There are serious problem if the codec wont sleep. The codec will heat up continuously and draws power. Now even with updates, when playing songs it also will heats up pretty bad.
That's maybe why Asus switch or changed the ALC for new models. I noticed that GL502, G752VS, GX700, GX800 prototype all using other variant ALC.
After some researches, ALC668 which used on G752VY causing bad audio quality as well as causing alot more problem on other branded laptop as well including Acer, Dell, HP.
Already brought a G752VY? Then live with it. Haha, have a nice day.