I just installed Dom's unit and in dash dvd with audio going to aux. When I'm in any other mode but aux, the system sounds normal. When I pop in a dvd and switch to aux, i can hear the revving of my engine coming through the speakers. What did I do wrong, and how can I fix it? I have an 08 Tl-s

 

I had that happen in my 01 CL-S when I installed an aftermarket headunit and kept the factory amp. In my case, the aftermarket headunit was connecting with RCA into a harness that plugged into the factory wiring for the Acura. 1 thing you can do is buy Ground loop insulators like These for example. I bought mine from best buy. The problem is that those are often really cheap, I had to return about 4 of them till i found a set that works. It did remove about 99% of the sound. But about 4 months later, it again died, at that point I was fedup with it, so I just used the built in amp of the headunit and bypassed the factory amp.

 

Ended up grounding the Dom unit to the same point as the system. Works fine now.

I did some reading on those ground loop isolators, and they really are a last ditch effort. From what I researched, you should almost always be able to get rid of the sound via proper connections/wiring. All those things do is elimate high range frequencies, so you are losing audio, not fixing the problem.