I think thats a mono amp. The RIAA is the eq curve for various types of record eq schemes. 78's used 27k I believe while most mono 33's used 47k to load the cartridge. Aux is line level as is Tape out. Tape head is a pre-amp for old tape machines. Check to see if that unit is a mono unit. If so start looking for the other channel on E-Bay. That is a keeper of a system. Look at the size of those transformers.