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    joshpoints's Avatar
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    High sqeal

    Well my new amp that sounded so great when the car wasn't running doesn't sound too good. I'm getting a high squeal on the front preamp outputs, it gets louder as my engine's rpm's go up. Heres the thing though, I swapped the rca's from the rear and hooked them to the front channel of the amp, and I still get a noise. But when the rear rca's were hooked up to the rear input of the amp, there was no hiss. I think that this proves that it is not the rca's, but rather something is wrong with the front preamp inputs on the amp, what do you guys think? I just received the amp, it is new. I was also using these same rca's when I was running two two channel amps to power my system before and I didn't have engine noise.







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    MikeofTulsa's Avatar
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    sounds like alt whine......i would suggest re grounding your amp somewhere else as well as re grounding your h/u......usually solves the problem.....if it doesnt u can get a ground loop isolator to help take care of the problem....




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    Originally posted by Goddyd4me
    sounds like alt whine......i would suggest re grounding your amp somewhere else as well as re grounding your h/u......usually solves the problem.....if it doesnt u can get a ground loop isolator to help take care of the problem....
    Actually I have a correction. All the speakers are getting some interfereing noises. Do you know why the other amps that I had powering my system before had no problems with noise? Could it be that they rejected the noise better? Right now I have my amps grounded on a bolt at the back of the car. Where do you suggest I ground them to? How much would a ground loop isolator cost, and does it have any cons, or does it decrease the sound quality of the system at all?
    Last edited by joshpoints; 05-22-2003 at 06:49 PM.




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    My headunit is using the car's factory ground, so I'm assuming that it must be my amp grounds. I noticed that there is engine interference noise even when I totally disconnected the rca's from the head unit with everything turned on. If I sand down the area that I'm grounding to would this be okay, or is it the location of the ground (in the trunk) that is the actual problem?




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    MikeofTulsa's Avatar
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    Originally posted by joshpoints
    My headunit is using the car's factory ground, so I'm assuming that it must be my amp grounds. I noticed that there is engine interference noise even when I totally disconnected the rca's from the head unit with everything turned on. If I sand down the area that I'm grounding to would this be okay, or is it the location of the ground (in the trunk) that is the actual problem?

    h/u using the factory ground can cause interference....seen it happen many times......and since there is no signal going to the amp from the rca's the it might be the amps grounds.....try sanding the area down first.....if that doesnt solve it make a diff. ground spot....




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    Originally posted by Goddyd4me
    h/u using the factory ground can cause interference....seen it happen many times......and since there is no signal going to the amp from the rca's the it might be the amps grounds.....try sanding the area down first.....if that doesnt solve it make a diff. ground spot....
    I was looking on ebay at one of those gound loop isolators and it said that the whining is alternator noise like you said, and they said it can be caused by having more than one grounding point, which is what I have. I'm running two separate grounds, one for my sub amp, and one for my amp powering my mids and highs. Can I run two separate grounding points like this, or should I ground them both to the same bolt?




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    MikeofTulsa's Avatar
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    generally speaking......its suggested to use one common ground point......all depens tho.......worst case u could always use the ground loop isolator......but regrounding everything usually works




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    Originally posted by Goddyd4me
    generally speaking......its suggested to use one common ground point......all depens tho.......worst case u could always use the ground loop isolator......but regrounding everything usually works
    I tried grounding them to the same point, but I still hear it. I took a good look at the grounding point and it isn't very good. It's not flat. I'm going to try to find a new ground point. Do the ground loop isolators reduce the sound quality? I would also like to say I hate my neighborhood. I can't even open my trunk with my speakers, I can't work on my stereo, because I fear someone seeing me and deciding to rip it off one night. It's darn near a ghetto. I wish I lived in a place where neighbors could be trusted and were friendly. Some are, but there are enough that aren't. I'll try to have to reground it tomorrow maybe on my lunch at work. It's a much nicer area, you don't have to worry about anyone over there. Thanks for all your help and if you could please respond if you know if ground loop isolators reduce sound quality. I plan on getting a cheap one made by audiopipe. If you know any fairly cheap good quality ones let me know.




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    If you have noise even with the RCA cables disconnected from the amp, then isolators won't help you. They help when the HU and amp grounds are at different potentials. But the amp by itself shouldn't make any noise. Is the amp case grounded also? If it is, try putting it on a carpet and trying it.



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    Running your RCA's along side your power cable can cause a lot of interference. If it's not the grounds or that then I have no idea what it would be. Good luck!




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    Originally posted by maylar
    If you have noise even with the RCA cables disconnected from the amp, then isolators won't help you. They help when the HU and amp grounds are at different potentials. But the amp by itself shouldn't make any noise. Is the amp case grounded also? If it is, try putting it on a carpet and trying it.
    The noise happens when the rca's are disconnected from the headunit, but when I disconnect the rca's from the amp the noise stops. Here's what I find strange. None of this happened with my other amps. I think they may have had better noise rejection. I'm going to try hooking one of my other amps back up and I'll see if it still makes noise. The amps case is on carpeting. Have any of you used isolators with success? I tried a new grounding place and I still have the noise. Will cleaning the ground surface help, or is this problem unavoidable when the HU and the amp are grounded at different potentials? Also what do you mean when you say grounded at different potentials?




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    Originally posted by joshpoints
    The noise happens when the rca's are disconnected from the headunit, but when I disconnect the rca's from the amp the noise stops. Here's what I find strange. None of this happened with my other amps. I think they may have had better noise rejection. I'm going to try hooking one of my other amps back up and I'll see if it still makes noise. The amps case is on carpeting. Have any of you used isolators with success? I tried a new grounding place and I still have the noise. Will cleaning the ground surface help, or is this problem unavoidable when the HU and the amp are grounded at different potentials? Also what do you mean when you say grounded at different potentials?
    I think Dave meant different grounding points. And yes, you will have a high probability of introducing noise that way (or so I've heard). It happened to me too, prior to getting a ground block. Move all your equipment gorund to one spot to try and eliminate ground loop.



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    Originally posted by joshpoints
    The noise happens when the rca's are disconnected from the headunit, but when I disconnect the rca's from the amp the noise stops.
    OK, that's good to know. It seems like the amp is picking up noise somehow in the cables. Try running the RCA wires a different route (do it ghetto first and see if it works).

    Also what do you mean when you say grounded at different potentials?
    The HU ground wire goes into the radio harness and grounds "somewhere". The amp is grounded to a different point, in your trunk. There is a possibility that there can be voltage differences between these points because of corrosion and whatnot in the car's ground system.

    The RCA preout terminals are grounded to the HU, and that is where the shield of the RCA cables connects to. Running RCA's between the HU and amp ties the two units together ground-to-ground. If there is a difference in voltage (potential) between the 2 units, you get a very small current flow through the RCA shield. That's a "ground loop", and it can raise hell with alternator whine. Ground isolator gizmo's separate the shield and couple the signal through capacitors. They isolate the DC levels between the 2 units while allowing the AC signal to pass through.

    I don't think they'd help in your case.



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    MikeofTulsa's Avatar
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    so as i said before....try re grounding your h/u.....would/could help tremendously




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    Originally posted by Goddyd4me
    so as i said before....try re grounding your h/u.....would/could help tremendously

    That's going to be a bizzitch. I don't know where I can ground the heaunit to. I don't think it's the rca's because they are running on the otherside of the car. They aren't any where close to my 0 gauge power wire. I think I'll try regrounding my headunit to a bolt on my seat. Everything is like snap plastic kind of parts in my saturn. There is very few metal bolts.




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