Homemade active speaker for radio with noise reduction function

I have a Tecsun multi-band radio and often listen to shortwave radio to learn foreign languages.

But there are some drawbacks: first, the speaker inside the machine has a small diameter and large distortion; second, the noise is loud when listening to shortwave, which is especially obvious when playing with an external general active speaker. One day, I suddenly had an idea: why not make an active speaker with noise reduction function?

Considering that the radio has a mono output, only a mono speaker is needed. And because the broadcast is mainly voice, there is no need to pursue frequency response too much. I designed the circuit shown in the figure.

The left part of the figure is a noise reduction circuit with LMl894 as the core, which can effectively reduce noise by 10dB per channel. Among them, w1 is a 1kΩ adjustable resistor. The right half is the power amplifier part, W2 is the volume potentiometer, and the low-priced and easy-to-buy TDA2822 is selected here to form a BTL circuit. This IC has the advantages of simple circuit and high power.

When debugging, adjust the volume potentiometer to the appropriate position, input the radio signal and adjust W1 to make the noise reduction effect obvious and the distortion small. When using this speaker to play the radio, especially the shortwave, the annoying high-frequency noise is reduced a lot, the human voice is more prominent, and the effect is very satisfactory.