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Yesterday I did the wiring for my upcoming Alpine amplifier and for testing, I used my good old Legacy LA-895 amplifier that I had previously installed on my E30 without any problems.

I have a major problem on the E46 though; Excessive noise!

The amplifier seems to pick noise from the HU CD Drive spinning, engine noise, alternator noise, spark noise, when I turn my carputer on, it picks the noise from the CPU fans as well at a point you can***8217;t listen to the music!

The LA895 is taking power directly from the battery with an 80A inline fuse. Ground is also direct on the battery negative although I tried grounding the amp on the chassis as well.

For wiring I did my own RCA connections with high quality wires with gold plated connectors, 2m max distance from HU to amp. I also tried routing the RCA wires from other points, away from amp***8217;s power line but still I got the noise.

Also tried an inline RCA audio filter which seems to eliminate 90% of the noise but also kills all the bass. The audio filter had a ground wire as well and when I used the ground, the noise came back as if there was no filter installed!

I have also disabled the HU***8217;s built-in amp, played with every setting I could find on the HU and amp with no solution!

Bear in mind that my HU, carputer are located directly above the battery if it makes any difference. Please give me some help because I don***8217;t want to spend £££ on a new amp and have such issues! Without the amp, my current setup works perfectly fine.

Here***8217;s a rough drawing of the current setup



Also tried today:

Made better RCA cables with shielded RG58 wire, did not help at all, with other routes as well.

Grounded carputer, HU, Amp, directly on battery terminal using same length wires ... nothing

Using the high-level input of the amplifier (inputs already amplified signal from HU's amp output) DID help eliminating (or covering) around 70% of the interference but I could still hear the spark/fuelpump/alternator/fans noise.

The only thing left to try is a 12v inline power filter/suppressor..

Any tips?
 

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Bump!!

I have the same problem. Has anyone found a solution?
 

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Does the noise level change when you adjust the volume?

Is the headunit really that close to the carputer? Noise may be getting radiated onto the HU from the carputer. You may not have heard the noise before as you werent making use of the RCA levels prior to the amp.
Try moving one or the other away to see if the noise persists.

One other thing which is probably obvious, but also check to see if your levels on the amp are turned up too high.

If the problem persists you may have to use a 12V noise suppression filter as you indicated. As a DIYer you may appreciate this alternative:

http://n4maa.us/alternator.htm
 

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Yesterday I did the wiring for my upcoming Alpine amplifier and for testing, I used my good old Legacy LA-895 amplifier that I had previously installed on my E30 without any problems.

I have a major problem on the E46 though; Excessive noise!

The amplifier seems to pick noise from the HU CD Drive spinning, engine noise, alternator noise, spark noise, when I turn my carputer on, it picks the noise from the CPU fans as well at a point you can't listen to the music!

The LA895 is taking power directly from the battery with an 80A inline fuse. Ground is also direct on the battery negative although I tried grounding the amp on the chassis as well.

For wiring I did my own RCA connections with high quality wires with gold plated connectors, 2m max distance from HU to amp. I also tried routing the RCA wires from other points, away from amp's power line but still I got the noise.

Also tried an inline RCA audio filter which seems to eliminate 90% of the noise but also kills all the bass. The audio filter had a ground wire as well and when I used the ground, the noise came back as if there was no filter installed!

I have also disabled the HU's built-in amp, played with every setting I could find on the HU and amp with no solution!

Bear in mind that my HU, carputer are located directly above the battery if it makes any difference. Please give me some help because I don't want to spend £££ on a new amp and have such issues! Without the amp, my current setup works perfectly fine.

Here's a rough drawing of the current setup



Also tried today:

Made better RCA cables with shielded RG58 wire, did not help at all, with other routes as well.

Grounded carputer, HU, Amp, directly on battery terminal using same length wires ... nothing

Using the high-level input of the amplifier (inputs already amplified signal from HU's amp output) DID help eliminating (or covering) around 70% of the interference but I could still hear the spark/fuelpump/alternator/fans noise.

The only thing left to try is a 12v inline power filter/suppressor..

Any tips?
Your problem is caused by the balanced differential outputs from the OEM head. See http://en.wikipedia.org/wiki/Differential_signaling for an explanation.

You've got to install a device such as a SVEN-4 to change the balanced differential signals into normal line level signals used as inputs by most amps. :str8pimpi
 

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Discussion Starter #6
Does the noise level change when you adjust the volume?
No it's the same across the volume spectrum.

Is the headunit really that close to the carputer?
It sits just above it. Here's my CARpc Install

You may not have heard the noise before as you werent making use of the RCA levels prior to the amp.
Before using the RCA output I could hear the alternator whine but very very faint - I had to focus to hear it. Now with the Amp+RCA I hear almost everything

Try moving one or the other away to see if the noise persists.
did not help ;(

One other thing which is probably obvious, but also check to see if your levels on the amp are turned up too high
Checked .. no difference!

As a DIYer you may appreciate this alternative:
I might as well try it!

Your problem is caused by the balanced differential outputs from the OEM head
I don't have an OEM head! I'm using a Kenwood KDC-6531 unit. Have a look at my carputer install!
 

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maybe its the amp? try swapping it out, it seems to me as you said before everything worked fine w/o it, so try swap it out.
 

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Discussion Starter #9
maybe its the amp? try swapping it out, it seems to me as you said before everything worked fine w/o it, so try swap it out.
I'll try that and see..

Keep signal wires away from high-current wires, this includes the battery!
There's at least 1m distance from the high current wires..

I'm getting an inline power filter tomorrow to see if it helps
 

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Didn't you say you have the computer, etc over the battery? - not a good idea if you want to avoid noise.

Don't waste your money on filters. Fix the real problem, don't patch it at the expense of sound quality.


Does the amp accept balance-differential signals? If not, you need an adaptor.
 

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Discussion Starter #11
I moved all the equipment away from battery but it didn't help.

I'm planning to test a power filter, 50A; it will be inline with the amp power wire. not an RCA type sound filter so there will be no compromise in quality. see the link at post #3.

I thought the balance-differential signal is only from OEM headunit. I have an aftermarket one..
 

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I moved all the equipment away from battery but it didn't help.

I'm planning to test a power filter, 50A; it will be inline with the amp power wire. not an RCA type sound filter so there will be no compromise in quality. see the link at post #3.

I thought the balance-differential signal is only from OEM headunit. I have an aftermarket one..
If you have an aftermarket head unit, then it doesn't apply.

Don't waste your money on a power filter (RCA or power). If you have noise because of the amplifier power supply, then you have a bad amp!

Click on my sig to go to my website, then follow the links to the alternator noise section. Good information on cause and troubleshooting tips.

This is how I would go about troubleshooting:
1. make sure power is far away from componets and signal wires.
2. check voltage at all system components, including battery. Should all be similar.
3. Isolate components from the system one by one to determine noise source. To make process faster, I always split the system in half. for example, remove RCA inputs from amplifier, add rca plugs with + and - shorted out. If noise goes away, go upstream.
 

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its most likely your amp, if you have removed all the equipment out of your car and wired them up outside and still get the noise.
 

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Did you check your ground wire on your amp. Make sure its at most 15 inches long, also make sure you're ground to bare metal (scrape away any paint under the connector). Also try running a new ground to the head-unit as a faulty oem ground wire can also be the cause of your noise.
 
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