Cassette tapes had quite a poor SNR... although much better with Dolby noise reduction;
Audio engineers in the 1970s became aware that many of the traditional distortion mitigating methods were unsatisfactory. In this context, dbx and Dolby
From what I've read so far I'm assuming the dynamic range and signal to noise ratio of dbx with a good chrome or metal tape is 90 db-ish. And with a chrome tape I got well into 19 kHz. I highlighted 20 kHz for reference and there wasn't much signal left at 20 kHz anyways.
This is a detail measurements of the iconic, Nakamichi Dragon Vintage cassette deck. It was kindly brought to me at a meet at our local audio store (Gig Harbor audio). For those of you too young to know :), the Nakamichi Dragon has the reputation of being the best cassette deck available at...