stubborn alt whine!

[gijoe 10+ year member]

I Just started getting some nasty alternator whine after installing my four channel amp. I have regrounded and reterminated both my sub amp and my four channel. I have also regrounded my head unit with 10 gauge wire to a non factory spot, I regrounded my ipod adapter to the same spot as the hu. I even grounded my rca's since I have a pioneer hu. After doing all of this, the noise isn't as lound, but I can still hear it if I turn the volume to 0. The noise increases with the engine, so i assume it's alternator whine, is there anything else it could be? The noise goes away when I disconnect either amp. There is no noise with just the sub amp on and there is also no noise with just the four channel. I have them grounded seperatly, about 4 inches apart. I took my dremel tool to the ground spot, so it's bare metal. I just can't seem to completly silence the noise. I have my rca's running down the opposite side from my power cable, but they mingle a little under my rear seat, before going into my trunk. Does anyone have any recommendations? I want to avoid a ground loop isolator if possible, but I'll do anything I have to to get rid of this horrible sound. Thanks!

Click to read more...

 

[gijoe 10+ year member]

Anyone?

 

[benzmansl65amg 10+ year member]

ground loop are both amps grounded at same point?

 

[gijoe 10+ year member]

Nope, about four inches apart. I've read conflicting arguments about whether or not to ground to the same spot. Should I try one ground point for both amps?

 

[IgnoreMe 5,000+ posts]

Nope, about four inches apart. I've read conflicting arguments about whether or not to ground to the same spot. Should I try one ground point for both amps?

1 ground point is good, but if your only 4" apart, that should effect anything (if both points are sounded down nice and clean). do you have a dmm handy?

have you tried disconnecting your radio atenna at the cd player? i had to do that to get rid of my alt whine.

 

[gijoe 10+ year member]

I do have a dmm handy, so far I've only used it for gains, so I don't know how to use is to check my grounds. I haven't unplugged the antenna but I'll try it. This noise is driving me crazy. I just got the amp and am eager to get my active setup dialed in, but I can't do anything until I fix the noise.

 

[IgnoreMe 5,000+ posts]

I do have a dmm handy, so far I've only used it for gains, so I don't know how to use is to check my grounds. I haven't unplugged the antenna but I'll try it. This noise is driving me crazy. I just got the amp and am eager to get my active setup dialed in, but I can't do anything until I fix the noise.

ok to check your ground do this.

1) turn the dmm to read ohms, and touch the leads together. you should get around .1-.2 ohms. this is your "baseline" if you will and you can consider it your "zero"

2) disconnect you negitive battery ground at the neg terminal and move it aside.

3) attach a piece of wire to the terminal at the end of the battery ground (the one that attaches to the battery post, and the other end of the wire to 1 lead on the dmm.

4) using the other lead on the dmm, probe your grounding points. they should give you .1-.2 ohms (depending on what your dmm read earlier). if they read any high, you need to find new grounds for them.

this can also be done for the HU ground up front.

 

[IgnoreMe 5,000+ posts]

this is a shitty drawing, but this is what you want to do

 

[gijoe 10+ year member]

Let me make sure I understand.

1. Disconnect the negative cable from my battery.

2. Attach a long wire to the now disconnected cable.

3. Attach that wire to one of the probes.

4. Poke around with the other probe until I find a spot that gives me the same reading as my baseline reading.

Did I get that correct? Once I find a good spot should I ground both amps there?

 

[IgnoreMe 5,000+ posts]

Let me make sure I understand.
1. Disconnect the negative cable from my battery.

2. Attach a long wire to the now disconnected cable.

3. Attach that wire to one of the probes.

4. Poke around with the other probe until I find a spot that gives me the same reading as my baseline reading.

Did I get that correct? Once I find a good spot should I ground both amps there?

you sure did. but check your current grounds for us. dont try to find new ones just yet. then let us know what you're reading.

 

[gijoe 10+ year member]

Haha, what do you mean, that's a great drawing. I see what's happening there though, so thanks a lot! Now hypothetically, what do I do If I find good grounds and still have noise?

 

[IgnoreMe 5,000+ posts]

Haha, what do you mean, that's a great drawing. I see what's happening there though, so thanks a lot! Now hypothetically, what do I do If I find good grounds and still have noise?

bad grounds are usually always the cause of alt whine. if you can, and it can be a pain, try grounding your HU to the same spot as your amps temporarily (just have the wire running in the car) and see if the noise goes away. you really want to check all grounds for your system. from the HU to every amp.

i would then check your rca's. try swapping your sub rca with the speaker rca at the HU, and then go back to the amps and do the same. see if the noise switches between them. little shit like that.

 

[gijoe 10+ year member]

Thanks a lot! I'll hopefully be able to tear everything apart and check everything tomorrow. You have been very helpful. Maybe you or someone can start a thread about all of the ways to use a dmm for car audio purposes, setting gains, checking grounds and speaker ohms. Something like that would make a great sticky!

 

[gijoe 10+ year member]

I haven't tested my grounds yet but I noticed something that may or may not be important. It seems (although it's difficult to tell for sure) that the whine is only coming from the right side speakers. I'm not sure if this is all in my head or not yet. I'll take off the door panel and check things out more closely, but is it possible that a bad speaker wire connection, or a terminal touching metal could be the problem?

 

[benzmansl65amg 10+ year member]

could be bad RCA's