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The magnitude of tape noise: Douglas Self
The magnitude of tape noise: Douglas Self
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Old 12th September 2019, 06:53 PM   #1
DouglasSelf is offline DouglasSelf  United Kingdom
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Default The magnitude of tape noise: Douglas Self

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.
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Old 12th September 2019, 08:50 PM   #2
gpapag is offline gpapag  Greece
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The magnitude of tape noise: Douglas Self
https://pdfs.semanticscholar.org/4c0...160.1568319156
http://mrltapes.com/mcknight_master-...-revisited.pdf
http://mrltapes.com/mcknight_sn-prob...d-a-new-eq.pdf
Page 25-26 https://nvlpubs.nist.gov/nistpubs/Le...calnote718.pdf
Page 4 https://ntrs.nasa.gov/archive/nasa/c...9650019351.pdf

Attachment is from this:
https://www.researchgate.net/publica..._magnetic_tape

I wish you success with your new research topic

George
Attached Images
File Type: png tape noise spectrun.png (367.3 KB, 306 views)
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Old 13th September 2019, 10:06 AM   #3
Mark Tillotson is offline Mark Tillotson
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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!
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Old 13th September 2019, 10:29 AM   #4
DouglasSelf is offline DouglasSelf  United Kingdom
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Quote:
Originally Posted by gpapag View Post

I wish you success with your new research topic

George
Thanks very much, there's a good deal to chew on there!
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Old 13th September 2019, 11:21 AM   #5
gpapag is offline gpapag  Greece
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The magnitude of tape noise: Douglas Self
Quote:
Originally Posted by Mark Tillotson View Post
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

Quote:
Originally Posted by DouglasSelf View Post
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
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Old 13th September 2019, 11:59 AM   #6
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Is it still worthwhile to put time into this old technology?
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Old 13th September 2019, 12:15 PM   #7
gpapag is offline gpapag  Greece
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The magnitude of tape noise: Douglas Self
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/i...etic_Tapes.pdf
https://ntrs.nasa.gov/archive/nasa/c...9820021703.pdf
https://www.ias.ac.in/article/fullte...6/01/0051-0054
http://www.simpatyrecords.com/PDF/24..._1_4_metal.pdf
https://static1.squarespace.com/stat...t-Standard.pdf
https://static1.squarespace.com/stat...Data-Sheet.pdf
https://www.fullcompass.com/prod/238...-tape-care-box
https://web.archive.org/web/20041230...0Type%20II.htm

George
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Old 13th September 2019, 02:05 PM   #8
Cloth Ears is offline Cloth Ears  Australia
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Quote:
Originally Posted by DouglasSelf View Post
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.
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Old 13th September 2019, 02:13 PM   #9
Mooly is offline Mooly  United Kingdom
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The magnitude of tape noise: Douglas Self
Quote:
Originally Posted by gpapag View Post
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
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Old 13th September 2019, 06:15 PM   #10
DouglasSelf is offline DouglasSelf  United Kingdom
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Quote:
Originally Posted by diyralf View Post
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.
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