ECU interference on door speaker

Ameer Antar antar at
Tue Dec 12 17:25:42 EST 2006

Huw, thanks for detailed reply. I have a few more questions below...
-------------------- Original Message --------------------
From:Huw Powell [audi at]
To:Ameer Antar [antar at]
Cc:Quattro List [quattro at]
Date:12/12/06 1:56:12 PM
Subject:Re: ECU interference on door speaker

>[insert reply about grounding]
>> Thanks for the info. Unfortunately, I already have everything setup
>> that way. I have a ground cable directly from the batt to the a
>> splitter and then onto the amps.
Could you explain what problems doing that might have caused?

> What you should try, and I don't mean "if it's convenient" is a bit more
>extreme ground management. All the components of the system should be
>well grounded to one point (like the battery terminal or a good frame
>stud). Line level cables are vulnerable to creating ground loops and
>picking up noise, and so ideally their shields should also all be ground
>to only one point - usually the head unit, but if there is one compnent
>connected to all the others, it might be a better choice. For this you
>need "directional" cables. Not that the signal flows differently one
>way or another, but that the sheild is only connected to the ground of
>the plug at one end.

The only component that has a different ground is the head unit. Would running a ground from the battery to head unit possibly help?
> It is being picked up in the head unit to amp run, obviously after the
>volume control. You mentioned a "splitter" as well, I suppose that is
>between the head unit and two amplifiers?
Yes, there are splitters for each line, but even after connecting the amp directly to main patch cable, it's still noisy. So, I guess I could test this by disconnecting all patch cables to the amps. That should clarify if it's a power or audiocable issue, right?
> You might also have a compromised line level cable - one that is not
> shielded properly, etc.
I'm using those twisted pair patch cables. Are these any good? How about those line-level noise filters? Do they affect sound quality much?

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