The magnitude of tape noise: Douglas Self

[DouglasSelf]

I am currently pondering tape replay amplifiers.

With vinyl there's no doubt that the noise floor of the medium (ie groove noise) is greater than the noise of a well-designed MM preamp by some 20 dB.

In the world of tape, the noise floor of the medium is set by random magnetic particles moving past the head gap. I have tried to find some information on the noise levels involved, with less than satisfactory results.

I would be much obliged if anyone could point me to some information on this.

 

[gpapag]

https://pdfs.semanticscholar.org/4c...441.906480097.1568319156-128242160.1568319156
http://mrltapes.com/mcknight_master-tape-eq-revisited.pdf
http://mrltapes.com/mcknight_sn-problems-and-a-new-eq.pdf
Page 25-26 https://nvlpubs.nist.gov/nistpubs/Legacy/TN/nbstechnicalnote718.pdf
Page 4 https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19650019351.pdf

Attachment is from this:
https://www.researchgate.net/public...the_recording_noise_in_advanced_magnetic_tape

I wish you success with your new research topic

George

 

[Mark Tillotson]

One fact I know is that the minimum particle dimension is constrained by the thermal stability of the magnetic domain - too small and the magnetism will flip on too short a time-scale. This is pushed to the limit in disc-drive technology(*), so there may be some information in that literature - and for digital backup tape drives. Video recorder technology may also have some useful data.
Clearly noise must be strongly related to magnetic particle size, so noise floor to the minimum possible particle size.



(*) I assume GMR effect heads have never been used for linear audio, but you never know!

 

[DouglasSelf]

I wish you success with your new research topic

George

Thanks very much, there's a good deal to chew on there!

 

[gpapag]

One fact I know

Hi Mark
It seems you know what you are talking about. See “magnetic recording trilemma” (SNR vs thermal stability and write ability)
(PDF) Advanced magnetic materials for ultra high density magnetic recording | Gaspare Varvaro - Academia.edu

Thanks very much, there's a good deal to chew on there!

You are welcome.
Please note the AC bias setting (depending on the tape formulation) also affects tape’s noise (tape noise is shown above ~1kHz, below it is “noise” of mechanical nature).
I think that as you progress in your search you may find out that noise variability among tapes even of the same magnetic type is much greater than noise variability among vinyl LP formulations.
The good thing is that today there are only few tape manufacturers, therefore a much smaller test candidate population than 20 years ago.

George

 

[diyralf]

Is it still worthwhile to put time into this old technology?

 

[gpapag]

Bear in mind that most of us here are of some age!

Looking into some docs in an older HD, I notice that noise is hardly on the tape specification list (only as S/N at a single freq), let alone noise freq spectrum. Often there is a reference to "System noise" (tape+rec+playback equipment noise)
https://ia801903.us.archive.org/33/...eiselmaier_Pigmentation_of_Magnetic_Tapes.pdf
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19820021703.pdf
https://www.ias.ac.in/article/fulltext/boms/016/01/0051-0054
http://www.simpatyrecords.com/PDF/24291_98_atr_40907_1_4_metal.pdf
https://static1.squarespace.com/sta...Master-Tape-Technical-Data-Sheet-Standard.pdf
https://static1.squarespace.com/sta...1504133824918/MDS-36-Technical-Data-Sheet.pdf
https://www.fullcompass.com/prod/23...aster-tape-on-105-nab-reel-with-tape-care-box
https://web.archive.org/web/2004123...om/Q472 Studio Audio Cassette IEC Type II.htm

George

 

[Cloth Ears]

I am currently pondering tape replay amplifiers.

With vinyl there's no doubt that the noise floor of the medium (ie groove noise) is greater than the noise of a well-designed MM preamp by some 20 dB.

In the world of tape, the noise floor of the medium is set by random magnetic particles moving past the head gap. I have tried to find some information on the noise levels involved, with less than satisfactory results.

I would be much obliged if anyone could point me to some information on this.

A bit (lot) off topic, but I like the way you're looking, Doug. I was a bit of a fan of the old laser discs - which could store audio as analogue as well as a variety of digital formats. And it could handle FM encoded Dolby Digital, which I thought might be an option for the out-moded vinyl format.
Unfortunately none of this was done, even when vinyl was being touted as a better format then the digital formats. I'm sad. Obviously, a tape (1/4" or larger) is a good way to replay audio, but it doesn;t bode well for long term storage.

 

[Mooly]

Bear in mind that most of us here are of some age!

I'm not quite as old as I thought I was when I spotted the venerable NE570 chip was now available in SMD outline.

One of those will bring your noise down

 

[DouglasSelf]

Is it still worthwhile to put time into this old technology?

Well it looks like it's timely.

There may be no shred of technical rationality, but tape is having a major revival at present. Also, it's an interesting technology. It avoids most of the horrors of vinyl reproduction.

 

[diyralf]

Okay, understood. Let's agree on VHS tape PCM audio recording

 

[gpapag]

It avoids most of the horrors of vinyl reproduction.

It has a lot more of it’s own.
Tape hiss is not one of them, therefore I stop here.

George

 

[dotneck335]

What would be interesting is to put Dolby's SR noise reduction technology into an affordable format for existing tape machines.

 

[edbarx]

Reference by posters to tape signal to noise ratio, gives the impression that tapes will used to record an audio signal in analogue form. This is very unattractive considering signals can be recorded digitally in media like USB sticks and hard disks. Why revert back to an obsolete technology that is grossly inferior to what is cheaply available these days?

If the reverting is for artists to sell their music and songs, they can still do so using online websites, that require authentication and payment for any downloads. Artists can make money that way: there is no need to revert back to a cumbersome system that would need shelving for media.

 

[Mark Tillotson]

The studios of world have rooms full of master tapes sitting there. Tape playback is vital in that context, Doug's researching for the next edition of his reference work "Small Signal Audio Design" I believe. Noone's talking about recording, just playback.

 

[PRR]

We have cameras, color cameras, in pocket phones. Why do I see people on hills and beaches with easels and canvas and brushes all over the scenic island? (The small bookstore downtown has aisles of art supplies.)

I remember three levels of tape noise:
1) virgin from factory
2) bulk erased
3) deck erased

#1 was clearly lowest and we "always" used virgin tape, in days when we bought tape by box-loads. However no matter how much "boom" tape has today, there must be much erased tape around. And have bulk erasers boomed too?

 

[lcsaszar]

Reference by posters to tape signal to noise ratio, gives the impression that tapes will used to record an audio signal in analogue form. This is very unattractive considering signals can be recorded digitally in media like USB sticks and hard disks. Why revert back to an obsolete technology that is grossly inferior to what is cheaply available these days?

You can ask the same about vinyl, about old timer cars, old furniture, but to go to the extremes: visiting the historical centre of a medieval town, playing a hundred year old violin, etc. It is about the feeling.

 

[edbarx]

You can ask the same about vinyl, about old timer cars, old furniture, but to go to the extremes: visiting the historical centre of a medieval town, playing a hundred year old violin, etc. It is about the feeling.

In some niche instances, using antique technology might be an advantage. At the moment, I am considering using a 2000+ year old method do extract oil from ripe olives, as this method is the cheapest method, considering my very limited production of olives. Hopefully, it works.

 

[gpapag]

All these have nothing to do with the OP specific request.

George

 

[Mark Tillotson]

Possible deep background material: Magnetic Materials and Devices | edX
I'd done a version of this course a few years ago (with optics and semiconductors thrown in) and it was excellent.