the mass of the chinch to the housing on the left rear out channel (which is not used). Is that enough, or do I have to do this for front AND rear out?? Or even on every channel (that would be 4 times in my case)?? At the moment, as I said, I only put the mass on one channel on the housing and there are still noises to hear (but much quieter than before!). Later I want to use the rear out as well. Then another question: What is exactly the urach of the whistle, if you get it away by connecting chinch mass and radio housing?? In my case, not only the whistle is annoying, but also the changer noises (change from tracks/CDs) and the noises when I turn the ignition key and and and and. As I said, all noises have become much quieter, but would be nice if you were completely gone Thanks gruss Pipeline