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CD player noise

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jrz126

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I recently blew the internal amp inside my cd player in my car. It's after market so it has the RCA outputs for external amps. So I have all my speakers running off external amps. Now I'm getting a ton of alternator interference. I already have a filter on my RCA's, and they arent run next to the power wires ect.

Also, I noticed that I'm getting noises from (i think) the laser head motor inside the cd player, I can hear it in the subwoofers, it's just a quick pulse every second or two. (This is with the car off). Is there any way to fix this without tearing my cd-player apart?

So this brings me to the conclusion that I need a filter on the +12V input to the head unit. Is there any sort of filter I can build to correct this, (choke filter?)
 
Try different size caps for this as I am not sure what frequncy range that this noise is in.

Try a 1uF ceramic to start with and just put it from +12volt to ground, if that don't work double it to 2uF, if that still will not work double it untill it does.

I am wonerding if this is an internal noise problem. How is your RCA's Filtered??

Using a choke will cause alittle more resistance to DC, causes a ground loop feedback to go through positive forced to find a loop tied to negitive, so if you use a choke use a cap behind it to form a signal or noise ground. Yes chokes oppose AC or noise riding on DC, but care must be taken or more worse things can happen.

RCA's are coaxial cables with a ground referance shield. If I had a chance I would O-scope the +12 volt, the Ground referance on the RCA's, Ground going into the amps, and the speaker outputs with no input, then find out what frequncy the noise is in otherwise it just a shot in the dark blind folded.
 
I measured the current draw of the CD player, It's only ~0.76A at the highest volume.

I was looking at filters, and I found this one here: **broken link removed**
Will this do the job?
 
Was it makeing this noise befor the amp i/c blew.
If it was ok before , then i would look for some blown
print (usually an earth track)
 
I would stick to using small caps, but if you want I don't see a huge problem with a choke just use a cap before the inductor to ground this will asure no kick back, or feedback loops. Better yet, cap both sides of the choke to asure the noise coming in and leaving the deck is signaled to ground.

The thing is impedance of the coil versus the supply source, if any noise riding on the 12 volt going into the deck sees this as higher impedance over the source the noise will loop back through the battery to ground effectily making the car a electrostatic antanna because the noise was offset by 12 volts the potential to get shocked is there at ground. Same goes for noise leaving the deck. If the noise sees the coil as high impedance over the deck itself it will positivly loop though the circuitry of the deck to ground.
 
hmmm....I was following you until the beginning of the second paragraph....what value caps would you recommend?

Should I just go out and buy a pre-assembled noise filter? it should only be like 10 bucks?
 
470uF for low frequency, and .02uf-10nF for high frequncies.

But do whatever you want.
 
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