Just me being picky, overly precise, or anal, or whatever.
And, just to add, nothing is ever magnetized by tape moving over it. The field is far too weak, and AC anyway.
Is tape head degaussing a myth after all?
- Thread starter soviet123
- Start date
And, just to add, nothing is ever magnetized by tape moving over it. The field is far too weak, and AC anyway.
It's that stuff used to repair torn pages and ripped up dollar bills, and sometimes is used for disenabling speech.
At one stage someone, maybe 3M? made a reader that you could put over a peice of tape, and the particles in it would line up to show you the magnetic fields on the tape. Ever heard of that one Jaddie? And to clarify, are you saying that screwdrivers can be randomly magnetised on a workshop bench?
Yes, I have a 3M magnetic tape viewer. It's a diagnostic tool. Was there a particular point you're making?
No.
maryjane99201
New member
I'm not sure if this post is still active, but I wanted to chime in on just HOW bad the infection can be on tape decks as they become magnetized. They can get bad to the point that it's literately a virus that stamp pops and clicks on tapes, and start to do it at multiple intervals, in addition to escalating beyond the point that these noises can EXCEED the recorded audio level of the recording. But wait, it gets worse.
If you play infected tapes in NEW decks, it eventually infects those decks, and apparently you cant erase the tapes because the infections BLEED perpendicular on the capstan infection the other side as your erasing it, in addition to the fact that the capstan is AFTER the the erase. Meaning it's useless, and destroys tapes and decks. But wait, it gets worse.
If you try to demagnetize your deck the infection comes back because it's additionally ON THE TAPES. I've worked in radio stations and recording studios and have reservations about bulk erasers as it could leave traces of the infections through the packed tape. But wait, it gets worse.
If you try to do an AUDIO DUB from one deck to another, because some of your store bought tapes are infected, and you really don't want to lose them, the infection PASSES through the audio, yes, I tried it, and found out the hard way.
I observed this issue that seems to start as an anomoly from just playing music that apparently has specific timing to keep striking the capstan at the right time, as mostly likely being the culprit, and it took me twelve years to realize what all was going on, and all the steps I mentioned. At the time I figured this out, I was sitting in class for my electronics tech program and realized what was happening. Opening sharing it with my class mates, one jumped out of his chair (CHAD) to go out to his car and bring back in a bag of infected tapes. They were actually worse than any I had ever managed to hear from my own equipment.
I decided to name this infection, and since it has all of the qualifying traits of a virus, I named it MTV, Magnetic Tape Virus.
I trashed all of my infected tapes and decks, and magically the virus was gone. It was quite an expensive move, but my collection is now clean.
If you play infected tapes in NEW decks, it eventually infects those decks, and apparently you cant erase the tapes because the infections BLEED perpendicular on the capstan infection the other side as your erasing it, in addition to the fact that the capstan is AFTER the the erase. Meaning it's useless, and destroys tapes and decks. But wait, it gets worse.
If you try to demagnetize your deck the infection comes back because it's additionally ON THE TAPES. I've worked in radio stations and recording studios and have reservations about bulk erasers as it could leave traces of the infections through the packed tape. But wait, it gets worse.
If you try to do an AUDIO DUB from one deck to another, because some of your store bought tapes are infected, and you really don't want to lose them, the infection PASSES through the audio, yes, I tried it, and found out the hard way.
I observed this issue that seems to start as an anomoly from just playing music that apparently has specific timing to keep striking the capstan at the right time, as mostly likely being the culprit, and it took me twelve years to realize what all was going on, and all the steps I mentioned. At the time I figured this out, I was sitting in class for my electronics tech program and realized what was happening. Opening sharing it with my class mates, one jumped out of his chair (CHAD) to go out to his car and bring back in a bag of infected tapes. They were actually worse than any I had ever managed to hear from my own equipment.
I decided to name this infection, and since it has all of the qualifying traits of a virus, I named it MTV, Magnetic Tape Virus.
I trashed all of my infected tapes and decks, and magically the virus was gone. It was quite an expensive move, but my collection is now clean.
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rob aylestone
Moderator
I'm sorry, but I really cannot accept this. In all my years of recording, nothing remotely like the attributes you describe work like viruses.
The tape, as a medium only has one significant attribute. It can be magnetised. In fact, when I did my BBC interview in the 70s, it was something I got tested on, and messed up bias current questions. I had some training to do. It is perfectly possible to subject a tape to very high levels of magnetism in a bulk eraser, or with some types of portable demagnetiser. The key feature of the process as trained was to make sure the field decayed and did not simply cut-off. The peak level could be high enough to permanently (semi-permanently ) magnetise the head, and the tape guides if they were made of certain materials. Passing a good tape over a head polarised in this way would indeed reduce the field recorded on the tape - reducing the level and introducing noise. However, the tape content itself was damaged, but not damaging to other equipment. It was possible for a tape recorded to extreme levels of saturation to be impossible to erase, and the tape could magnetise the next machine played on it, but only at levels perfectly capable of being demagnetised in the next cleaning/demag service.
You cannot call this a virus. It's just something that appears to have virus like action, but physics wise, it's not, in any shape or form.
Tapes had magnetic saturation limits, set by the formulation and going too high could be unfixable. With magnetics, transfer is possible under certain circumstances. It is NOT a virus that stamps pops and clicks - this is just silly and based on making conclusions on what you hear, and then imagining the cause.
Demagnetisers worked perfectly well used properly. One of my teachers maintained that a badly magnetised head block could be sorted by applying the damag power virtually touching the head gap, then only turning it off when right across the room, then repeating three times, then three times on the other two head - so 9 in total on a three head machine. You're totally right that the problems appear to move from machine to machine, but ONLY when a tape recorded with total saturation is laced up and played for a time. By time, I mean maybe a ten minute playout of a saturated tape. That ten minutes will leave the recorder needing demagnetisation. Any other tapes played on it could well be reduced in level - as tapes get when played on a machine needing head and guide demagnetising.
Don't attribute this process to some kind of virus. It's plain bog standard degradation caused by magnetised heads and guides. Perfectly normal.
This was known in the formative years, and processes to deal with it established in the UK and US by the broadcasters and detailed in the manuals of the day. You are attributing things already documented, understood and managed as something they are not. This is dangerous practice and needs rectification. You have not discovered anything and your methodology is faulty. The tapes are NOT infected, they're simply magnetised and recorded on machines needing service, cleaning and alignment. Demagnetising was an everyday practice. Any over-recorded tapes would be spotted in lineup and a quick test would prove or not if they were consigned to the bin. A session in the bulk demagnetiser would possibly salvage some. The Leevers-Rich ones could inflict substantial field strength - but it was reduced to nothing over a period of time and did a good job of erasing tapes but leaving them neutral.
If you really threw the equipment away, that's tragic, but they were not infected, just magnetised - and with care and attention residual magnetisation is rarely unfixable. The BBC got rid of loads of old but serviceable equipment when tape was phased out - NONE I am aware of were terminally magnetised.
You've drawn an understandable, but very wrong conclusion from your observations. Sorry. I've been doing tape for over 40 years and this just made me smile.
The tape, as a medium only has one significant attribute. It can be magnetised. In fact, when I did my BBC interview in the 70s, it was something I got tested on, and messed up bias current questions. I had some training to do. It is perfectly possible to subject a tape to very high levels of magnetism in a bulk eraser, or with some types of portable demagnetiser. The key feature of the process as trained was to make sure the field decayed and did not simply cut-off. The peak level could be high enough to permanently (semi-permanently ) magnetise the head, and the tape guides if they were made of certain materials. Passing a good tape over a head polarised in this way would indeed reduce the field recorded on the tape - reducing the level and introducing noise. However, the tape content itself was damaged, but not damaging to other equipment. It was possible for a tape recorded to extreme levels of saturation to be impossible to erase, and the tape could magnetise the next machine played on it, but only at levels perfectly capable of being demagnetised in the next cleaning/demag service.
You cannot call this a virus. It's just something that appears to have virus like action, but physics wise, it's not, in any shape or form.
Tapes had magnetic saturation limits, set by the formulation and going too high could be unfixable. With magnetics, transfer is possible under certain circumstances. It is NOT a virus that stamps pops and clicks - this is just silly and based on making conclusions on what you hear, and then imagining the cause.
Demagnetisers worked perfectly well used properly. One of my teachers maintained that a badly magnetised head block could be sorted by applying the damag power virtually touching the head gap, then only turning it off when right across the room, then repeating three times, then three times on the other two head - so 9 in total on a three head machine. You're totally right that the problems appear to move from machine to machine, but ONLY when a tape recorded with total saturation is laced up and played for a time. By time, I mean maybe a ten minute playout of a saturated tape. That ten minutes will leave the recorder needing demagnetisation. Any other tapes played on it could well be reduced in level - as tapes get when played on a machine needing head and guide demagnetising.
Don't attribute this process to some kind of virus. It's plain bog standard degradation caused by magnetised heads and guides. Perfectly normal.
This was known in the formative years, and processes to deal with it established in the UK and US by the broadcasters and detailed in the manuals of the day. You are attributing things already documented, understood and managed as something they are not. This is dangerous practice and needs rectification. You have not discovered anything and your methodology is faulty. The tapes are NOT infected, they're simply magnetised and recorded on machines needing service, cleaning and alignment. Demagnetising was an everyday practice. Any over-recorded tapes would be spotted in lineup and a quick test would prove or not if they were consigned to the bin. A session in the bulk demagnetiser would possibly salvage some. The Leevers-Rich ones could inflict substantial field strength - but it was reduced to nothing over a period of time and did a good job of erasing tapes but leaving them neutral.
If you really threw the equipment away, that's tragic, but they were not infected, just magnetised - and with care and attention residual magnetisation is rarely unfixable. The BBC got rid of loads of old but serviceable equipment when tape was phased out - NONE I am aware of were terminally magnetised.
You've drawn an understandable, but very wrong conclusion from your observations. Sorry. I've been doing tape for over 40 years and this just made me smile.
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maryjane99201
New member
Rob, thank you so much for your response, I felt like I should give you the respect of responding with a little more detail.
I have to applaud the fact that you have never personally witnessed this going on, and I certainly hope you never do.
You might be accurate that with proper maintenance and management, it could have PREVENTED this from going off the deep end, but I will still stand by the diagnosis.
Yes, you can damage tapes and decks through inadequate maintenance (which is specifically why it's even mentioned in the owners manuals) throwing in just the right circumstances of timing and exposure, you can end up with some virus worthy issues .
I'm shocked you would not believe these circumstances could result in what I have shared, knowing you have worked in a related field, but again, I think it's very niche things required to experience this
Yes you can magnetize tapes and capstans and heads, Magnetism happens to be the scientific method used for the system to work, understanding however that these magnetic levels are so low, that these problems are not common, adding the fact that in the early stages ones ear might not be able to realize what's going on, adding to the fact that they are completely unaware of how it started to begin with, and the fact of how, and that it spreads.
The reason I call this a virus is simply because it has all the necessary traits living up to the definition. No, it's not biological, no you can't see it with a microscope, and it's not computer based, so some would rule it out of the data catagory, so it must be in a class of it's own.
Virus, I'm following the 2nd paragraph on this because it is perhaps the closest.
- 1.
an infective agent that typically consists of a nucleic acid molecule in a protein coat, is too small to be seen by light microscopy, and is able to multiply only within the living cells of a host.
"a virus infection"- an infection or disease caused by a virus.
"I've had a virus" - a harmful or corrupting influence.
"the virus of cruelty that is latent in all human beings"
- an infection or disease caused by a virus.
- 2.
a piece of code which is capable of copying itself and typically has a detrimental effect, such as corrupting the system or destroying data.
It is capable of copying itself by re-stamping that magnetic charge on every rotation of the capstan. Keep in mind, it's pretty tuff to get to this point, but once it's here, not even a demagnetizer will fix it. This eventually leads to multiple pops and ticks out of that timing, which later on leads to them stacking, and eventually can exceed the original volume of the original recording.
I'm not sure if I mentioned this earlier, this isn't a theory, or a hypothesis, it was observed for over twelve years.
Keep in mind that just because you have worked with recording gear doesn't necessarily mean your going to be unlucky enough to ever witness it, which additionally doesn't mean it's not real.
Clearly the recording level plays a factor, in addition to the timing, in addition to how much it's played.
A simplistic way to understand why this happens, I like to use the analogy of magnetizing a screwdriver with a magnet. Keeping in mind that the magnet is thousands of times stronger then in the way audio tapes work. Yes, you can magnetize a screwdriver with a magnet. Now can you take that magnetized screwdriver and use it to magnetize something else, In a very small way, YES. Sometimes after picking up screws with a magnetized screwdriver, the screws themselves become slightly magnetized. it's a fact.
A magnetic domain is a region within a magnetic material in which the magnetization is in a uniform direction. This means that the individual magnetic moments of the atoms are aligned with one another and they point in the same direction. ... These are the ferromagnetic, ferrimagnetic and antiferromagnetic materials.
There are additional issues tied into this infection going on with tape deck designs that I have yet to delve into, but it just depends on how versed you are into the general theory of electronics.
Cassette tapes are made of a polyester-type plastic film with a magnetic coating. The original magnetic material was based on gamma ferric oxide (Fe2O3).
It might seem harmless at this point, but a magnetic coating on one side, with a polyester coating on the other, again, in the right circumstances can cause some issues, and your going to have to look at the tape path to ideally understand the picture here.
When you have these components together in such a way, they are in many ways much like a capacitor, but missing some key points. Those points are they are not WRAPPED
ED tightly together, (they are at the ree when wrappedl, but the infection point in this way of infection would come from the recording head, which is not close enough to the reels) and we only have one dielectric and one conductor. This can still hold charges, but again, not as well.
Most capacitors contain at least two electrical conductors often in the form of metallic plates or surfaces separated by a dielectric medium. A conductor may be a foil, thin film, sintered bead of metal, or an electrolyte. The nonconducting dielectric acts to increase the capacitor's charge capacity.
....
maryjane99201
New member
I think bigclive shows a good home made example.
If you want to understand how it's possible to have one of the conductors missing, and still have a reaction, here's a good video.
the reason I'm sharing a DIY on this example is so that you can see for yourself that emitting end of this build is a pop can. Most people might not realize the capacitive effect here totally missing the fact that the can does have a thin polyester lining, thus as a very good example of a one conductor one dielectric capacitive effect. Does this work like a capacitor, yes, just not as well.
Assuming you additionally are aware of how motors and starters, generators work, passing conductive wire or material (not necessarily any specific type btw) induce a voltage into the path. you can google ( inducing a voltage by breaking lines of magnetic field ) and pick any one of them.
Assuming you are up to speed at this point on all of this, you might be able to fully understand one of the ways this infection can occur.
During a point of recording, A high volume, possibly high frequency, high volume bias resonates off the head, as the tape is MOVING. It's key to understand what's going on here. Inducing a voltage directly ONTO the tape. This has to be a LOW voltage BTW. Keep in mind the tape is CONDUCTIVE, and keep in mind that it has a polyester backing, now realize the capstan is grounded, and about 21mm from the head in tape travel. Audibly this appears to create static discharges that you can audibly hear (a fraction of a second later) usually after loud high frequency cymbal crashes.
If you would like to actually HEAR an example of this infection yourself, There are literately hundreds in not thousands of professional recordings sold today on the market, with these infections. Most studios of course would not distribute music having sever damaged recordings as I'm sure no artist would approve much less the audience, however there are those situations, probably in a specific time period where people didn't really understand what was going on. So it's going to be the lighter cases that made it onto professional recordings for the most part. I like to use the example of the beastie boys, off the pauls boutique album shake your rump.
This song was recorded in sections, in what sounds like different equipment for those sections, in addition to the entire structure of the song changing throughout the song, explaining why it's not simply a constant infection. You can hear static pops that follow cymbal crashes at the following times.
in seconds 3,8,203,300,305,309,314 While they are weaker in that ending of the song, it could be because of the volume of that crash in the recording appears to be lower volume, but it's certainly there.
These noises will STAY on that tape, and because of the way that magnetic fields work and affect surrounding material, will align the domains on the capstan IN THAT ONE SPOT. They can stack if the same infection lands on the exact same spot, or they can end up making multiple static pops on that same capstan at different times after different loading times. I think something that might be throwing people off when I'm trying to explain this, is the idea that the capstan then becomes a magnet but that's not exactly how it turns out, as it will damage the very purity of what was originally suppose music or silence and eventually put multiple infections on that one capstan. It's not our simply understanding of how a magnet works in the way the capstan gets infected.
This is where I probably confused you with using a commercial bulk tape eraser. To better explain, if an entire has gotten to the point of infection, it's clear to me, in my experience that a bulk eraser might miss percentages of the tape, allowing the infecting to once again regrow. Maybe it's possible that the static discharges are only aligning a small section of the domains on the capstan.
The end result is the same regardless, if you have gotten to the point where you have even just ONE hot spot on the capstan, it will spread and multiply, and grow, in both volume and position, until it destroys the media, That's the last section of the definition of VIRUS.
To be clear, it might start out as an anomaly, but can quickly escalate to where it's able to copy itself, and destroy the data. That's a virus.
Play that infected tape in a new deck, and you will infect it very shortly. Play a new tape in an infected deck, and you will infect that tape. Because it's origination was sound and tape deck mechanics timing, it can replicate through an audio dub as well.
I hope this better explained some details. I additionally have a screen shot of one of the infection points from that beasti boys track, and I'll TRY to post it.(new here, not sure how) You can see from it's frequency it's VERY high, and very high in volume compared to the other data.
maryjane99201
New member
Your description sounds like either Modulation Noise- slang "bias rocks", misaligned recorders or a failiure to understand gain staging/recording levels. Making up terms like "infected" just confuses the reader. Re: your Beastie Boys example: They used a Tascam ATR-80/24. I know because I was the guy who set it up after being delivered. That example is bad tape. I would ask your technical qualifications to state your opinion-or are these subjective? Mine is 25+ year working on analog multi tracks. I wish I would have been around when you threw away those "infected machines."
dimarzio99
New member
hi, I have a question. I bought an used Nak B100 deck. On one channel it works fine, the other has a high pitched hiss. I read in the manual about demagnetizing. I have a demagnetizer, which I occasionally use on my r2r. I did a short demagnetizing, and the other channel "healed" and played back well for some hour, then that channel was lost again, and nothing but hiss remained. I repeated the process, with longer time and insisted on the rest too, not just the heads. It healed again for some hour, then symptoms came back. What could be wrong? At this point I should suspect a faulty head? or something else? Please help me.
Thank You kindly
rob aylestone
Moderator
I'd suspect fault components. Remember that when you demagnetise a head, you induce a fair amount of energy into the preamp that the head feeds. Your fault is more likely to be capacitors - and the 50/60Hz blasting with the demagnetiser saturates them, and they behave, like an electronic slap in the face, then the degradation creeps in again. Magnetised heads usually results in dull replay - muffled being a common description, while dirty heads can appear to raise the noise floor because you also turn up the level, bringing up the noise. I have never come across the left or right channels being different - you could have a head cleaning issue on one section of a head - but not magnetisation.
dimarzio99
New member
Thank You. So I give the another clean, and if does not help, I will look up all capacitors starting from the head wires to the output..and check/replace them out.
More likely to be a faulty part, because when the channel "disappears" and is replaced by noise (much lower in intensity than the good channel which plays music), it is instantaneous, and remains so.
Thank You again, that was really fast.
More likely to be a faulty part, because when the channel "disappears" and is replaced by noise (much lower in intensity than the good channel which plays music), it is instantaneous, and remains so.
Thank You again, that was really fast.
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May I humbly 'sum up' the comments in this thread? A 'magged up' deck (not just heads) will have two consequences.
1) increased noise build up on tapes.
2) 'wiping' of the very highest frequencies, really short "wavelengths' because 'f' depends on tape speed.
I would aver that only those with very top end machines will notice the first effect? Many tape machines had indifferent attention paid to record amplifier noise or bias waveform symmetry both of which bugger the S/N ratio plus of course the playback amplifier must be beyond reproach. NOT an easy thing to designs for low noise and high headroom.
2) I bet the VAST majority of tape enthusiasts do not own a test tape nor the gear to measure the results of using one? Yes indeed, IF you are going to run a first gen', expensive test tape, clean and demag meticulously (check yer tensions as well!)
Bottom line...IMHO the average Joe does not need to worry about de-gaussing but, IF you are going to do it, FFS do it properly!
Dave.
1) increased noise build up on tapes.
2) 'wiping' of the very highest frequencies, really short "wavelengths' because 'f' depends on tape speed.
I would aver that only those with very top end machines will notice the first effect? Many tape machines had indifferent attention paid to record amplifier noise or bias waveform symmetry both of which bugger the S/N ratio plus of course the playback amplifier must be beyond reproach. NOT an easy thing to designs for low noise and high headroom.
2) I bet the VAST majority of tape enthusiasts do not own a test tape nor the gear to measure the results of using one? Yes indeed, IF you are going to run a first gen', expensive test tape, clean and demag meticulously (check yer tensions as well!)
Bottom line...IMHO the average Joe does not need to worry about de-gaussing but, IF you are going to do it, FFS do it properly!
Dave.
jamesperrett
Active member
I'm not a fan of wholesale capacitor replacement - especially if you don't have much electronics experience. You could easily end up introducing new faults due to poor soldering or inserting a capacitor the wrong way round. Nakamichi decks are a cut above the average cassette deck and it is best to find a tech who knows what they are doing to service it in order to preserve the audio quality for which they are famous.
I completely agree James. Electrolytic capacitors do indeed have a finite lifespan (don't we all!) but it is far longer than most people think.
The failure mode for Ecaps is either partial or full short, very very rare but obvious. Otherwise there is a slow reduction in value.
The latter can be tested by measuring the frequency response of the equipment and the harmonic distortion at very low frequencies, say below 40Hz. If, and it is a big IF, these measurements are out of specification* then a general re cap of the signal path may be in order.
However, most ananlogists don't have the gear nor the skills to do such measurements and therefore should leave it to the pro techs.
*And you need to find and UNDERSTAND that!
Dave.
TheSynthDev
Member
It is not necessary to degauss tape heads, as they are not susceptible to becoming magnetized.
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Jason Hook. I enjoy remixing old songs using Audacity together with UnMixIt for vocal removal or isolation
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Jason Hook. I enjoy remixing old songs using Audacity together with UnMixIt for vocal removal or isolation