The problem cames from the parasitic capacity of the two transformers and the sound card. I connected the speker and there is no any noise. I listen to the amplifier and it sounds great.
I was also able to repair my amp. It was some kind of short that went away while measuring...
That PCB has a lot of wear due to age, heat and soldering.
That PCB has a lot of wear due to age, heat and soldering.
One year of using there is no any issue with the amplifier, I have made a short video of the rebuild progress.