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Bluetooth Speaker TPA3118

 

 
When I was digging though the attic I found some speakers I wasn’t using, and it occurred to me I could turn them into Bluetooth speakers for my bedroom. I believe they originally came with the sub-woofer I converted to a powered speaker in a previous build. I purchased The XH-M314 Bluetooth board off Aliexpress for the job. I purchased this particular model since it had everything I needed all in one board, and the TPA3118 AMP chip was made by Texas Instruments, a manufacturer known for quality. I placed the module in the right speaker and used the original speaker connector to send the signal to left speaker so only need to drill holes for the power connector and switch. Then it was only a matter of soldering 6 wires to the board.



 
Unfortunately the board is way too load for my tastes. The gain is maxed out, it sounds like the lady that says Bluetooth Connected is yelling at me, and unfortunately maxing out the gain raises the noise floor, so there is a bit of a hum (That could probably be solved using better power adapter). If you like cranking your music the default configuration might work well for you. It’s possible to modify the gain by adjusting the 2 resistors connected to the gain pin. The gain pin also sets if this AMP works as a master or a bridged slave, so only the resistor values in the data sheet work. Personally I’m going to remove both resistors and replace the one that connects the gain pin to ground with 5.6K resistor, that should drop gain to 20 decibels, but that’s a project for another day. 

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