Dolby NR encoding - did it ever work

"11-09-15: Raymonda
... all Sony D 5's engaged a brick wall multiplex filter when dolby was engaged. This cut off all frequencies above 14,000 hz."

No, this is mistaken. First, it wasn't a brickwall filter at all. What the Sony had was the same multiplex filter used by other cassette decks of the era, although some did allow the filter to be switched in/out independently. The filters were designed to gently roll off any of the FM stereo pilot tone (which is at 19 kHz) that might be passed on from an FM tuner. Absent a filter, the tone could "fool" the Dolby circuitry into thinking the signal had HF content, thereby compromising the Dolby circuit's effectiveness at reducing HF noise. These Dolby circuits were on chips that included the multiplex filter.

It was possible to make excellent recordings using a Sony TC-D5 or TC-D5M. If Deadheads had trouble doing that, it had nothing to do the the Sony's multiplex filter.

I stand corrected. Early on I didn't use the units dolby but rather used metal tapes and saturated the tape for low noise. Later I used Dolby because it worked for me. It was in an article where I read the multiplex issue........around 1989 or so....by that time I had gone digital.

I still remember being at a party and seeing a guys Nak 550, you want to talk about droop inspiring! And thank God for digital in terms of convenience, sound quality, and depth of catalog available.

Boy, I never dreamed I would be discussing Dolby B again. It sucked on cassettes. Yes, it took the tape hiss out along with the highs. In fact, I used to record with Dolby and play back without it for increased high-frequency response. Dolby A, used on studio recorders, didn't seem to have as drastic an effect. Buying a collectible cassette player? That's a new one. Well, to each his own.

Let me tell you something about well-executed dolbyB. It is great. My perfectly aligned and calibrated Nak 682ZX sounds incredible for a cassette deck, especially with Maxell Vertex tape. Forget those TDK, Sony , Denon etc. tapes. I tried everything. And my Nak is not even specifically calibrated for the Vertex. There is no roll-off, nothing that matters is lost. In most cases I do record with dolbyB. No live recording, only from records and cds. DolbyC sucks, I never use it.