How many get some level of line noise?

judoGTI · 03-19-2008, 04:19 PM

I have my car wired fairly safe to prevent line noise, but no matter what I cant get rid of all of it.

I was curious if I am always to expect some level of line noise, or if some people have none.

for instance, driving around with the PC on, and no music playing, where do you hear your noise?

If I hit RPMs over 3000 with no sound playing I do get a little of teh "whrrrrrrrr" sound, but very minimal.

NotYou · 03-19-2008, 04:41 PM

Generally, you shouldn't hear any whine or "wrrrrrrrrrrrr" anytime. If I had to guess, I would say it sounds like you have a bad ground somewhere, or a different resistance between your grounds. A dead-on sign of this is the "alternator whine" that your hearing, especially if it's different at different engine speeds or if you still hear it when muting your audio.

Dunno if your interested, but some suggestions on things to try to get rid of it:
- Undo all grounds (or rather, all grounds related to your a/v) and clean the metal thoroughly
- STRIP ALL paint away from the grounding point, no matter what.
- Reduce the amount of different "metals" that your grounds go to. For example, try to have all grounds attach directly to the frame. As compared to, say, one ground directly on the frame and another on the floor sheetmetal. In this example, although the sheetmetal contacts the frame, there will be different resistance in the electrical part between the two grounds and will cause hum.
- Upgrade the "big 3" wires, especially if the amount of amps you're pulling is close to the limit of the alternator --- alternator positive to battery positive, battery negative to chassis, and engine ground to chassis.

I had this in my Jeep Wrangler, and it took a little bit to get rid of. Turned out the third one was my culprit.

greatwhite · 03-19-2008, 05:49 PM

Nope.

Dead quiet (well, as quiet as a car can be).

You're experienceing a ground loop. Causes can be varied. Form a poor ground on you equpiment, a poor ground on an attached piece of equipment, to simply having your ground in a bad area.

I've moved a ground point in some people's systems 6 inches and eliminated a ground loop problem.....

You just have to keep at it using the time honored elimination methods and you'l get rid of it eventually (or you'll go nuts first, one or the other

).

Cheers

HiJackZX1 · 03-20-2008, 03:33 AM

You can also do the quick and lazy way. My first PC install suffured from engine whine, I was able to get rid of it with a ground loop isolator from Install Edge. They sell them at Best Buy, they are more expensive (17.99), but they dont muffle the sound like other isolators. I dont know if my new setup will have the same issue, since the ground has been moved and shortened. I dont have all the PC parts yet (MoBo) so I cant tell.

judoGTI · 03-20-2008, 11:29 AM

Yeah all my power comes straight from the battery, (I even ran the neg all the way there too).

The noise I get isnt bad, its barely audible at all, especially while driving. But since I go straight to the battery, I thought maybe it was normal to always have a little.

One of these days Im going to buy a PICO board and redo my PC. I'll re-run all the wiring then too and see what that does.

I appreciate the input! Very good info there.

HiJackZX1 · 03-20-2008, 12:36 PM

Quote: Originally Posted by judoGTI

Yeah all my power comes straight from the battery, (I even ran the neg all the way there too).

The noise I get isnt bad, its barely audible at all, especially while driving. But since I go straight to the battery, I thought maybe it was normal to always have a little.

One of these days Im going to buy a PICO board and redo my PC. I'll re-run all the wiring then too and see what that does.

I appreciate the input! Very good info there.

I heard that running a ground wire for such a long distance is bad..... You may want to check into that.... Im sure some1 can chim in and give the reason.... I think it has to do with if something over loads it will take longer to reach the ground point, thus destroying the equipment.......

NotYou · 03-20-2008, 01:15 PM

Yea, you really don't want to run the ground directly back to the battery. Most likely that is the reason for your engine whine.

Running the ground back to the battery is not a cardinal sin, but it's one of those "really bad things (tm)" because of the problems that could develop. I'd guess the length of that wire is around 10ft, much longer then any other ground wires in your car. The resistance, albeit small, of a wire that long can lead to the whine (especially if using a 16guage wire or thinner) since your other ground wires will be much shorter.

Also, your bypassing the normal flow of return electricity and creating two grounding paths. Again, not the end of the world, but if you ever have a short and something's not fused right you could end up hurting the car's ECM or similar. Trust mean, it can happen -- I had a power wire going to my amplifier sag from heat and end up toucing my exhaust system. Eventually melted the plastic coating of the wire, and shorted out when metal hit metal. Blew almost all my fuses and could have been alot worse -- just saying unexpected things can happen =).

Don't mean to sound like I'm lecturing, but giving that background information on the topic to help others!

judoGTI · 03-27-2008, 12:17 PM

No thats definitely good info. I'll need to find a good ground.

Any metal surface ok (as long as I get any paint off, etc.. if there is some)?

I'm more of a 'circuit' guy so going to the true ground is something Ive always done....

HiJackZX1 · 03-27-2008, 12:39 PM

Quote: Originally Posted by judoGTI

No thats definitely good info. I'll need to find a good ground.

Any metal surface ok (as long as I get any paint off, etc.. if there is some)?

I'm more of a 'circuit' guy so going to the true ground is something Ive always done....

I know what you mean, im the same way.... took me a bit to get the logic of the electrical for the car. I do have to say its easier, lol. Alot less wiring. Make sure that if you do create a new point you really get down to the bare metal. Use sandpaper and get the paint and primer off. I think your also not supposed to make it a smooth metal surface so it has better contact, should be ruff.

crooper · 04-01-2008, 11:05 PM

Mine whines til the sound card inits, then silence. I haven't built up the motivation to figure out the serial port relay thing for turning on my amps. Just doesn't matter to me for those few seconds before Windows wakes up. I did all the grounding stuff a while ago, and it helped.