Ground noise in system

TyBong · 09-18-2005, 11:26 PM

I've got an old receiver I have modified into a carPC, I currently am powering this system by a power inverter (might I add is a complete waste of energy). I threw this system in my 02 camry, jack everything in, works fine. the problem is when the car is on, I have alternator whine through the speakers. I have made previous generations of carPC's in my other vehicles and I have always stressed to myself "ground everything" (pretty much), and the typical way I solved alternator whine was to ground the audio signal before it goes to my alpine deck to the frame of the car, usually that works. Except in the camry, when I ground the system, I get MORE noise and TONS of noise lines on the TVIEW monitor. I have also thrown this same system in my 91 full size blazer, no issues with that.

If I just break down and get a DC-DC PSU would that solve the noise issue?
Is the electrical system in the camry so different then the blazer where I would need a ground loop isolator?

does anyone have any ideas?

Thanks

EpRiDaZ · 09-18-2005, 11:28 PM

I think if you buy a dc-dc psu it will benefit you. It may or may not make the ground loop go away

Jason_K · 09-19-2005, 08:18 AM

Switch-mode Inverters generate a hell of a lot of switching noise, which could be one of the problems.

Grounding the audio negatives from the PC is not a good idea. They use what's called a "floating earth", which is not necessarily 0 volts.
The best way to do it would be to use an isolation transformer/line isolator. You can get them many places, and work really well.

Additionally, use a noise filter/suppressor inline with the power input to both the PC and the monitor. That should cure the problems.

neon_eddy · 09-19-2005, 09:06 AM

are you the guy from minnesota?..

I would agree, an inverter will most always make things more sucky, and indroduce that 60hz buzz.

I made my own ground lift, or "audio isloator" from radio shack parts.. cost around $10 but it worked, and saved some money from using BestBuy's $40 solution. just get 2 audio isolators, as they are mono and use the common ground and I also got 2 audio connectors, male and female so it could be in-line. hope those help.

TyBong · 09-19-2005, 11:12 AM

Cool, I work at a tv station with nuthing better to do somtimes, I think I may give that a try today, thanks for the imput

oh yea, yes I am the guy from MN
mabie I will not be lazy and fill out myprofile..... nope still too lazy Lol

neon_eddy · 09-19-2005, 11:27 AM

ahh what do you do there? I do some TV production work.. animation and whatnot.

you can try mine if you'd like.. as we live fairly close.

TyBong · 09-19-2005, 04:51 PM

Cool, I do pretty much everything here, from production to managing playback, I suppose my main title would have to be a tech. i.e. right now sitting in the server room full of fans blairing in my ear Lol

bdrezner · 09-19-2005, 05:47 PM

Please someone, correct me if I'm wrong, but I've read that inverters also create ~20% overhead in power draw. Just another reason to switch to DC-DC. Also, are all your components sharing a common ground or are they simply connected their nearest ground points?

PURDooM · 09-19-2005, 11:03 PM

Quote: Originally Posted by TyBong

Cool, I do pretty much everything here, from production to managing playback, I suppose my main title would have to be a tech. i.e. right now sitting in the server room full of fans blairing in my ear Lol

He works in champlin for clarification.

TyBong · 09-20-2005, 11:12 AM

One more question, what would explain the same system in the blazer not having issues?

neon_eddy · 09-20-2005, 03:13 PM

well I would say, one of 2 things
1) better, newer alternator that intriduces little noise
2) better grounding in the veichle

better ground overall cna fix these issues .. the ground lift is more of a band-aid solution..