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static 'hissing' noise problem
static 'hissing' noise problem
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Old 9th December 2011, 12:40 AM   #1
hakentt is offline hakentt  United States
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Join Date: Feb 2008
Default static 'hissing' noise problem

I bought two NEW rockford fosgate PRIME amps, one to power the subwoofer and other to power 6x9s. Car is 1995 BMW 325i engine that has 6 ignition coils. Head unit is new Pioneer connected to the stock wiring harness.
RCA cables are quality but they are not twisted kind and they run alone to the rear of the car. Remote is run from other side. Amp main power is in the trunk sense BMW has batteries in the trunk. all connections are clean and I use quality power cables.

There is no noise when RCA cables are not connected to the amps. Soon as I connect them I get ignition noise static even to speakers that head unit powers as well as speakers that amps power.

There is a whine that can be heard as well though but not nearly as prevalent. At 0 volume there is no noise. At 1 volume the hissing static shows up. As I increase the volume there is no change in the volume of this static noise, but when I rev the engine I can hear the whine change tone. The radio increases with the volume just fine though and at higher volumes I can't notice the static.

Where should I start checking? What do I need to do?
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Old 9th December 2011, 01:19 AM   #2
Perry Babin is offline Perry Babin  United States
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The fact that setting it to 0 volume kills the noise means that it's being affected by the muting in the head unit. Try running an RCA cable directly from the head unit, over the seats (or around the outside of the car) to the amp. Does that affect the noise?
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Old 9th December 2011, 01:48 AM   #3
hakentt is offline hakentt  United States
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Quote:
Originally Posted by Perry Babin View Post
Try running an RCA cable directly from the head unit, over the seats (or around the outside of the car) to the amp. Does that affect the noise?
Perry Babin to the rescue, you are my hero and I told you that many times before.

I just removed the Pioneer CD deck from the dash and ran another RCA cables from the deck to autside the car into the trunk into the RF PRIME r250-1 amp and static noise to the speakers that deck controls is gone, nice clean sound. But I still get static into the woofer that r250-1 amp controls but less, when I turn the deck down to volume "0" I get the engine noise at the woofer, then when I disconnect the RCA cables from the amp the static is gone.

What would be my next step?

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Old 9th December 2011, 02:01 AM   #4
Perry Babin is offline Perry Babin  United States
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What if you disconnect the subwoofer control cable from the amp?
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Old 9th December 2011, 02:13 AM   #5
hakentt is offline hakentt  United States
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Quote:
Originally Posted by Perry Babin View Post
What if you disconnect the subwoofer control cable from the amp?
I am not using the bass boost knob that comes with the amp. There is no static when I disconnect the RCA from the amp. When I connect the RCAs to the amp even if the deck is at zero volume I get static. This mean that noise is comming from RCA that I rerouted outside the car. I don't know what would be my next step?

Run separate power lines to the deck?
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Old 9th December 2011, 02:18 AM   #6
Perry Babin is offline Perry Babin  United States
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Is the head unit in it's normal location?

If so, pull it out of the dash and see if that changes the noise level.
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Old 9th December 2011, 02:25 AM   #7
hakentt is offline hakentt  United States
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Quote:
Originally Posted by Perry Babin View Post
Is the head unit in it's normal location?

If so, pull it out of the dash and see if that changes the noise level.
I pulled it out and held it in hand outside of the dash when I was testing. There is noise.

I searched google pioneer deck rca noise and found out this:

static 'hissing' noise problem


Quote:
Try grounding your rcas if that doesn't work go look at neofrogs build he was having the same issue and ray responded and knew exactly what was occurring
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Old 9th December 2011, 02:28 AM   #8
Perry Babin is offline Perry Babin  United States
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That's generally the cause of engine noise and it doesn't stop when the volume is set to 0.
RCA Shield Repair
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Old 9th December 2011, 02:32 AM   #9
hakentt is offline hakentt  United States
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Thanks for the link. The photo of the head unit is the exact same that I got. DEH-P3700MP

Quote:
There should be less than 1 ohm between the RCA output shields (the shiny outside part of the connector) and the case of the HU.
I am not getting any continuity between RCA output shields and the case of the pioneer unit
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Old 9th December 2011, 02:35 AM   #10
Perry Babin is offline Perry Babin  United States
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Install the jumpers (fused jumpers suggested) to see if it helps.

Before connecting the RCAs to the amps, measure the DC voltage on the shields of the amp RCAs (black probe on amp ground) to see if there is any significant DC.
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