Well as I mentioned before, I can hear all kinds of noise through the speakers when using the carPC. Initially I ground using the center console cig adapter. Yesterday I removed that and grounded it to the chassis next to the fuel pump (thanks for the advice E), but this seemed to provide no improvement whatsoever.

Mouse movements and HD access can still be heard, as well as alternator whine. I didnt sand down the ground connection, but I thought that I should at least get some improvement re-grounding it to the chssis. I dunno what else to do...

 

If you feel you have a good ground, Then you might need a voltage regular or filter that will get rid of all the noise on the 12v line. Computers need a cleaner power source than the 12v source from your car. Just my 2 cents

 

I do have a 12V regulator in place feeding into the mobo. Using a multimeter I tested various conditions, i.e. car running, off, A/C on...etc to ensure the regulator was putting out a true 12V, and it was. Maybe i should add a noise filter...

The only other thought I have is that I should take power directly from the battery. Currently I am taking it from the interior fuse box...maybe this is not a good source.

 

Connecting directly to the battery might work, but remember the battery is connected(indirectly) to the alternator so you might still have noise feeding back to the battery. Just another thought... you might have noise on your ground but you can't really tell with a voltmeter, on the other hand, if you had an oscilloscope.....
Food for thought- I have a grounding system in the car and I have noticed the car is slightly quietier than before.

 

I went through hell trying to get rid of alternator hum in my car pc when it was in my Golf. I tried 3 brands of inverters and endless models of filters/regulators all with no improvement.

I eventually broke down and bought a real DC-DC power supply and all was good... no hum, just clean power. I honestly can't remember what brand it was but this one looks very similar:
http://www.amtrade.com/pc_power/dc_t...r_supplies.htm

I bought mine off eBay for about $200US.

 

If you are hearing mouse movements and hard drive access I would think that the Computer Itself is at least partially responsible for the Noise. Filtering the power source to the computer is not going to eliminate noise coming from the computer itself.

 

I am running a DC-DC PSU. Its actually a custom design PSU for Epia Mini-itx boards called PW-70A. it takes 12V straight from the battery to the mobo, which is why i cant figure out why i have so much noise...

 

This is a good point. I wonder if i can add an additional ground from the mobo to the pc case itself...

 

AFAIK, the mobo is grounded several times in the ATX power plug as well as at the stand-offs so I don't think you're going to get much better than that.

I'm actually going through the same problem with my home machine so I'll be watching this thread carefully...

 

OK I find this strange. Let me back up. I was previously using FM modulation, but tonight I installed the logjams aux input adapter, no problem.

First, all of the alternator whine and HD noises are still there, which I expected. However, when I toggle between the CD and Aux, I can hear the whine during BOTH playback, including when the CD is playing. I can immediately hear it dissappear when I unplug the RCAs. In fact, I can hear it through all speakers when not playing anything...even though its only RCA stereo connections. I dont understand why this is.

Shouldnt the CD still play crystal clear? I dont know. I guess I really should address the grounding issue to take care of everything...

 

That sounds like the ground loop noise others have had, most have resolved it using a ground loop isolator from the Shack for about 15 bucks. Somehow I doubt that will help the mouse and hard drive noise though. I do have a question, can the soundgate adapter itself be grounded? That might be part of the problem. Also the better the shielding is on your RCA cable the better (it is actually acting as an antenna and picking up some RF noise that way as well and that could also be the source of the noise from the mouse and hard drive as well IMHO)

 

i dont know about the soundgate adapter being grounded, but i dont think thats the problem, since all the same noises were there when i used fm modulation.

actually i dont think the aux adapter can be grounded. in a way it is already grounded through the head unit.

 

http://www.pie.net/sec11sb2.htm

EIS-ILNO

The EIS-ILNO is shielded for protection from radiated noise. Non-directional, one-to-one transformer isolation.





Works like a charm and is only 20 bucks