Thread: Induced noise/Ground loop trouble shooting guide.

If you own Intel's D945GCLF, you might want to read this post:
http://www.mp3car.com/vbulletin/show...39#post1255639

Couldn't eliminate whining/noise during boot coming from Rear Spk output ("blue" jack normally used as line-in and as rear spk output in 4-channel mode), so had to change back to 2-channel mode. Tried all reasonable solutions described on this thread.

I am facing the noise problem when i connect my laptop to the DC-DC power supply. Its working fine when i run it on the laptop battery.

Can anyone tell me how to MAKE a isolator on my own.(i guess its different from ground loop...)

regards

Originally Posted by jaguar999

I am facing the noise problem when i connect my laptop to the DC-DC power supply. Its working fine when i run it on the laptop battery.

Can anyone tell me how to MAKE a isolator on my own.(i guess its different from ground loop...)

regards

Your problem is still ground loop. When you run off the laptop battery the ground is "isolated" from the rest of the vehicle electrical which is why there is no whine.

Most likely you need to change the ground location for your psu?

Originally Posted by jake789

Your problem is still ground loop. When you run off the laptop battery the ground is "isolated" from the rest of the vehicle electrical which is why there is no whine.

Most likely you need to change the ground location for your psu?

Im having the same problem with a DC/DC laptop charger. I made a post on the "how to power a laptop" section in case anyone can give me ideas on how to fix it.
http://www.mp3car.com/vbulletin/how-...ger-noise.html

(If this is considered cross-posting please move my thread if needed)

hey guys, i have installed my carpc on saturday and from then i have serious problem with my sound! Before carputer i had the stock HU of peugeot with a custom 2-channel AMP and a woofer. Since i got my pc installed i used the RCA cables to connect the AMP to the sound card (with 3.5mm jack to RCA) but i get no sound from the car speakers, only from the woofer in the trunk. Also i get a lot of noise from the woofer which is from the RCA cables and i also have problem with the alternator as i can hear it spinning through my only one left woofer!

this is my setup before (left) and after (right) carpc install.


can you help me what to do? I think to buy a Ground loop isolator and plug it right before the AMP. what else then?

even a ground loop should not prevent speakers from emitting audio, a GL will just add a audio signal that you don't want..

from your diagram:
was the amp connected using the high-level inputs off the radio?
this would be why your main speakers don't work-- you'll need another amp.

and for the subs, as long as one has a signal, the other should have a signal-- check your connections.

thank you for the reply. Look this setup was made by a technician from the previous owner of the car. Today i figured the connections out.

The AMP is a rockwood 2-channel. From the one side there there are : 2 RCA connectors for the LOW-LVL signal, 2 pairs (2 red and 2 black) connectors for the HIGH-LVL input and the spinning thing to set the input settings. From the other side there are : 2 pairs of SPEAKERS output (2 red and 2 black), the ground, B+ and remote.

Today i also found that i have 6 speakers (2 tweeters, 2 front and 2 rear)

The initial setup was the 2 pairs of the speakers in the car cabin connected in HIGH LEVEL INPUT and another big speaker connected to one of the 2 SPEAKERS OUTPUT.

What i did was to buy a ground loop isolator and put it near the AMP and disconnected all the cables from it. Then i connected the 2 pairs of the speakers to the SPEAKERS output of the AMP and i removed the woofer completelly! This made the rear speakers work but i can hear nothing from the front-tweeters speakers! Maybe they are damaged??? But they did work before the pc!

Putting the GL isolator, isolated completelly the RPM noise but i can still hear noise from the rear speakers. While system boots, noise goes louder than when system is up&running. So i think that something's wrong with pc's sound card.


Car setup

mini-itx ASUS AT3IONT-I (NOT the deluxe version)
kingston ddr3 1066ghz 1x2gb
seagate momentus 5400.6 320gb sata
lilliput 669gl touch

Audio
Rockwood 2-channel amplifier
2 tweeters in-dash }
} I cannot hear anything! i dont know why
2 front speakers }
2 rear speakers : i can hear sound from these but there's something with the signal, maybe the cables! In random times i can hear music in great quality from both speakers but in other times i hear only from the one side or the other.

I completelly removed the woofer!!

rear speakers: you have a ground loop. this is what is causing the noise to come through the speakers--double check this thread for the proper grounding procedure. the GLI is only a bandaid, and as you found is never a cure-all, and many times will not work..

a poor power connection can also cause audible noises from the pc as well-- if the pc and/or amp were not properly grounded, or grounded to different locations.

the rear speakers should not go in and out--this indicates a wiring problem-- either a faulty connection, or a short..


front speakers: being that you only connected the rear speakers to the amp, these will not work. you will need to run wire from the front speakers to the amp.

note: you can make a 2 ch amp work with multiple speakers, but you need to first understand that connecting everything wrong could hurt the amp, or speakers.. you will also need to understand ohms law, and series/parallel wiring configurations..

so i would recommend getting either 1) another 2ch amp for the front speakers, or 2) get a 4ch amp.


this is also a good time to remind you that while i, and others on this board will do what we can to help, this is still only a online forum, and that can make it very tough to help with wiring, and ground loop issues.. if you run stuck at any point, i would highly recommend trying to get help from a local car stereo shop.

I started this project not only for my in-car entertainment but also to learn things off it! That's why i'm trying to do my best If i reach a point i cannot go further, i'll surelly ask help from a professional!

On topic now, i completelly found what's going on in my audio. First of all as i said i have 6 speakers, 4 front and 2 rear. The 4 front speakers go directly to the ISO port. The 2 rear speakers go to ISO port and then with 2 pairs of shielded wires go to the trunk, into the amplifier. That's why i can only hear sound from behind!

As for the grounding.
M3-ATX is grounded to the black wire of the ISO port.
Lilliput touchscreen is grounded to the same black wire.
Amplifier's ground is in the screw of the central safety belt of the back seat.

As for every other ground in the car i hope car manufacturer did a good job. Should i check every ground in the car? And if i have to, how is it possible?