Oppo Udp-205 HDMI ARC volume issue


I am using an Oppo UDP 205 HDMI ARC connection to route sound from the Sony TV to the Oppo to utilize the DACs on board. From there it goes to my Luxman C02 stack. When utilizing the connection I do get sound but the volume is so low I need to turn the amp up three quarters to get to a decent listening volume. This is while the TV setting is on external stereo- not tv speakers. Any idea as to why this might be ? Connecting the tv to an aux input on the amp relieves this issue with 1/4 volume being almost too loud, but bypassing the Oppo all together. Appreciate the thoughts, 
Check settings on both TV and BDP-205...
Can't comment on your set-up, but when I watch ordinary TV I send TV sound to my Oppo 105 using the optical out on the TV and the optical in on the Oppo.  Works perfectly.
Make sure its going to the HDMI IN ,  not HDMI audio out, on the Oppo,  and turn the volume on the Oppo up to 100 percent .