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Help! Alt Noise Question - Driving Me Nuts!

madmoomoo

By madmoomoo,
in Car Audio & Electrical

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RANDY Veteran

RANDY

Posted
Posted

Heh! They certainly don't do much!

Heath: Did you run the head unit off the floor or seat? Or was it still sitting in the bay? As mentioned earlier, I found a harness that runs in that bay-area, and behind the AC unit that has MASSIVE electrical interference. I could hold the rca's near it, and the whine was louder than the music (at mid-levels).

If you can't test it that way, then grab a 3.5mm stereo mini jack (same as your earphones) to RCA cable. 3.5mm->2xRCA

Plug in your walkman/ipod/whatever into the minijack, then the RCA end goes into your RCA cables (in or outside the car, test both) and see if the noise is there.

If you still have noise, then your head unit is ruled out. It's either your RCA cables, their positioning, or your amp.

Run the rca's from the amp straight out the boot, and use the ipod plugged into them, so you're nowhere near the body.

If that is still noisy, change your RCA cable... use a short one to test with the ipod to the amp. Grab one out of your TV/DVD player and test with it. If the noise is still there, try and borrow a friends amp, and retest all of the above.

Turn your gains down on the amp. Put a massive earth on the battery.

Jetdat Veteran

Jetdat

Posted
Posted

had the same annoying problem when i installed 2 amps in the boot, used supressors which help a little but the noise remained...

i finally tracked the problem to the rca cable being too close to the battery...once i moved it away from the battery noise totally gone..

madmoomoo Collaborator

madmoomoo

Posted
  • Author
Posted

There are certainly some very good suggestions here to try - I just have a question for the not-so-audio-genius-people like me: For the people suggesting to check the fuses on the GROUND wires and also the "fuseable link" on the rca outs, are these like your normal inline fuse that would be on the wire going from the head unit to the ground or rca out, or is it on the head unit itself or somewhere else??

Last I remember, There were no fuses in the wiring behind the head unit, except for the +12v one. The ground wire went straight from head unit to the chasis and the rca cables had no visible fuse in them...

Thanks for the great ideas. (Still have the damn noise - tried head unit ground points. I guess next would be fuses as suggested, or new rca cables...)

cheers!

growtalski Contributor

growtalski

Posted
Posted

I had the same problem. Tried all options (moving earth point, new rca leads etc...) and nothing worked.

The problem was that on my pioneer head unit RCA outputs there was no earth reference on the shield. So I soldered a copperwire onto the shield (earth) of both of the rca outputs and earthed it to the chassis of the head deck. No more noise.

I'm not sure if my headdeck was faulty from factory as i and the other techs at work couldn't see a earth track to the circuit board. I have Audiobahn amps which are american(purchased at JB in Aus along with head deck) and the headdeck is australian. Not sure whether this had something to do with the problem as i've heard that some american cars are positive to chassis.

Stocka Apprentice

Stocka

Posted
Posted

I had the same problem went and baught a 60amp noise suppressor from jaycar and that didnt fix it but i left it on anyway , i even shortend the +12v cable so there was less chance of noise still just as bad. a month or so later i was doing the earth on the fuel pump and happend to move the negative cable coming from the amp heard that the noise was quieter. i changed the earthing point from the left where the cable was behind the battery to up under the parcel shelf on the right hand side with minimum length cable . fixed . hope this helps i think if your still getting noise do what the other fellas said and re earth the head unit .

RANDY Veteran

RANDY

Posted
Posted

The earth fuse on the RCA output is actually built into the headunit. Sometimes it's a tiny fuse that is replaceable. That fuse blows if you plug RCA's in while the amp is on, or the RCA's short on the body or something.

Grounding the RCA negative side to the head unit can act as a workaround...

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