This Amp was part of the mainstream at best mediocre amps. If it is the PM 500 it is not one that I would hang on to. I fixed these through the 80s and they were pretty much throw aways and problematic. sort of the beginning of a bad phase in the company history. If you find someone with not to much knowledge they may buy it thinking it is a classic great amp but not so. It is not the 500 series that people love it is a cheap department store amp manufactured by gold star I believe but can't remember for sure. Sorry