Sounded good. Soldering the boards deficient.

I'm very satisfied with the sound.
After a few days, there were first misfire of the left or right speaker.
The frequency increased continuously. Since I had no desire to return the huge thing, I have disassembled the unit.
Result: The conversion to lead-free soldering had apparently not worked for the devil.
Creepy soldering on both boards.
Here had to be improved over a large area.
By repairing the soldering and the 50Hz hum, which was clearly heard before without input signal disappeared.