Demag question

famous beagle

famous beagle

Well-known member
So I've heard plenty of times that the little $20 demagnetizer jobs on eBay and such may be fine for a cassette recorder, but for a RTR, you need a Han-D-Mag. This is cool and all, and if that's the case, no big deal.

But my question is: how can you tell if a demagnetizer is doing is job or not?
 
Audible hum and high frequency loss are the signs that a deck needs to be demagged and if those tell-tale signs do not appear with regular demagnetizing, then you can assume its working well enough.

The Han-D-mag will definitely do the job but so would a Teac E-2 and the Teac might sell for a bit less too.



Cheers! :)
 
famous beagle said:
So I've heard plenty of times that the little $20 demagnetizer jobs on eBay and such may be fine for a cassette recorder, but for a RTR, you need a Han-D-Mag. This is cool and all, and if that's the case, no big deal.

But my question is: how can you tell if a demagnetizer is doing is job or not?
Click to expand...

I've got a couple of Han-D-Mag units...they are certainly the right tool for the job.
That said...I don't get too preoccupied with demagnetizing on any regular basis. There's just not obvious reason to do it daily or some such thing.
Also, you have to really do it correctly and methodically...or you risk adding greater magnetism instead of removing maybe a very tiny bit of accumulated magnetism.

See...now that you brought it up...I may end up doing a demag this weekend....then I'll let it go for a long period again. :D
 
famous beagle said:
Ok, thanks. So there's not any way to tell right after you've done it whether it worked or not?
Click to expand...

Like Ghost said...the audible sign is an *obvious* loss of HF content and hum....but IMHO, that's something I've not encountered even when I don't demag for months and months.
Otherwise there are gauss meters, but you need a very sensitive one to pick up those minute magnetic fields that might cause HF loss on your audio tape.
I just find that with the more modern decks and especially the well built pro decks, coupled with the right tape formulations and good backing...it just doesn't seem to be much of an issue. With the real old decks and consumer-ish grade stuff, it might be more obvious.

If you really are concerned....just come up with some schedule. Like every xhours of use, do a demag...regardless of what you hear or don't hear or any measurements with meters.
I just don't see it as necessary as it was always implied. Heck, when I started tape recording, it was part of my daily ritual...'cuz everyone always made a point of saying you need to clean and demag before each session....but after years of tape recording, and extending the time between demags...I've found it made little to no difference.

Here's a basic Google link asking "is tape recorder demagnetizing necessary"
You can formulate your own conclusions, but there are a few links with posts from guys that have done extensive testing...and the answer was no, it's not that necessary, with cassettes showing least amount of need.

https://www.google.com/search?q=is+...microsoft:en-US:IE-Address&ie=&oe=&gws_rd=ssl

I think once in awhile just to do it...and certainly when you are gong to do a recalibration of the whole deck...but not with any daily/weekly regularity.
I haven't demaged my Otari 2" in over a year now...I hear no difference.
 
The Ghost of FM said:
Re-read the first line of what I wrote in post # 2. Your answer is there.



Cheers! :)
Click to expand...

Yes I saw that thanks. I was talking about something immediate and without previous recordings to which you could compare. In other words, say you get a new (used, obviously) RTR, and the heads are extremely dirty. You can logically assume that, since cleaning the heads wasn't part of their ritual, demagging probably wasn't either. If you cleaned the heads right then and demagged right after that, there's no way to tell whether it did anything, other than the gauss meters that Miro mentioned. Correct?
 
Also .... is there a way that you can tell the demag is even functioning period? I mean ... is it supposed to vibrate, hum, or do anything once you plug it in? Are you supposed to feel a magnetic pull when you touch the heads (with tape or a rubber sleeve over the demag tip, obviously)?

I bought one of these (I think this is it) a long time ago for use with a cassette 4-track.

New Tape Deck Head Demagnetizer Cassette Reel to Ampex | eBay

And I could never tell it was doing anything. I mean ... it would feel the same whether I had it plugged in or not. So at this point I'm just trying to tell whether it's even functioning or not.
 
If you want to test whether your demag is working, try this easy test.

Take a screw driver and magnetize the tip of it by placing it on the magnet of your woofer from your speaker system for about 10 seconds. Once done, confirm that the tip is magnetized by putting it near a metal screw and seeing if it sticks to the screw or not. Once the screwdriver is confirmed to have been magnetized, get out your handy dandy demagnetizer unit and practice demagnetizing the screwdriver tip by slowly moving the wand up to the tip, circling it around the tip and then slowly pulling it away a few feet before shutting off the wand. Then go back to your screwdriver and test it again to see if it will still pick up that screw. If it doesn't, all is well and your unit worked as it should. If it didn't, it may be a faulty unit you got there. The Teac one that I used to own had a definite vibration to it when it was on. If yours doesn't buzz or vibrate, it may be dead.

Hope that helps.



Cheers! :)
 
famous beagle said:
Why do you need two?
Click to expand...

I have two hands.


:D

Actually...one I bought a long time ago, and the other one came as part of some bulk purchase (maybe it was with the 2" deck..???...don't remember)...so that's how I have two.

With the Hand-D-Mag...you'll know right away that it's "working" because it vibrates, and within a minute it will start to get quite warm...which is why they tell you it's not meant for continuous duty.

And like Ghost said...just bring it near some steel/iron and you will feel the pull.

I've actually used it to demag screwdrivers just to keep them clean for when I use them around other gear that I don't want any magnetic field.
You'll see that it's not always straightforward using the demag...you have to really follow the procedure, otherwise you leave some magnetism behind, or worse, you add more than there was in the first place.
 
Thanks for the tips y'all. I'll try the screwdriver tip.

Yeah I've watched a lot of videos and read up on proper demag procedure, but the few things that never seemed to be answered were 1) does it vibrate (or give any indication that it's working) and, 2) As I asked earlier, how to tell if it's actually working.

So now I have a good way to test it. Thanks much!
 
You should be doing a periodic test of the response and noise performance of a tape machine and this will show up any magging up of the tape path.

The only true test for magnetism or its absence is repulsion. If the screwdriver REPELS one pole of a compass it it still magentized

Dave.
 
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