Audio issues - maybe ground related?

badass101 · 04-03-2005, 06:51 AM

Hi all,

Finally got around to the first proper road test of the car pc yesteday, but came across a problem.

I had given it a bit of a test by wiring up the car pc +12v and 0v to the same feed as the amp a few weeks back, but had terrible noises.

So, I've now done the proper thing and run a 12v feed from the battery, and the ground is tapped onto a nice nut in the engine bay - it's a good ground.

I took the car out, and when i powered up the pc with the audio cable disconnected everything is fine, and the picture on the tft is great.
When I connect the audio cable, there is a bit of fizzing and popping when the pc boots (I think because the audio levels are at 100%) then when windows loads the outputs go back down to about 10% each and it sounds fine - except i can hear the whine of the engine when i rev it if there is no music playing.
However, there is now intereference on the tft, best described as a kind of 'bar ripple'. It doesn't ruin the picture but is very visible.

Is this a ground loop problem?

The tft is running off the cigar lighter, the pc is run of it's own power and ground, and the amp is too.

The only thing I was thinking is that, with the way I've built my case, the pc m/b is mounted on plastic lugs so has no metal contact with the case. The pc's ground only comes from the psu. Should I spur a wire from one of the screw holes onto the case and then ground the case from the psu too?

Thanks in advance,

Craig!