jjh221

What kinda vehicle? Where is your computer located at? Im still confused on how you have the audio hooked up? is it out from pc to HU and you also have a cd changer? Where have you tried grounding? Have you tried grounding your mobo, not the case, to another ground that is factory in your car like cig lighter?

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davem

Ok, I guess that's right, since we already know it's a ground-loop problem we must isolate where it's coming from exactly.

Here's another idea that might isolate whether it's a car wiring problem or the computer itself causing a grounding problem... Since you have an OPUS you can fairly easily hook it up temporarily to someone else's car (aligator clips to the battery would suffice). Then see if the noise is still there. If it is then you know you have to ground out your computer better!

Or you could just try another computer in your car, but that's a bit harder to do.

antimatter

I think that there are to many variables that come into play while running the wires to the actual location for that test to work

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dragonBTV

first things first

connect your opus150 to battery derictly by a pair of twisted lamp wire

and tell me the result (start engine/stop engine)

NO GROUND AT ALL NOW!

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antimatter

If that works let us know.

The concensus is to keep ground as short as possible.

I think that there is something else going on here. I think that he has two sets of noise.

I think that he may have some problems with the opus power wires (the ones that plug into the drives and such) running near the motherboard circuitry.

The other alternator whine is becasue of a bad ground.

What gauge wire are you using. Use atleast 8 gauge

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MatrixPC

From computer audio ground, just connect it to the audio ground from the changer. Treat the audio ground just like another signal wire.

From PC -- To -- CD changer cable.
PC Audio Right ----> CD/HU Audio Right
PC Audio Left -----> CD/HU Audio Left
PC Audio Ground --> CD/HU Audio Ground. NOT to HU or CD case/ground although they seem to be the same, but I have engine whine if connect audio ground to the case.

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89 Supra Turbo P3 600E@750/Abit BE6 II, Alpine M-BUS Car2PC.
Y2K Accord Dell GX150
RoadRunner is the best FE PERIOD
EmoRebellion is a SCAMMER

yunusyu

I have not heard you say that you RAN THE POWER WIRES ON ONE SIDE OF THE CAR and AUDIO WIRES ON THE OTHER..Any power wire...check all the amp wires..black and red good luck..

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Matthew230

Thanks for the advice, though this is not my problem, since the actual audio wires run with the CD changer cable. I have also tried wiring direct to the battery over the roof of the car with no improvement.

Matthew230

Thanks for the info. You'll have to bear with my, I am quite technically stupid, but how do I find the PC audio ground??

And when I do I link it with CD changer ground....right ?????

(I have a feeling this may be the answer, it seems to make the most sense!!)

davem

Whoa... I just got my new 4-channel amp and my 'carputer totally installed. Big problem, Horrible alternator noise!!! I quickly panicked because I have been keeping up with this thread and I was scared I was going to have huge problems! I went to RadioShack and got their ground loop isolator and it works great now, no signal noise whatsoever (inverter issues though ).

So all I can add is... you definately tried a good ground-loop isolator?

EBFoxbat

Did you ground the PC case?

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*Tone*

Hi there,

I had a similar problem with my own car mp3 setup, running under an opus 150w. I would get a high-pitched noise based on engine speed and volume, even after grounding everything and adding magnetic shielding - I use a high-quality audigy soundcard as well.

The only way I managed to "fix" it was to reduce the signal-to-noise ratio on the soundcard output by making sure all volume levels (master volume, line out volume etc...) were set as high as possible. By doing that the 'noise' that was introduced stayed the same volume so was inaudible when playing music. As a bonus the sound quality is better and the head unit doesn't need as much amplification. If that has an effect on your system then you can probably guarantee the noise is being introduced after it leaves the PC, otherwise the engine noise would be amplified by the soundcard too I think.

Hope this helps.

Tone

MatrixPC

What is your HU/CD changer made and model?
Do you have the pin out for your CD changer/HU CD changer port?
Usually they must have (GROUND, POWER, Audio L, Audio R, Audio/Signal Ground, Data+, Data-) and they all vary among protocol/manufacturers.

As for the PC audio. If you use a 3.5mm headphon jack, the outter most is Ground.

Technically all Ground in the car are the same, but I just don't know why it work on the PCB but not the HU case.

__________________
2004 Matrix XR A7N8X-VM/400 AMD XP-M 2500+, DS-ATX
89 Supra Turbo P3 600E@750/Abit BE6 II, Alpine M-BUS Car2PC.
Y2K Accord Dell GX150
RoadRunner is the best FE PERIOD
EmoRebellion is a SCAMMER

Matthew230

My CD changer has a cable that has an audio ground on it. Do i connect my PC audio ground to the CD changer ground ??

Is there an easy way of isolating the PC Audio ground ???

Matthew230

Thanks, I have tried many different volume adjustments, with no results. I think the noise is coming before it leaves the PC

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