X5 after market amp ground locations...lets hear it!
 

I am fighting a ground loop problem that is kicking my butt, I just can't get it fixed.

Where are you guys grounding your after-market amps? I have two hifonics amps in the trunk and I have the grounds both run below the spare tire location on the screw post (north of the battery). It seems as if there already was a black ground cable run to that location (factory).

Here is a picture of the install, I wish it sounded as good as it looked. It's been unplugged since November because I can't tolerate acceleration whine and I would rather listen to nothing at all.

http://www.chrisandkristy.com/pictures/genmay/subs3.jpg

Make certain you have a clean connection at your amp ground. The paint should be removed with a dremel or file to make certain you are getting good ground contact.

The noise may have less to do with your amplifier ground and more to do with your signal source. How are you getting the signal to the amps? I had horrible engine whine in my previous vehicle. I had to try a number of solutions before solving. Line drivers, different rca cables, different routing, etc. My amp ground was never the source.

From where your amps are located, I don't think grounding directly to the battery should be too hard of an option.

I always thought it was not a good idea to ground to the battery? I am grounded to a factory grounding stud just north of the battery. At least I think it's a factory ground because there was already a thick black ground cable connected to it and it's not painted. It's located below the spare tire (which I removed).

I will take pictures of it all tomorrow and post them, if anything maybe this could turn into a good thread for the archives. I will try to get as many detailed shots of the wiring as I can.

I spoke a little bit with El_dude on another forum and he suggested trying to move my SVEN 4 converter to a different location, if that doesn't work I will look into changing the grounding locations of the amps or cutting the factory grounding cable of the head unit and running it to a different location.

The negative battery cable is always the absolute best grounding point. The only reason that it isn't normally recommended is that in most cars, the battery is in the front, and this would mean an extremely long ground cable.

Brilliant thread, just in time because I installed my Stealthbox and Zapco i-250 amp this week and am getting very low frequency high excursion noise that looks like it will kill my woofer if I don't get rid of the noise. In my case, I'm using speaker level balanced differential inputs on the Zapco amp so no need for a line output converter. I also thought that balanced inputs would be better for noise rejection but I was wrong. Anybody else use speaker level balanced inputs on their Zapco or JL amps?

I wasn't sure at first where to ground the balanced input signal so I called Zapco and the guy said to ground to the amp chassis. He said that was the signal ground and was not the same as grounding to the car chassis. Our stock amps are not easily accessible, so I figured the top amp mounting bolt would be good enough as a amp chassis ground. The noise did get quieter, but is definitely still there. I can hear the cabin lights dim!

Does anyone know if the amp mounting bolts and tabs are conductive enough to be used as grounds? I'm not sure what the amp really looks like because I've never taken it completely out, so maybe there's a better spot to connect to the amp chassis? Better yet, is there a wire from the amp that is acting as a grounding wire that I can tap into? Some previous posts listing the amp (non DSP) pinouts are a little confusing.

I was going to try using a line output converter to see if that would get rid of the noise, but I can see here that people still have noise problems with LOCs.

The negative battery cable is probably the best grounding point if you're using non balanced inputs. I tried grounding my speaker level balanced differential Zapco amp to the same post that the negative battery cable goes to, and the noise was really bad. This was before I called Zapco and found out that the balanced signal needs to be grounded to the "signal ground" on the amp chassis.

Could you elaborate more on how you grounded your balanced inputs? I am using a peripheral electronics SVEN4 to convert my wire outputs to RCA. Do I still want to use the battery as ground for my amps? My SVEN4 unit (comparable to the OEM-1) is not grounded.

I used PAC-SNI-35 before the SVEN4, the quality was crap but there was no noise. Ever since I added the SVEN4 I introduced a ground loop. I am not sure if I had it all along and the better quality of the SVEN4 just makes it easier to hear or what. I had the PAC-SNI-35 connected to my factory outputs (removed stock amp) and used them to convert to RCA. My SVEN4 is currently setup like this, my ground loop doesn't exist if I plug my ipod directly into the amps and disconnect the head unit/sven4 rca's. I am thinking my problem is:

1. Ground location but from the looks of this thread I think I am ok
2. Factory head unit is using stock ground, I may change this
3. SVEN4 is picking up interference, I am in the process of extending my factory outputs and moving the SVEN4 far away from the trunk area.

Did you do the amps instal? It looks like a custom job. Maybe you already have thought of this, but will a audio shop not be able to fix it quickly? I don't know but I tried once to instal speakers in a my old Mercedes and it didn't work. Actually the amp caught fire in the car! I always take it to a pro. Good luck.

Yes, but keep in mind that I am not using a line output converter like the SVEN4 right now. My speaker level inputs are grounded to the bolt that goes through the holes circled in red below.
http://img147.imageshack.us/img147/6681/ampfg7.gif
By doing this, I am hoping to ground my signal to the amp chassis, but I'm not sure if that bolt is cutting it. For the record, with high level balanced inputs, this grounding location still gives me a good bit of noise, but it is not as bad as when I used to battery cable ground. I may try a line output converter down the line, but I'm trying to make this work first.