Aright I have an MTX Thunder4244 which I use for my interior speakers. The problem is I hear really bad noise when the car is started, which I believe to be alternator whine, since there is a much lower noise when the car is off. The thing is when I tested my connections with a different amp, an Alpine, there was no sound, just small buzzing when the volume is all the way down which I figured was acceptable. I Then bought a ground loop isolator from radio shack to try on the MTX and it worked, no sound, however the bass doesn't hit and the music just doesn't sound good, seems to get a bit muffled. I tried it on the Alpine amp too and it does the same thing, the bass goes down significantly and volume seems to be lower as well. So it seems to get rid of the noise, but at a significant expense to sound quality. Any suggestions on whats going on? Could it just be a bad quality isolator? The one I bought had male connectors on both sides so I had to buy a coupler to connect the wired RCA's from the head unit. Could this be a problem as well? Thanks for any help.