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Old 10th November 2007, 04:33 PM   #1
diyAudio Member
Join Date: Nov 2007
Default engine noise problem, HELP!!!!

hi all, i need help.

I drive a toyota corolla, 2004 reg.
i have a pioneer avic x1r head unit.

i then have a sub and amp in boot, 6/9's on shelf, and all speakers re loaded but thats niether here or there really for my problem.

when using the headunits amp there is no engine noise.
when i start using the RCA loom there is engine noise on outputs coming straight out of the head unit.

i have whittled it down to know its coming out of the unit and not picked up on the wires etc.

i tried giving the unit a better ground, no luck.

any ideas?


marc x
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Old 10th November 2007, 05:47 PM   #2
diyAudio Member
Join Date: Nov 2003
Location: Louisiana
Disconnect the RCA cables from the head unit and measure the resistance from the shields of the RCA jacks on the head unit to the case of the head unit. The resistance should be ~0 ohms. If it's significantly more, the shield ground of the RCA jacks has opened.
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Old 14th November 2007, 04:29 AM   #3
mda185 is offline mda185  United States
diyAudio Member
Join Date: Feb 2007
Location: New Jersey
Default Is amp in the trunk? Long cables = ground loop problems many times

How far is the amplifier mounted from the head unit? I have frequently seen this problem when the signal coming out of the head unit had a signal ground that was tied to chassis ground. IOW, there is zero ohms resistance between the negative rca output and the chassis of the head unit. If this is the case and there is a long cable run from the head unit to the amp, you can have different ground potentials at the head unit and the amp. This results in a ground loop and noise that tracks with the alternator output - a whine that goes up and down in frequency with engine speed. Best way to solve this is with differential input and output line driver such as those marketed by David Navone and Audio Control.

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