Ground Loop

[sicilianbulldog]

So I decided to install my own amp and headunit to save a few pennies. I have a ground loop and it's very annoying.

I went and bought a ground loop isolator and hooked it where the RCAs connect to the amp. It had a minnimal effect. However, I decided to try it where the same RCAs connect to the Head Unit, and it works significantly better. Obviously, this is a good piece of useful information.

The problem is, I don't know exactly what it tells me. Does it tell me that the issue is a poor ground from the head unit, or the amp? What would the next step be to completely remove this noise?

Thank you.

[Proven Guilty]

i always run my RCA's as far away from any type of power as possible. this includes running from the trunk (assuming you are going off the battery in the trunk to power your amp).

where is your ground connected? i have no issues running 3 class-A amps grounded to the battery in the trunk, and the ground wire is probably 2 feet total in length.

[sicilianbulldog]

The ground wire is only around two feet. I ground it on the verticle piece of metal near the spare wheel well.

I've been trying to read up on ground loop issues, and a lot of people solve it by re-grounding the head unit. I was just wondering if the difference in the location of the isolator tells me where the problem is. If it is the head unit, has anyone done their own ground on that, and if so, how did they do it?

[Proven Guilty]

1) Try moving the ground for your amp to the negative battery terminal. the reason its usually advised against, is because rarely do you have a stereo installation that allows you to ground to a battery in the trunk. Perhaps you're just not getting a clean ground off that tower, or it's too close to the power lines running through the car.

2) When you installed the head unit, did you use a comparable german wiring harness, like that of a BestBuy/Circuit city harness for VW/Mercedes/Audi? or did you simply cut and splice the existing wiring to work with the new head unit.

3) The stock head unit's ground should be sufficient, and the power to the head unit is fused. the only thing i recall about doing the mercedes head unit installation is that you typically have to reverse the 12v ignition power (red) with the 12v constant memory line (yellow) because they are reversed so that it goes yellow to red, and red to yellow.

4) which side of the car did you run your RCAs on for the head unit signal to reach the amp in the trunk?

[sicilianbulldog]

2: I did use a comparable wire harness, I think it was VW?

4: The RCAs are running on the driver's side.

[AirPost]

RCA's should be ran on the passenger's side. Driver side, as I understand, is where the power lines run. Someone correct me on this...

[pnsji]

easy test, try to connect another device to your amp, for example your ipod and then test to see if you have ground noise.

if you still have noise with your ipod -> the ground for the amp is weak.

if you don't have noise, then you need to re-run your rca to be away from any power lines.

[Logic]

ground loops are the hardest to figure out....if possible try substituting the headunit. if you have another deck try using it out side the car like with a power supply( or try wiring the deck you have with a different power and see if you notice any difference, does it go away..if it does then its a power or ground issue, if the noise still there its a rca issue...does the sound get louder with the lights on? do you hear amp pop?some time wiring the ground from the deck to the same area where you ground your amp eliminates one potential area DES

[Markland556]

In my many experiences with alot of cars that have had alternator noise it was either the head unit that had a bod ground. Best way to fix it is to ground the cage of the headunit to a main ground that are easy enough to find in our cars. Just use the nut that is on the back of most headunits. If not that then you ran too close to a power wire. Our cars have the alternator to battery wire running underneath the the drivers seat. I had my RCA's running along the plastic enclosure on the drivers side of the car without any problems. Another big one is the quality of the RCA's, if you get some super chepo ones they are alot more sensitive to outside interference.

[Logic]

as far as grounding the deck it would be better to isolate it but if you do ground it run the ground with the remote turn on lead and ground it at the amp ground, this way it takes any potential of a ground loop at the deck it self, even tho it see's ground threw the antenna , radio ground, and rca's too