Culprit for HU noise?

[ratedrookie 10+ year member]

I've been doing alot of searching on several audio forums to try to find an answer, but finally I am at the point where I have to post my own question.

Recently I am hearing plenty of noise coming from the HU. I installed the system about one year ago and never had a noise problem until a few months ago. The noise is only there when the engine is running and not with the ignition in the accessory position.

Doing some troubleshooting I found that if I remove the RCA's from the amp or the HU the noise goes away. Does this mean my RCA cable is bad?

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[ratedrookie 10+ year member]

any thoughts?

 

[Team Hammer 10+ year member]

Check all your grounds and connections from alt to HU.

 

[ratedrookie 10+ year member]

I checked all my grounds and all of them are fine. I just ran a new ground for my HU to the same spot as my amps. I now have a HU and 2 amps grounded at the same location.

I also swapped out one of the RCA cables for a spare set I had. New HU ground and a new set of RCA's and there is still the same noise! //content.invisioncic.com/y282845/emoticons/mad.gif.c18f003ab0ef8a0d9c27ca78d77a6392.gif

The noise is not coming from the speakers, it is definately coming from the HU and only during certain sound frequencies because I can hear it loud and clear in some music and not at all in others.

Again, the noise is only when the engine is running, but it does NOT vary with acceleration. It only gets louder when I turn up the volume from the HU.

The RCA's are run on the opposite side of the power cable and both my amps have the same gain settings.

I don't know what else to try and this is really starting to annoy me. Like I said, I installed this system over a year ago and had no such noise issue until recently. During that time I did not make any changes to the system that would induce the noise.

Any help or suggestions are greatly appreciated!

 

[supa_c 5,000+ posts]

where are you in cali ?

 

[supa_c 5,000+ posts]

I think your RCA preouts are fried man.

When you unplug rca's while a signal is still goign through them you create an arc and that fries the board inside the h/u.

If you can, check it with another h/u, if it goes away, there's your problem

 

[ratedrookie 10+ year member]

I think your RCA preouts are fried man.When you unplug rca's while a signal is still goign through them you create an arc and that fries the board inside the h/u.

If you can, check it with another h/u, if it goes away, there's your problem

I never unplugged the RCA's while the power was on. If what you are saying is true, wouldn't the noise be there regardless of whether or not the engine was running?

 

[supa_c 5,000+ posts]

The same thing happened to my friend, when the car was off, it was normal.

As soon as he turned his car on the nastiest ground loop was there.

We didnt even do anything, it was just there one day.

Do you have a pioneer h/u ?

 

[ratedrookie 10+ year member]

The HU is a Clarion DXZ845MC.

I also did another test where I ran one amp at a time and the noise was gone. Once I reconnect both amps and start the car, the noise comes back.

 

[supa_c 5,000+ posts]

swap the h/u and come back with some results

 

[ratedrookie 10+ year member]

swap the h/u and come back with some results

Wish I could, but I don't have any spare HU's lying around.

Do you think it would be a good idea to try to ground my RCA cables? Don't know if it would help, but it might be worth a shot since others have solved some noise issues by doing that. I have a bunch of spare remote wire lying around so could I use that to ground the RCA's? Could I connect it to the factory wiring harness ground?

 

[supa_c 5,000+ posts]

you could try, wouldnt do any harm

 

[ratedrookie 10+ year member]

swap the h/u and come back with some results

Okay, I just finished swapping to a different HU that I pulled out of my other car and guess what, the noise is still there so the problem is not with the HU.

I've checked almost everything else and I'm at a loss. I've elimintated the RCA's, amps, grounds, and now the HU as the problem.

What else can I check?

 

[supa_c 5,000+ posts]

Is it only from one amp ?

 

[azbass 5,000+ posts]

what kinda car was this in?