Bluetooth Controlled Speakers.

[Scottie_Digital]

I have having issues running the 3W x 3W amplifier power supply with the bluetooth transmitter power supply together. It gives a small feedback hum. It completely goes away though if you have them both run off of separate power supplies. So my question is? How can I run both of them off same power supply without the problem? I don't want to charge 2 different batteries when they are low!

[adafruit_support_mike]

You're probably getting noise on the power rails.

Start by finding the current loops for the two circuits. Trace the path current will follow as it leaves the battery, flows through each circuit, then goes back to the battery.

The noise is happening in the places where those two loops overlap, especially in wires that carry current for both circuits. Eliminate as much overlap as you can by running separate VCC and GND wires for each module. Ideally, the battery will be the only place where the two loops overlap:

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Once you've gotten rid of as much shared path as you can, put a large capacitor (100uF or more) between the point where the VCC paths meet and the point where the GND paths meet. The cap will absorb noise from each circuit and keep it from getting into the shared path.

[Scottie_Digital]

Ok I am a little confused where I should put the caps? Where do the positive and negative leads go?

[adafruit_support_mike]

You want the cap's polarity to match the power supply's.

The positive lead from the cap goes to the power supply's positive output (the VCC rail). The cap's negative lead goes to the power supply's negative output (GND).

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[Scottie_Digital]

Ok yeah I was pretty sure I did try this already. But I went ahead and tried it. It only made matters worse. It made the noise alot louder and worse than what it originally was.So yeah I am lost on this one. I tried a 100uf and 220uf. BTW it also even happens when I have both with separate power supplies but when you want to charge they can't even come from the same charging supply. That also runs a ton of interference.

[adafruit_support_mike]

Post a photo of your hardware and connections and we'll take a look.