Thank you for your help Nice Monkey, I finally got the RCA connection but, I have tried several configurations:
Music from hiby player via hdmi
Music from hiby player via RCA
Music from zidoo player via hdmi
Music from zidoo player via RCA
And to tell you honestly, I don't hear too much difference
,Of course, I'm not an audiophile and I don't have absolute hearing
. However, I expected to improve the sound quality via RCA.
Perhaps this is due to the fact that my music system is not from the top shelf.