From the Sound Devices MixPre-D Manual• TA3: unbalanced mic-level output, pin-2 left, pin-3 right, pin-1 ground, 200 ohm output impedance
• Tape (3.5 mm) Unbalanced, tip-left, ring-right, sleeve-ground, 2.1k ohm output impedance
TA3 to 3.5mm cable, Sound Devices XL-3R or equivalent