Unable to locate source of Audio Ground Loop / Noise

**phuz** · 05-24-2008, 04:02 PM

I have been troubling with this issue for the past 8 days and I have exhausted all my options.

I am using the factory amp / speakers.

The factory amp input cable has 4 audio channels and 1 common ground, so I made RCA cables with the center pin for each channel, and tied all the grounds together. When I hook up my iPod, there is no noise, and it sounds great. When I have it hooked up to my soundcard (external USB Sound Blaster Live 5.1), there is a very small amount of noise with the key off, but as soon as I turn the ignition on, there is all kinds of noise. It picks up throttle movement with the car off (throttle is drive-by-wire). It almost sounds like a microphone is plugged in and picking up all kinds of ambient noise. Against better judgment, I bought ground-loop-isolators for all the channels, and that didn't really seem to do anything.

My last option will be to buy an aftermarket amp that actually uses 4 independent channel grounds, instead of a common ground, like my factory amp. I just am at a loss for where this noise is coming from.

**BlackStealth** · 05-24-2008, 09:11 PM

It still sounds like a ground loop problem. Are you 100% positive you actually have "ground loop isolators" and not a noise condensor or something instead?

When I plugged in my notebook (ran from the battery) my amp was crystal clear. As soon I plugged in my carpc I had a lot of noise. Ground loop isolators from PAC worked perfectly for me.

**phuz** · 05-24-2008, 10:34 PM

Absolutely. I bought them at Circuit City. They are made by Tsunami...and even say "Ground Loop Isolator" on them.

I have been advised to isolate the power supply from the PC to see if that helps anything.

It has to be something with the soundcard and/or PC because the sound is crystal clear with my iPod plugged in. For the heck of it, I will try my laptop output tomorrow to see how that sounds, but I imagine it will sound as good as the iPod.

**HiJackZX1** · 05-24-2008, 10:54 PM

They may be just cr@ppy GLIs. I bought one from BestBuy. Its made by a company called InstallEdge. They eliminated all the noise and it gives you a 3 db gain and does not muffle sound at all. I do not know your setup, but mine is massive with over 17+ components and devices and the GLIs eleminated the GL 100%.

PS: How old is you alternator? I heard when one is about to kick the bucket it will create alot of noise. Also on some trucks they have high output alternators which cause noise too.

PS again.... I see you drive a 2006 car... How many ground points do you have? Is it a factory ground point or your own made?

**phuz** · 05-24-2008, 11:05 PM

Originally Posted by HiJackZX1

They may be just cr@ppy GLIs. I bought one from BestBuy. Its made by a company called InstallEdge. They eliminated all the noise and it gives you a 3 db gain and does not muffle sound at all. I do not know your setup, but mine is massive with over 17+ components and devices and the GLIs eleminated the GL 100%.

PS: How old is you alternator? I heard when one is about to kick the bucket it will create alot of noise. Also on some trucks they have high output alternators which cause noise too.

PS again.... I see you drive a 2006 car... How many ground points do you have? Is it a factory ground point or your own made?

I am running a 2.4ghz Intel with 2gb of ram...8" in dash touchscreen, 2 PCI serial cards, USB 5.1 soundcard (Sound Blaster). Since the factory head unit powered the center channel in-dash directly, I had to add an external amplifier to power it, which is doing fine. The GLI eliminated the noise in that line.

I have the PC, the factory amp, and center channel amp...all in the trunk. That is where my battery is factory-located, so naturally, I have all the grounds tied to the negative terminal.

**HiJackZX1** · 05-24-2008, 11:21 PM

Im not to familiar with this stuff, but I have been told its bad to run directly to the neg post on the battery, but thats only when length of cabling is involved. Yours is right there next to it. My setup is diffrent. I have one heavy duty ground, that is less then 4 inches (the shorter the ground the better), anything else is attached to a factory ground points. Like the rear AMP, and all cameras and what not that were in remote locations. Have you treid connecting to a factory ground point rather then directly?

**phuz** · 05-24-2008, 11:25 PM

Originally Posted by HiJackZX1

Im not to familiar with this stuff, but I have been told its bad to run directly to the neg post on the battery, but thats only when length of cabling is involved. Yours is right there next to it. My setup is diffrent. I have one heavy duty ground, that is less then 4 inches (the shorter the ground the better), anything else is attached to a factory ground points. Like the rear AMP, and all cameras and what not that were in remote locations. Have you treid connecting to a factory ground point rather then directly?

I haven't tried that, but I will include that in tomorrow's adventures!

**phuz** · 05-25-2008, 12:01 PM

I may have fixed it. I isolated the Power Supply from the PC Case and this removed 99% of the noise. If I put my ear to the speaker, I can hear a very faint bit a noise, but unless you do that, you won't hear it. However, now I have some subtle wavy lines on my VGA (which already has a power filter).

I must say I'm pretty happy at the moment.