Help on ref 845 mastersound

I have an early version of the 845 reference integrated, No. 13. At the back there are rca inputs labelled cd, tape, aux and rec. I am wondering what the rec is for? Is it a fixed line preout, or can i use it to turn the 845 into just a power amp, and use an external preamp......thk you all for the help.

Cheers