Do I have a ground problem
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=32403
Printed Date: July 18, 2025 at 6:29 PM
Topic: Do I have a ground problem
Posted By: bcntx84
Subject: Do I have a ground problem
Date Posted: May 19, 2004 at 4:00 PM
I am running a Punch 3002 amp pushing 2 Punch P1 Stage 1 subs. My problem is a humming sound that gets worse when I begin to close the trunk, as soon as I begin to open the trunk the problem decreases dramatically. Could this be a ground problem? I have swapped RCA cables with no change. The vehicle is a 2000 mazda millenia. Any ideas as to what is causing this???
Replies:
Posted By: stevdart
Date Posted: May 19, 2004 at 6:41 PM
It could be a ground loop picking up the metal in the trunk lid, but I suspect it might have to do with the amp/subs. Closing the trunk lid closes up the air space, and acoustics are going to be different. So the humming may just not be as apparant with the trunk raised. First, disconnect battery negative before making any changes. Relocate the ground wire, make sure it is less than 2 feet long, gauge is same as power. Then verify the ohm load on the amp to make sure it is correct, that the speakers are wired properly. And reset the amp gain. Let us know what you find out.
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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
Posted By: bcntx84
Date Posted: May 19, 2004 at 8:03 PM
Relocated ground and tested ohm load, which was good at 4 ohms. With engine off sounds fine, start engine and slowly turn up gain and get humming again. Unfortunately, it doesn't seem to be acoustics when the trunk is lowered, because the speakers jump more...like there is a stronger signal when it is lowered..sounds weird, but definetly happens. I'm definetly at a loss at this point.. Possibly a bad RCA Signal converter???
Posted By: stevdart
Date Posted: May 19, 2004 at 8:58 PM
Well, you should set the gain with the engine off, so it can be at the correct setting and you're not turning it up randomly. After that, inspect the wiring at the engine, spark plug wires, etc. Look at it in pitch blackness with the engine running and see if there is light along any wires. Looking for a leak, so to speak.
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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
Posted By: shredder130
Date Posted: May 20, 2004 at 10:13 AM
i had the same problem, how long is your ground wire, mine was too long
Posted By: chevyman26
Date Posted: May 20, 2004 at 11:10 AM
I had a similar prob. in an s-10 when the doors were shut. Try running a smaller guage wire (about the size of your remote wire) from a screw on the casing of your hu to a screw on the casing of your amp. I used the stud where the mounting strap is supposed to be hooked up on the hu and a mounting screw on the amp to be sure the screw didn't pass by any critical electronics in the component. It fixed it. I didn't believe it would either, but I had nothing else to try, and an installer suggested this to me. Something to try, anyways! Good luck.
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You'd better get me out of this lord... or else you'll have me to deal with. -- Hunter S. Thompson "F.A.L.I.L.V."
Posted By: forbidden
Date Posted: May 20, 2004 at 1:18 PM
Did I read your second post correctly, have you got this amp running off of a LOC attached to the factory head unit?
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Posted By: bcntx84
Date Posted: May 20, 2004 at 8:18 PM
Forbidden...Yes I am running this AMP off of an LOC attached to the factory HU.
Posted By: forbidden
Date Posted: May 20, 2004 at 9:17 PM
What kind of LOC is it and does the LOC have gain controls or a brown / black wire that may need to be grounded. Some LOC devices have a separate ground wire in case of a scenario like this.
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Top Secret, I can tell you but then my wife will kill me.
Posted By: stevdart
Date Posted: May 20, 2004 at 9:21 PM
I didn't catch that like forbidden did, referring to the LOC as a RCA signal converter. It looks like a good possible way for interference to get into the signal. It's best to place the LOC close to the amp, instead of at the HU. Run twisted wire up to the head, or use shorter length and grab the signal at the rear speakers. Upgrade the LOC if you're not using a high quality type. Peripheral makes a good one, and I like this one. Did you find any electrical leaks at the engine? ------------- Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
Posted By: DYohn
Date Posted: May 21, 2004 at 8:26 AM
Ditto to the above comments, your problem is very likely in the LOC. Also, the comment you made about "slowly turning up the gain" and the humm begins has me worried. Why are you turning up the gain? ------------- Support the12volt.com
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