Dinky little 2-valve Chinese pre-amp

[Yorkie]

To some extent, the Sony is more sophisticated that the average turntable - at the very least it has to have some means of switching between the two cartridges for each side of the record, so given that, it's not so impossible that they decided to put in a preamplifier at the same time. Either that, or the cartridges are ceramic, so won't need the usual RIAA equalisation. Google wasn't terribly forthcoming about that particular model.

Not sure whether the output from the cartridges is insufficient to drive his amplifier and he thought this little pre-amp would uplift the signal sufficiently, but for what it's worth, I've attached the mind boggling circuit of the Optonica RP114. It's certainly a well engineered and very complex bit of kit and I think they're still quite sought after. Top end stuff I imagine, given that it was produced more than 40 years ago.