the hiss that dolby adds can be easily heard. record without dolby, with dolby b and with dolby c and play without dolby - you'll hear the particular hiss associated with dolby
If you play back Dolby recordings without Dolby, you'll be listening to a compressed version. Any hiss hasn't been "added" by Dolby, it's noise in the original source which has been increased in amplitude along with any low amplitude signal in the same frequency bands.
the hiss that dolby adds can be easily heard. record without dolby, with dolby b and with dolby c and play without dolby - you'll hear the particular hiss associated with dolby