Ground Noise

Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=50416
Printed Date: July 13, 2025 at 1:35 PM

Topic: Ground Noise

Posted By: dholling13
Subject: Ground Noise
Date Posted: February 18, 2005 at 9:26 PM

Help!!!

I have a 1991 911 and I can't seem to get rid of the ground noise in my system. I moved the ground to a sanded down spot on the chasis and it didn't help. What could be some of the contributing factors? Thanks 12 volt members for your time.

Drew

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1991 PORSCHE 965
ECLIPSE 5303R
SONY XE-744
1 PAIR OF BOSTON PRO TWEETS
4 ROCKFORD POWER 5 1/4"
1 JBL GTI 1200
PUNCH 150 HD
ORION HCCA 225
PPI-FRX-456

0 TO 60 TO 0 IN UNDER 10 SECONDS...

Replies:

Posted By: geepherder
Date Posted: February 19, 2005 at 7:56 AM

Just looking at your signature, it looks like you have a lot of signal processing going on in this car. Try bypassing one component at a time, and see if that helps. Also try turning your gains down. Have you measured ground resistance?

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My ex once told me I have a perfect face for radio.

Posted By: dholling13
Date Posted: February 19, 2005 at 9:42 AM

Dear member,

In the past, all I have had to do was move the ground and the noise went away. Can you walk me thru step by step how to measure ground resistance? What tool will I need to purchase? Thanks so much for your time.

Drew

P.S. I changed rca's, and hooked the amps up to the Eclpise head unit and still got the noise.

Posted By: supradude
Date Posted: February 19, 2005 at 1:10 PM

Try hooking some speakers straight up to the HU. The noise may be coming in from it. It is best to start from the HU and work your way back. I have found in most cases the HU is the culprit. If so, ground it someplace else. Try unhooking the ground wire on the HU and grounding it to metal in the dash nearby.

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'85 Toy

Posted By: dholling13
Date Posted: February 19, 2005 at 1:19 PM

Dear Supradude,

The eclipse has 3 RCA outputs, that's it. There's no internal amp. I moved the ground for the radio. I think it has something to do with my wires? Is there some set of rca's out there which block ground noise; or are more resistant?

Drew

Posted By: DYohn
Date Posted: February 19, 2005 at 1:33 PM

Porsche makes a fine driving vehicle but not so good for audio installations. Their unibody construction creates very poor ground planes and ground loops like you describe are very common. You may want to ground the HU and the amps directly to the battery and see if this helps.

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Posted By: dholling13
Date Posted: February 19, 2005 at 1:39 PM

That's where I started, and the nose was worse! I think I am left with the forgon conclusion of; play it loud and you can't hear it! Thanks for all of your help guys...

Drew

Posted By: supradude
Date Posted: February 19, 2005 at 2:01 PM

I had a Corvette once and I had the same type of problem. I never was able to solve it. Do you have your power wires to your amps on the opposite side of the car from your rca's? There are several things that you can try, don't give up yet. Also, try putting a noise filter in the power wire to the HU. Yes, you can get high quality rca's that will help eliminate noise.

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'85 Toy

Posted By: dholling13
Date Posted: February 19, 2005 at 2:35 PM

I forgot to mention that I had purchased monster cable's "claimed" rca ground noise eliminating adapter to see if that would help... Couldn't return it fast enough.

The Porsche has the battery in the front trunk. I have the amps and the crossover in this area too. Have I mentioned there is no room in the trunk?

The RCA's are run from the eq under the dash, thru a hole in the firewall, and down the right front fender, but they don't come near any powe wires. The power and ground are run along the front and left of the car's trunk. The remote is fed thru this same hole in the firewall, and is then routed along the cowl area and down the right side. I have a ground and power distribution block on the opposite side of the trunk from rca's.

However the speaker wire does come to same area as the power because the hcca amp has all of its inputs, except rca's, on the side of the amp to where the power is hooked in.

The PPI x-over also has the outputs to each amp on the same side adjacent to the front area where the power distribution is located. The approximate distance would be 8 inches away... What are the best RCA's out there? Maybe the noise is being picked up thru the rca's that are located on the ppi's outputs (front 8 inches away from the power distribution block).

Drew

Posted By: geepherder
Date Posted: February 19, 2005 at 9:09 PM

Drew,

to measure ground resistance, you'll need to get a multimeter. Set your meter on resistance, and put one probe at the negative battery terminal, and the other at the grounding spot. In many cases, these don't reach, so use a jumper. Measure the resistance of your jumper wire first, so you can subtract this from your reading to get your ground resistance.

Dyohn is definitely right. Ground loops can be tricky in these German cars. After reading your noisy results from grounding at the battery, I believe you just need to ground your head unit and amp at the same spot. Do this, and I think your noise will go away.

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My ex once told me I have a perfect face for radio.

Posted By: dholling13
Date Posted: February 20, 2005 at 8:59 AM

Dear Geepherder,

Measuring the resistance will be a piece of cake then, the battery and my ground are less then 3 feet apart. Thanks...

Now the common ground theory will be another story. Nearly all of the grommets leading into the firewall of my car are blocked by a 21 gallon gas tank. I ran all of my rca's around this, and to be honest I would have no clue how to run a new ground wire away from this area. I have to keep this new ground wire seperate from my rca's right?

Thanks 12volters for all of your help. I will get out to purchase a multi-meter today or tomrrow; then post my results!

Drew

Posted By: dholling13
Date Posted: February 20, 2005 at 9:21 AM

Dear Members,

I measured the ground resistance using a multi meter. At the RX-1 setting it measured just less then 3 OHM's. If the ground must be a 1/2 or less, am I really high over the limit? I already moved the ground from the battery terminal, should I look to cut back on the noise from someplace else? Thanks again members for all of your time on this...

Drew

Posted By: DYohn
Date Posted: February 20, 2005 at 9:33 AM

3 ohms to ground is definately a candidate for noise. ALL your equipment should be grounded at less than 1 ohm to the battery negative terminal. And remember that all the current used by the equipment runs through the ground wire, so it must be of sufficient gage to handle the loads.

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Posted By: geepherder
Date Posted: February 20, 2005 at 7:12 PM

Yeah, what DYohn said. I agree completely.

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My ex once told me I have a perfect face for radio.

Posted By: dholling13
Date Posted: February 20, 2005 at 7:50 PM

I do have a 4 gauge ground connected to a stinger distribution block; then there's 8 gauge running from the block to all 3 components. I definitely think the wire is a sufficient ground for my system. So I will pull everything out and work on lowering the ground resistance. Thanks again 12 volters for all of your helpfull posts...

Drew

Posted By: dholling13
Date Posted: February 21, 2005 at 4:43 PM

Update on the ground resistance.

Every single area in which I attempted to move the ground to, of the Porsche's chasis, has a resistance of 2 1/2 ohm's grounded to the battery. Is there anything else I can do to try and clean the noise up?

Thanks forum for all of your help on this...

Drew

Posted By: forbidden
Date Posted: February 21, 2005 at 6:19 PM

I have encountered a noisy 5303 and 5303R before and it was an internal grounding issue. Is this a new install into the Porsche or did it just occur? Keep working on the grounding issues to get that return resistance as low as possible. It may be necessary to upgrade the factory battery to chassis ground to improve things. If you have a cd player that you can borrow from someone, that is the next place that I would start, eliminate the source as being the issue. Try unplugging the antenna from the cd player as well to see if the noise goes away. Unmount the amplifiers and place on some cardboard to test as well, a ground loop can be as simple as the casing of the amp going to ground through the mounting screw.

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Top Secret, I can tell you but then my wife will kill me.

Posted By: DYohn
Date Posted: February 21, 2005 at 6:31 PM

And also remember that the alternator grounds to the chassis through the engine, and there is an engine ground strap. Since in your car the engine is in the rear and the battery is in the front, there could be a high resistance between the engine and the battery negative, which will cause engine noise everywhere in the chassis no matter what you do. Check the engine ground strap, make sure it is secure, clean and not corroded or rusted where it connects. And check the engine ground strp to battery resistance. If THIS is greater than an ohm or two, you may want to consider running a cable the length of the car and connecting it between the battery and the same place the engine ground strap connects.

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Posted By: dholling13
Date Posted: February 21, 2005 at 6:33 PM

Dear Forbidden,

The 5303R was fixed under factory warranty 2 years ago... But the funny thing is, the ground noise is a lot less noticable when you play the radio... The amps are mounted on MDF which is elevated by the spare tire... This is a new install...

Drew

Posted By: dholling13
Date Posted: February 21, 2005 at 6:45 PM

Can I reground the alternator solely by itself somewhere in the engine compartment, like to the strut tower? Would that help?

Drew

Posted By: forbidden
Date Posted: February 21, 2005 at 7:18 PM

That may help but sadly I think the ol Eclipse needs some love. A difference in noise between cd and tuner points directly at the head unit.

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Top Secret, I can tell you but then my wife will kill me.

Posted By: geepherder
Date Posted: February 21, 2005 at 9:35 PM

Rob may be on to something. Does turning the gains down on the amp help some? I'm thinking the signal may not be as strong on radio as on cd. My car is like this, so while I have distortion at about 85% volume on cd, I can turn it up past that on radio sometimes without noise.

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My ex once told me I have a perfect face for radio.

Posted By: dholling13
Date Posted: February 21, 2005 at 9:42 PM

I can turn it up in cd mode, and the noise goes away, it doesn't intensify with an increase in volume. But when the radio is on, at the same volume as the cd player, the noise isn't that apparent. Interesting...

If I do decide to replace my *! Eclipse; what are some nice in dash units that come with an xm tuner built in? Thanks again...

Drew

Posted By: forbidden
Date Posted: February 22, 2005 at 12:01 PM

Keep to a nice cd player like the Eclipse still. They have improved substantially from the 5303R (if one could). There are all sorts of sales on right now clearing the old stock out. Look for at the least a CD5444 (no sirius or XM but does have a aux input), or the new CD5415 or above. All the new models except the entry level model support Sirius.

www.eclipse-web.com

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Top Secret, I can tell you but then my wife will kill me.