Qiaomo amplifier board, chasing high fidelity

The author purchased two power amplifier boards composed of ST K3048A and ST K 6153 . I connected the power supply and the speaker according to the wiring and tried listening, but I was disappointed. The sound playback effect was far from what the manual said. The bass was dry and stiff, and the mids and highs were not transparent, clear, harsh and unpleasant. It was like putting the speaker into wood. The sound played in the barrel is average, and the entire sound field is messy. 6 Carefully compare the circuit diagram in the instruction manual with the actual circuit (see Figure 3-44). It is found that the two circuits are very different. After figuring out the actual circuit principle, I suddenly had the idea of ​​​​trying to figure it out.