So I've been trying to get bluetooth working on my diy boombox and I've been running into some issues. I bought one of these: Amazon.com: Esinkin Wireless Audio Receiver for Music Streaming Sound System Works with Smart Phones and Tablets, Wireless Adapter for Speakers: Home Audio & Theater and installed a voltage step down chip? board? (idk the technical term) so I could run it from the boombox's battery at 5v. The receiver works fine, but at very low volumes there is annoying feedback and chirping. I tried powering it with the provided power supply and there was no feedback, but as soon as I tried powering it with the boombox's battery, I got static and hiss. Is this a grounding issue? I'm not very familiar with electronics, does anyone know what's causing this? It doesn't seem to be affecting sound quality, but it is very annoying at low volumes. It reminds me of a $5 portable speaker 
Also, I have checked the output voltage of the step down and confirmed it's giving me 5v, if that's relevant.
Also, I have checked the output voltage of the step down and confirmed it's giving me 5v, if that's relevant.