Basic 12VDC Power Filter Circuit Design for Bluetooth Stereo Engine Noise Removal

Hello,
I recently built a Bluetooth adapter for a stereo that I added to my 4 wheeler. With just the audio cable connected to my device I have no noise. With the Bluetooth connected to the line I get a hum from the engine. I was wondering what a basic design would be for a 12VDC source filter circuit? I would imagine it would be some type of low pass filter. I just not sure of the design. I don't have much experience in power electronics.

Try optical fiber link. Kills the noise for sure but you need to know OC transceiver. You can buy it on alibaba.

If you could provide a diagram it would be helpful.

So the device sounds good when not using Bluetooth. When not using Bluetooth are you still using the 4 wheeler batter?

It sounds like a noise coupling issue with the Bluetooth part of your system. Coupling issues are either conducted or radiated. I would look for grounding or power issues in the way that the Bluetooth device was powered. Look at your cabling and maybe consider shielded cable.

The Amplifier has it's own filter circuit built in so when using just the RCA cable to my device no "noise" is heard through the speakers. The Bluetooth has the audio ground as the common ground. So when the bike is running there is a lot of noise heard through the speakers. So I need to isolate the circuit somewhat but without going to AC. So I figure I can build a filter to remove the noise.