Electrical noise/interference, tried everything!

**stiloluke** · 05-18-2009, 07:14 AM

I've recently installed an Acer EEE pc laptop into my dashboard, and everything is working perfectly, except I'm having the very common problem of engine noise..

I've looked through the various threads on here explaining how to isolate the noise, but I've hit a wall..

My car is a Fiat Stilo, currently set up like this:

Input voltage is the old headunit +12v, I've split that to go into the Amp and Laptop power inverter.

I have this inline noise supressor on the + of the cable between the laptop charger and the laptop. (This didn't help at all!!)
http://cgi.ebay.co.uk/ws/eBayISAPI.d...m=220410645381

The laptop then has it's standard sound card line out connected to the amp.

The amp and laptop are ground to the same point. If I ground the amp, the noise gets louder. They're currently ground to the chassis, but I've also tried grounding them straight to the battery with no luck.

If I run the laptop on battery, the noise goes away. If I listen through headphones there's no noise either.

The next thing that I'm going to try is getting an external USB sound card.. Do you think that's the best way to go, or will I be wasting my time??

Thanks for anyone who can shed any light on this!!

If you want any more info about the setup just ask..

**colin** · 05-18-2009, 11:17 AM

Are you making sure that the power lines are thick enough? Seems to me that it would be insane to power an inverter AND an amplifier off of some old headunit wires! The headunit wires are designed to spec so that the headunit can run off them, nothing more.

**DarquePervert** · 05-18-2009, 11:24 AM

Originally Posted by stiloluke

If I run the laptop on battery, the noise goes away. If I listen through headphones there's no noise either.

There's your answer.
Inverters (especially cheap ones) are notorious for EMI interference.
Pick up an auto power adapter for the laptop and use that for power instead of the inverter.

I agree that using the OEM radio harness for power is not the best source for power for a PC in the car.

**stiloluke** · 05-18-2009, 11:53 AM

Thanks for your replies.. I'll try it with a seperate wire run from the battery..

Originally Posted by DarquePervert

There's your answer.
Inverters (especially cheap ones) are notorious for EMI interference.
Pick up an auto power adapter for the laptop and use that for power instead of the inverter.

What do you mean by an auto power adapter? Do you mean an adapter which will allow me to plug the original power cable into the laptop (like a wall socket in a house)?

Thanks again

**colin** · 05-18-2009, 11:56 AM

I THINK he means to use one of those cigarette lighter adapters. The kinds that use 12v to power your laptop. This way, you aren't converting from 12VDC -> 120VAC -> 19VDC, but rather 12VDC -> 19VDC directly, which will definitely eliminate your interference issues.

**stiloluke** · 05-18-2009, 12:00 PM

Oh.. I should have been more clear - I am currenty using a cigarette lighter adapter.

Just a cheap one: http://cgi.ebay.co.uk/ws/eBayISAPI.d...m=320355859462

**hari-bhari** · 05-20-2009, 03:49 PM

get a proper power supply for the laptop. interference in the power supply to the laptop is the source of your noise. any of the carnetix power supplies should do the job. and DO NOT power the amp off the the 12v line meant for your headunit. it needs to be at least a 8 or 6ga cable (depending on the power of the amp), fused, running directly from the battery and grounded to the chassis. the way you are set up right now is asking for all kinds of trouble like a short, or even worse: a fire.