I've built a little soundmachine using a Raspberry Pi 3, the Adafruit MAX9744 Amp(datasheet: http://www.kynix.com/uploadfiles/pdf...9744ETH2bT.pdf) and two recycled Car-Stereo-Speakers. Since this installation is ment to be used on a boat, I have an incoming 12v current. To reduce the voltage down to 5v for the Pi3 I use a DCDC stepper. The wiring can be seen in the poor diagram attached

The Amp runs on 12 volts, so it is directly connected to the power source. For if it matters, here at home I'm using an AC/DC stepper (to simulate the boat battery) which turns the local 230 volts AC into 12 volts DC.

On to the problem. When I connect this setup I hear a very audible humming in the speakers. When I disconnect the audio jack from the PI and I use my phone as an audio source, the humming disappears.

I should mention that the picture doesn't show the entire setup. The 12 volt power source feeds another DC/DC stepper which in turn sends 7.5 volts into an arduino. Also a I have used the same power curcuit to feed 12 volts via Power over Ethernet into a device. Since I believe (or rather hope) that these do not have anything to do with the problem at hand, I didn't include them.

I'm a beginner when it comes to electronics, please take this into account when providing a solution

 

What are you attempting to do? Is this for a Harley Davidson Motorcycle? If so which one?

 

Might come down to availability of equipment. His location is in China!

 

Spam.