Review on Enhanced Noise Filter B25N: BOSS Audio Systems Ground Loop Isolator for Optimal Car Audio Performance by John Butler

3 years ago I upgraded the head unit and speakers in my 1995 Mazda Miata. Since it's a convertible, I wanted to make sure I had enough power and volume to even hear the audiobook's words with the top down at 80 mph on California freeways. For the past 3 years I've had issues with the speakers "howling" when I had the amp gain set too high (which always kept the volume too low). I made sure both the stereo and amp were properly grounded, but couldn't fix the problem. I put this simple filter in and now the hum is completely gone. While this device may not be for everyone, it has worked brilliantly for me!