ok i thought i got lucky when i installed my dvd headunit because amazingly there was no hum. anyway i get about half way home from the shop today and guess what i cant hear my damn dvd because of ground loop noise. I dont know where it came from or how it started but i gave it a temporary fix by grounding out the rca cables to the chassis. I guess when I go into work tomorrow I'll have to pick up a GLI, thank god i work at a tuning shop and get all items at cost. oh and if anyone wants a kenwood excelon mask headunit just PM i have my old one for sale. thanks for listening to me vent. oh and if anyone else gets this problem its and easy fix just get a GLI from your local audio store and plug that into the rca's. Problem solved

 

Im looking to buy the 969 :/

 

GLI??
What is that, how much and where can I get one??

I have the same ground loop problem.. it's a real pain trying to listen to music when you can hear your alternator spooling up in the background

 

alternator whine is a different problem than ground loop. ground loop introduces a distinct hum or buzz. this is solved by upgrading grounds, making sure you have clean contacts, and grounding things at the same point, also keeping grounds as short as possible.

alternator whine is caused by power line transmission interfering with the signal in your speaker wire. make sure that rcas are on opposite sides of the car as power wire, and that your amp is grounded to a clean spot on the chassis, and any point that rca and power wire crosses it is at 90 degrees.

 

a gli is a ground loop isolator. this allows the signal from your rca's to be filtered out to reduce noise caused by an inductive ground loop. it seems that these are a running problem with the eclipse indash dvds as we have had many people come in with this problem and its only on this unit. we have contacted eclipse and they just say that they have never had this problem and it must be our installs, however we have been doing this for the past 10 years and have never had this problem with any other unit. so if you get an eclipse dvd unit watch out you may get a ground loop.

 

to understand ground loops, you have to understand what causes them, then maybe you can fix them.

a ground loop is caused when you have a circuit that is grounded in two different places. usually these places have a similiar enough voltage potential that they act as one ground. but if the potential is different from one ground point to the other, even a few millivolts, then instead of a zero volt reference the circuit now has a few millivolts as the ground. this causes the phenomenon known as ground loop, which basically allows interference to be introduced much easier into the circuit.

in order to fix this, you can ground your circuit at the same point. this isn't always feasable. some things you can do to help reduce ground loop interference:

make sure your grounding contact is very clean. sand the paint away exposing the bare metal of the chassis.

limit the length of your ground wire. if possible, it should be no more than 18"

make sure your ground wire is at least the same gauge as your power wire. it's better to match it so they have the same resistance, so if you get thicker ground wire it might be a good idea to get thicker power wire too. check a standard table to find out what gauge wire you should use to carry a particular current at a certain distance.