Next I will go into speaker config settings and look what levels they are even though the manual says on p.17 "
"The STEREO AUDIO OUT terminals automatically down-mix the multi-channel audio source into the stereo signals. However, STEREO AUDIO OUT will NOT be affected by the “Down mix” modes and other speaker settings in the Audio Processing of Setup Menu (described in the page 68)."
If n/g, then as someone at AVS and Steve Hoffman suggested, it’s possible that in order to prevent overloading the stereo outputs by the 7.1 surround sound analog outputs, that rather than appropriately buffering (isolating) the stereo outputs Oppo instead applied some overall gain reduction to them. Thus, I will try connecting the front surround sound speaker pair and then go into settings and enable downmix and see if that stereo pair will give me higher output voltage.
As for mods, AFAIK there were none. I will ask the ebay seller about that. I have to get in touch with him and ebay anyway because the player was advertised as region free. But it’s not as it won’t play this "all zone" PAL-encoded DVD from South Africa. https://raru.co.za/movies-tv/37567-ride-the-high-wind-dvd The image rolls and is monochrome not in color.
And the player gives and "Invalid Region Code" message when loading this DVD set from the Netherlands .
https://www.catawiki.com/catalog/dvd-video-blu-ray/carriers/dvd/4166045-het-derde-seizoen
So I will be asking for reimbursement to purchase a mod kit like this.
http://bluraychip.dk/product.php?id_product=17