Splash-X

Ok, so after migrating from a on-board sound card that simply did not work to a Turtle Audio USB sound card I've run into a problem.

On my bench in the house it sounded perfect. The audio was supurb.

I have a Mazda 3 with a factory aux jack. I took the acc line directly from the radio harness and I also grounded the carPC to the ground in the radio harness.

I took it out to the car, hooked it up and gave it a shot. With the engine on acc so the radio would come on I turned the carPC on and it booted. Radio sounds fine. I switch over to the "Media" (aux jack) and I hear fuzz. The engine is NOT on at this point.

Crank the car over to turn it on and when the car runs you get the alternator noise.

So, maybe a bad audio cable. Swapped it out, nope, not the cable. Plug in head phones and no noise what so ever (other than the audio of source).

I hooked up my house dvd player using a power inverter and a RCA to 3.5 standard audio jack (monster cable) and the audio is just fine, even with the inverter

So, I'm left with noise when using the Aux Jack with the carPC only. Plug anything else in to the aux jac and it works. Plug headphones into the carPC and the audio is great.

What gives? Yeah, I'm sure you're going to tell me its the ground wire or maybe even the acc wire. What give, shouldn't the radio do the same thing when I switch back to it while the carPC is on?


I did run across this site:

http://www.crutchfieldadvisor.com/IS...de.html?page=2

I'm not sure where I should supress the noise though. Any thoughts?

MP3Car.com

 

pokki

Don't tap into existing power wires when connecting your car pc. Run a new wire direct to the battery.

Splash-X

I ran the powe from the battery to the carPC directly. I ran the ground from the radio to the carPC and from the Remote/Acc to the carPC.

I understand what you're saying by running the ground to the carPC but I'm not looking to run more wires until I can isolate what the problem really is.

The only time I get noise from the alternator/power is when the audio cable is hooked up to the carPC and the radio is set to Media (aux).

1.) The car can be on radio and the carPC on and plugged into the aux jack but no noise
2.) The car can be on Aux with the carPC on and the aux jack disconnected but no noise
3.) The car can be on Aux with the carPC on and any other audio source hooked up to the Aux but no noise (including a mp3 player, laptop, dvd player, tested them all).

ONLY when the carPC is on, hooked up to the aux, and radio on Media do I get the noise.

From my understanding, if it were a grounding issue the noise would be present ANY time the carPC were on, not just when it was hooked up to the aux.


I'm mainly looking for some sort of resource (person or web page) that can outline causes for noise and how to correct them. Car Audio is not really my thing so I don't know alot. I will run a ground wire today to the battery and hook up the aux to the battery line to see what I get but I have a feeling its going to be the same, but you never know.



thanks for your input, it was much appretiated (even if it doesnt sound like it from my above post)

2k1Toaster

It sounds exactly like a ground loop with the PC. Obviously your HU isnt going to sound weird because it is not in a ground loop. Your PC is because you even said you grounded it to the factory harness, which is rediculous.

Ground it properly.

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pokki

What Toaster said.


The electrical power needs to travel down the ground as well as the +power. Hence sharing of either +power or -ground with factory equipment on factory wires is a big no no.

If you don't want to run a long ground wire, go direct to the chassis. Remember to sand back any paint and bolt it down solidly.

Splash-X

2k1Toaster,

Why so negative, I am trying to troubleshoot the problem. If you don't approve of what I have done, or what anyone else on the forum has done for that matter, simply post constructive criticism for ways for them to improve their knowledge and their setup. Being flat our rude helps no one at all.

As i said, car audio is not a strong area for me so I knew OF a ground loop but not WHAT it was.


pokki,

the Pc is under the passenger seat and provides very little access to mount to the chassis. It would be just as easy to run the ground wire to the battery, that way I can be sure to have a proper ground.


Can I still use the radio Acc line for PSU? for the ignition sensing of the PSU.

2k1Toaster

Ground Loops are covered multiple times in the FAQ, and also return a bagillion results when you search all with what it is, hence the bluntness.

Also if you are under the seat, then does the seat have a seatbelt? I bet you that is bolted to the chassis. Ground it there.

And running to the battery is a good way, but you have to be even more careful. If the wire passes by audio cables, video cables, or whatever, it is just as bad if the +!2v power cable passes by. So you are making your chances of having a ground loop even higher if not done properly.

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pokki

Yes, using the headunit/radio acc for ignition sensing/remote turn on is perfectly acceptable.

MP3Car.com

 

Splash-X

2k1Toaster,

It isn't a problem of not having searched the forum. Let me put it this way, what good is searching for "grounding loop" to get results that say "hey, don't do it" if you don't understand what it is, what causes it, and the symptoms.


I'm having trouble understanding what +!2v is. I think you may mean +12V (the power line from the battery to the carPC) and if so, that is where I had intended to run the wire but from your advise I see that doing so may also cause another ground loop.




As for the actual grounding to the seat belt, I'll look in to it to see if I can trace where the actual bolt for it is and if it is easily accessiable.

Thanks for your help

2k1Toaster

yes +!2v = +12v.

Basically run all the power lines, positive and negative on 1 side of the car, and data signals like video and audio and data (usb), on the other side. If you can run down the centre, then seperate the video from the rest. But usually you only have 2 channels on the far left and far right.

And all seats are bolted to the chassis in at least 4 places. Usually covered by little bits of plastic that just snap off. Your seat probably goes back and forth right? Look at the very end (towards the back of the car) of the track, and there should be a little cover there over a bolt. That is a good bolt. Just sand away the paint and greasy grimy stuff.

__________________

Splash-X

Maybe I misunderstood your first post about positive and negative wires.

So it IS ok to run a positive and negative wire side by side?

it IS NOT ok to run a positive OR a negative accross and speaker wires OR av/usb/etc


I ran out of time on Sunday and got home after it was dark on Monday. I hope to get the proper ground and retest.


A side question Toaster, will this bad ground affect USB as well? I'm thinking that a poor ground may be causing power problems on the USB rail. It doesn't happen often but I sometimes see devices become unrecognizeable (spelling?) . Of course vibrations could cause that but I think it may be the power.


Thanks again for all your info

HiJackZX1

Oh wow, Ok, here is how you do it..... run a main cable, like 4 guage, from the battery to a fuse, then from the fuse to the distrobution block then to the PC. The ground should be a main ground specified by your car manufaturer. The ground should only be 3 feet in length. If you still here noise, go to Best Buy and pick up 2 ground loop isolators, one for rear speakers and one for front. They are made by Install Edge. They are pricey at 17.99, but they work, with no sound quality and 3 db gain. All others I have tried are muffled. Hope this helps. Although Toaster seems like he is being an @$$, he actually isnt...... at least he didnt post the toaster wiring picture, lol...... LOVE YOU TOASTER, you have always been a good help to me.

Yes an improper ground will cause everything to run awkward.... i tried to bolt my ground to the bottom of the car, my PC ran very slow and most USB devices did not work, turns out the ground cable came off and was dragging on the ground. I then took out the whole driver side interior from front to back and searched for the main ground point that Dodge created for my SUV, bolted on and have had no issues since.

Splash-X

From the battery to the car PC I have a run of less than 8ft using 8 gauge wire with a fused terminal bock.

My noise, as pointed out by both Toaster and Pokki, is most likely caused by the ground loop. My orginal translation of what he said was "running a ground next to a +12V will cause noise". After his latest post I see he means running EITHER the ground OR the +12V over any audio,video or USB will cause noise. This I now get.


If proper ground fails, I have considered a ground loop isolator (as pictured on this page http://www.bestbuy.com/site/olspage....=1122655296186)

Now, the ONLY problem I see from this is I would need to go from the 3.5 speak jack to RCA into the isolator using a 3.5 => RCA cable by Monster (I already have two).

Then on the out of the isolator I would a Female extender for RCA to plug the second 3.5 to RCA into the extender and then the 3.5 into my Aux jack.

So, my parts list would be:

Isolator (http://www.bestbuy.com/site/olspage....=1122655296186)
2x 3.5 to RCA (http://www.bestbuy.com/site/olspage....=1114639085343)
1x RCA Couplers (http://www.bestbuy.com/site/olspage....=1184768166914)


If proper ground does not fix my problem, what are the other possible causes of this "noise"? Assume that the +12V comes up the drivers side and crosses NO other wires. Assume the ground is directly to the seat belt bolt, properly preped with no paint, etc. The audio cable goes directly from the jack to the aux jack, no wires ever cross.

pokki

Alternator or battery trying to push to much power through stock grounds. Which is why I often recomend upgrad their ground wires.

rich3327

Does it matter if you turn the ground loop isolator around? I noticed that the output (female) and input (male) seem to be opposite of what I'd actually need for my Zune/car stereo solution.

EDIT: Nevermind, I just went to Radio Shack and bought a ground loop isolator and it fixed my problems...

MP3Car.com