To convert phono in to aux u should bypass phono amp.
To do so u must open LBT, locate components near phono jack and remove 4 wire jumpers: one near R1001, one near R1051, one connecting R1005 to R1006, one connecting R1055 to R1056. After that u should wire PHONO IN L to R1006, PHONO IN R to R1056.
Enjoy!
I did it last friday when I got service manual.
Works GREAT!