AK 4440 ic connection wth single vol and dual bass and terrible with bt module

0:20 – Volume connection 5 pin
0:50 – audio connection
2:13 – Bass & treble connection
3:50 – Treble connection right
5:13 – Speaker connection (right speaker conn)
5:40 – Left speaker conn.
6:10 – BT panel conn. ground
6:40 – BT 5V power connection
7:12 → BT audio connection from BT module to IC board
7:33 → 12V connection to the IC board
7:46 → 12V transformer connection to the board
8:10 – Checking