Demagnetizing your heads. How often, and with metal tape

[gonzo]

are you supposed to do it more often than standard type I and type II tapes? I had come across a statement to that affect somewhere online and wondered if this was true. And totally unrelated to this question. What are the differences between the nak 680 zx, 681zx and 682 zx lines. Thanks Norm

[Marc Hugo]

Gonzo!!

Not necessarily. With a two head deck, provided you record with it now and then, demagging is not especially necessary. It is the process of repeated running of magnetised tape over a head that is always running in a passive (play-back) mode that magnetises heads (and the tape path in general). As you record with it, the de-magnetised condition, or neutral polarity is restored. Of course, in fairness to the theory, by this time, you may already have made a poor recording . The other thing is that recording will not resolve residual magnetivity in other areas of the tape path.

Thus you would need to demag. Hand held units are more flexible for this task than electric demag cassettes.

Metal tapes are theoretically more likely to leave a more magnetised trail, but in practice it is hardly noticeable. Just record periodically and be done with it. Doing so obviates the need to demag on 2-head decks.

Three head decks whether discreet designs (Naks, Tandberg and Akai GX95 - maybe 75, not sure) or sandwich/siamesed heads, you would need to pay more attention to this. The former more so for obvious reasons.

If you use a particular deck more often, magnetivity builds up more and dissipates less. Magnetivity in a deck left fallow for a long period would decline.

Never try to demagnetise a thin-film/amorphous-Z type head as used on DCC machines and the RS-A series from Technics. These machines playback heads work on flux level and not flux density.

I can't remember the exact difference on the 680s but it is not much. The 680ZX can play tapes at half speed (15/16"/sec); the others can not; other differences possibly relate to rec. monitoring function and/or Dolby C installation. All have rec-head azimuth adjust. Don't forget to visit naks.com for precise information. As I have mentioned, you will, especially at this level surrender facilities, not fidelity. All those decks are top machines from the heyday of cassette. In fact, to put it in perspective, the 682ZX retailed (new) for $1800 and the CR-7 for $1850-$1875.

Cheers - Marc

[gonzo]

Marc, I have to thank you for your replies. You have been quite helpful in this and other questions I have posted. I appreciate you sharing your experience. Even though I used to make tapes back in the 70s, those decks are long gone and my knowledge is "gone" too. THanks again. Norm

[Mr. Lin]

The importance of demagnetizing was impressed upon me quickly when I got into the whole cassette thing (this time around). I was using a demag cassette that I don't think did much of anything, because over time my Nak started producing poor recordings, wherein the music would suddenly blur for a second or disappear altogether. Once I acquired and used a hand-held demagnetizer the problem went away.

Obviously Marc knows waaaay more about this topic than I, but the Nak I'm using is a two head deck. I started demagnetizing the hads once a month, then every two weeks, and now I try to do it every single week. Is this overkill? Perhaps, but now the deck performs beautifully and I'm no longer paranoid about it.

Gonzo I'm going to take advantage of your thread since I was going to start one myself to ask a particular question about demagnetizing. I know you're supposed to run the demagnetizer over all the metal parts in the cassette well, but what about the door itself? It never occurred to me to to this until a few nights ago - the door is metal and close to the tape, after all. Any thoughts on that Marc?

[Marc Hugo]

Hi Gonzo - its a pleasure.

Hi Mr Lin - your experience with de-magging is wonderful and this is really what our hobby is all about!! There are many variables, believe me. The power of the de-mag wand, the way it is used, the heads themselves too.

Why does it take more effort or persistence with some heads than others?

A little bit about composite-combination heads such as your Nak.

Some of the Nak 2-headers, such as the 480s and I think 580 and 580M to name a couple, used "Sendust" heads which had many layers to get a desired hardness, saturability and coercivity. A concern at Nak was to enable an unusually high gauss value across an unusually narrow head gap but at the same time take advantage of the benefits that thin multi-lamination provides. It was a balancing act. These heads are extremely dense and have successive layers of alloys with the required characteristics. Eg. permalloy (soft but low coercivity), sendust (very hard but high coercivity which has to be annealed) molybdenum alloys and sendust/chromium alloys etc.

Most subsequent series of Nak 2-headers (eg RX, DR, CR) applied laminates of an oxide magnetic material such as polycrystalline ferrite (over an iron and nickel core) and a magnetic metal material such as monocrystalline Sendust. There would be multiple layers. Triple laminated meant three metallurgic stages repeated over and over. Thus, "crystalloy" was born. Nakamichi incorporated a synthetic glass crystal of, amongst other things, barium oxide and phosphorous pentaoxide in a triple lamination design.

Matt's Yamaha KX-930 features a 16-layer design. Whether it’s a double or triple laminate, I don't know.

Mr Lin, take off the door to demag it- although it is, as far as magnetic fields go, rather far from the affects of passive magnetism to be problematic.

For a cassette deck that demags its own playback head at the end of a recording, get a Beocord 9000!! This beautiful Danish machine doesn't get the recognition it deserves (made in B+Os component heyday). Perhaps our good friend Dolph can tell us more.

Cheers - Marc

[Mr. Lin]

Marc, that's one very thorough answer - how do you know so much about the Nak deck heads?

I actually do remove the door when I'm demagnetizing the heads so I can get in there more easily, but aside from the part that can be removed, I also tried demagging the frame (for lack of a better term) that the door is attached to. Again, I don't know if this is really necessary, like you said the magnetic field is not particularly close to the tape, but I figure better safe than sorry.

Now, on to the actual method. I read about proper demagnetizing procedure before I did it, but I'd like to double check by telling you what I do to see if there's anything I'm doing wrong.

First, I unplug the deck and take it down to the basement, away from all my other equipment and tapes, because I'm paranoid about that too. Then I remove the door. I plug in the demagnetizer while holding it about 3ft. away from the deck, then move it towards the deck. As I understand it, the speed at which you approach the heads with the wand is not important. I then touch the heads and all metal parts with the wand, but very, very slowly (what I read suggested imagining that you're pulling something through molasses) and very smoothly, no quick or jerky movements. Finally I begin to move the wand away from the deck, but again, extremely slowly, as I read that one can actually build up a magnetic field by moving the wand away too quickly, thereby doing exactly the opposite of what you intended to do in the first place. Once the wand is again about 3ft. away I unplug it. That's it.

[niklasthedolphin]

Marc, that's one very thorough answer - how do you know so much about the Nak deck heads?

I actually do remove the door when I'm demagnetizing the heads so I can get in there more easily, but aside from the part that can be removed, I also tried demagging the frame (for lack of a better term) that the door is attached to. Again, I don't know if this is really necessary, like you said the magnetic field is not particularly close to the tape, but I figure better safe than sorry.

Now, on to the actual method. I read about proper demagnetizing procedure before I did it, but I'd like to double check by telling you what I do to see if there's anything I'm doing wrong.

First, I unplug the deck and take it down to the basement, away from all my other equipment and tapes, because I'm paranoid about that too. Then I remove the door. I plug in the demagnetizer while holding it about 3ft. away from the deck, then move it towards the deck. As I understand it, the speed at which you approach the heads with the wand is not important. I then touch the heads and all metal parts with the wand, but very, very slowly (what I read suggested imagining that you're pulling something through molasses) and very smoothly, no quick or jerky movements. Finally I begin to move the wand away from the deck, but again, extremely slowly, as I read that one can actually build up a magnetic field by moving the wand away too quickly, thereby doing exactly the opposite of what you intended to do in the first place. Once the wand is again about 3ft. away I unplug it. That's it.

Don't let the defluxer actualy touch the machine anywhere.
Let it just pass the tape path slowly with a distance of some millimeters.

If you can let the defluxer touch some other magnetic material when you have moved it those 3 ft away, you will be sure that the magnetics will stay away from your deck.

Besides that, I fully agree with your procedure.
Make sure you don't, by accident, demag while the cassette deck is on power.

"dolph"

[Mr. Lin]

Don't let the defluxer actualy touch the machine anywhere.
Let it just pass the tape path slowly with a distance of some millimeters.

If you can let the defluxer touch some other magnetic material when you have moved it those 3 ft away, you will be sure that the magnetics will stay away from your deck.

Besides that, I fully agree with your procedure.
Make sure you don't, by accident, demag while the cassette deck is on power.

"dolph"

What's the problem with letting it touch the tape heads? It's covered with rubber so it won't damage anything, if that's the concern. But I hope it's nothing serious besides that because that's how I've been doing it.

[niklasthedolphin]

The reason for the rubber over the defluxer is that it will severely, extremely and forever damage the heads on the deck if it was to be touched by what's on the inside of the rubber.

Not to touch the heads, even though rubber is there to protect, is a precaution.

The job is done just as well with the distance of a few millimeters or even more.

If the rubber has cracked or is made too thin by some of those manufacturers that just don't do the items good enough, your deck is doomed.......forever.

Well, it's up to you how you wanna do it.

Just a piece of discrete advice.

"dolph"

[Mr. Lin]

The reason for the rubber over the defluxer is that it will severely, extremely and forever damage the heads on the deck if it was to be touched by what's on the inside of the rubber.

Not to touch the heads, even though rubber is there to protect, is a precaution.

The job is done just as well with the distance of a few millimeters or even more.

If the rubber has cracked or is made too thin by some of those manufacturers that just don't do the items good enough, your deck is doomed.......forever.

Well, it's up to you how you wanna do it.

Just a piece of discrete advice.

"dolph"

Ah I see Dolph. Well if it's not necessary to actually touch the heads (I thought you were supposed to) then I definitely won't do it anymore.

[Marc Hugo]

[QUOTE=Mr. Lin;8575]Marc, that's one very thorough answer - how do you know so much about the Nak deck heads?

QUOTE]


Hi Mr Lin, right on the money with the demagging process.

Heads - a number of years ago on Naktalk, a Japanese guy who had been a staff member of Nakamichi related many aspects of Nak manufacturing and design to members. At first he related his experiences through another member (as far as I recall also in Japan), then he did so directly. I have his name somewhere. I was hungry for information then and printed / stored everything that was to be gleaned. He had left when Niro handed the company over to Enzo in about '97.

Cheers - Marc

[niklasthedolphin]

For a cassette deck that demags its own playback head at the end of a recording, get a Beocord 9000!! This beautiful Danish machine doesn't get the recognition it deserves (made in B+Os component heyday). Perhaps our good friend Dolph can tell us more.

Cheers - Marc

I can say that they come fairly cheap on the used market today.
They didn't come cheap from new.

They are kind of fragile.
They communicate by lights and are these lights blown out there is no communication.

They sound great as long as they work.

They are idiosyncratic.
E.g. the DIN connectors are out of standard.
Fortunately, there are RCA/phono plug connectors on the Beocord 9000.
On older B&O equipment DIN was the only option.

The design is a one-off.
Either like the looks or hate it.

http://radio.gort.dk/images/1570.jpg

http://radio.gort.dk/images/1571.jpg

Normaly B&O would not be credited for their quality of sound.
But these Beocord 9000 (http://www.beoworld.org/prod_details.asp?pid=607) machines were different.
It was the end development of the 6000/8000/8002/8004 series.

For pure sound quality they come in the same liga as the top of Revox and Teac, maybe even competing with the best of Nakamichi.

Still serviceable though.
And that might be needed.

Featured auto calibration of bias and rec level for each channel and eq auto, peak level for each tape.
Storable for each tape type.
You could get the reading of the calibration and you had PB azimuth.
Mic jack and Mic DIN input.
Headphone socket, adjustable.
Real Time counter, programmable w/ flags and search on flags or time.
Time programming of recordings built in. Repeat function on play.
Input/output adjustable for each channel.
The machine is remote controlled.

B&O inventet HX-Pro (http://www.beoworld.org/article_view.asp?id=145) and built it into the Beocord 9000.

A few specs:
Tape head Double sendust/ferrite
Metal: 10-25,000Hz +/- 3dB
All other types: 20-20,000 Hz +/- 1,5dB
S/N Chrome w/ NR: B: >70 dB, C: >80 dB
S/N Chrome w/o NR: >60 dB (BASF chrom ll C90)
Wow and flutter WRMS <0.045%

Stay happy.

"dolph"

[niklasthedolphin]

By the way.............

I think I will purchase one of these for my self.

Just for fun.
For starting..........or continuing...............my collection.

Within a few months, ½ a year or slightly more, the machine should be mine.
*Spin*

"dolph"

[Marc Hugo]

Bravo Dolph. Keep us posted!!

Marc

[niklasthedolphin]

Bravo Dolph. Keep us posted!!

Marc

Thx.

However............the Beocord will never get to replace my TCD 910.

I even doubt if it can leave my Revox B710 in shame.

"dolph"