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Why does alt whine occur through speakers

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Old 06-14-2011, 06:05 PM
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Why does alt whine occur through speakers

So I am asking this question because have had issues in the past , As yet today I still struggle with solving it. In some cases it is as easy as a bad deck gnd. or maybe a body gnd, or always a gnd in general. Several things can fix this issue by rectifing the problem . Now what if any of these does not stop the noise ? I remember my brother in law asking about this long ago and I dont know if he got the issue fixed or not. But for me atm I have it coming through 4 channels and cannot find a fix for it. I have tried the following .....

Ensure all gnds up front and at rear have solid connection to batts, alts, frame, body etc. I have power and gnd feeding deck from same bank that amps are fed from. The rca donot run near power runs. And I have yet run another run outside vehicle and does nothing. Have tried a diff deck and still same issue. Used power source to feed deck and still same. Gnd the outer sheild on rca at deck and at amp , nothing........... very very strange. Now I disconnect alts to see which is causing it and the oem one is fine , the big ones are the ones who do it. But the oem is not yet connected to rear bank.
But here is the real kickers. When i plug an rca cable into amp , and nothing on other end the noise is same as if plugged to source. If I put in PPI A600 or A300 in place of 4 channel there is no noise at all............ Manufacture says no problems with 200 + amps out there and so doesnt feel it is an amp problem. But how can it not be ? if one amp does it and yet another make does not ? I am out of ideas. The last things I can think of is to wire oem alt to back bank and see if still does it. This will rule out problem with big alts. The other thing is to put some old stinger 1/2 fared caps on each alt and see if that will bleed it out ??

any Ideas ? Other than replacing amps , which maybe done later this week.
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Old 06-14-2011, 11:13 PM
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I fixed my alt whine with 2 noise filters ($15 each), put one on constant battery and the other on ACC wire of your source unit.
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Old 06-15-2011, 03:18 AM
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Power noise filters can work. Also can try a ground loop isolator, though some can limit frequency response. They are more of a bandaid, but if that's what it comes down to, why not?

How old is the amp that's seems to be the noisy one? Sometimes a leaky cap or another semi-failed part inside or a bad solder connection can cause noise. If the noise goes away when the amp is replaced, I'd lean that way.
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Old 06-15-2011, 09:56 AM
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The amps is 2 weeks old maybe. noise been there since day one. I can't find the old rca filter I had yrs ago but I know that is not the problem, It is coming in through power supply, So last night I temp installed a 1/2 fared cap on one alt at a time and found the upper one to be generating the noise into it. Mounted Cap and wired in and now the noise is hardly there on front end but it didnt do a damn thing for the other amp . So pretty have condemned it for good now. Will get it replaced on thursday if not both.
Really strange . First time ever I have had to condemn a piece of equipment.
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Old 06-15-2011, 04:03 PM
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It's the amp. Take an RCA end and connect the pin to the shield (shorting plug) and plug it into the amp. If it whines, it's pooched. If the manufacturer won't help you, spam their *** all over the net. Everyone makes a bad unit here or there - to dismiss it as impossible is myopic.

This pretty much put the nails in the coffin for your suspect amp(s):

If I put in PPI A600 or A300 in place of 4 channel there is no noise at all
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Old 06-17-2011, 11:24 PM
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Yes Dukk, It was the amp, Removed and installed in another vehicle to test and does exact same thing, Manufacture was like wow, never seen that happen to one before, but had no issues replacing it. Funny thing is when connecting the power/Gnd into it there was no cap charge spark... just like there is no fuse in it... But is all good now.

Thanks for the info, just wanted to make sure I was not missing anything and had never encountered this before as well.
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Old 06-18-2011, 01:20 PM
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You don't always get a charge spark. Maybe the power filter caps were defective
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Old 06-20-2011, 03:39 PM
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Yes maybe, But to add to my stress on this issue I was doin more to it on saturday and I cannot get this noise to go away I have never had such an issue ever before. I have the 1/2 fared cap on the alt output, Added another and didnt help. The noise is induced through the power input. I can plug anything into any amp powering front end and the noise still comes through. It is not as loud as once was but the fact of the matter is that is there and it is burning me up trying to stop it. I have talked to my alt guy and he doesnt really have an answer atm, but is looking into it. Funny thing is that this has come into effect only after all gear was installed. It was not there before hand. So at this point I think that I am going to run a separate power from the vehicle battery and feed anything front end related of the oem side and leave sub amps on the rear bank and the aftermarket alts. Load tested them this weekend and got 351.7A out of one and 351.9A out of the other. So it not a diode problem inducing added ac voltage. Although the cap on the top alt makes the differance , jsut really strange. I have no ideas left if running a separate power to front end componets dont work, other than a power supply , But where to find a 12v to 12 v 100 A power supply That doesnt cost huge $ ?
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Old 07-07-2011, 02:07 PM
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So have now got the issue fixed. Was something I shoulda done long ago but didnt have any issues before and didnt think it mattered if everything was isolated to rear bank of batts... But apparently not... So have all componets installed in the truck again and no noise other than a tiny bit from the 30 band that you can only hear when the system is muted and doors closed with engine off.

Had to take all alt charge wires to the front battery and then run charge wires to rear bank , funny how it make that difference. gnds all the same as was so was not a gnd issue. weird...
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