https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.gearslutz.com/board/attachments/geekslutz-forum/111879d1235602544-apex-460-mod-u47-apex-460-mods.pdf&ved=2ahUKEwi8vainhvzuAhVQ-yoKHffmB9UQFjAJegQIDxAC&usg=AOvVaw1I-syRKnjuHX-vtbTtEF40&cshid=1613947360270
And posts from Dave Thomas
http://advancedaudio-europe.com/forum/viewtopic.php?p=72#.YDLiMlPp1Pw
This is a variant of Apex460 so all existing mods apply to yours as well. Compare your components to 460 schematics, find out if there's anything different, and mod it to your needs.