Dolby S is a type of noise reduction that’s done in the deck, and actively works on the audio stream as it’s being written to and read from the tape. It’s best

Dolby S is a type of noise reduction that’s done in the deck, and actively works on the audio stream as it’s being written to and read from the tape. It’s best used with a high quality tape, but I believe it can be used with any of the 3 major tape types.