I have one of these. It's not a bad unit, although it does have its limitations. It apparently shipped as part of a bundled system (receiver, turntable, and bookshelf speakers) as suggested by the cover illustration on this KS-4000 service manual. The RCA speaker plugs were common on integrated systems back in the '70s and early '80s. The model number is also a giveaway. Kenwood components of that era had an alphanumeric model number consisting of two letters followed by a four-digit number. The first letter was always 'K' for Kenwood and the second letter was suggestive of the type of component (e.g., 'A' for amplifier, 'D' for tape deck, 'R' for receiver, or 'T' for tuner). The letter 'S' in this unit's model number would appear to be an anomaly. Logically, it should be an 'R' for receiver but instead it has an 'S' for system. The 'R' for receiver follows the numerals, which is inconsistent with Kenwood's standard model numbering system but makes sense when you realize the model number applies to the collection of components as a whole, rather than the individual piece. The turntable was apparently a KS-4000T and the speakers would have been similarly numbered.
