Ground noise. Can't find where to fix it.

[smm1099]

I have a 2000 explorer XLT. It has a Pioneer DEH-P2900 CD deck and a Pioneer TS-W3001D4 Champion Series Pro subwoofer powered by a 950w Planet Audio amp. Right now I'm picking up some slight ground noise. It's pissing me off cause I've done basically everything to fix it.

So far I've changed remote wires, remote wire connections (went from cd player to fuse box), ran the remote wire in a different spot, changed out power wire (found that the fuse had melted and got really hopeful), changed the fuse, changed the RCA wires twice, ran the RCA wires in a different spot, separated the remote and RCA wires, put them next to each other, moved ground locations, changed ground wires, and I even tried one of those ground loop suppressors. Also, all fuses are good.

I can't figure out what else to do. I even thought it could've been a faulty amp, but it's not cause I put it in my buddy's car (with his wiring) and it worked just fine.

Any help will be much appreciated.

 

[rhauf]

It's probably a ground loop. ground all parts of the system in the same spot and see if it goes away.

a ground loop is caused when there is a slight voltage difference between where (say amp) and (head unit) or whatever are grounded, causing a current flow through the shielding of the signal wire, which gives you a nasty hum. (pitch would change with RPM in a car)

 

[Beastb15]

It's probably a ground loop. ground all parts of the system in the same spot and see if it goes away.

a ground loop is caused when there is a slight voltage difference between where (say amp) and (head unit) or whatever are grounded, causing a current flow through the shielding of the signal wire, which gives you a nasty hum. (pitch would change with RPM in a car)

Yep. If you have a multimeter, set it to check resistance. Test the resistance to where you are grounding your amps vs. where the head unit is grounded.

 

[smm1099]

So basically run a wire from the ground on my head unit to where I have the amp grounded?

And it does change with the RPMs so it's definitely a ground loop.

 

[Beastb15]

So basically run a wire from the ground on my head unit to where I have the amp grounded?

And it does change with the RPMs so it's definitely a ground loop.

That is probably your best shot unless you can find 2 separate areas in the vehicle with a similar resistance

 

[smm1099]

Well I just ran a ground wire from my head unit to where the amp is grounded. It sounds alot better but it's still slightly there.

 

[Beastb15]

Check these:

- Are your speaker wires running along side the power wire?
- Are your RCAs running along side ANY power wire?
- If you are experiencing the noise in your component set, are your crossovers really close together?

 

[smm1099]

I originally figured it might've been the RCA's so I re-ran them down the middle of the interior, by themselves of course (I also replaced them in the process). The Amp is mounted on the back of my backseat, the ground is directly underneath the seat, and the power wire is ran down opposite side, so the speaker wires aren't near those or any other wire. And the noise is only being picked up by the subwoofer so it can't be within the crossovers.

This is why it's really annoying me. I've tried everything I can think of.

 

[Beastb15]

I originally figured it might've been the RCA's so I re-ran them down the middle of the interior, by themselves of course (I also replaced them in the process). The Amp is mounted on the back of my backseat, the ground is directly underneath the seat, and the power wire is ran down opposite side, so the speaker wires aren't near those or any other wire. And the noise is only being picked up by the subwoofer so it can't be within the crossovers.

This is why it's really annoying me. I've tried everything I can think of.

2 more things you can check.

- Trying turning down the gains on your amp slightly to see if this reduces any floor noise.
- Hook the HU's power wire directly to the battery and circumvent the ignition. See if it's not being induced through the ignition or HU's power wire

 

[smm1099]

Pretty sure it's not the HU's fault cause when the HU is off and the car is on, it still does it. I'll try the gain switches though.

 

[Beastb15]

Pretty sure it's not the HU's fault cause when the HU is off and the car is on, it still does it. I'll try the gain switches though.

well when the radio is off the remote wire should lose voltage. If the amp is off there is nothing to amplify the alternator whine

 

[BrianDye]

I had the same problem, although when I changed songs, or stations it was a HUGE ass ear pounding BUMP when I pressed a button, and when I put a CD in I could hear it like loading through the subs, so I went to Walmart (or meijers both have them) and got this little thing called a ground loop isolator or something, its a small black box with a set of RCA inputs, and a set of outputs. I plugged the outputs into the amp, and the inputs come from the headunits sub RCA wires, and it cleared it right up, now theres no interference, I think theyre like 10-15$

 

[toypaseo]

Maybe try grounding to factory grounds...

 

[smm1099]

@BeastB15:
I don't have the remote wire for the amp hooked up to the remote wire on the HU (accidentally pulled the connection out of the harness), instead it's linked into the fusebox on the CD player fuse. Thus why it hums with the HU off.

@ BrianDye:
I tried one of the Ground loop isolators, I think it was made by scosche. It ended up just taking away all sound. I tried it both ways just in case I messed it up. I returned it since I thought it didn't do anything.

@ Toypaseo:
I have it grounded to a bolt that links directly to the frame so I figured that would have been a good spot to ground.

 

[rhauf]

Well I just ran a ground wire from my head unit to where the amp is grounded. It sounds alot better but it's still slightly there.

No, thats not exactly what i meant.. i mean, ground your head unit and amp in the same place, dont run a wire connecting the two grounding places together.. completely eliminate all but one of the grounding points, and run all the ground wires back to that point

as for using an ohm-meter, that wont tell you anything, the resistance may be a fraction of an ohm but still cause a ton of hum.. you could test voltage between the 2 ground points (on the AC voltage setting) but this is kind of a waste of time... just bring all the equipment back to the exact same grounding point (also if your antenna is grounded, you may want to run a wire from the antenna cables shielding to that ground point as well)

(it also probably wouldn't hurt to source the +12v to the amp and head unit from the same place as well)

 

[Beastb15]

as for using an ohm-meter, that wont tell you anything, the resistance may be a fraction of an ohm but still cause a ton of hum.. you could test voltage between the 2 ground points (on the AC voltage setting) but this is kind of a waste of time...

Actually, that is wrong.

I was completely correct in what I said, however, I didn't provide enough information. It doesn't matter how much resistance either grounding point has (the HU and the amps). However, they need to be similar. If one spot has a considerable amount of resistance compared to the other, you will probably have alternator whine. You can use a multimeter to test each grounding point to make sure the resistance in each spot is similar.

 

[smm1099]

I didn't run a wire connecting the ground points. I disconnected the HU from it's ground location. Then I ran a length of wire from the ground wire on the HU's wiring harness to the point where the amp is grounded. So they are grounded in the same place.

 

[rhauf]

I didn't run a wire connecting the ground points. I disconnected the HU from it's ground location. Then I ran a length of wire from the ground wire on the HU's wiring harness to the point where the amp is grounded. So they are grounded in the same place.

just to rule out a possible problem with grounding through the antenna, try disconnecting the antenna and see if the hum goes away.

when you turn headlights and stuff on and off, does it make your speakers thump?

 

[smm1099]

When you say disconnect the antenna, do you mean disconnect the remote/antenna wire? Wouldn't that render the amp useless by not being able to turn it on?

As for the other question, no it doesn't thump when I turn the lights on.

 

[rhauf]

When you say disconnect the antenna, do you mean disconnect the remote/antenna wire? Wouldn't that render the amp useless by not being able to turn it on?

As for the other question, no it doesn't thump when I turn the lights on.

No, i meant the radio antenna that is sticking out of your fender. there is a coax cable that comes back from it and plugs into your head unit, unplug that cable as an experiment to see if the hum stops.