Tape Head Demagnetizing

MylesBAstor

Well-Known Member
Apr 20, 2010
11,236
81
1,725
New York City
How does everyone stand on tape head demagnetizing. Do you do it every 10 hrs or so as many recommend.

Reason for asking is that I've talked to some in the know who don't demag their heads that often since they claim one can also screw up the heads just as easily as fluxbusting them.
 

Steve Williams

Site Founder, Site Owner, Administrator
The technique of demagging is quite interesting. I do have a unit and have used it but probably not as often as every 10 hours. When I do I get all my Tape Project tapes out of the room. It is most important to demag when your machine is off (duh)
 

Mike Lavigne

Member Sponsor & WBF Founding Member
Apr 25, 2010
12,471
11,367
4,410
Fred Thal, the Studer Guru who refurbed my A-820, felt very strongly that the heads on the Studer A-820 should never be demag'd. his perspective (hopefully i'm relating it accurately) was that Studer went to a considerable effort to eliminate any materials which might be magnetized from around those heads, and therefore any demaging would do harm and not good.

Ki Choi, whom i have considerable respect for his technical accumen, did demag my heads after he installed the head switch on my Studer to allow us to audition the Cello Repro.

Jeff Gilman of MDI Precision Motor Works, who refurbed my Ampex ATR-102, does recommend frequent demaging on the ATR.

personally; i have no clue what to do. i certainly don't ever want my valuable tapes to be screwed up by magnatized heads.
 
  • Like
Reactions: Zeotrope

MylesBAstor

Well-Known Member
Apr 20, 2010
11,236
81
1,725
New York City
Fred Thal, the Studer Guru who refurbed my A-820, felt very strongly that the heads on the Studer A-820 should never be demag'd. his perspective (hopefully i'm relating it accurately) was that Studer went to a considerable effort to eliminate any materials which might be magnetized from around those heads, and therefore any demaging would do harm and not good.

Ki Choi, whom i have considerable respect for his technical accumen, did demag my heads after he installed the head switch on my Studer to allow us to audition the Cello Repro.

Jeff Gilman of MDI Precision Motor Works, who refurbed my Ampex ATR-102, does recommend frequent demaging on the ATR.

personally; i have no clue what to do. i certainly don't ever want my valuable tapes to be screwed up by magnatized heads.

Yes, I don't think there's any area that I'm more confused about and presented with more contradictory info than on tape head demagging :(
 

Phil_in_CA

Well-Known Member
Apr 25, 2010
2
0
388
Hi Steve,

Thanks for this forum. I am new today, and joined so I could enter this thread (I would have joined anyway, really...). I have a Technics 1500 that I have been refurbing for the past year, and now that I have like new heads, I wonder about using the demag unit that I got but worry about using! I have heard horror stories about the improper use of a demagnetizer and would like to ask if you or someone else could steer me to a reference guide on using it?

I would really appreciate some straight info about the proper use of the demag unit, so as to NOT ruin my deck or tapes!

Thanks,
Phil

Oh yeah, I almost forgot to ask..."are you the Steve Williams that was Astrotoy's house about a year ago listening to the Tape Project tapes??"
 

Steve Williams

Site Founder, Site Owner, Administrator
The way I was taught is to make certain everything is turned off and your tapes are well out of the way. I usually start 10-12 feet away and turn on the unit and then as I slowly walk towards the tape heads I am rotating the demagger in a circular motion with the circles getting ever smaller as you approach the heads and touch the demagger to the heads. Once done I slowly step backwards as I again begin moving the demagger in a circular motion.

Like some others here I haven't been demagging on a regularbasis with my Studer
 

Ki Choi

Member Sponsor
May 13, 2010
764
29
1,590
Seattle WA area
Myles told me to come here. Now I see where all the boys hang out...

As for the Studer heads, I don't know the exact make up of the material but do know the head material can easily be magnetized if one is not careful while tinkering around the head and preamp. In my case, I have never noticed any needs to demagnetize any of the Studers' head from recording and playing tapes in normal use. Even my very first Studer A810 is performing as well as it did since ~ two years ago when it was demagnetized initially and brought up to the Studer spec and not had been demagnetized since. On the other hand, one of my other A810s' repro preamp in the headstack had +supply power filter cap shorted and the event magnetized the head. In another time, I had accidently plugged in the headblock into the connector with deck's power still on (it was a very last night) ... magnetizing the heads. Both incidents, I had to demagnetize the heads to get them back to normal. However, all the tapes I had played before demagnetizing the heads were ruined...embedding low rumble noise that sounded like playing improperly bulk erased tapes.

At the time when we were doing the surgery to rewire Mike's A820 repro head for the first time, we ran into issues with unexpected outboard tube preamp malfunctions and had to rearrange the wires and made connections and disconnections to the preamp several times while troubleshooting for the source of the burst of noise. I demagnetized the repro head when we were done - just to be sure - all of Mike's valuable tapes are safe and will not have the low rumble noise after I left his house.

Ki
 

c1ferrari

Member Sponsor & WBF Founding Member
May 15, 2010
2,162
51
1,770
Hi Ki,

Did you see the You Tube vid in this forum relevant to demagging? If so, does your technique mimic what is demonstrated on the video?

Thanks,
Sam
 

stellavox

Well-Known Member
Apr 23, 2010
284
61
1,583
Guys,

I think this demag thaang may be overrated.

From my perspective, a head can (only) get magnetized in two ways. Exposing it to some fairly large external magnetic field, or applying some kind of electrical impulse to its coil. If you believe this then to mitigate "one", I'd keep anything that could be magnetic - like (magnetized?) tools as far away from the heads as possible. As regards "two" it seems that the only way you might screw this up is possibly removing/inserting a headblock with the power on.

I've actually never come across or "heard" a magnetized head. When working on a deck, as a matter of course I do demagnetize everything in the tape path when finished and before loading the "first" tape - especially (expensive) calibration tapes. If you think about it also, most well designed heads are quite well shielded, with pretty narrow "windows" - the only place where magnetizing flux can actually get in. You'd have to have a pretty strong field in close proximity to the head to do anything "permanent". Of course I have reversed the connections to my preamp (tape head to output instead of the input) and recorded hum and noise on the tape when "playing around" wondering why I wasn't hearing any signal. And of course the tape I was playing was a WONDERFUL dupe - what an asshole.

Charles

ps -You might want to worry more about where you PUT your tapes - like right on top of your speakers - NOT

Charles
 
  • Like
Reactions: Zeotrope

MylesBAstor

Well-Known Member
Apr 20, 2010
11,236
81
1,725
New York City
Found this on my hard drive:

CLEANING AND DEMAGNETIZING TAPE
RECORDERS
All tape recorders require periodic cleaning of the heads, tape guides, pinch roller and capstan. Most manufacturers
suggest cleaning after every 6 to 8 hours of use, but cleaning will be required more often at faster tape speeds,
if low quality tapes are used, or in archival situations when transferring tapes suffering from sticky oxides or
excessive shedding. You need to clean the recorder before enough oxide had shed on the heads, and before adhesive
has built up on the rollers, to cause problems such as mistracking, high frequency loss, jamming, or excessive
head wear.
Cleaning requires the use of cleaning swabs and a solvent, or “head cleaner”, to dissolve the tape oxide particles
and other contaminants that adhere to the tape heads, metal tape guides, capstan and rubber pinch roller.
The cleaning swabs can be made of cotton on a wooden stick, a chamois patch on a plastic rod, lint-free cloth
or open-cell foam on a short rod or stick. Choose whichever swab reaches into every nook and cranny easily, fits
your budget, and is easiest for you to handle. All types work equally well.
Several excellent solvents are sold for cleaning tape heads and guides. The “best” head cleaner is the one that
quickly removes the most contamination with the least time required. Cheap off-brand tape head cleaners sold in
budget stores and on eBay is usually dyed rubbing alcohol. Avoid them. All head cleaners MAY damage the heads
if used improperly. The secret is to use the head cleaner properly.
The most commonly used solvents are alcohol, but alcohol is not necessarily the best. Only 99% pure isopropanol
or 99% pure anhydrous isopropyl alcohol should be used; nevertheless the use of alcohol is discouraged. Avoid
all other types of alcohol because they contain water. Despite what anyone may say, denatured alcohol from the
hardware store is not acceptable, and neither is rubbing alcohol.
Alcohol’s only “advantage” is its low cost and the fact that it can be mishandled without too much concern
for damage to adjacent plastic parts or surfaces. Otherwise, DON’T USE ALCOHOL if you can afford to use
anything else. Alcohol is a very heavy and dense liquid, therefore it doesn’t allow contaminants on the heads
and pinch rollers to rise to the surface, where they can be easily wiped off. Alcohol, when mishandled, can drip
onto circuit boards. Because it is electrically conductive it could cause shorts. Do not be afraid to use head cleaners
containing Xylene or MEK. In the past, the popular Ampex Head Cleaner contained Xylene. Recommended
head cleaners include American Recorder S-721H Head/Pinch Roller Cleaner, which is the best choice of all, and
Chemtronics Head Cleaner™ II, which has a similar composition and is more widely available.
CLEANING HEADS
1.) MOISTEN the swab with the solvent, but do not soak the swab or get the swab dripping wet. Wring
the swab out against the inside of the bottle to remove excess solvent. Think DAMP, not WET. It is
important that you DO NOT DRIP the solvent onto anything other than heads, the capstan and metal
tape guides! [Suggestion: never put a dirty swab into the bottle of solvent because you’ll contaminate
the solvent.]
2.) Rub firmly only in the direction of tape travel with enough pressure to remove the contamination, but
not excessive pressure.
3.) MINIMIZE the amount of time the head is exposed to the solvent. Use the minimum solvent for the
least time to do the job.
4.) When the swab no longer shows any contamination being removed, you’re done. In other words, when
the swab stops getting dirty then you’ve removed all the contamination. Do not be surprised if you have
to use several swabs.
5.) Do not let the heads air dry. Daub the heads dry using a clean swab. Use a light touch.
CLEANING HEADS AND PINCH ROLLERS
Next, clean the pinch roller using American Recorder S-721H Head/Pinch Roller Cleaner or other RUBBER
CLEANER, such as Caig RBR. Do not use platen cleaner or rubber restorer; these are different products and
using them more than twice a year can make the rubber sticky. Alcohol WILL dry out rubber with extended use,
shortening the life of the pinch roller, requiring use of a rubber restorer or replacement of the pinch roller.
BE CAREFUL! Some products sold as rubber cleaner are actually rubber restorers; inquire from the manufacturer
whether the product may be used routinely without damaging the rubber pinch roller. Some technicians recommend
using alcohol because it is “safe” for rubber but consider that alcohol dries out the rubber, so the assertion
of alcohol being “safe” is dubious. As alcohol dries out the pinch rollers it creates fine hairline cracks where
adhesive from the tape oxide binder and tape oxide particles can remain hidden. This residual adhesive can cause
the recorder to “eat” your tape. Pinch rollers are supposed to remain pliable. Dried out rollers can warp easier
causing tape alignment problems.
1.) Put the recorder into play, then use a swab to apply the rubber cleaner onto the pinch roller using a light
touch.
2.) Don’t get the swab caught between the pinch roller and capstan.
3.) MINIMIZE the amount of time the pinch roller is exposed to the rubber cleaner. Use the minimum
rubber cleaner for the least time to do the job.
4.) When the swab no longer shows any contamination being removed, you’re done. In other words, when
the swab stops getting dirty then you’ve removed all the contamination.
5.) Do not let the pinch roller air dry. Instead, brush the pinch roller dry using a clean swab or a lint-free
cloth. Use a light touch. Don’t let any cotton fibers remain on the pinch roller if you used cotton
swabs.
6.) Stop the tape recorder.
7.) Re-clean the capstan to remove any residual rubber cleaner using the method for head cleaning.
8.) Finally, give the machine about ten minutes to be sure all of the cleaning solvents have evaporated
before running a tape on the machine. Otherwise, you risk allowing residual solvents damaging the
tape.
9.) After cleaning, turn off the recorder’s power and demagnetize the heads, tape guides and metal capstan.
This paper describes the procedure later on.
DEMAGNETIZERS AND DEMAGNETIZING
The purpose of a demagnetizer is to remove the residual magnetism that builds up on the tape heads, and all metal
parts contacted by the tape, as a result of magnetic fields running across the tape. This is the same principle that
occurs when you rub a nail with a magnet, causing the nail to become magnetized. Residual magnetism will erase
the tape over time, beginning with the high frequencies first; extreme levels of residual magnetism will increase
distortion and noise.
How quickly residual magnetism builds up depends on several factors, including tape speed, recording levels, the
type of tape, and the composition of the tape heads. How often you should demagnetize depends on both how
quickly residual magnetism builds up and how much quality loss from residual magnetism you are willing to
accept. Slow tape speeds and low recording levels (low fluxivities) will require infrequent demagnetizing, while
high tape speeds and high recording levels (high fluxivities) will require frequent demagnetizing. Similarly, if you
are not willing to allow any quality losses to occur to your tapes then you must demagnetize often.
2
A demagnetizer applies a strong magnetic field strong to totally magnetize the part, then reverses the field rapidly
to cancel out the magnetism. A demagnetizer runs on 60 (50) Hz AC, so the north and south poles of the magnetic
field reverse 120 (100) times a second. The magnetic field’s strength must then be very, very slowly reduced until
it reaches zero by slowly moving the demagnetizer away from the heads and tape guides. ALWAYS REMEMBER
that quick, jerky motions will magnetize metal parts and will not demagnetize them.
Efective demagnetizing applies the strongest possible magnetic field to all metal tape path parts. This requires
that the demagnetizer’s tip makes close contact with the parts, because a magnetic field’s strength lowers with
the square of the distance. So, choose a demagnetizer that creates a strong magnetic field, the stronger the better.
Avoid cheap demagnetizers because they are barely strong enough to demagnetize a cassette machine head, and
will not demagnetize a capstan or a metal tape guide. The Han-D-Mag, made by R. B. Annis Co., is the strongest
unit made. Contact: R. B. Annis Company, Inc.; 1101 N. Delaware Street, Indianapolis, IN 46202. Or contact
them by telephone at (317)-637-9282.
When you buy your new demagnetizer, cover its tip with heat shrink tubing or plastic electrical tape so it will not
scratch the delicate tape heads.
1.) Turn the power off on the tape recorder or duplicator. Demagnetizing with the power on can damage the
recorder’s circuitry.
2.) Turn the demagnetizer on 3-feet (one meter) or farther from tape or tape machines.
3.) Move the demagnetizer in, very slowly, so its tip touches the head(s), guides, and the capstan.
4.) Move across the surface of each part, and from one part to the next, very slowly and smoothly. If you
accidentally move quickly, go back over that part.
5.) After you have gone over the surface of every metal part in the tape path, very slowly and smoothly
move the demagnetizer away from the recorder until you are at least 3-feet (one meter) away.
6.) Turn off the demagnetizer.
You do not need to hold the demagnetizer in position for a long time; a second or two is sufficient. The only way
you can cause damage while demagnetizing would be to leave the recorder’s power turned on, or to shut off the
demagnetizer while it is close to the recorder or to tapes, or to move the demagnetizer quickly or jerkily. Some
technicians are concerned that the flux from the demagnetizer may damage transistors by strong currents induced
by the play head, even with the power off. This has never happened to my knowledge, but this emphasizes the
need to move the demagnetizer toward and away from the recorder slowly.
3
Compiled by: Kermit V. Gray
KVG Labs
16371 Lake Point Drive
Bonner Springs, KS 66012
USA
 

R-2-R

New Member
Aug 10, 2010
9
0
0
Reel to reel HEAD DEMAGNETIZING is a very sensitive process. I would recommend having it done only by an individual who knows 'exactly' (or if you feel your up to doing it yourself practice it a few times first before actually trying it, I did) what they are doing, and yes the reel to reel definetly should be turned off along with all other components that may be near by. In other words turn off everything just to make sure. This source of audio deals with a magnetic process which after several periods of usage there will be a build-up of magnetizism on the heads and there is no way of ignoring it and if demagnetizing is not done you will soon start to hear the effects on your playback and recording of tapes.
Now as far as frequency of doing so and how exactly it should be accomplished, well I would suggest following the owners/users manual (if you still have it) and go by their instructions as to how often one should demagnetize the heads and how to perform such a task but if you do not have the original owners/users manual (or can't download it or find it online) then I strongly believe that this process should be done based on how much record & play time the reel to reel is used. Base it on a monthly basis, if you used it everyday for a couple of hours than suggest demagnetize the heads once every two weeks? If you use your reel to reel say once a week than demag the heads every other month? If you use your reel to reel every so often (say once a month) than demag the heads every six months? This is just my opinion and my suggestions but I would strongly recommend you read the manufacturers owners/users manual as mentioned before for confirmation on this particular process. I am just making suggestions as to handling this process if one does not have the owners/user manual or say the instructions for this particular process are not available.
 
Last edited:

About us

  • What’s Best Forum is THE forum for high end audio, product reviews, advice and sharing experiences on the best of everything else. This is THE place where audiophiles and audio companies discuss vintage, contemporary and new audio products, music servers, music streamers, computer audio, digital-to-analog converters, turntables, phono stages, cartridges, reel-to-reel tape machines, speakers, headphones and tube and solid-state amplification. Founded in 2010 What’s Best Forum invites intelligent and courteous people of all interests and backgrounds to describe and discuss the best of everything. From beginners to life-long hobbyists to industry professionals, we enjoy learning about new things and meeting new people, and participating in spirited debates.

Quick Navigation

User Menu

Steve Williams
Site Founder | Site Owner | Administrator
Ron Resnick
Site Co-Owner | Administrator
Julian (The Fixer)
Website Build | Marketing Managersing