Forget grounding and get a ground loop isolator. Something like this: http://www.radioshack.com/sm-see-all...i-2062214.html (I know this particular one is out of stock).
Sorry if it sounds stupid but i was wondering on how to ground my macmini?
I am trying to resolve the whining noise when my mac volume goes higher than 50%
Right now what i am using
18.5v 4a power supply
3.3k resistor tapped to isense
my other alternative is to have a ground loop.
Ground Loop Isolators are really just bandaids (and still don't always fix the problem). Go after the real culprit and try grounding the system first. I can't offer any info as to where at on the minimac to attach the ground to as I don't have one, but attaching to metal on the chassis, say a screw that goes from the case to the motherboard mount or something similar should be good.
A great guide written by a member here
Induced noise/Ground loop trouble shooting guide.
Good luck and Cheers
I wouldn't be looking at the mini, but more the audio you have fitted in the car....!!!
It is very unlikely the signal is bad coming out of the mini...!
Check it by running computer speakers plugged in while in the car on the drive and if it whines then it is the mac, if it doesn't then it is the audio....!
Smart Car due for completion beginning of march....
Log with pictures to go online shortly after.
Given that you custom built the cable, i'm going to go with it as the first thing to look at. Either your connections aren't solid, or in striping it for your connections you've exposed it to interference by removing the shielding (maybe from your power supply itself?).
Another idea for isolation is to run an extension cord out from the house and run the Mini off A/C. If the noise goes away, then it is your cable/power supply.
Has this power supply been involved in your audio system prior to installing the Mac? (e.g. was it driving a previous computer or something?) You might try moving it's ground wire around a bit too to see if that helps.
If you can determine the problem is in the audio end (I agree it probably is), check the following:
- If you're using RCA's, make sure the RCA cables aren't running next to factory wiring. If at all possible move it away.
- At the amp(s), make sure the ground is super tight to metal, you should be able to move or wiggle the ground cable. Scrap away as much paint from the ground spot as you can and use a star washer to really bit into the metal when you tighten it. Keep the ground less than 18"s.
- Is the amp mounted to metal? try removing it if it is and put it on wood or carpet.
- Are you also using an after market HU? Make sure it's using the factory ground in the factory wiring harness. If it is try removing the ground from the harness and ground it to the firewall or metal brace in the dash.
- Has the alternator been replaced? Do your light flash on bass notes? May have a battery going bad, go to an auto parts store and ask them to load test it.
just an update
installed a ground loop isolator and the noise is removed.
however, the sound quality of the audio drops drastically. i played the same song before and after the installation.
guess i have to open up the mac and get do a proper grounding.