Crazy ground loop- is isolator safe?

107 · 10-05-2004, 01:58 AM

I just finished installing my CarPC and I get a lot of noise when I connect it to my DSP accompanied by my Xenarc screen getting fuzzy/wavy. There is no noise caused by the PC when the audio is not connected.

I'm assuming this is a ground loop issue and hope to fix it with an isolator. Assuming the isolator fixes the noise, will it be safe on my audio equipment?

I have an old Rockford Fosgate Symmetry 2 connected to my head unit and two amps(and now the CarPC). The Symmetry and Amps are grounded to the trunk, while the CarPC is up front grounded to a factory ground(where the cig. lighter used to be).

Any suggestions on how to fix the problem if the isolator won't work? I can't use an external USB soundcard because I am running an advantech 5.25" form factor PC with a 90W Opus and am having voltage issues with my 5 attached USB devices as is.

ppgt94 · 10-05-2004, 02:31 AM

Most ground loop isolators are made to go in-line of the audio RCA cables. I would guess they are safe. I haven't tried any yet though. I have a ground loop as well. Sucks.

nirvanades · 10-05-2004, 02:48 AM

Find better grounding points. Don't use factory ground wires - run your own.

107 · 10-05-2004, 09:29 AM

Yeah it does suck, right when I thought I was done- had it all working perfectly outside the car, I put it in and have 3 major problems... This being one of them! I have my own ground wires on everything except the PC. I've spent so much time on this thing I'm about to toss it out the window- about 2x budget and a lot more time than I thought, the novelty has worn off! I will try the isolator first, and if need be I will run my own ground wire- but the PC is so far away from my amps I'm afraid I would have a ground loop even if I did that.

ppgt94 · 10-05-2004, 12:45 PM

You should have only one ground point, if possible. You can then then daisy chain from that ground point if you need.

Nic · 10-05-2004, 11:10 PM

ground loop isolators are safe but i have heard they degrease some of the sound quality, this isnt speaking from experience tho i have never used one

antimatter · 10-05-2004, 11:51 PM

Nic is right. You should avoid them at all costs. They are completly safe although they may degrade you sound quality and are frowned upon by most car audio sound fanatics. They are essentially a bandaid to the greater problem. I say just out of moral reasons fix the problem and don't put a bandaid over it. Also search this forum. I have offered many troubleshooting tips to others having noise problems.

Tidder · 10-05-2004, 11:53 PM

I agree. Most audio noise issues are caused by grounds having different lengths of travel. If you ground them all at the same point, that should do it.

antimatter · 10-06-2004, 12:24 AM

Quote: Originally Posted by Tidder

I agree. Most audio noise issues are caused by grounds having different lengths of travel. If you ground them all at the same point, that should do it.

It is not the length that effects it (well it does but indirectly) it is the resitance or impedance of the wire. Theoretically all of your grounds should have 0 impedance. We all know that is not true to real world situations so a low impedance of 25 milliohms is good. The point is the get all of you grounds at similar impedances. That will eliminiate componants grounds traveling extended unfortunate routes that cause your ground loops

ea972271 · 10-06-2004, 12:34 AM

I just installed a ground loop isolator tonight, i've been playing with grounds for 2 weeks and just couldn't make the noise go away, after installing the isolator, all noise is gone and I couldn't be happier. I did so much troubleshooting i felt like tossing the whole lot out, why didn't i buy that 2 weeks ago?

My and my buddy do car audio stuff all the time, but we could not get rid of this ground loop.

I wouldn't worry too much about sound quality, i couldn't even notice a difference. Now if your building a strict SQ system, then i'd say don't use it.

It is a band aid, but it works for me. I may try in the future to solve the real problem but for now it's nice to hear clear sound from my carputer!

Best $20 I ever spent!

loscooby · 10-06-2004, 01:18 AM

I too had some noice issues so I bought a ground loop isolator off ebay and all the noice has gone...

Regarding the sound quality there are a lot of other issues when dealing with the environment of a car that is equally important to the sound quaility as the ground loop isolator.
For most people it works great if you are not seeking the ultimate audio experience in the car.

At the end of the day the audio quality is not better than the weakest point in your setup all the way from your speakers to the wiring...

Go for the ground loop isolator!

Rob Withey · 10-06-2004, 02:42 AM

Quote: Originally Posted by antimatter

It is not the length that effects it (well it does but indirectly) it is the resitance or impedance of the wire. Theoretically all of your grounds should have 0 impedance. We all know that is not true to real world situations so a low impedance of 25 ohms is good. The point is the get all of you grounds at similar impedances. That will eliminiate componants grounds traveling extended unfortunate routes that cause your ground loops

25 ohms...!

That's really high. With that much and a 1A load (most people's systems take a lot more than that), you'll be dissipating 25W just in your ground wire...! (P=I*I*R).

25 milliohms might be more like it.

antimatter · 10-06-2004, 01:06 PM

my mistake

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