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  #1  
Old 02-15-2017, 08:30 PM
kfbkfb kfbkfb is offline
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Dolby B and non-Dolby playback

My Chase Ennea (EPIC/CBS ET 31097) prerecorded cassette
made in 1972 is Dolby B encoded.

The paper insert says:
This tape is mastered to Dolby "B" standards for noise reduction.
Decrease treble response when playing on non-Dolbyised equipment.

Did Dolby Labs ever provide a treble decrease curve (to optimize
the sound quality of Dolby B encoded source material played back
without Dolby B decoding)?

Kirk Bayne
  #2  
Old 02-16-2017, 12:21 AM
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svampen svampen is offline
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I beleive there is a very detailed specification how Dolby noise reduction is implemented. Cant find the official spec, but here is some reading:
http://educypedia.karadimov.info/lib...on_Systems.pdf

Since it is a dynamic system one can simply not just turn down the treble and get a 100% result.

Although, when recording a tape with Dolby B the treble is enhanced on the recording, so when you play it back the Dolby again reduces the treble thus reducing the hiss but the recorded sound should remain the same level.

Turning down the treble is a quick-fix when playing back Dolby B encoded tapes. Not the best, but one would probably get a fairly satisfactory result on a lower end device not equipped with Dolby. Better turning the treble down than don't, in that case.
  #3  
Old 02-16-2017, 01:04 AM
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For such an old cassette I would leave the Dolby Off, unless the noise is bothering you.
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  #4  
Old 02-16-2017, 01:14 AM
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I generally leave Dolby NR turned off. So many cassettes sound gross and muffled with NR turned on, even if the shell and J card specifically says it has Dolby NR.

I only use it for tapes I made myself... I was thinking my deck's azimuth was off, but it decodes Dolby NR perfectly on tapes I recorded on other decks too.

Last edited by SKguy; 02-16-2017 at 01:17 AM.
  #5  
Old 02-16-2017, 01:33 AM
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Quote:
Originally Posted by SKguy View Post
I generally leave Dolby NR turned off. So many cassettes sound gross and muffled with NR turned on, even if the shell and J card specifically says it has Dolby NR.

I only use it for tapes I made myself... I was thinking my deck's azimuth was off, but it decodes Dolby NR perfectly on tapes I recorded on other decks too.
The tape loses highs over the time, some mechanical, others decreased their magnetic field through rough storage.

A playtrim deck is the best solution to restore it before the Dolby decoder makes it even more worse.

Unfortunately many top notch Digital Bin recorded real chrome prerecorded loses highs.....
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  #6  
Old 02-16-2017, 03:27 AM
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If it says dolby, i hit the dolby button.
Simple.
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  #7  
Old 02-16-2017, 10:12 AM
ModMan_70 ModMan_70 is online now
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I have some decks where Dolby B sounds very good. The playback head needs to be in good shape and properly aligned. And the rest of the Deck's electronics need to be good. Some Dolby IC's are better than others.

That said, I do use Dolby B on occasion. But normally, I leave it off.

If I'm listening to a piece of music with a very quiet passage, and I have the stereo cranked.... I want it on. At low levels, the hiss that is inherent with tape will be competing with those quiet passages.

That said, most chrome tapes are so quiet, it's hardly ever needed...IMHO.
  #8  
Old 02-16-2017, 03:38 PM
Dude111 Dude111 is offline
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Quote:
Originally Posted by Lowtone
If it says dolby, i hit the dolby button.
I prefer to find cassettes that dont say anything about DOLBY to be honest!
  #9  
Old 02-16-2017, 06:17 PM
debiani386 debiani386 is offline
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seems the dolby noise reduction systems work differently on different decks (because of different Dolby ICs) - I just got a Marantz PMD520 and both dolby B and C tapes that I have recorded on the deck during testing sound pretty amazing. I am curious how they will sound after a few days/weeks/months though?

I have also found some tapes that are recorded with Dolby NR sound worse with dolby NR enabled, and some sound better with it enabled (you can hear the compression artifacts with the dolby NR disabled).

I usually just roll off the 10 and 15 k bands (usually by -3 to -6 db) if I am playing back on a deck with dolby NR off, or no NR, and the high frequencies are too shrill for my liking.
  #10  
Old 02-16-2017, 10:08 PM
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Quote:
Originally Posted by Dude111 View Post
I prefer to find cassettes that dont say anything about DOLBY to be honest!
Yes... I have a small handful of factory tapes without Dolby NR... one in particular sounds absolutely fantastic, it's one of my best sounding cassettes. (It's an RCA though, and they're generally very good.)
  #11  
Old 02-17-2017, 04:18 AM
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vince666 vince666 is offline
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Quote:
Originally Posted by debiani386 View Post
seems the dolby noise reduction systems work differently on different decks (because of different Dolby ICs)
i don't agree with the highlighted part... dolby works differently on different decks mostly because of different/wrong alignment or frequency response on some decks... the difference from different dolby chips alone would be negligible compared to the bad effects of misaligning or different frequency response.

do consider that dolby is sort of a magnifier of differences and problems then if you notice it performs badly on some decks then you should try to find the true reason for it... i.e. the tape was wrongly calibrated during recording, the recording and/or the playback deck is misaligned or with "non standard" frequency response, etc... dolby simply put all of this in much greater evidence as any errors are multiplied if there is NR involved.
  #12  
Old 02-17-2017, 05:33 AM
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Irrespective of what it is written on to IC (or if not on how the discrete stage is realised), these would not get the Dolby certification if the results they provided were different (AFAIK we talk about 1dB over the whole bandwidth, again IIRC was up to 10kHz only).

As Vince said, there are higher differences elsewhere not in the ICs. Those +-1dB variances prompted the golden ears to give a ranking of those ICs, but the keyword here is "golden ears", not "compatibility".
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  #13  
Old 02-17-2017, 09:32 AM
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Quote:
Originally Posted by ModMan_70 View Post

That said, most chrome tapes are so quiet, it's hardly ever needed...IMHO.
If you live in a block of flats, 60dBA is much to loud for your neighbours. Other lives on the country side like me, no neighbours, only cows and fields.

...my Horns can go up over 126dBA peak. Every hiss and distortion is a pain in the ass and can be heard very well and not only in silent passages. So MUST be the weighting of Dolby complete different !
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  #14  
Old 02-17-2017, 11:03 AM
Dude111 Dude111 is offline
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Quote:
Originally Posted by SKguy
Yes... I have a small handful of factory tapes without Dolby NR... one in particular sounds absolutely fantastic, it's one of my best sounding cassettes. (It's an RCA though, and they're generally very good.)
Ya...I just got a Madonna cassette (TRUE BLUE) -- No DOLBY @ all...... No 'HX PRO' CRAP,nothing...... Sounds 1000% better than the other one Madonna one thats DOLBY B HX-PRO


Why bother putting B on it???? -- THERE IS NO NOISE @ ALL ON THE 1 I JUST GOT!!! (And the sound is much better)

Probably right from the reel to reel master? (It doesnt say HX-PRO so Im assuming this copy is straight analog... Sounds much better)
  #15  
Old 02-17-2017, 01:20 PM
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Quote:
Why bother putting B on it???? -- THERE IS NO NOISE @ ALL ON THE 1 I JUST GOT!!! (And the sound is much better)
So what are you maximum loudness ? With "no noise" of a tape with a usual FE type of -52dB noise ?

30dBA ? Or are the Madonna album so heavily compressed for car use, that the noise is not more audible ?
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  #16  
Old 02-17-2017, 04:11 PM
Dude111 Dude111 is offline
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There is nothing....I can turn the volume up quite loud and I dont hear a thing (No more than I do on 1 that has dolby B)

This NR crap is just BS to make it sound worse in my opinion!!!!!!
  #17  
Old 02-17-2017, 08:01 PM
drumbum drumbum is offline
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Tsk, Tsk......naughty, naughty
  #18  
Old 02-17-2017, 09:05 PM
debiani386 debiani386 is offline
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Vince666 said:

Quote:
do consider that dolby is sort of a magnifier of differences and problems then if you notice it performs badly on some decks then you should try to find the true reason for it... i.e. the tape was wrongly calibrated during recording, the recording and/or the playback deck is misaligned or with "non standard" frequency response, etc... dolby simply put all of this in much greater evidence as any errors are multiplied if there is NR involved.
Ghitulescu said:

Quote:
these would not get the Dolby certification if the results they provided were different (AFAIK we talk about 1dB over the whole bandwidth, again IIRC was up to 10kHz only).

As Vince said, there are higher differences elsewhere not in the ICs. Those +-1dB variances prompted the golden ears to give a ranking of those ICs, but the keyword here is "golden ears", not "compatibility".
Good to know. Thanks for correcting me. From what I can tell, this Marantz PMD520 of mine is aligned quite differently from my Technics M205 deck I once used (The Marantz deck sounds far better than the Technics deck does with NR enabled).
  #19  
Old 02-17-2017, 09:21 PM
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cmag69 cmag69 is offline
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Neither For or Against NR Use

I'm neither for or against the use of Dolby noise reduction.

In my experience it's the tape brand and quality that makes a difference in recording quality and playback quality.

On a side note, I live in Canada and when I did buy pre-recorded cassettes in the early 1980's to early 1990's all the cassettes I saw were recorded with Dolby B NR and later on with Dolby B NR HX Pro. I didn't buy many pre-recorded cassettes. Probably about 50 in total. I would buy vinyl and copy to high bias cassette using Dolby B NR.

My first HI FI cassette deck had Dolby B-C NR HX Pro and dbx NR. I liked using dbx NR but I was restricted to listening to dbx tapes on the deck I recorded it on.

Today I use quality high bias cassettes and use Dolby C NR with HX Pro. The tapes I make sound great on the deck I recorded them on. However on the deck I use for playback some tapes have no treble and others sound great. So it makes me wonder it it's the quality of Dolby NR decoder IC in the deck I use for playback. I don't think it's a mechanical problem with head alignment because balance and output of left and right channels is equal. It's just some tapes playback with low high frequency output. If I turn off the Dolby NR the tape sounds fine. Treble response sounds normal.

Sometimes I think it's the brand and quality of the cassette tape. My Maxell XLII cassettes sound flat in my playback deck and TDK SA cassettes sound bright in my playback deck.

So I don't have an idea why Dolby NR seems to work well and not well.
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  #20  
Old 02-18-2017, 01:44 AM
lucky lucky is offline
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Quote:
Originally Posted by Dude111 View Post
There is nothing....I can turn the volume up quite loud and I dont hear a thing (No more than I do on 1 that has dolby B)

This NR crap is just BS to make it sound worse in my opinion!!!!!!
What is quite loud for you if you dont hear the hiss ? I turn my pot to 9 o'clock and there is hiss without Dolby ?
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