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

Pros:+ Does what it says on the tin - reduces noise to a point where you can't hear it unless you crank the amp/out volume almost all the way up ( which you'll probably never get to, since at that point you'll likely either be corrupting your signal or damaging your equipment). It also does a good job of cleaning the built-in sound card in a computer. In combination with ferrite chokes the result was slightly better than with a filter. Cons: - Glossy plastic case. While I was hoping for a metal body based on the picture, given the price I won't complain too much about it. This filter changes your sound profile slightly. (See below) Other thoughts: * The mids sound a bit set back (making the soundstage more compressed) and there's some bass rolloff. Here, too, the change is quite small, so it can be compensated for by the EQ curve without major losses in sound quality. In my application, I use studio monitor headphones, so this effect might also be less noticeable in a speaker setup. It does solve the problem, though, and for an $8 solution, it does a darn good job for the price. This is me before the purchase. *Although the diagram on the back of the box shows the jacks connected to the source, I have tried it in both orientations in my setup and its impact has not diminished and the change in sound profile was no different between the two configurations. I'm pretty sure this jack configuration is just for the convenience of a car setup as head units usually have RCA jacks on the back and amps are connected with MM RCA cables.