The other systems of the era (Beomaster 3500, 4500, 6500 and 7000) with Powerlink sockets didn’t have RIAA pre-amps, as they relied on the Beogram having a pre-amp built in.
It was a very rare accessory but BM6500 and BM7000 could be fitted with an internal pre-amp, as described back here:
https://archivedforum2.beoworld.org/forums/p/7576/67094.aspx#67094
EDIT: The last couple of posts of the linked thread above also refer to RIAA add-ons for the BM3500 and BM4500 – I would imagine that these are quite rare!
