The TDA7396 is made for low impedance speaker that is 2 ohms or 4 ohms. Its output is bridged for 15W into a 4 ohm car speaker or 30W into a 2 ohm speaker when the battery is 14.4V. You are using a low supply voltage and only one of its outputs. Then its output power into an 8 ohm speaker is only about 0.6W, slightly more than a little LM386 amplifier.
Pin 5 is one of the outputs of this amplifier. But you use C31 (10uF) to short high audio frequencies to ground. The short circuit current makes lots of heat.
Your output coupling capacitor is 22uF plus 10uF= 34uF. Then it passes frequencies above 588Hz to an 8 ohm speaker. No bass.