Mazda2 alternator whine through aux input

DrWebster

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2013 Mazda 2 Touring
So we took a short road trip in Aoi a few weekends ago, and I connected my phone to the factory stereo aux input, along with using a USB power adapter in the lighter socket. Ended up with alternator whine. The factory stereo in Shiroi (our 2013) doesn't do this, but when I connect the phone I use the built-in USB port for power (instead of an adapter in the lighter socket).

Anyone encounter this with their 2, and have a good solution other than buying one of those noise-isolating cables (that also make the sound terrible)?
 
You could try the "big 3" upgrade which is using a bigger gauge wire for your power/ground wires coming/going to/from the alternator
 
You're introducing a ground loop between the amplifier in the phone and the amplifier in the radio. Either use a high-quality lighter plug for USB charging or digital connection(bluetooth, USB) for audio connection. I get the same issue on my aftermarket radio if I plug a phone into the USB port and use AUX for input.
 
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