I have a Yamaha receiver 1040b, Samsung smart TV... I'm using Arc via HDMI cable... The sound sink's compared to music, using 7,1... When listening to sports channels I must turn the volume all the way up
HDMI-ARC and optical are the same so changing the output of the TV won't make any difference.
There is nothing unusual with having to change the volume when you change inputs. Some receivers have a way to adjust the volume of each input so the volume doesn't vary.
The sports channels may not be sending Dolby Digital to the receiver.
Try using a different surround sound mode for the sports channels.
I wager you are using one of those FAKE surround mode, they sux, don't use them. When playing a stereo source, your AVR has a mode that will enable all speakers anyway, without faking anything, unfortunately is called by different names depending on vendor. U may have to read the manual [gasp!]