Cassette Tapes..Dolby B or C?

I agree, dolby off at low volumes, you be the judge at higher levels, B,C might take away fatigue.

Every prerecorded cassette that incorporated Dolby noise reduction should have a Dolby logo/marking on the tape or the box. As I recall there were many prerecorded cassettes that were made in Dolby B, but I never saw any prerecorded tapes in Dolby C. I personally recorded many cassettes in Dolby C from material off of CDs. I had excellent results, especially when using high-bias blank tapes.

To address your question, you should not assume that prerecorded tapes are Dolby B unless they are marked as such. In any case, if the playback sounds best to you with the Dolby B switched on, then go ahead and listen that way – you won’t hurt the tapes.

If the tape is pre-recorded and marked Dolby, it is Dolby B. Dolby C was available to consumers while recording their own tapes, but was not used on commercial tapes. As it has a more agressive EQ curve for encoding and decoding, it will make the prerecorde3d (Dolby B) tapes sound duller if used on playback.

Dolby HX Pro is a playback only processing and is not, to my recollection, usually selectable.

The tapes are plainly marked "Dolby" but no indication of B or C. I guess B is the right answer.

Definitely B.

But Dolby C, on a good deck, with a good tape, was a real treat.