1Pcs Bluetooth 4.1 Stereo Sound Module Audio Transmitter Stereo Module Wireless Speaker Headphones......

I bought this to try and connect my Nintendo 3DS to a pair of bluetooth earbuds. I wired it up as per the diagram for "line audio input connection" with the exception of the "connect" switch and the power indicator LED since the board had both already onboard. It connected to my earbuds with no trouble, but the audio had a constant whine or buzzing. The company suggested that I try an AC power supply instead of the 18650 battery I was using. That didn't make sense anyway because it claims that the transmitter can be powered with only 3.3v and the 18650 is 3.6v. Plus, a battery is a clean power source and I would expect whine or noise coming from an AC power adapter before I would a battery anyway. I tried it, though, but there was no difference. They sent me a new board and this one, I hooked it JUST to power (with the filtering cap). I didn't hook up the audio input just in case there was something in the cable causing the noise. Sure enough, the replacement board had the same issue. I also tried connecting both boards to a different pair of bluetooth headphones, just in case THAT was the cause of the noise. No matter what I tried, I could not get either board to ever connect to the JBL headphones. In the end, the company just refunded my money. I don't know what the issue is and I don't know if it's just me and/or my usage - and the company did TRY to help - which is why two stars instead of one.