It would be pretty difficult to do that and get it RIGHT.
What is it about the Oppo sound difference that you want to change?
Are using the "audio outputs"? Or as a transport to a separate DAC?
If using the "audio outputs" line outs;
You could look into Swapping the audio output coupling caps to Mundorf EVO aluminum/oil caps.
I wouldn't change anything on the Oppo.
Wait to see if others reply; who know WAY more than me about good mods.
What is it about the Oppo sound difference that you want to change?
Are using the "audio outputs"? Or as a transport to a separate DAC?
If using the "audio outputs" line outs;
You could look into Swapping the audio output coupling caps to Mundorf EVO aluminum/oil caps.
I wouldn't change anything on the Oppo.
Wait to see if others reply; who know WAY more than me about good mods.