Is this what you have?
I downloaded the manual but I'm none the wiser. Mac refer to those connectors as L connectors. They are nothing like modern L connectors. I never saw preamp outs like those ever and that is in over 60 years.
You will have to make you own leads. I would bet that in the RF environment of the modern home they will hum like the Devil.
Also I can tell they are the old style RCA connectors which are slightly out of spec with the modern ones. They do not make good connection with modern RCA plus.
If it were me I would replace those RCA sockets with modern gold plated ones. I would also convert those preamp outs to RCA sockets as well.