Dolby Options and Playback

[Moby2]

Please don't laugh, this is probably a very basic question to you all, but I'm a little confused by which options to choose (Dolby, MPX filter etc) when playing back cassette tapes.

I have a Yamaha KX-R470 cassette deck from the early 1990s that I bought last week from a thrift store for $30 (excellent looking and playing condition other than no owners manual and broken knobs for balance, bias, play trim etc---can still turn but need to use thumb fingernail to get right at center positions). There is a button called Dolby NR that when you press it, gives you different options. You can select Dolby B, Dolby C, MPX Filter With Dolby B, MPX Filter with Dolby C, or nothing. How do I know which option to select? Will it say on the tape? I have pre-recorded tapes from the 80's and 90's that say Dolby, Dolby HX Pro, and nothing.


There is also a feature that I assume automatically detects whether a tape is Normal, High Bias or Chrome because when I put in a TDK high bias cassette tape, even before I pressed play, the deck automatically detected the tape was high bias and high bias was illuminated. A couple pre-recorded tapes I played today like Abba Gold and the Police Message in a Bottle Box are chrome tapes, yet they still showed up as normal. I know high bias (type II) tapes are higher quality and more audiophile than type 1, so why would a Chrome Tape come back as normal. Wouldn't the record company want to put out a high biased best sounding tape? Do I also need to play around with the bias button after putting in a cassette tape or is that for recording only?

This is my first real cassette deck after using a boombox to play tapes all these years.

 

[EchoWars]

The MPX filter (multiplex filter) is basically for recording from FM tuner sources (filters the 19KHz pilot signal which can cause Dolby mistracking). As far as which Dolby to use, there's no reason to use anything except Dolby C when recording. You might use Dolby B for playing back pre-recorded tapes which are Dolby B encoded, but I see no reason to use 'B' for anything except that.

 

[niklasthedol]

I recommend to use no Dolby at all on good quality tapes.

If you find the tape hiss annoying on a certain tape, then it's not good quality and you might benefit from using Dolby B.
Only use Dolby C when the tape is really bad.

MPX is for recording FM from a tuner without build in MPX filtering itself.
Today you will have to look deep into the FM market to find any tuner with a frequency response that makes MPX filtering needed.

Be Aware that Dolby B,C,S; dbx I and II and a few other systems are double ended noise reduction; meaning that tapes recorded with the technology also has to be played back with the same technology.

HX-Pro and Dolby HX are single ended noise reduction systems and are only to be used during recording. So if a pre-recorded tape states these, no action on your machine's buttons are to be taken.
If you have any HX, then use it every time you record.
It will also be compatible for playback on any choise of machine.

There will very often be compatibility problems between two decks in the allignment of the circuits for the double ended noise reduction systems. This can make it sound dull or sharp or in other ways "wrong" when a tape with Dolby B, C etc. is played back on another machine than it was recorded on.

MPX filtering and double ended noise reduction systems also has some "cooperation-issues". If possible, avoid using them at the same time.

Pre Recorded tapes sometimes have the double D symbol for dolby but is not encoded for use with dolby B (or C for that matter) unless it is directly statet that the encoding is used.

Anyway, you will not get any good sound out of the machine unless the tape path is clean.

The Tape indicates to the machine what tape it is (at least after the mid-70's period) with the configuration of holes on the upper back of the cassette where you also can protect a tape from further recording by cracking the taps off.

If a tape is recovered with adhesive tape at the point of recording protection to make the tape recordable again, you can experience that the tape also covers the holes for tape type indication. This will cause the problem of the machine not recognizing the tape type correctly.

There are four tape types:
Type I is Ferro
Type II is Chrome
Type III is FerroChrome
Type IV is Metal

On the best tape machines made, you can find options to manually adjust equalization and record level for each track, for each speed and both for recording and playback. Bias will be adjustable seperate for each speed and track.
Furthermore you will find option for adjusting the azimuth angle on the record head and the playback head on some cassette decks.

Theese adjustments serve to pull out the best quality from any tape selected.

Most cassette decks have static internal adjustment or automatic functions for these adjustments.
This makes it less precise but more consumer-friendly.
If you have only one bias adjustment button it will serve for bias when recording.
Forget it when you play back tapes.

When you use a tape, you should at least find out what eq and bias settings should be.

Not all cassette decks have options for metal type IV.
If not then avoiding metal tapes would be the best general advice because some heads can be worn very fast when not made for metal tapes when you then try to play them.

Not all cassette decks have option for FerroChrome type III.
If not, play the tape as a Chrome and set the eq at 120 μs if possible.

"dolph"

 

[AnalogDigit]

I would experiment with different setting with no Dolby, Dolby B or Dolby C on music that you are familiar with. Most people have different opinions on what setting to use. Keep in mind if you do record with Dolby, and if you play back the tapes without Dolby Noise Reduction, it will boost the highs, which would be useful if you have a cassette deck in your car or on a portable boom box that has no Dolby Noise Reduction.

 

[BrocLuno]

Listen and let your ears decide. MPX filter only if recording off-air. B kind of sucks, but older tapes may be encoded that way, so flip it on when playing older factory tapes and see what it sounds like (probably dull and muddy). C is much better, but will still steal some of the highs on most tapes. If you can get away without it, leave it off. If it's needed, you'll know - there will be a lot of hiss and the signal will be too bright.

 

[goldear]

I need to make two minor corrections to Dolf's excellent comments above:

HX-Pro and Dolby HX are single ended noise reduction systems and are only to be used during recording. So if a pre-recorded tape states these, no action on your machine's buttons are to be taken.
If you have any HX, then use it every time you record.
It will also be compatible for playback on any choise of machine.

HX pro is a single ended system, but it is not noise reduction system. It is a high-frequency Headroom extension system that significantly improves your high-frequency response at higher recording levels. It does its job very well. On most machines that have this feature, it is not defeatable. And I on those few where it is defeatable, there is no reason that I can ever think-of to ever turn it off.

MPX filtering and double ended noise reduction systems also has some "cooperation-issues". If possible, avoid using them at the same time.

Actually this is backwards. The multiplex filter specifically desinged for recording off of FM while using Dolby. The reason why it is included is to filter-out the 19khz pilot that out of alignment can emmit, which will cause havok with your Dolby tracking.

But for other non-FM recording, I do agree that it is best to leave this off, so that you don't filter-out everthing above about 16khz.

 

[niklasthedol]

I need to make two minor corrections to Dolf's excellent comments above:

HX pro is a single ended system, but it is not noise reduction system. It is a high-frequency Headroom extension system that significantly improves your high-frequency response at higher recording levels. It does its job very well. On most machines that have this feature, it is not defeatable. And I on those few where it is defeatable, there is no reason that I can ever think-of to ever turn it off.


Actually this is backwards. The multiplex filter specifically desinged for recording off of FM while using Dolby. The reason why it is included is to filter-out the 19khz pilot that out of alignment can emmit, which will cause havok with your Dolby tracking.

But for other non-FM recording, I do agree that it is best to leave this off, so that you don't filter-out everthing above about 16khz.

I stand corrected.

Usually Dolby-HX or HX-pro is not defeatable.
On some cassette decks, in particular when it's Dolby-HX in stead of the much better HX-Pro, it is defeatable.
I agree that there is no reason, whatsoever, to turn this circuit off in a recording process.

HX-Pro was patented by Bang & Olufsen and is seen in the very top of professionel studio open reel tape decks like Lyrec and Studer.
Dolby-HX was marketed by Dolby laboratory and was only seen on low- to mid market machines.

It is correct that it is the multiplex pilot tone at 19 kHz that interfere with the double ended NR systems.
My mistake to write it "upside-down". (English is not really my tongue. I'm danish, you see)

When using the MPX stop-filter this tone is damped. It will even be better when using HX because this helps machines with uneven HF response to flatten out.
However, MPX filter should be very bad designed if it filters everything above 16kHz as you state.
It is designed as a frequency band stop filter and in particular this filter should go after only 19 kHz +/- a very few Hz, with a dampening efficiency of 3dB; 6dB or maybe even higher factors.

It is correct that Dolby-HX and HX-pro was original developed as headroom expansion.
As was the Tandberg Dyneq system.
But both systems tend to better S/N ratio pretty much as a side-effect so why not count them in as NR systems as well.

"dolph"

 

[rushfan]

Nice tape deck - I own one too. It's a handsome machine, IMHO. I also have a top of the line KX-690 that needs some adjustment, something that I should get done soon.

I have always recorded using Dolby C, even when using top quality tapes. I have never really done without it so this is something that I'll look into. The KX-690 even has Dolby S - a rare feature, it seems.

Goodwill and Salvation Army stores can be a good source for blank and pre-recorded cassettes. I bought two Metal tapes a couple of nights ago, a Sony and a TDK. The TDK wasn't even opened yet. Not bad for 49 cents apiece! You might want to stock up on blank tapes while you still can.

 

[Moby2]

Thanks

I want to say thank you to everyone who replied. You all gave me a college level course on the different Dolby's and made me understand things better.

 

[Pyrrho]

Please don't laugh, this is probably a very basic question to you all, but I'm a little confused by which options to choose (Dolby, MPX filter etc) when playing back cassette tapes.

I have a Yamaha KX-R470 cassette deck from the early 1990s that I bought last week from a thrift store for $30 (excellent looking and playing condition other than no owners manual and broken knobs for balance, bias, play trim etc---can still turn but need to use thumb fingernail to get right at center positions). There is a button called Dolby NR that when you press it, gives you different options. You can select Dolby B, Dolby C, MPX Filter With Dolby B, MPX Filter with Dolby C, or nothing. How do I know which option to select? Will it say on the tape? I have pre-recorded tapes from the 80's and 90's that say Dolby, Dolby HX Pro, and nothing.


There is also a feature that I assume automatically detects whether a tape is Normal, High Bias or Chrome because when I put in a TDK high bias cassette tape, even before I pressed play, the deck automatically detected the tape was high bias and high bias was illuminated. A couple pre-recorded tapes I played today like Abba Gold and the Police Message in a Bottle Box are chrome tapes, yet they still showed up as normal. I know high bias (type II) tapes are higher quality and more audiophile than type 1, so why would a Chrome Tape come back as normal. Wouldn't the record company want to put out a high biased best sounding tape? Do I also need to play around with the bias button after putting in a cassette tape or is that for recording only?

This is my first real cassette deck after using a boombox to play tapes all these years.

For playback, when selecting Dolby B, C, or S (or if you have it, the non-Dolby dbx), always select whatever was used in the recording. If the prerecorded tape just says "Dolby", it will be Dolby B, because for many years, type "B" was the only kind on cassettes so there was no point in trying to distinguish it from other kinds of Dolby. And if there is no mention of Dolby (or dbx) at all, then it will be with no noise reduction at all.

For details about the Dolby noise reduction formats, the Dolby website is a great resource. See:

http://www.dolby.com/uploadedFiles/..._Dolby_B,_C_and_S_Noise_Reduction_Systems.pdf

There are many other things at the Dolby website just waiting for you (and others) to read them.

If you want to record, I recommend using CDs and forgetting about tapes, but if you want to record tapes, always keep in mind where you will play it back and use the noise reduction most appropriate for the playback equipment. Thus, if you were going to play the tape in a car stereo that had Dolby B noise reduction and no other, than using Dolby B for recording that tape would make the most sense.

 

[SaSi]

I would agree that HX Pro is actualy a NR system (and it was marketed like that). But I've seen HX Pro almost in every Japanese deck that sported Dolby C, like it was part of the Dolby B+C IC. The only deck I have seen Dolby C but not B is the Revox! I bet there are more.

 

[niklasthedol]

I would agree that HX Pro is actualy a NR system (and it was marketed like that). But I've seen HX Pro almost in every Japanese deck that sported Dolby C, like it was part of the Dolby B+C IC. The only deck I have seen Dolby C but not B is the Revox! I bet there are more.

Don't you mix up HX-Pro and the Dolby-HX when remembering that a lot of Japanese decks were featuring it?

Oh, and what Revox tape deck would have Dolby C and left out Dolby B?

"dolph"

 

[niklasthedol]

For playback, when selecting Dolby B, C, or S (or if you have it, the non-Dolby dbx), always select whatever was used in the recording. If the prerecorded tape just says "Dolby", it will be Dolby B, because for many years, type "B" was the only kind on cassettes so there was no point in trying to distinguish it from other kinds of Dolby. And if there is no mention of Dolby (or dbx) at all, then it will be with no noise reduction at all.

For details about the Dolby noise reduction formats, the Dolby website is a great resource. See:

http://www.dolby.com/uploadedFiles/..._Dolby_B,_C_and_S_Noise_Reduction_Systems.pdf

There are many other things at the Dolby website just waiting for you (and others) to read them.

If you want to record, I recommend using CDs and forgetting about tapes, but if you want to record tapes, always keep in mind where you will play it back and use the noise reduction most appropriate for the playback equipment. Thus, if you were going to play the tape in a car stereo that had Dolby B noise reduction and no other, than using Dolby B for recording that tape would make the most sense.

The Dolby symbol on pre-recorded tapes could also indicate other Dolby patents in use than Dolby B.
Dolby A, which were widely used in the mastering process, Dolby-HX and others could also have been in use.

I have pre-recorded tapes from early 70's, mid 70's, late 70's and from the 80's and even the 90's; stating Dolby was used and that it should be played back with dolby B activatet.

I have pre-recorded tapes only stating that Dolby should be activated when played back.............without specifying B or C or any.

But I also have pre-recorded tapes with the Double D symbol without stating any Dolby should be activated during Playback.
Playing these tapes defenitely sounds like no dolby should be activated during playback.

This is why I disagree on what you write about Dolby symbols on pre-recorded tapes.

"dolph"

 

[Pyrrho]

The Dolby symbol on pre-recorded tapes could also indicate other Dolby patents in use than Dolby B.
Dolby A, which were widely used in the mastering process, Dolby-HX and others could also have been in use.

There are many patents relevant to mastering equipment, but they are not typically listed on tapes sold to consumers, as there is no point in doing so. Now, if you can find a link at Dolby's web site that says that they did what you are suggesting, then I will accept it. Otherwise, I will not, for the simple reason that it was not done for other patents held and it would be not only pointless, but would mislead people, to put it there.

I have pre-recorded tapes from early 70's, mid 70's, late 70's and from the 80's and even the 90's; stating Dolby was used and that it should be played back with dolby B activatet.

I have pre-recorded tapes only stating that Dolby should be activated when played back.............without specifying B or C or any.

Any tape made before 1980, when Dolby C came out, would not likely specify the type of Dolby to use because there was only one consumer type to use at all. The tape decks themselves typically just said "Dolby" and did not specify that it was Dolby B.

Since that was the standard way to specify the use of Dolby B, they often continued to designate it that way after 1980. So, if it says to activate Dolby, but does not state the type, the proper type is going to be Dolby B.

But I also have pre-recorded tapes with the Double D symbol without stating any Dolby should be activated during Playback.
Playing these tapes defenitely sounds like no dolby should be activated during playback.

This is why I disagree on what you write about Dolby symbols on pre-recorded tapes.

"dolph"

I have encountered many people who prefer to listen to Dolby B encoded tapes without decoding them with Dolby B. The treble is boosted that way. So, when you say that your subjective preference on playback for something is without activating Dolby, I find that unconvincing as an argument that it is not Dolby B encoded. It is typical for Dolby B encoded tapes to sound okay when not decoded. Many old tapes have inadequate treble, and they might actually sound better if they are not "properly" decoded.

In fact, Dolby themselves describe certain listening tests that they conducted in which people preferred the sound of tapes played without the proper decoding! See:

http://www.dolby.com/uploadedFiles/.../Newsletters/413_Dolby News - Spring 1995.pdf

You will need to scroll down to the part titled "Analog Cassette vs. CD: The Winner is..."

They also say something similar at:

http://www.dolby.com/about/who_we_are/history_3.html

In 1970 Dolby began to promote the idea of releasing prerecorded cassettes encoded with the Dolby B-type® characteristic, so that they would have low noise when played on players equipped with Dolby B-type noise reduction. Listening tests performed by several record companies, notably Decca in the UK and Ampex Stereo Tapes in the US, showed that Dolby B encoded tapes were even preferred over non-encoded tapes when played on players without noise reduction, eliminating the need to release cassettes in both encoded and unencoded forms. ...

Within a few years, virtually all prerecorded cassettes would be encoded with Dolby B-type NR, which remains true today.

If you look at that link, they seem to imply that their logo on a cassette indicates that the cassette is Dolby B encoded, as I have stated.

 

[BrocLuno]

For those fortunate few who have Dolby S, make a tape and play it back in S. If the machine is in spec and the system is too, it will rival good pre-over compression CDs for quietness in the quieter passages. Too bad it came along when CDs were on the ascendancy. It is quite a remarkable system

 

[niklasthedol]

There are many patents relevant to mastering equipment, but they are not typically listed on tapes sold to consumers, as there is no point in doing so. Now, if you can find a link at Dolby's web site that says that they did what you are suggesting, then I will accept it. Otherwise, I will not, for the simple reason that it was not done for other patents held and it would be not only pointless, but would mislead people, to put it there.





Any tape made before 1980, when Dolby C came out, would not likely specify the type of Dolby to use because there was only one consumer type to use at all. The tape decks themselves typically just said "Dolby" and did not specify that it was Dolby B.

Since that was the standard way to specify the use of Dolby B, they often continued to designate it that way after 1980. So, if it says to activate Dolby, but does not state the type, the proper type is going to be Dolby B.





I have encountered many people who prefer to listen to Dolby B encoded tapes without decoding them with Dolby B. The treble is boosted that way. So, when you say that your subjective preference on playback for something is without activating Dolby, I find that unconvincing as an argument that it is not Dolby B encoded. It is typical for Dolby B encoded tapes to sound okay when not decoded. Many old tapes have inadequate treble, and they might actually sound better if they are not "properly" decoded.

In fact, Dolby themselves describe certain listening tests that they conducted in which people preferred the sound of tapes played without the proper decoding! See:

http://www.dolby.com/uploadedFiles/.../Newsletters/413_Dolby News - Spring 1995.pdf

You will need to scroll down to the part titled "Analog Cassette vs. CD: The Winner is..."

They also say something similar at:

http://www.dolby.com/about/who_we_are/history_3.html



If you look at that link, they seem to imply that their logo on a cassette indicates that the cassette is Dolby B encoded, as I have stated.

From your quotings and links it would be reasonable to believe it is the way you describe.

However, when I have tapes with the double D symbol and some of them describe how to activate Dolby and if played back on machines without any Dolby option, the treble should be adjusted down a bit, and some, still with the Double D symbol don't state anything about this, I will still tend to believe that the Double D symbol can symbolise the use of different Dolby patented techniques.

The issue about some people preferring to play back dolby encoded tapes without dolby is true.
This is generaly more due to lack of frequency response in the deck than on the tape, if you ask me.
But don't count me in there.
I know the sound characteristics of my gear very well and I would for shure be able to discover if any dolby had been in use during the recording process.

Anyway, maybe only 5-10% of my thousands of tapes are pre-recorded.
They will always be in the shadow of own made tapes when it comes to quality of sound.
And the very best quality tapes are without dolby of any kind.

"dolph"

 

[Ronald1973]

I'm certainly far from an audiophile, lol, but I've never been a huge fan of Dolby C. IMHO Dolby C muffles the sound too bad to the point of losing crisp highs and just a general lackluster sound. I keep my cassette deck in good working order via cleaning the tape path and demagnetizing, etc. Dolby B on the other hand is a must for me. Any tapes I do automatically get the Dolby B treatment.

Now, off topic, what is Dolby A? I remember someone here mentioning it once and I'm curious as to what it's use was, etc.? Thanks and Merry Christmas!

 

[KentTeffeteller]

Dolby A type NR is used only in professional studio equipment. 7 1/2 IPS and upwards. Not for narrow track format use. Never used on consumer level equipment. Dolby B was made for 1/4 track open reel use at slow speeds, cassette and even 8 track cartridge use.

 

[niklasthedol]

If the master, from which the Pre-recorded Cassette Tape is downmixed/dubbed from, involved the use of Dolby A, the Pre-recorded Cassette Tape might have the Double D symbol.

"dolph"

 

[r_brumett61]

Actually Dolby A was available from Teac(AN 150-I believe) in the the 70's and this was not considered a pro line series but for people who did not want to cut their high end at 15khz that Dolby B did(AN 50).