TPA3118 2X30W Bluetooth Digital Power Amplifier for Modified Bluetooth Speaker

I have this old BO speaker that's built like a tank, but what good is it when it does not connect to anything. I was going to throw it out, but had one more idea for it.

So I got this Bluetooth amp module from eBay:

TPA3118 2X30W Bluetooth Digital Power Amplifier for Modified Bluetooth Speaker
US $10.89

The DIY mod:
  1. Open the speaker enclosure
  2. Uninstall the crossover board
  3. Connect the woofer to the module's right channel output
  4. Connect the mid-range and tweeter (in parallel) to the left channel output
  5. Drill a hole for the power cable and push it through
  6. Attach the module to the inside cover of the speaker enclosure with tape
  7. Close it up

Currently the system is powered by 4x 18650 lithium battery pack that sits on the outside -- it lasts for about a day before needing a recharge). The audio signal connects via Bluetooth.

When it powers up, a voice prompt (in a Chinese accent) asks to pair, and then says that it's connected.

At minimum volume the sound can be quite hissy. The only volume control is via the source device, so I assume that the module is set to maximum preamp volume, hence the hiss. I am yet to try the 3.5mm input and test the hiss, but at low priority.

Later, I upgraded the battery holder to a single four pack, which looks a bit more tidy.

  1. The amp module suffered catastrophic failure during an incident when I accidentally connected a battery with reversed polarity at the power terminals. There was smoke and some of the speaker wadding got burned, but I managed to pull the plug quickly enough to limit the damage.
  2. In the coming months the amp and the battery were upgraded.
  3. It was found that connecting via an analogue cable instead of Bluetooth produces far superior sound quality by way of a much better performance in the high frequencies. Hence no more Bluetooth for now.