need a bit help with sierra

hi, i installed sierra os.
but y have some problems.
when i switch on the pc, i need plug the usb to configure grafics. with clover. then, the pc its perfect, but i don´t have sound.
my motherboard is a gigabyte z97 d3h with intel i5 4690k and 24 gb ram. without grafic dedicated.

sorry for my english .

thank you