If your Mono albums were pressed after 1968 they were pressed on a stereo lathe. Recording studios in the USA eliminated the mono lathe. The way mono recordings are made from 1969 and on is they use a 2 track stereo tape recorder w/the mono tape. On occasion these records may be prone to trouble if not folded to mono properly. If it sounds phasey or loses the top end it needs to be played in stereo even if its mono. The groove on the stereo lathe is different than the mono lathe groove. If you have current mono albums you should be fine w/a stereo cart. It’s compatible w/the record grooves. Steve Hoffman explained this.
