Broken Microlab Solo 6. Amplifier needs to be replaced. What do you advise?

Question

Audio

Broken Microlab Solo 6 ( 2.0, total power 100W, 55-31000 Hz, signal-to-noise ratio-88 dB).
They began to crack. From the beginning they cracked when turning the volume knob - replaced it. Did not help.
When you turn it on, the first 20 minutes play normally and then they start to "knock", the sound is such as if you touch the computer case with the plug on the speakers + the sound of interference. I changed sockets, connected to different computers, to the player. Everything is the same. They crackle on their own, even when not connected to a sound source they make a crackle.
I wanted to replace the amp. I wrote to the manufacturer - there are no such parts for sale. There was also an idea to make the speakers passive and buy an external amplifier.
Question - what amplifier to change? External or internal? Can you recommend a specific model?