NOTE: Please check that you have an aux input before buying anything!
Materials required:
1) A bluetooth receiver that is powered from a USB connector.
2) A cigarette lighter USB power adaptor with a suitable cable to power the bluetooth receiver
3) An audio cable that connects from the bluetooth receiver to 2x RCA phono jacks (usually a 3.5mm headphone jack to 2x RCA)
If you really wanted to spend the absolute minimum on this, you could do it for under £10, however the quality will be terrible as you will have the basic bluetooth codec and a lot of electrical noise on the signal going into the aux ports...
I used the following, and the sound quality is pretty good. I get a small amount of audible electrical noise if I turn the volume above 40 with nothing playing. Music at normal listening levels masks any noise (your ears may be better than mine)
1) For the bluetooth receiver I used an Avantree Oasis. This has the APTX HD codec, so is about as good as it gets with bluetooth audio. I have been using the same one since 2018, it doesn't mind the power being shut off abruptly (i.e. when the ignition is turned off), and it hasn't let me down yet. These are currently £60 from Amazon.
2) For the USB power adaptor, be wary of using a cheap no-name one from the pound shop or eBay. I learned that when I installed the Oasis in my previous car! The cheap USB power supplies are electrically noisy, and will interfere with the audio signal (this isn't a hi-fi snake-oil thing, this is genuine interference). I'd also advise using the shortest cable you can find. I've used a 15cm USB cable for power and a PortaPow cigarette socket adaptor. Cable was £6 for a pair of them, power adaptor was around £6 (but that was a few years ago)
3) For the audio cable, it doesn't need to be expensive but you are looking for the shortest one you can get, and that is thick enough to have some shielding. I bought a 30cm one for about £7, this was a 3.5mm to 2x RCA in the case of the Oasis.
Connect it up in the armrest, pair your phone with the receiver (it will remember your phone, and won't interfere with bluetooth telephony). Here is the cludge part if, like me, you are doing this with a car that has the rear-seat entertainment system:
Press the "Disp" button on the head unit. Then press the button on the touch screen or remote that makes the rear TV screen flip down. For the first time you will need to jump into the back to ensure you have set the screen to use "VIDEO" input and set the output to "SPEAKERS". Your bluetooth receiver is now playing through the stereo system.
How does it behave when you power cycle? Well, if you leave the rear screen down, then you can turn the car off and on without needing to do anything to switch to bluetooth audio. If you flip the screen up using the front touch screen, you will lose the audio until you flip the screen down again. If you flip the screen up using the remote, you keep the audio playing until you turn the car off, then when you turn the car on you need to flip screen down again. It might get annoying. I might end up doing a Grom VLINE tutorial. 😁
Picture shows the installed article. Armrest closes just fine and it doesn't take up much room in there.
