I found a solution for car stereos lacking the ability to transmit a BT signal to a set of BT capable speakers. Most modern car stereos come with bluetooth, but only receive, not transmit. First I found a cheap FM radio at Wallyworld and made a case for it for my galley.

In addition to the speaker wires for F&R and L&R that model has a set of pre=amp RCA jacks on the rear panel as well. Turns out that is the signal I needed for a handy little bluetooth transmitter I found on ebay. It is shown temporarily laying on top of the stereo cab.
https://www.ebay.com/itm/Wireless-Bluetooth-5-0-Transmitter-A2DP-Audio-RCA-to-3-5mm-AUX-USB-Adapter-HUB/153868793145?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649The transmitter comes with a patch cord with a 3.5mm stereo plug and RCA jacks. The RCAs plug into the back of the radio's pre-amp output and the 3.5mm jack plugs into the transmitter. For now the transmitter then plugs into a USB on the front of the radio to power it. I'll eventually hard wire a 12v to USB step down adapter behind the bulkhead wall to hide that plug.
https://www.ebay.com/itm/DC-DC-12V-to-USB-5V-3A-15W-Power-Converter-Regulator-Step-Down-for-Car-GPS-Phone/283898167184?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649I'll probably install a simple toggle switch to power the stereo as well as the bluetooth transmitter so they aren't both needlessly pulling phantom power full time. I won't have station memory active since power will be off except when using the radio. Not a problem as I have to search for station at each stop anyway.
I built a set of speakers from the drivers from a salvaged stereo. They aren't much, 3W-8ohm cheapsters, but, for the cabin in my TD they'll do nicely. The cabinets I built are just at the sweet spot interior volume of .07 cubic feet that makes those little cheapies sound their best. They are wired directly to the car stereo speaker outputs and will live in the cabin full time.


I'm in the process of building a small bluetooth stereo speaker (2x50w). I expect to have the bluetooth amp in tomorrow's mail. I'll be able to move that speaker around where I want it. In the galley while prepping meals, or, by the fire while relaxing or splitting firewood. For now I will need to have 12v power for that speaker, so, its range will be limited somewhat. As soon as I learn how to add a charger and 18650 Li-Ion battery pack to the speaker I'll be in business for hours of operation without wires.



Why did I go to all this trouble you ask? Couldn't you just play music from your phone through the radio with its built in bluetooth? Yes, but, I like to listen to radio when I can. I get a mix of music, news, NPR, etc. I can't do that on a phone without a cell signal and most places I camp will have an FM signal more often than cell signal. This was a fun way to experiment. Not everyone wants FM radio so I admit this work around isn't for everyone. However, if you like a little FM variety now and then its a fairly easy and inexpensive way to go about it. I almost forgot to mention that I built an FM dipole antenna from coax cable (of course I did!). It blows away any commercial whip antenna when is comes to picking up FM signals.
The radio was $17, BT transmitter was $10, the 12v to USB is $9. Salvaged speakers were "free" using plywood I had on hand. Antenna was free with old coax I had laying around.
The new bluetooth speaker will be $14 for the bluetooth amp board, two new full range speakers were $35 shipped and $1 for a panel mount 12v jack. Converting to Li-Ion battery pack and charging board will run about $20 I think. I have a lot of studying to do before having that total wireless capability.
Tim