Alternator Whine (Mean Green)

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I've noticed some Alternator Whine coming from my subwoofer (via amp thats directly attached to the battery). I didn't have this before I had the MG, do I need to put some kind of isolator in? The whine doesn't always happen, in fact I think if I turn the radio off before I turn the car off, when I turn it back on after the car is started it isn't there. Its only when the radio comes on with the car that I get it. Its a whistling sound coming from the subwoofer thats directly associated to engine RPMs. How can I get rid of it!?
 
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Usually when you get this whine it is coming from the power cables to the Amp. Try putting a cap in between the car battery and the amp power. I had the same problem in my mustang, and that fixed it for me. Another cause could be too small of a guage wire for the amp power leads.

Dave
 
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90FJ62 said:
Usually when you get this whine it is coming from the power cables to the Amp. Try putting a cap in between the car battery and the amp power. I had the same problem in my mustang, and that fixed it for me. Another cause could be too small of a guage wire for the amp power leads.

Dave
The power lead is 2 GA and the amp only draws 300watts, its way overkill. How come I never had this problem with the stock alternator? A capacitor isn't going to "clean" the power, all it does is store it for quick release so there isn't a quick voltage drop in the system.
 

Spook50

I just got an idea....
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WALoeIII said:
The power lead is 2 GA and the amp only draws 300watts, its way overkill. How come I never had this problem with the stock alternator? A capacitor isn't going to "clean" the power, all it does is store it for quick release so there isn't a quick voltage drop in the system.
Actually a good cap will give you a very steady "clean" output regulated down to a hundredths of a volt. You are right that the primary purpose is to store large amounts of power for quick demands, but they do have other benefits as well.

Something else that helps is go overkill with the amp's ground. Go two sizes bigger than what the directions say to use. Another trick is to ground the head unit and amp to the same spot on the chassis (run a wire from the head unit's ground lead to where you have the amp grounded to the chassis), and using signal wires with the ground loop isolation wires on them (the little pigtails). I did all this and completely got rid of any and all noise in my stereo. Made a HUGE improvement in the quality of the sound.

I still haven't installed my cap just because I'm waiting to have the second battery installed and wired first.
 
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Spook50 said:
Actually a good cap will give you a very steady "clean" output regulated down to a hundredths of a volt. You are right that the primary purpose is to store large amounts of power for quick demands, but they do have other benefits as well.

Something else that helps is go overkill with the amp's ground. Go two sizes bigger than what the directions say to use. Another trick is to ground the head unit and amp to the same spot on the chassis (run a wire from the head unit's ground lead to where you have the amp grounded to the chassis), and using signal wires with the ground loop isolation wires on them (the little pigtails). I did all this and completely got rid of any and all noise in my stereo. Made a HUGE improvement in the quality of the sound.

I still haven't installed my cap just because I'm waiting to have the second battery installed and wired first.
Hmm good info. Right now the Amp is powered and grounded by the same 2GA wire. The head unit is grounded in a different location, and it would be a bit tough to get it to the same spot where the amp is. It could be as simple as having some signal wires crossing the power wire since things got moved around with the new alternator install. What I don't understand is why its random, I haven't figured out how to cause it yet.
 

Spook50

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WALoeIII said:
Hmm good info. Right now the Amp is powered and grounded by the same 2GA wire. The head unit is grounded in a different location, and it would be a bit tough to get it to the same spot where the amp is. It could be as simple as having some signal wires crossing the power wire since things got moved around with the new alternator install. What I don't understand is why its random, I haven't figured out how to cause it yet.
If they're crossing it at a 90 degree angle and not running along side at any point, you're pretty safe as far as picking up interference from the power lead. Odds are you've got a ground loop that's only manifesting itself when the radio starts pulling power at the same time the alt starts putting it out.
 
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Spook50 said:
If they're crossing it at a 90 degree angle and not running along side at any point, you're pretty safe as far as picking up interference from the power lead. Odds are you've got a ground loop that's only manifesting itself when the radio starts pulling power at the same time the alt starts putting it out.
That sounds right, because if I turn the car on with the radio on I get it (alt doesn't put more than about 12 right after a cold start because it idles a bit low) but if I turn the radio on after the car is going its no problem. Making my ground bigger will solve this?
 

Spook50

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WALoeIII said:
That sounds right, because if I turn the car on with the radio on I get it (alt doesn't put more than about 12 right after a cold start because it idles a bit low) but if I turn the radio on after the car is going its no problem. Making my ground bigger will solve this?
It might help, but I'd bet money your complete solution will be to eliminate all ground loops like I mentioned earlier. It's a bitch, but well worth the effort. You'll be surprised at the difference it makes.
 
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Thanks for all the help. I'll extend the ground for the head unit to where the amp grounds (bolt of driver's seat) and if that doesn't solve it I need new wires for my speakers anyways, so I'll get nice ones that also ground.
 

Spook50

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WALoeIII said:
Thanks for all the help. I'll extend the ground for the head unit to where the amp grounds (bolt of driver's seat) and if that doesn't solve it I need new wires for my speakers anyways, so I'll get nice ones that also ground.
For your actual speaker wires, you don't need to worry about ground loop isolation since they're grounded to the amp. Just get some quality wires capable of carrying the current for the speakers. Where I would recommend ground loop isolation along with the head unit and amp is the signal wires (the RCA ones) going from the head unit to your amp.

You can also buy ground loop isolation transformers, but those are just snake oil. Properly wiring your system will give you excellent sound quality (and so will about 500 bucks worth of Dynamat :D )
 
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