My brand new car's factory sound system sounded terrible so I decided to upgrade it. I had to keep my factory radio because the car's functions depend on the screen/radio of the car. I installed a JL audio 300/4v2 along with Focal components and after I was done installing everything, there was a tremendously loud static noise coming from the speakers, even with the volume all the way down. When I would rev up the engine, it would make a whistling, whining noise from the alternator. I spent 2 days trouble shooting the problem. Separating wires, re-grounding, running new wires, adjusting gains, etc. and none of that worked. I saw this LOC from NVX and decided to give it a try since it claimed to have a digital noise filter feature. Man, as soon as I installed I was blown away. That annoying noise was GONE! The music sounds crystal clear now. I purchased that particular set up because I wanted an SQ sound system and now it delivers that very clean music with absolutely NO distorting noise. I was stressed out for 2 days wondering how to fix it. If you are in the same situation, buy this LOC. It will end your problems with all that unwanted noise. Forget those "solutions" people talk about all over the internet about re-grounding, ground isolation, and all that junk. This LOC solved it for me. It was so easy to install, it has adjustable gains, and feels very sturdy. Even if you turn the gains all the way up on the LOC, you will still hear no unwanted noise.