jgarza

Ok, so just so have a little inside knowledge here is the setup:

2005 Chevy Trailblazer

• Kenwood DDX812 Headunit
• JL Audio 1000/1
• Alpine Type X Sub 12"
• Alpine MRP-F600 (4-channel amp)
• Alpine Type R Components Up front
• Alpine Type R Coaxials in the back doors
• Kinetics HC-600 battery

Ok, so for about a year I had the same setup, except I had a Hifonics Amp pushing two Kicker L7 Solobarics, everything else was the same, had all the tweeters and same 4-channel amp. The only issue I ever had was a ground loop which I suspect from having the extra battery grounded at a different location, but I purchased a ground loop isolator, slapped it in the Sub RCAs, and voila, solved the problem.... Well, about a month ago, I decided to ditch the solobarics and upgrade my subs and amp. So I purchased the Alpine Type X 12" Sub, 1000watt RMS 3000 Peak and also got a JL Audio 1000/1 amp to go along with it. After I got everything hooked up and swapped out I noticed a TERRIBLE ground loop when the radio is at low volume. What is strange is that I get the noise coming from my midrange/tweeter combo up front, and my coxial speakers in the rear. It never did this before I upgraded to the 1000/1. The only I have found to remove the noise is by disconnecting the ground to the JL amp, but obviously this is not a solution. here is a list of what I have tried, so you guys know what has already been done.

New RCA's to both channels of the 4 channel Alpine
Tried grounding both amps to seperate ground locations.
tried running a ground from the headunit back to the alpine.
inspected all RCAs to make sure there is no pinch.
Tried Ground loop isolators on all 4 channels
I have tried everything I can possibly think of, and it is DRIVING ME NUTS! I am to the point where I am ready to slap my old system in it and be done with it. I have heard excellent things about the JL amps, but everything leads me to believe it is something with the amp. everything works flawlessly with the Hifonics. It is just so strange that it is causing some kind of interference to my 4-channel....

so.... has anyone ever ran into a similiar situation? any tips, or guidance would be GREATLY appreciated.

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DarquePervert

Where's the computer?

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Bugbyte

From your post, here's what we know:

1. Your old install had a ground loop, most likely caused by grounding your second battery in a different location. You never eliminated that GL but instead used a GL isolator to remove it from the audio.

2. Your new install has a GL until you disconnect the amp from ground.

3. You tried grounding the amps at different points but never tried grounding them at a common point.

I'm no expert, but I think the issue is that you don't have all of your gear grounded to the same location. Maybe try removing the extra battery from the setup and see if you have a ground loop without it. If that's not possible, try grounding all batteries and amps and equipment to the same location.

Basically, start with simpler stuff and then add more stuff. Remove the computer from the system and see if that eliminates it. Then, add the screen. Then add the PSU, and so on until the loop re-emerges.

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soundman98

he never said he has a carputer (yet)

like bugbyte said it sounds like you already had a issue, you just bandaided it with a GLI, the new amp propably has different sensitivity, and also happens to be more sensitive to ground loops

i know it sounds wierd, but where is your main power wire running, and is it next to the factory wire loom that stretches for the lenth of the car?

i have a similar issue(search the car audio area for the thread i made on this)-- and GLI's don't work, neither does any extent of grounding to different locations, because, i have come to believe that it is becuase my power wire runs next to the main factory wire looms for the entire lenth of the car, and becaue of a poor ground becasue my car is a unibody(a bunch of thin sheet metal, spot welded together).

so far, i have come up with a very simple, cheap, economic solution... Crank It Up!! it works everytime...

djvillar

TRY THIS FIRST...

hook up an ipod or whatever directly to your amps, at your amps. By that I mean have rca's run no more than a couple of inches to a foot max. then see if the noise is coming out of your subs... then plug in the player to the component amp... check to see if you have any buzz.

If your speakers are absolutely quiet and noise free,.. then your picking up EMI in you rca's somewhere along the run from your stereo to the amps. If so, you need to buy 100% shielded rca's... streetwires, monster, etc. they're expensive. Or you can go DIY.

With a civic a know about EMI issues. I feel your pain. The only RCA's I trust are the one's I make myself with 100% alum. shielding and a drain wire for any EMI that might creep past the shield. They're also pennies on the dollar compared to Monster.

soundman98

most car audio cabling these days(from walmart to monster brands) is twisted pair-- if you don't want to make your own true sheilded cables, use home audio cables-- they usually have better shielding-- just order from monoprice, and save some money on them.

diatomis

So I would like to assume that a vehicle that new would have a voltage stabilizer/regulator however it did not on my 03 jetta and so if I where you I would probably try to locate one from your local internet supplier to maintain consistent voltage output which will most of the time resolve abstract ground issues... I know this seems backwards however in the world of DC power our definitions are backward so... they aren't supercheep but if you have a decent VOM you can check what's coming out of your battery to the amps.. and if it's bouncing more than 1 volt either direction you should buy one to put either inline with your entire electrical system or between your power distro block and your battery... though it would be more beneficial to put it into the entire charging system. PM me if you want some more tips that have helped me with the electrical systems in my 03 Jetta and my 74 Westfalia...
Hope it helps.
Diatomis

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djvillar

"Twisted pair" is a gimmick. If you have access to or can make a "noise sniffer" to measure the amount of noise in the lines after amplification, the difference between twisted and non twisted is negligible. That's why they advertise them as noise reducing as apposed to shielded... as long as the method of twisting the wires "reduces" noise by .001%, they can say technically it reduces noise.

That being said, if your running RCA's from your source directly to your amp (12" or so) without running by/over any power sources then "twisted pair" or non twisted pair would be perfectly fine... But if your running your RCA's from the dash (fuse box and a whole mess of other wire there) to the sill or through the center console (more electrical components there) then over the rear seat (fuel pump power lines probably there) then your going to run into EMI.

If you don't want noise in the line, you need proper shielding. If you don't care about money then buy from monster or streetwires. If you do care about money then make them... they're super simple to do, crazy cheap, and you know exactly what your getting.

You can buy everything you need to make the RCA's from:
http://www.markertek.com/

For your wire:
-Gepco makes some two conductor wire (1 rca) for .15 a foot 100% shielded
-Canare makes two cond. microphone wire with tight braided copper shielding for .50 a foot
-Neutrik makes some great, cheap rca ends

If you want to pretty up your wire:
http://www.techflex.com/

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audiophyle_247

Seems the last few posts in here should have answered your question.
I assume the new amp is larger than the old amp, which can also add to the preexisting ground loop you had.

foko

I'm very interested by this thread because a ground loop ruined my last car audio installation AND ruined my interest in car audio. Basically I had done a very nice install in my 2003 MiniCooper S (Nakamichi, Audiocontrol, JL Audio, Dynaudio, and RE engineering). Unfortunately, months of troubleshooting and mucho dollars went into the car/system trying to eliminate the GL..... and in the end it was so frustrating I gave up. I'd done numerous nice installs before and never had this much trouble. I even took it to the local pro installer and while he eventually got it quiet, there was so much stuff in the signal path by the time it was done, that it sounded terrible. WE DID EVERYTHING to it. I never got to spend my time on the fun part (tuning and tweaking for SQ).

Now I'm thinking of a new car (BMW or Audi). I've never owned a car with a stock audio system and would love to go with a computer front end sourcing high end DAC/Amps/processors/speakers. But damn I don't want to go through that noise thing again!!

Someone please tell me it will be ok to try again

Fabian

audiophyle_247

It will be alright. Just put a little more detail into your system planning.
Like planning all your grounding locations, the best place to run your wires in your particular vehicle (best place, not easiest place), and get ahold of a wiring schematic of your car.

The more components you have the greater the risk of introducing noise, thus the more thorough you need to be with the install.

JuniorGeezer

First I had separate grounds for CarPC and amp and I got processor noise and alternator whine.

Then I ran a ground wire from the amp to the CarPC and things got better, but not perfect.

Then I ran a fat ground wire from the battery to the amp and left the ground wire from the amp to the CarPC, now it's perfect.

Before I used the battery minus for ground, I used a seat bolt, which is a bad idea.

Wisdom: A bad ground can mess up things, even if everything is hooked up to it.

You should at least for testing purposes hook every damn thing directly to the battery minus. If that cures the ground loop, take it from there.

pulsarsimon

The JL has balanced RCA inputs, so there won't be a ground loop there.

checked the battery ground? - That's a likely candidate, as a bad (high resistance) ground can have similar symptoms to a ground loop in the audio circuits.

otherwise, maybe the JL is faulty. I have lots of JL 'Slash' amps and never a ground loop problem.

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JuniorGeezer

How is this possible? A balanced input requires two conductors and a shield per channel and RCA has only one connector and a shield. And even if this thing had balanced inputs, if the source does not, there's no benefit to it.

I've read that amplifier's manual. It doesn't explain how balanced can be done with RCA either. Edit: Maybe they have the RCA shield floating as opposed to connected to ground. Is that it, anybody know?

foko

In my situation, that was nearly the first thing I did. ALL the components, including the headunit, grounded to the battery terminal still made noise. I finally was able to improve things by using the stock HU feeding the processors and amps. A replacement Nak HU did not help. Only using the stock HU worked. Sounded relatively bad, but no noise. The problem was somehow associated with the Nak HU's.

PS....JL slash amps have regular RCA inputs (at least mine did).... Not balanced.

Fabian

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