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I say "Genuine" because apparently so many are not!

I wanted to add the ability to send streamed music from my phone (which happens to be an Iphone SE) to the aux input in my car radio, and also from my windows laptop to my home stereo equipment. To do this I bought several stereo BT (BlueTooth) receiver adapters, but soon ran into an unexpected frustration. Despite being advertised as stereo, not one adapter I purchased was able to deliver anything but monaural sound. Pairing and sending audio was never problem, but the sound was always mono. There are simple tests available online (youtube) which you can use to isolate left and right sound.

So I suspected the adapters were at fault and non-destructively opened them up. I was shocked and angered to find that in three of the four adapters I had bought, I could clearly see a trace on the PC board connecting the left and right outputs. Obviously there couldn't be any stereo separation there, so I took some photographs and promptly returned all three. But inside one of the adapters, which actually had power leads and external 1/4" RCA plugs, I could clearly see that it was likely a true stereo device. In that case, the wires from the two external plugs went to separate resistors and capacitors, and finally connected to different pins on the internal BlueTooth IC. This was encouraging but sadly, this one behaved identically. No problem linking/pairing with my phone or playing music, but once again the sound was always mono. (FYI, The chip was labeled "AC23BT-1P365-69A2". Likely from China).

So now I was suspecting my Iphone, because I was able to find complaints from people experiencing monaural BT sound from some wireless earbuds on Apple forums for iphones. There is an option to request audio output to be MONO in one of the Iphones settings, which was the usual advice given. But that was not the problem. My "mono only" setting is off. I can also test my phone with wired earbuds connected an adapter (to the "lightning" port) and the sound there is definitely stereo.

I still suspected an Iphone problem or a bug in the operating system (IOS) that had survived despite multiple upgrades but I was wrong there too. I have a fairly new laptop running windows 10 which also has BT capability. So I was able to link (pair) the laptop with the one adapter whose internal circuitry seemed to indicate a true stereo device, and send the Left/Right outputs to my home stereo system. But once linked and tested, the left and right channel outputs were once again identical (monaural).

At this point and for now, I'm going to just rig a wired input to both my car's stereo system AUX port, and do something similar with my home stereo system. But obviously I'd really like to have the convenience of a true wireless stereo link using blueTooth. It should not be rocket science since BT is specified to be capable of stereo. But I really don't want to keep buying and returning adapters hoping one of them will do what it is supposed to do. Can someone can offer some advise explaining why this is such a problem, and I also wouldn't mind product advise for adapters that will definitely work. They can be bare boards, as I'm well versed in soldering and DIY builds. If I have to buy a pair of BT devices, one a transmitter and one a receiver, and I have to plug the transmitter into my phone's wired audio output I'll do that too as long as the result is stereo. But I don't think it should be this hard.

Thanks for any help.

Some Bluetooth adapters advertised as stereo, which only output mono

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