I sourced an old tube radio from an good will store. Since it was defective I got it for free. Anyways, I have already striped the electronics inside so this does not matter. I am going to build a Bluetooth speaker box with the case. Bluetooth receiver, Class-D Amplifier, bass reflex loudspeaker, lead-battery, USB-charging port and a carry handle.
A shot of the interior of the radio. I discarded most of the stuff in there.
I got the Bluetooth receiver in the mail. It is an APT-X Bluetooth 4.0 from sure electronics ((Link to the ebay offer of the bluetooth module)). I bought the amplifier from the same company (( Link to the ebay listing of the amplifier ))
Some thoughts on the BT module and the amplifier chip. The Amplifier chip is an TPA3110D2 ((Product website TPA3110D2)) from Texas Instruments. It is capable of driving 2x15W at 4Ohms. I will use only mono audio for this project so it comes handy that this chip can be set to drive a single speaker (mono as well). Another nice feature is a power down mode which reduces the power consumption drastically when no audio output is needed i.e. Bluetooth is not connected. For both features to be used a little modification to amplifier board is necessary. The Bluetooth module (BTM98-8AA) provides a amp-mute pin to power down the amplifier so no complicated hacks are necessary. The module even provides sophisticated functions such as button inputs for play/pause, next, previous, vol+, vol- which can be programmed but the datasheet that I found online does not provide the information on how to set this features. I asked Sure-Electronics if the can provide me the this information and I hope they do. The even sell just the module, without a breakout board ((Link to the ebay offer of the Bluetooth module))
In the meantime measured the volume of the donor speaker box. So I need to fit 8,8 liter into the radio chassis. This will be a bit more complicated than I have thought but it can be done. I removed the ornament-fabric from the front panel – without damaging it – yay.
Next step is fitting the speakers in a new box and hope that I get the datasheet for the BT module.
Further information will be posted here as I continue working on this project.