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I connected a Raspberry Pi 2 in the car to add OSMC media player capabilities. However, there seems to be a buzz / hum of background noise in the audio. The noise is correlated to the engine speed so it seems to be coming from the Alternator.

What are some different method of fixing this?

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    How did you connect the Pi up? (Also what car are you using?). It may be interference from the car's electrics, in which case you may need some form of shielding. – Wilf Dec 15 '15 at 19:05
  • I've tried both an "HDMI to RCA" converter and using the A/V output from the Pi2. Both have the same background noise. It's in a '12 Suburban with the stock integrated DVD player. What kind of shielding could be used? – Chris Pietschmann Dec 15 '15 at 19:07
  • I don't want to shut this question down, but I'd think that the decoupling of the supply voltage is a question better served at EE. It's mainly independent of the Pi (and while the answer has benefits to our site) I expect to get better answers over there. – Ghanima♦ Dec 15 '15 at 19:10
  • Thanks for the suggestion, I've posted it over there too. electronics.stackexchange.com/questions/206232/… – Chris Pietschmann Dec 15 '15 at 19:15
  • @ChrisPietschmann - please make it clear how you connected it up, and what exact hardware you are using. EE has a schematic editor which may help u. – Wilf Dec 15 '15 at 21:41
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There ended up being 2 issues to solve in fixing the background noise issue.

1) I bought a ground loop noise isolator. Put this in line with he RCA audio cable, with ground lead connected to the cars battery ground.

Here's the noise isolator I bought: http://www.amazon.com/gp/product/B000K50HJE

2) The 12v to USB power adapter / converter I was using initially was a really cheap one that wasn't providing good power to the Raspberry Pi. I replaced this with a much better one.

Never use cheap USB power adapters. Here's the USB power adapter I bought: http://www.amazon.com/gp/product/B00VH8VHWO

After making these 2 changes to the system, the audio no longer has any hum or background noise.

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I moved the USB connector from my 5V audio supply adapter to RPI USB port. That eliminated the buzz totally. The problem may be same for you, if you take the power from two separate 12V to 5V power supplies.

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