new amp. new ground loop
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=29134
Printed Date: May 10, 2025 at 3:16 PM
Topic: new amp. new ground loop
Posted By: pickandpray
Subject: new amp. new ground loop
Date Posted: March 27, 2004 at 9:12 PM
I replaced what I thought was a dying kenwood amp with a us acoustics amp and am getting all kinds of ground loop noises.
Got rid of the kenwood before I thought about using it for swapping to check for stuff. Damn!
Anyway, does using noisy power to the head unit contribute to ground loop noises? I think the us acoustics is a bit more sensative to the noise than the kenwood was.
Waiting for some parts to reroute the head unit power to the battery. It's currently going to the cig lighter.
thanks
Chi
Replies:
Posted By: Clean Install
Date Posted: March 27, 2004 at 9:27 PM
where to begin....humm. how are your grounds...what did you ground them too? what size power and ground wire are you using? what size amps? how did you run your wires? why did you choose the cig lighter for a power wire? how is your HU grounded? ------------- If we learn from each success and
each failure, then we can improve ourselves
Posted By: pickandpray
Date Posted: March 27, 2004 at 10:43 PM
I've been searching for ground loop stuff on the net and know that my grounds are not ideal. I'll fix them when I finish getting all the parts but my install is based on what the previous owner of my car did.
He had the old head unit wired to the cigarette lighter with a noise filter for constant power and another wire (no noise filter) going somewhere else for switched power. I'll probably ground the head unit to a new spot on the transmission tunnel with a stinger screw and the amp in the trunk will be grounded to a lower part of the trunk. Ground leads will be 12 inches max using larger gauge wire than the power leads. I will run 2 power wires to the battery with one switched with a spare relay I have lying around.
Grounds were going to wherever he could find a convenient bolt. Monster RCA cables go down the left side of the car away from the car's electrical components. It's an old audi with the battery under the back seat and a fully galvanized body (more chance for ground loop).
What perplexes me is why was the system quiet with the kenwood amp but noisy with the us acoustic amp.
Posted By: Clean Install
Date Posted: March 27, 2004 at 11:06 PM
well I would find a 12volt constant at the factory HU wire harness, rather than the cig lighter thats just me....and as far as running wire to the battery it should be all right there in the harness for you.... and your HU ground I would ground it to the car frame.... what does your system consist of? what size amp? and if it was me I would not be using that noise filter....thats me I feel that you can solve the noise trouble without the noise filter.... I would rewire your HU and your amp, just make sure your ground is again grounded to the cars frame.... ------------- If we learn from each success and
each failure, then we can improve ourselves
Posted By: DYohn
Date Posted: March 27, 2004 at 11:08 PM
Could be a million things - including a defective amp. What kind of HU are you running?
Posted By: Clean Install
Date Posted: March 27, 2004 at 11:09 PM
DYohn  ------------- If we learn from each success and
each failure, then we can improve ourselves
Posted By: DYohn
Date Posted: March 27, 2004 at 11:24 PM
Right back at 'cha, Mr. Clean, as your advice is right on about using the proper power/ground connections and getting RID of noise filters (also known as current robbers.)
Posted By: pickandpray
Date Posted: March 28, 2004 at 8:27 AM
My car (91 Audi 200 quattro) came with an old Sony HU which I replaced with an Aiwa cdc Mp3 deck 2 years ago. Don't know where the old head unit harness went because I don't recall seeing it behind the dash openning last weekend. I did remove that noise filter and found it didn't make any difference with it off.
I just purchased the us acoustics usb4065 which is 65wX4. I'm driving an 8" sub and a cheap pair of 5.25" pioneer coax in front. I had a pair of HU driven Alpine 6x9 triax in the rear but removed them to vent the trunk. (planning on running separates in front with simple cross-overs).
I have an older model of the same amp in the wife's minivan and it's quiet. Should I try swapping them to see if the van becomes noisy?
My cigarette lighter based digital voltage meter indicates my battery is at 11.5v with the engine off and it never gets above 13.5v while I'm driving. Seems low to me.
thanks everyone!
Posted By: DYohn
Date Posted: March 28, 2004 at 9:05 AM
Ah, so you changed more than the amp. Like I said, a million possibilities... Re-do all your connections and make sure you have not pinched or damaged your RCA cables. Yes, try swapping the amps and see if the noise follows the amp or stays in the car. If it follows the amp, the amp is the problem. US Acoustics makes good sounding equipment for the price, but like anything else there might be a lemon.
Posted By: pickandpray
Date Posted: March 28, 2004 at 7:58 PM
initially, I only swapped the amp. I replaced the HU 2 years ago so I doubt it was the problem.
Only after I got the ground loop did I start changing things.
Did the amp swap with my wife's car when I had a free hour this afternoon. It's quiet there with the engine running. Time to start re-checking the connections.
I noticed you said to check if the RCAs are pinched. Well they do make a hard right angle bend to plug into the amp. Should I correct this?
RCA unplugged from the amp = no noise.
RCA unplugged from the head unit = no noise.
antennae removed = just as noisy with it on.
Posted By: Disaster092
Date Posted: March 28, 2004 at 8:33 PM
If there is limited space for the RCA's to make connection to the amp, hence the hard bend you mentioned, I know that Radio Shack sells 90* adapter for RCA cable connections. They work great, i had to do it behind my HU because i couldn't slide it into the chassis all the way without the adapters. My RCA's were hitting an air duct. So if there is a lack of space i'd recomend giving these a shot if this little problem isn't solved by new cables. just my .02 -------------
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