How to remove bluetooth from ZK-TB21 or ZK-MT21 ZK-TB21 is 2.1ch power amplifier. ZK-MT21 is 2.1ch power amplifier. Bluetooth chip is JL AC23BP. No datasheet available. Remove the chip from the board. Removed IC. Short the power signal. short IC pin No 6 and C9. Pin 6<-- short -->C9 * M5350B regulator is MST5350BTS. 35v to 5v. Bypass audio signal. short C2 and C15. Left audio channel signal. short C3 and C17. Right audio channel signal. C2<-- short -->C15 C3<-- short -->C17 Board with Bluetooth removed. AC23BP chip pin layout AC23BP 1unknown24unknown 2unknown23unknown 3unknown22unknown 4unknown21unknown 5unknown20unknown 6Power signal19unknown 7R signal out18Vcc 8L signal out17unknown 9unknown16unknown 10unknown15unknown 11GND14L signal in 12unknown13R signal in Cheat sheet Pin 6<-- short -->Pin 18 Pin 7<-- short -->Pin 13 Pin 8<-- short -->Pin 14