NOISE help with laptop setup

**kuo** · 02-18-2005, 12:16 PM

i'm running a laptop setup and i'm almost completely done except for this noise issue. i am using a dc-dc cigarette adapter for laptops for power.

http://store.l-f-l.com/cgi-bin/cp-ap...=DC-DC-ADAPTER

the noise is only there when the laptop is plugged in. when it runs off it's own battery, i have zero problems. as soon as i plug it in, lots of bad things start to happen. the speakers make annoying buzzing/crackling sounds. buzzing is constant, crackling is random. this is with the engine off. when the engine is on the noise gets worse as rpm's go up. also the xenarc starts flickering so the noise is going through my audio and video when i plug the laptop in.

i've done some searching and someone had similar symptoms and ended up saying that his laptop's sound card was messed up, but it seems to me that if the sound is fine when the laptop is running off batteries, then it shouldn't be broken. please help. i have no idea what to try next.

**grepzen** · 02-18-2005, 12:29 PM

Does the pitch (of the noise) rise and fall w/ engine RPM?

Most likely, a simple noise filter will do the trick for ya.

**kuo** · 02-18-2005, 01:45 PM

it does go with the engine rpm's but there's also noise when the engine is off. is the noise filter still the answer?

**kuo** · 02-18-2005, 06:12 PM

ok so i went and got a noise filter from radioshack. so do i chop the connector off the cigarette light adapter for the laptop and wire this in between?

**WhiteRabbit** · 02-21-2005, 01:59 AM

I think he meant an RCA filter. try grabbing a scrap of 20 gauge wire and wrapping it around the shield of your phono to RCA converter plug, on the RCA side. ground it and see if the noise goes away.

I found a noise filter got rid of a vast majority of the sound, but not a perfect fix. grounding the rca shield finished the job. later I found it worked fully without the noise filter in place.

**kuo** · 02-22-2005, 01:32 PM

thanks whiterabbit. i'll give it a go.

**ccblanket** · 06-25-2005, 01:07 AM

kuo, I wonder if you ever got rid of that noise. I am having the exact same problem with my laptop setup. When it runs off its battery, it is fine. as soon as I plug in the dc-dc laptop adapter, it starts that nasty noise which is worse than the engine whine.

I'd appreciate if you could share your solution (in case you found one).

**anode** · 06-27-2005, 10:57 AM

Run all grounds, the ciggy lighter, the amp, etc to one single point. You are probably creating a ground loop with the grounds scattered through out the car.

**tbethune_87** · 06-29-2005, 08:36 PM

Ive had that same problem, not running audio and everything, but wen i had my standard cd system playin, plug tha laptop in to the cigarette lighter, it would crackle and the backlight on the cd wen with the beats.....i put a 4wd battery in my car, now shes all good....

-Newbie