Zepo.

If you experience a high pitched noise that is parallel with your acceleration, make sure you check the following common problems before creating a new thread.

1)Proper Ground - This is the main cause of any feedback. This is because the difference in resistance between the HU and amp. In the RX-8 there is no perfect ground in the trunk. I've had really good luck running a ground wire back the the engine bay and grounding it there. Remember if you do run a wire to the front, make sure it is a bigger gauge then the power wire and to sand off any paint or primer from the area of contact.

2)Running RCA's - When running your RCA cables be sure to run them on the opposite side of the car then the power supply. The RCA's can pick up signal from surrounding wires therefore creating feedback.

3)Grounding LOC - Be sure to properly ground your line output converter. Running a wire to the side of the car is the best idea.

4)Using a Ground Loop Isolator - If everything else fails, you can purchase a ground loop isolator. A GLI plugs into the RCA's and clears the current from the line, but you sacrifice high pitched tones.

*If anyone has anything else to add or finds an error in my post please reply and i will update this post.

Quinchu

Actually, the Line-level converter doesn't need to be grounded.. I do about 3-4 of those a day, and never once have I used the grounds if your other wires are connected / run right. And the GLI will still give you high tones if its placed closest to the amp, and not next to the GLI (Or head unit).

WikkedOne

I would like to add that having a cheapy walmart LOC is much more likely to induce noise than a higher quality one. also - the more you have to turn your amps up the louder it will be - so if you can get a higher pre-amp signal (either by getting a HU that has higher voltage pre outs or turning your LOC levels up and the amp gains down, you will have much less noise.

and on the same note as a quality LOC you should ALWAYS solder and shrink wrap any wires in your system. never rely on T-splice or krimp connectors to give you any good quality. Every step the music has to take from your source to your speakers is going to degrade the music and possible induce noise. so have as few, and as high quality, steps as possible.

Zepo.

Well, for some reason it gave me feedback until i tried grounding it. So just passing on my results.