Oh year i also have this Bluetooth speaker, it has the same AMP and a BT A2DP from DX (LINK) and also here the audio quality is just amazing.

The casing is from a old B&O LX2802 TV, the speakers are from a surround stereo i can't remember the name of.
The Volume control was necessary in the beginning because the BT A2DP was sending noise in the power and the BT and AMP was on the same battery, now the single battery is going to the BT, and the dual battery is going to the AMP.