Sound Cutting off!!

Hello,i am new to this forum so be gentle to me :)

Let me start about my problem,5month ago i got my pc,and evrything worked fine,few days ago i buyed i7 procesor and computer case,i put evrything in new case and assemble it. Now evrything is working fine until i try to play games or music on players or you tube,or any type of music,

Here is what is going on,if u turn on BS Player and i put volume up to 100% music is playing

but then problem start when sound start cutting out and this happen


Now trick is if i reduce volume to mybe under 50% it will work no problems but as soon i set volume over that limit somehow sound start cutting out, I tryed 2 headsets,speakers and nothing just played music widouth anything plugged in same thing like on pictures happen, music playing then disconect and it say to me like no audio device conected but music is playing


Whole pc is assembled in same place where i buyed it,even case and procesor i took it to them and they did assembly now they checked connections from motherboard to jacks evrything is fine,i tryed reinstaling windows 8 to 7 to try tryed uninstaling audio drivers and instaling again,instaling diferent no joy.

I would aprechiate if anyone know what is the problem here and how to fix it. Thank you,Hope you guys can understand me english is not native language :)

D.Jankovic.
Thank you!