The wav file with 20kHz sine played via foobar/DAC gives expected spectrum with no extra stuff(300kHz spectrum range on analizer).
Put this 20kHz on CD and played on CD player I see frequency component on around 24kHz with rather high amplitude.(see pic)
Any suggestion, folks, as I see now my brain limits ?(can not believe that it is a side aliasing component 44kHz-20kHz which is not supressed enough though).