Ground Loop Fun!

8640 Views 6 Replies 4 Participants Last post by rockinridgeline, Apr 28, 2009

Ryebread

Discussion Starter · Apr 28, 2009 (Edited)

So, I found out I had a ground loop yesterday! Awesome!

I plugged my iPod into my new charger with a line-out, and heard the popping/revving engine bliss.

This also was the night that I decided to hook up my amplifier to test it out. I heard no ground loop coming through my components. I did not check to see if the ground loop still existed, like a *******. I was told the JL 300/2 has a built in filter - perhaps that's why. Shrug.

I then unhooked the ampifier and unfused the 1/0, back to it's original setup. Ground loop was there this morning driving to work.

So, here is my current situtation:

1/0 gauge wire at the battery, unfused, going to the back of my car to a distro block, one 4 gauge coming out of it (hooked to nothing)

1/0 gauge wire to a bolt in my car, ground down to shiny metal, going to a distro block, one 4 gauge wire coming out of it (hooked to nothing).

So, no wires are currently "live" right now.

I don't want to do anything potentially stupid to try to fix this, but I have a feelilng like my problem is obvious (such as, I have to hook my UNFUSED powerline to my ground distro temporarily until I permanently put my amplifier in).

Just looking for better insight than my own. Thanks.

EDDDDITTT:

When I say UNFUSED I meant that the line is fused, but I removed the fuse for the time being to keep the line from being live.

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VP Electricity

· #2 · Apr 28, 2009

Since I haven't been following any threads describing your build, I'm not clear on of what your system consists - or what your last suggestion actually means

I hear a lot of talk about ground loop "filters". No such thing. There are ground loop isolators and they can do a decent job, and many amps have a good degree of isolation onboard. (It should be noted that most autosound ground-loop isolators have souch a lousy frequency response that if you hooked one up to an RTA, you would throw it in the river.)

An iPod on a charger in a car often is a noise source. Usually that is a ground loop - but it can also be a charger without power filtering! Cig lighter sockets are famous for having LOUSY grounds, btw.

So I don't know if our iPod is the preamp (driving the amp directly) or is connected to a HU or what, but I would improve the cig lighter ground first, and I MIGHT put a powerline filter in series with the cig lighter power wire (nned a high-amperage one if it ever gets used for a real lighter : )

If the iPod is the preamp, how high is the JL gain? Remember, all systems have noise, it's just inaudible in the good systems

If the iPod is connected to the HU, I guess I would take the cig lighter ground and re-route it to the HU ground (the HU ground in my installs would have already been run to the amp ground).

BTW, if I recall correctly, the iPod preamp out can't really drive a Jensen Iso-Link well (best ground-look isolator on the market). Markertek also has a cheaper one that tests pretty well. (Rolls?)

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rockinridgeline

· #3 · Apr 28, 2009

So can you run the output of the ipod into your HU without having it plugged into the charger? That might help you narrow it down a little.

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Ryebread

Discussion Starter · #4 · Apr 28, 2009

VP Electricity said:
Since I haven't been following any threads describing your build, I'm not clear on of what your system consists - or what your last suggestion actually means

I hear a lot of talk about ground loop "filters". No such thing. There are ground loop isolators and they can do a decent job, and many amps have a good degree of isolation onboard. (It should be noted that most autosound ground-loop isolators have souch a lousy frequency response that if you hooked one up to an RTA, you would throw it in the river.)

An iPod on a charger in a car often is a noise source. Usually that is a ground loop - but it can also be a charger without power filtering! Cig lighter sockets are famous for having LOUSY grounds, btw.

So I don't know if our iPod is the preamp (driving the amp directly) or is connected to a HU or what, but I would improve the cig lighter ground first, and I MIGHT put a powerline filter in series with the cig lighter power wire (nned a high-amperage one if it ever gets used for a real lighter : )

If the iPod is the preamp, how high is the JL gain? Remember, all systems have noise, it's just inaudible in the good systems

If the iPod is connected to the HU, I guess I would take the cig lighter ground and re-route it to the HU ground (the HU ground in my installs would have already been run to the amp ground).

BTW, if I recall correctly, the iPod preamp out can't really drive a Jensen Iso-Link well (best ground-look isolator on the market). Markertek also has a cheaper one that tests pretty well. (Rolls?)

Let me clarify my current setup:

- An Eclipse CD8443 Head unit
- Wires to hook up an Amplifier

That's it.

To further specify my wiring setup, I have a wire from the battery to my spare tire, and a 1-2 foot ground wire hooked to a bolt in my wheel well

Other than that, everything is stock. No amps, no alternate speakers, nothing. I'm going to be putting in all of my stuff this summer.

I've taken the fuse out of the power wire, to keep it from being a live wire.

So essentially, there's just a wire chilling under the hood, routed through my car, and ending in the wheel well.

I'm curious if just having this wire hanging out under the hood can cause a ground loop, since it's not hooked to anything, and if it's safe to link my loose power wire to the ground cable for the time being (or if there is a 0% chance of that doing anything at all).

Like you said, it may just be that the cigarette lighter outlets have ****ty grounds, and I have to re-ground it (to my head unit ground preferably).

If my iPod is unhooked from the charger, the ground loop is gone (obviously).

So, is it OK to "ground" my wire that's hanging out under the hood with the fuse taken out? Would that... COULD that even be a problem?

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Ryebread

Discussion Starter · #5 · Apr 28, 2009

OK - So I did a bit more research on a forum specific to my car (Mazda 3) and pretty much ALL Mazda 3's have this issue. There's thread after thread of people reviewing ground loop "isolators" (I put it in quotes) and whatnot. Everyone says to ground the cigarette lighter to my stereo's ground as being the best fix - I think I'll go this route.

So, I locate the ground wire, and splice it into my wiring harness ground for my stereo - correct?

Just for the sake of asking, if I were to plug in my cigarette lighter after doing this fix-up, would bad things happen? That's a lot of current.

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VF84

· #6 · Apr 28, 2009

Ryebread said:
I'm curious if just having this wire hanging out under the hood can cause a ground loop, since it's not hooked to anything, and if it's safe to link my loose power wire to the ground cable for the time being (or if there is a 0% chance of that doing anything at all).

i doubt it, if u took out the fuse, there's nothing running thru it. don't link the power to the ground. if then u forget and put the fuse in by accident, u'll probably short it (someone double check with me

). just leave them be. if u want, maybe insulate the open end of the power wire with some tape or something.

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rockinridgeline

· #7 · Apr 28, 2009

The power wire running through your car has nothing to do with the ground problem. You can forget about that as a source.

VP's suggestion of grounding the lighter's ground to the radio is a good one. There is potential, however, that the radio ground is not that great. Since you are going to have it apart, if you really want to make sure it is all good, ground both the radio and the lighter to metal that has had any paint or coating removed. make sure you get a good tight connection. This would eliminate if there is an issue with the factory radio ground, which could be a problem if you are seeing this on forums. As another poster suggested, you absolutely do NOT want to ground the power wire from the battery under any circumstance. It just creates the potential to short it later.

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