Dolby NR encoding - did it ever work

What I mean is, if you record something with Dolby NR engaged, the sound should have the high frequencies boosted and the noise floor unaffected during playback without Dolby NR engaged. I had a Kenwood tape deck that would reduce the noise floor during recording, which isn't right. I am considering buying a new, collectible tape player.
I don't use tapes anymore but as a Deadhead back in the day it took just a few experiences with Dolby NR to never use it. It just quashed dynamics and took the life out of recordings, "stepped on" was how I used to describe them. The one proviso there is I never really recorded any commercial recordings just live bootlegs.
Yes, Dolby B and Dolby C both work. (Dolby A was a professional system.) They require careful level matching however, and that meant that many consumer rec0orders were often out of Dolby alignment. Better recorders such as Nakamichi offered built-in matching alignment tools.
Of course it worked although DBX was even more efficient.

Once Dolby NR was invented virtually no pre-recorded cassettes were issued without the now familiar DD symbol on the spine of the cover.

It achieved it's goal of reducing tape hiss. The penalty was perhaps not quite as terrible as Jon describes (otherwise it never would have achieved such widespread use on pre-recorded material) but you could easily discern such effects so home made recordings were better off without it.

One reason that commercial recordings used it was due to the poor quality tape which tended to shed its oxide easily and had virtually no surface polish.
HQ blank tapes such as TDK Super Avilyn (a high energy cobalt-doped ferric which was an offshoot of their video tape research), and Maxell, had a mirror finish (generating low noise) could use the "chromium dioxide time constant" of 70uS without the severe wear properties of that material thereby giving quite a few decibels of noise improvement without recourse to Dolby NR. (Not as much as Dolby obviously but enough to render tape hiss sufficiently insignificant.)
Hope this helps...
There was plenty of commercial compact cassettes recorded with Dolby B (Dolby symbol on the label). Dolby C was much more effective but less common.
Jon said it exactly right. ( I was a taper Deadhead too, and came to the same conclusion.) You just had to live with some hiss.

When you played back a live concert recorded with Dolby, you would often play it back without the decoding. The highs were then too bright, but it was usually better than the alternative, a dead recording. (sorry about that.) In those days, we had tone controls...
+1 Cleeds. Exactly correct. The deck has to be correctly biased for the specific tape, the user has to have the correct equalization selected for the tape formula and the record head has to be correctly aligned or it won't work properly. I have cassettes I recorded in the early 80s that blow away anything digital to this day. Took a lot of work and $$$ to make it happen, but the results spoke for themselves.
The biggest difference on my Aiwa deck made Dolby HX-Pro, an
invention introduced in 80s, that extends high frequency range of
the tape by providing servo on the bias (reducing self biasing of the
The issue with dolby when used for live dead recordings is that all Sony D 5's engaged a brick wall multiplex filter when dolby was engaged. This cut off all frequencies above 14,000 hz. It wasn't a problem with dolby but rather a problem with the D5, which was the deck used for 95% of all in field use for Dead recordings.

I too was a Deadhead taper from years back, circa 1982-1995.
"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 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.
Only a select few ever had access to a cassette deck of that quality. I'm sure the Naks can extract some excellent sound from a cassette, with or without dolby. Frankly, I never found tape hiss that offensive. Listen to Brubeck's Time Out. Loaded with hiss, but it doesn't distract from the music IMO.
One thing about cassettes I am finding is they apparently escaped the fate of overly agressive dynamic compression that befell their compact disc bretheren. The cassettes are by and large more dynamic, more musical and highly entertaining compared to their papier mâché sounding bretheren. Imagine, all this on a humble portable cassette player. And this is true even for digitally remastered cassettes.
This may be hard to believe, but recordings that I make from cds sound better than the cds. Noisier, yes, but better in everything else. This deck, or maybe any good deck, does something in the proccess of the recording. My CEC TL5100Z belt drive player is pretty good, especially the transport, but not high end at all, so I don't know how it would be with top of the line players.
That's one of the reasons why I make recordings from cds, another being that I make compilations. And yet another - deck is much more involving to interact with.
Inna, I don't find that hard to believe, not at all. The problem is not with the CD, I mean except for all the dynamic compression we see going on, it's with the CD player. There are so many things wrong I could write a book.
I used a Nakamichi BX300 with regular maintenance (de-mag, roller cleaning) for years and the Dolby C was amazing…you could instantly verify this since it was a 3 head player. Could be that Nak just did it right somehow…the machine is retired (no room in my rack..damn…) but served me well!
BTW Dolby SR is state of the Art and approaches digital for S/N ratio.
I'm with Wolf---the Dolby C in my BX300 is great. The deck is great with metal tape (I've used TDK and Sony), by the way. But the BX series Nak's design has a flaw---it's transport is not the most robust. I believe the CR series Nak's may be the one to get.
I will partly correct what I said before. I think, my cartridge and new cables were not fully broken in when I was making comparisons while recording from my Spacedeck turntable, though they had over 150 hours on them.
First of all, the deck cannot really compete with the turntable. The dynamics gets compressed a little but the biggest difference is in the soundstage - it loses both depth and width, but the deck still sounds very very good. The same can be said about the difference between recordings made without Dolby B and with it. They do sound better without it even though they are noisier, of course.
If anyone ever experienced the dynamics of their recordings being compromised while using Dolby B, C or S, then your machine was not calibrated for the tape you were using. 
Once calibrated and proper recording levels set Dolby would have no ill effects on your recording. 
This is funny because I just had this conversation with another audio nut. I have hundreds of tapes many that are 40 years old that sound excellent and were made with Dolby. 
That said I do know the sound of a machine that is killing the Dynamics of your recording when using Dolby. Nearly all of my Teacs did this. It wasn't I until someone showed me their Advent 201 in which you could calibrate the Dolby that I realized how good it could be and how bad mine were. Since that time I have always owned a deck that allowed calibration of the Dolbly NR system. 
I am really surprised at the number of audiophiles who snub cassettes as 'mid-fi' crap. Properly recorded cassettes are very enjoyable and convenient. I use my ancient Nakamichi all the time with excellent results. 
I don't know, Norman, my Nak was aligned and calibrated by Willy Hermann five years ago, and I did send him Maxell Vertex tape along with the deck. But I cannot be certain what he did with Dolby if anything. The deck still sounds exactly the same as when it returned from him. The sound is definitely not mid-fi, the deck just reached its limits. As I said, the drop in dynamics with Dolby is not dramatic but quite noticeable. In any case, I don't really need Dolby, some extra noise doesn't bother me. And of course I record directly from phono to deck, I never use tape-out on the amp.

How is it that you are recording directly from phono to deck?  I know Eckart mentioned that he does this too.  You must be using some type of phono preamp out?  Yes?

Last night I calibrated the Dolby on a Nakamichi 500 Dual tracer.  It has the built in 400hz test tone for this.  After calibration, it was almost impossible to tell the difference between the source and the deck.  And this was a two head deck.  (it does benefit from the magnificent  focus gap head however).  This feature is also included in my Nakamichi 1000 MKI.

Which Nakamichi are you using?  I am certain that if the Dolby was calibrated to your tape, the result would be excellent.

It is Nak 682ZX. I just disconnect the phono stage from the integrated amp and go directly to the deck. I of course calibrate each cassette when recording, this makes a lot of a difference.