1 minute ago, Arcanekitten said:
Would a simple cable be sufficient? Or would this require an active adapter of some kind?
No, rca is analogue, you would just need two of these: https://www.amazon.com/AmazonBasics-1-Male-2-Male-Audio-Cable/dp/B01D5H8N8K/ref=sr_1_11_sspa?keywords=rca+splitter&qid=1556497587&s=gateway&sr=8-11-spons&psc=1
(the purple end goes into the turntable, then one of the other two ends goes into each preamp/phono preamp)