The Most Incredibly Un-killable Ground Noise ever. Please Help.

Nola111 · 04-20-2008, 02:29 PM

I've been a user of the forums for some time now, and I've read every thread about killing ground noise that I think is on here. I've done everything (I think) to kill the noise I have, and it's still there. I would MUCH appreciate any suggestions anyone might have.

Here's what I have:

Auzentech X-Fi Prelude PCI audio card
Front and surround outs from that card go into two Sonic Tio digital preamps.
Out from the Tio's into my amplifier.
The sound quality is absolutely killer, but I have ground noise.

Here's what I've done:

-A 8-gauge ground wire is attached to an unpainted piece of metal of the car. Everything is grounded to that.
-Ran a ground wire to the chassis of the pc.
-Tried ground loop isolators... the problem there is my amp doesn't seem to get a hot enough signal to turn on when I'm going through the GLI. I've tried two different ones and get the same result, so I don't think the GLI is bad. I didn't think the GLI units did anything to dampen the signal strength?? Anyone know?

So I don't know if the GLI would help or not, but I get NO sound at all when they are hooked up.

Finally, I tried running a ground wire from the ground of the power input of the Tio amps to its audio output, and it just created another ground loop (bad hum) so that did no good either. I HAVE narrowed the down the noise to coming from the outputs of the Tio amps. That's about as far as I can see so far (in other words, it's not the sound card and it's not my car's amplifier).

One more interesting fact to note is that, sometimes, when I'm stopped at a red light, the sound will be more prominent, but when I start going again it fades a little bit.

Any other ideas as to what it could be?

trititan · 04-20-2008, 03:02 PM

whats the sound like w/ no preamp?

typically car pc's dont need a preamp.

how i have it in mine, is computer-> GLI -> amp...

max volume is loud enough that i have to yell for my passengers to listen to me. but i never have it that high.

as for the sound changing at higher speeds, well that could be because there is more background noise, drowning out the music.

Nola111 · 04-20-2008, 03:07 PM

Trust me, I wish I could get rid of the preamp. I have a VW/Dynaudio amp which is kind of a pain b/c it requires speaker-level inputs, but I wouldn't trade it for anything because it has a built-in DSP and the sound quality is unreal.

The Tio's are required because they get the signal to the level the amp needs. I tried it without the Tio's, with a line driver, you name it, this is what works unfortunately.

greatwhite · 04-20-2008, 03:30 PM

Are you running rca's from the puter to the Tio preamps?

Do they run parallel to any ohter wires in the vehicle?

If so, they may be amplifying line noise picked up in the parallel run.

You might also want to try a jumper wire from the ground side of the rca's to a chassis ground. Just use some gator clips for testing. Probably won't work, but you never know....

The gli's killer the sound altogether? Most gli's only result in a loss of frequency, not power. I think your auzentech should put out close to 2v which should be enough signal for an amp. You're using a factory amp though, so you never know.....

Did you put the GLI's between the puter and the tio's? or the Tio's and the amp?

Cheers

greatwhite · 04-20-2008, 03:36 PM

Is this what you're using when you say "tio"?

http://www.si5.com/products.php?pID=4038

Nola111 · 04-20-2008, 09:03 PM

Quote: Originally Posted by greatwhite

Is this what you're using when you say "tio"?

http://www.si5.com/products.php?pID=4038

Yes. Two of those.

Nola111 · 04-20-2008, 09:07 PM

Quote: Originally Posted by greatwhite

Are you running rca's from the puter to the Tio preamps?

Do they run parallel to any ohter wires in the vehicle?

If so, they may be amplifying line noise picked up in the parallel run.

You might also want to try a jumper wire from the ground side of the rca's to a chassis ground. Just use some gator clips for testing. Probably won't work, but you never know....

The gli's killer the sound altogether? Most gli's only result in a loss of frequency, not power. I think your auzentech should put out close to 2v which should be enough signal for an amp. You're using a factory amp though, so you never know.....

Did you put the GLI's between the puter and the tio's? or the Tio's and the amp?

Cheers

Yeah I know, crazy that I lose sound altogether when going through the GLI. And I have two of them, so I know it's not a bad GLI b/c I tested them both. I need to keep troubleshooting that too. Very strange.

The Auzentech claims 5v actually, which is supposed to be more than enough to turn on the factory amp. It's not though. The Tio's have to be there. My former setup was using a Panasonic HU for the sole purpose of turning on the factory amp. Dumb and wasteful. Got rid of the HU and boy what a great difference in sound that made! But, at least with the HU, no ground noise!

Even though I tried some jumper wire configurations, I'll try some more. Thanks for the reply.

AWehmeyer · 04-22-2008, 06:26 AM

The TIO is an amplifier, not a preamplifier. Check to see if the TIO's output negative connection is continuous to chassis ground or if it's not connected directly, how much resistance is there between the negative and chassis. If there's no connection between TIO's output negative and ground, and if the GLIs you're using have a common connection for the RCA input shields, that connection kills the output of the TIO and that's why you have no sound.

If there is some resistance between the TIO's output negative and chassis, that's the source of the noise. The resistance unbalances the input of the VW amp. A transformer ought to take care of that. If that fails, you can put a potentiometer in the Tio's output positive lead and tune the noise out by matching the impedance. That's a bizarre fix, but it works sometimes.

Nola111 · 04-22-2008, 11:03 AM

Quote: Originally Posted by AWehmeyer

The TIO is an amplifier, not a preamplifier. Check to see if the TIO's output negative connection is continuous to chassis ground or if it's not connected directly, how much resistance is there between the negative and chassis. If there's no connection between TIO's output negative and ground, and if the GLIs you're using have a common connection for the RCA input shields, that connection kills the output of the TIO and that's why you have no sound.

If there is some resistance between the TIO's output negative and chassis, that's the source of the noise. The resistance unbalances the input of the VW amp. A transformer ought to take care of that. If that fails, you can put a potentiometer in the Tio's output positive lead and tune the noise out by matching the impedance. That's a bizarre fix, but it works sometimes.

I know the Tio is an amp, I guess for purposes of usage, I explained it that way to avoid the "why are you using three amplifiers?" question. But yes, you're right, the Tio is in fact a Digital amplifer.

Ok, so very interesting point about the possiblity for why the sound is killed by the GLI. I'll look into this more with your suggestion. I appreciate the detailed response!

What kind of transformer do you refer to?

AWehmeyer · 04-22-2008, 11:08 AM

It's just a simple transformer--like the ones that should be inside that GLI. If you want to spend a fortune, you can go for these: http://www.jensen-transformers.com/datashts/ci2rr.pdf

Just measure the reistance of the shields on the GLI that you have. That shold answer the first question.

Nola111 · 04-22-2008, 04:20 PM

Ok will do.

On the Jensen, I noticed this in the stat sheet: "To avoid excessive high
frequency losses, no more than 3 feet of cable should be used on its outputs" My output cables are more like 16 feet! (trunk to the dash).

AWehmeyer · 04-22-2008, 08:43 PM

I can't imagine any "excessive high frequency losses". Anyway, put the transformers near the amps. The length of the input cables won't matter.