I have a couple of machines with yaskawa MX1 controls that use 12v single ended encoders. A while back I pitched the idea of building a board that converts the 12v signals to 5v differential and allows using the original wiring. My electrical engineer friend laid the board out and it is in testing process right now, so far it works flawlessly. You pug the original encoder and drive plugs on one side and wire the other side to your favorite I/o hard ware, for testing I used a mesa 5i25/7i77 combo. The board will also work with 5v yaskawa encoders with a jumper change.
After a bit more testing these will be available for sale. Pm me if you are interested. thanks for looking.