ok so in my beater I've developed alt whine. I installed this system with some friends in their shop probably 6 years ago. It's served me well. Through time the front speakers and subs stopped working. Just one day they were no longer there. So through some testing I found out the RCAs and line drivers went bad. So I just removed the line drivers and replaced the pheonix gold RCAs with some decent radio shack ones. All my speakers work now, but I also now have alt whine.

Someone on another forum suggested that my RCAs were crossing paths with the power wire, which they were. Not knowing, I ran the new RCAs right next to the power wire. I went back in and moved them so they never came in contact with the power wire. But this did nothing to help the alt whine.

So i started to dig through the internet. All the professional sounding sites all seemed to say alt whine was a result of a ground loop. But not being an electrical engineer I'm not exactly sure how I've created a ground loop and how to get rid of it. So let me ask some questions and know what you know think.

First off I have a 4 channel amp to run the speakers and a two channel to run the subs. 4 gauge power wire comes to the back, hits a splitter into two 4 gauge wires. The 4 channel wire goes directly in, while the sub amp goes through a capacitor first. I know the ground wires off both amps are 4 gauge and believe they go to the same spot.

*So is it a bad ground spot? Should i just be looking for a better spot in the car to ground the cables to?

*Is it because I have both amps going to the same spot? Should both 4 gauge ground cables go to their own spot?

*Does the ground spot's distance from the amp have anything to do with it?

* I also read in a few spots that shielded RCA cables are worse than unshielded. how is this possible? I was under the assumption that all the high $$$ RCA cables had better shielding and the stuff I was using would have relatively weaker shielding?

* Could other components like the head unit, crossover, cap, bass cube, etc. be the source of the ground loop? is there an efficient way to figure out what is causing it?

Any help or advice in this matter would be appreciated.

Thanks,
Mike

 

My guess is it is your RCA cables causing the noise problem. If I remember correctly, the cheap Radio Shack cables use wire similar to speaker wire with the two conductors running parallel side by side. The better RCA cables, likely the same as the ones you removed, would have used a coaxial type cable with a center conductor surrounded by a braided shield. Whoever told you shielded cables were to be avoided did not know what he was talking about. The Cheapo's are good for home multimedia application, but not good for high noise environments like your car.

To answer your grounding question: The Amps should be grounded to the car chassis as close to the amp as conveniently possible. The 2 amps can, but need not, be grounded on the same lug. Use steel wool or sandpaper to make sure the ground bolt (or bolts) have a good metal to metal contact free of paint or other insulating materials. I like to put a star washer on either side of the lug ring terminal to ensure good contact.

 

before playing with the grounds from your aftermarket stuff, start by upgrading/ adding additional ground from the battery to the chassis.

 

Could someone then possibly suggest a goodreasonably priced brand and/or type of RCA cable?

Mike

 

Beefing up the battery ground connection may not be a bad idea, if his amplifiers draw a huge amount of current. But, that is not causing his noise problem.

Buschman,

You mentioned using the Phoenix Gold series RCA cables before without problems, I'd go back to those.

 

If you try all the above, and you still have whine I would:

1. run another thin ground wire from your head unit to your rear amp grounds so they are all on the same ground.

2. get your alternator checked out - you may have blown a rectifier diode

 

Well they were good about alt whine, but 4 of the 6 runs disconnected over a 6 year period. I suppose that could be the way they were installed, but I'm also worried that PG doesn't quite live up to the hype.

Anyone else have experience with PG stuff?

Mike

 

So can I assume from what you're saying in #1 that's it's best practice to run both the amps to the same ground spot? I do have a thicker than usual ground to my head unit. I believe it's an 8 gauge ground to the body that runs into the Pioneer's ground. It used to feed the ground for the pioneer and both line drivers, but I took them out.

In reading all that stuff about keeping the power and ground wires the same guage due to voltage consistancy, would an oversized ground cause the same problem as an over sized power wire? Or do problems only occur when the power wire is larger than the ground wire?

2. This is a 10 year old car and I don't believe the alt has ever been replaced or anything. Is there a way for me test the rectifir diode with a multimeter? Any help here would be appreciated.

I'll start off by beefing up the RCAs. If that doesn't help then I'll move the amp grounds to a different location. If that doesn't help I'll try adding a battery to body ground and moving the head unit ground back to the amp spot. If that doesn't work I'll try and get the alt tested. If that doesn't work I'll probably have to sell the car cause I don't know if there is anything left to try.

Thanks for the help thus far guys,
Mike

 

I have PG RCAs in my truck and They were better than the old RCAs I had. I think the ones I had before were RFs

 

Hey Mike,

Well, I have heard that if you cannot get rid of alt whine, is a good idea to have your radio grounded to the same spot as your amps. It makes some sense because if you plug in patch cables in the radio, they use the radio's ground. When you run the patches into the amp, if the amp is on a slightly different ground, you could get some differential there. I would just splice a wire into the present radio ground and run it to the rear amp grounding point. So that you are 100% positive they are on the same ground.

As for the alternator, I don't know if you can get to the individual rectifiers on newer amps without taking the entire thing apart. As far as I know, a typical alternator has 6 rectifier diodes, which I guess you could check with a meter if you could get to them! If you had a scope, you could check out the ouput of the alternator - if a diode blew, you'd see alot of noise coming off it, instead of relatively clean DC.

BTW, I would try the easier stuff first, just in case it is the connectors.

-Alex

 

No. There is no electrical advantage to having the radio grounded way back by the amplifiers. And you do not want to splice an extra wire into the radio ground to run back there while leaving the existing ground where it was. Assuming the car has a steel body/frame, you should get less of an electrical potential difference between the ground points if you ground the radio under the dash and amps close to where-ever they are mounted. Then you would thru wires ran accross the car to try and ground all components at a common stud. Running a wire from one ground point to another would do absolutely nothing when they are already electrically connected thru the body/frame.

If you have a good ground connection from battery, alternator, amplifiers, and radio, to the chassis, you should not have any grounding issues.

If you checked the ground connection and found nothing loose, rusted/corroded, or otherwise suspect, forget about it. Grounding is not your problem.

If you burnt up a diode or other component in the alternator's voltage regulator, I'd think you'd have more problems than a simple whine from your stereo system.

 

A bad/pinched speaker wire,or shorted out apeaker can cause a ground loop as well.It will send a bad signal thru the system.If every thing was fine for six years and then this all of a sudden happened,it could be another possibiltiy.

I just spent 4 days trying to figure out a similiar problem on my wifes Trailblazer.I bought rca groundloops,wire in ground loops and snap on RF chokes.I even replaced all brand new rca's with new rca's.Used the batterry ground straight to the radio,nothing worked.

I thought maybe it was the deck.So I bought a Pioneer Premier Deh-P8mp (the one I just bought before that was a Deh-770 mp Premier),hooked it up and everything worked great.Not a single noise!But then the amp started clipping and the pass. rear door speaker started popping.

Needless to say,that speaker had a pinched wire under the rear seat,some how shorted out the speaker and was causing all of my problems.The speaker sounds fine but if you hook it up to anything and play it for a few seconds it starts to short out and make a buzzing noise to whatever its hooked up to.

Just another suggestion.

 

As for losing the RCAs it was not all at once. I would just notice speakers weren't working anymore. Sometimes it's hard to notice just by sound and it's not till a door is open or your in the trunck that you can really tell that something doesn't sound right.

I ronically I bought RF RCAs today at Best Buy to try and fix the problem. Are you guys thinking RFs are not going to help? I got the performance series($21.99 for 5M). The next series was $14.99 for 5M. Seemed excessive.

What's funny is when I did all this work I had to pull the amp rack. When I put it back in i didn't realize one of the sub speaker wires was sitting funny and ended up screwing an amp board screw through the wire. Obviously causing a short. Everytime I hit the brakes or the car moved I would hear very loud pops. I finally figured out what I had done and fixed it. but as far as i remember I had alt whine before and after this happened. The short didn't seem to make anything worse.

Mike

 

One other question. Is there something, like some kind of tape, I can wrap my RCAs in for additional shielding?

Thanks,
Mike

 

Let’s start by
1. Check the grounds and make sure they are all to bare metal (scrape the paint for a good connection). Running the head unit ground wire all the way to the back is a bad idea. Just make sure it has a good ground with no or as little splices as possible.

If that doesn’t fix it
2. Replace and rerun the patch cords away from +12v with a good wire. I recommend stinger. Try not to go cheap on that the preamp (we have already done that once)

If that doesn’t work then
3. The diodes in the alternator are probably on their way out. I would look into getting it rebuilt or replace it with a bigger alt.

 

Yes. They make copper shielding tape. But' I think it's overkill for this situation. THe tape is basically an adhesive backed thin ribbon of copper sheet. Usually 1/2 to 1 in. wide. It's not cheap.