The Tape Out on the 970 is for analog input only. There's a note in the manual that says you can record analog-analog OR digital-digital but NOT digital-analog or analog-digital.

The only crazy idea I can come up with would be to use the headphone output as a pseudo-line output. The manual doesn�t say but I�m assuming that the digital inputs are routed to the headphones also. The manual is clear that the headphone volume is totally independent of the main and remote volume controls.