The BC9300 does not have an internal RIAA pre-amp, hence you need to get a Beogram with RIAA such as the Beogram 3500, 4500, 6500 and 7000, which all have RIAAs fitted as standard.  The Beogram 9500 will not work unless you add a separate external RIAA pre-amp, which then complicates the ability to remote control the deck because the datalink will need to be connected separately. See this link:  

Here's a solution from another enterprising small workshop in Denmark. RIAA amplifiers to fit different BeoGram models: https://claudius-elektronik.dk/designs-og-l-sninger.html