Matthew230

Good evening,

I have built and installed everything to perfection, except for my noise issue, (high pitched tone, alternator whine, mouse and HD activity noise)

I have taken it apart and tried to identify the source of the noise with a plethora of different tests. It comes down to the noise being present when the PC is switched on and the audio lead is plugged in, even with everything else disconnected.

I have it running through the audio feed from the CD changer, though have tried it with other sources such as portable CD player and it runs fine.

I tried a ground loop isolator, but I couldn't hear the music, just made things worse.

I obviously lack the technical expertise to solve this issue, as I have spent many hours trying.

So my new solution - Add a digital output to my sound card, hopefully this will send out a clean sound then further down the line a digital - Analouge converter.

Will this work? Or is there any other solutions to my noise that I haven't thought of ????

Many thanks for everyone's time and help.

Matthew

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Grayscale

i had to unground my motherboard from the case, sounds silly i know but yeah. optical isolation would definately work though.

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CarPC install is starting to come along again...

Matthew230

How did you do that ??

zPilott

I thought about that too, but the D/A converter is the hard part

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Grayscale

It's a custom case I made, so didn't have to worry about metal touching it or anything. I just put slices of balsa wood between the case and the standoffs and the panel that touches the ports i used a simlar technique to keep it from grounding.

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CarPC install is starting to come along again...

sq_geek

Grayscale, did the isolation of the motherboard from PC case make your noise go away 100% or just only help reduce the noise?

What I don't get is how is the motherboard or PSU grounded to the PC case? I don't see any wires connecting into the metal case, but my voltmeter clearly shows my case is indeed grounded.. Any idea how?

I'm thinking it would be easier to block the case from being grounded rather than building a noise-resistant case...

netboy

First of all isolate where the alternator whine is coming from, amp, rcas or computer. Unplug the rcas from the computer, if the whine goes away then the noise is coming from your computer, if you still got whine then unplug the rcas from the amp. if your whine goes away then it is coming from your amp, if it is still there then it is coming from your amp. Do this then let us know so we can further help you.

Matthew230

If your case is metal and your PSU is screwed into it with metal screws, then there's your ground. The motherboard is also grounded via the ATX wire.

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Cat Monkey

tis grounded via the spacers

sq_geek

What ATX wire? I pulled my PSU (DC-DC) out entirely and left the wires hooked up -- it made no difference...


I thought it might be. Is that both on top and bottom? (Would adding a red felt washer which came with the case help or would I need one on each side of the motherboard mounting hole?)

lawrence

try using nylon stand offs.
you can get them at most computer store that sell mother boards

sq_geek

I'll get the nylon stand-offs. What about where the peripheral components touch the backside of the case? (Like the USB and PS2 ports).

lawrence

use electrical tape to insulate between the case

sq_geek

YESSSSS, I am finally making progress after several weeks of this BS..



So, I got those vinyl stand-offs, but bah humbug, if my casetronics cubid 2699R case doesn't allow for different stand-offs, like a traditional PC case does.. DOH! So scratch that.

BUT..

While I was disassembling my motherboard/case to do this, I had to yank my PCI sound card, or at least the PCI riser to get the motherboard free to pull out. So now instead of using nylon stand-offs, I basically ran the motherboard outside of the case...

NO NOISE!!!!!!!!!!!!!! WOOOHOOO!

So then I hooked it up to the PCI soundcard (Creative Labs Audigy 2ZS), and NOISE IS BACK! Then my dumb *** realized that the PCI card wasn't even hooked into the motherboard/riser!!

SO NOW I GOT IT! It's coming from the PCI card which is grounded to the CASE!

So then I put the motherboard back in and left the PCI riser out and used the on-board audio. NO NOISE STILL! So now I know that the sound is coming:

- In from power wire
- In to case which is grounded
- NOT into motherboard
- But into PCI sound card which is touching metal case in rear-mounted sideways PCI slot
- From PCI sound card out to RCAs out to Amp

So I have two options as I see it now:

1. Find a way to keep the PCI sound card from touching the metal case (how the F am I going to do this, any ideas guys?? Below is a pic of how it is mounted and looks).

2. Use onboard sound which isn't as good and doesn't have cool features like AdvancedHD and TimeCorrection/Delay... *sigh*

3. For those of you who think grounding the case would help, it does not. For whatever reason there is still noise, which essentially means that there is lower resistance through the PCI card, through the RCAs, into the amp, to the car chassis, than there is through a direct wire to the car chassis, which makes no sense whatsoever, but when I added ground wires to the pc case, it didn't help a bit so there is the laws of electricity being broken I suppose!!


The case setup with the riser looks like this, except my riser is for only one PCI slot. The PCI card slides in and screws into the back of the case itself. I think I would need to take the silver faceplate off of the PCI card itself, thus losing my port labels, btw, and then find some other way to secure it in place?? (= GHETTO! )



I'm just glad this is all almost over with!

Also one side-effect of using the onboard audio is that now I get a turn-on thump when my PC gets power (not even powered on, but when the ITPS gives it the 12v power and before it gives it the turn-on command (3 seconds delay)). Any ideas how to avoid this? Maybe I need a 5 second relay for my amp to turn on? *shrug*

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