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      09-08-2011, 05:19 AM   #22
Technic
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Drives: 2012 E92 M3, 2014 528i
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Location: Ft Lauderdale, Florida

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Quote:
Originally Posted by sunpole View Post
Did more testing this afternoon, here is another update,

I think I've ruled out the following factors:
- Not an amp issue, tried with 2 amps
- Not a RCA cable issue, I tried with 2 sets of RCA cables
- Not a ground issue - tried 4 ground points
- Not a speaker/tweeter issue. 2 reasons, first I can hear hissing noise distinctively from
both when gain is turned up, 2nd the noise is gone with unplug the HU or replace it with another source ipod

What is left
- HU noise. but this is unlikely, because it wasn't there before.
- Harness connection related problem, it is creating some sort of feedback or harsh connection? Not sure how to test this, any idea? Should I try with another harness?
- Lastly do you think a MS8 equalizer would help with this problem?
Replacing the OEM HU balanced outputs with the iPod non-balanced outputs will give you different results by themselves, so it is not a valid comparison.

In the non-balanced signal the ground is part of the signal, and it is also a ground that it is not shared with the car -you have the iPod in your hand. None of that applies to the OEM HU -the output signal does not have any ground and the ground of the OEM HU is shared with other devices in the car.

So you could be masking a ground/interference problem in the car.
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