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Old 28th August 2004, 09:38 AM   #1
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Default Anyone got any opinions on this?

I posted this over at AA, let`s see what you guys think also?

http://www.audioasylum.com/audio/tub...es/147873.html
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Old 28th August 2004, 09:41 AM   #2
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BTDT
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Old 28th August 2004, 09:54 AM   #3
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BTDT What??????????
Give some technical reason. I used to call it voodoo also. but i could`nt say for sure that nothing can get magnetised inside a tube, what with all those electrons flying around anything is possible.
Alot of people are doing it. So i decided to have an open mind, and give it a go.

Cheers George
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Old 28th August 2004, 10:37 AM   #4
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Well electrons in motion are deflected by magnetic fields that cross their path. I won't go into details but check some school physics books. So electrons traveling from cathode to anode will have their path altered by any magnetized parts within the tube or by magnetic fields comming from outside. This will have the same effect as changing the tube geometry and hence the tube characteristics. So demagnetising the tube will put everything right again. Now if the effects of magnetized tube parts is audible I don't know.

I vaguely remember doing an experiment in school that involved winding a coil around a tube and passing a current through it thus causing a magnetic field in the tube. If the coil current is turned up enough the tube would cut off. I don't remember the magnetude of that field though.

Just now I held a powerfull magnet up to a 5687 in my amp and I could feel the attraction to the tube. So magnetization is surely possible. Did not here any effect on the sound though.

Damn, now I have to demagnetize my tubes.
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Old 28th August 2004, 11:46 AM   #5
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Hi,

Tubes contain ferrous materials so , yes, they can become magnetized....
Whether that affects their performance is a different matter.

However, by using the force of a magnetic field it's not unthinkable that some parts inside a tube can be dislodged.
IOW, I'd be careful with a strong magnetic field in proximity of electron tubes, you may just as well cause some permanent damage IMO.

If you're convinced demagnetizing makes an audible difference, there are more "gentle" means around to do just that.

Cheers,
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Old 28th August 2004, 06:54 PM   #6
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Especially for AC, read music, currents inside a tube or conductor travel with an electric field. An alternating electric field goes together with an alternating magnetic field.
This is what we learned at school, some long time ago.

And just like Heater mentioned, in every CRT electrons in motion are deflected by magnetic fields that cross their path.

I just happen to have a worn out 6DJ8 and a 12AX7.
Broke the glass and removed it.
Got a magnet and hold it close to the internal parts.
I was surprised, the Anode, Getter, and all the supporting metal are all attracted by the magnet on both tubes.
This I didn't expect.

We have to demagnetize our tubes !
Now, is there somebody who can clearly here the difference when a tube has been treated ?
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Old 28th August 2004, 10:10 PM   #7
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BTDT = there was a big huge thread started here (on the Else forum?) a while ago, from the same thread, AAMOF. Consensus was an uneasy "it might do something but for the most part, no". Akin to resistors, capacitors and wire, but plausible this time. (Hey, you're modifying the dynamics of the active device. Now you can actually change things. For the better? Probably not.)

FWIW, nickel, like mild and silicon steels, doesn't retain a significant magnetic field. It's not a magnetically hard material.

Tim
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Old 28th August 2004, 10:34 PM   #8
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"Magnetic force is a tiny, tiny horse."

It would be a nice project for an enterprising physics student to:

1. Measure the remanent magnetism on a variety of tubes and tube structures to see how much is ever there.

2. Taking the biggest number and doing some simplifications estimates on geometry, calculate the order-of-magnitude magnetic force on the electrons.

3. Calculate the order-of-magnitude force on the electrons from the applied electric field.

4. Compare 2 to 3.

While you're worrying, think about the effect of that magnetism on the population of the "up" and "down" spin states.
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Old 28th August 2004, 11:48 PM   #9
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Quote:
We have to demagnetize our tubes !

I think so, there was a definate change for the better i belive.
What we need is a few more (voodoo sceptics) to try it and give their impressions. (common Frank give it a go, does`nt cost anything, we know the Belgiums are tight with their money, so this should be right up your alley, you should hear something on your high res system) wish someone could measure what`s going on.

Cheers George
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Old 28th August 2004, 11:56 PM   #10
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BTW I'll reflash your tubes for 'ya. They sound clear and brighter. The sound stage really...glows... searing hot highs...

http://webpages.charter.net/dawill/t..._IndHeat1.html

(It's not shown but I've heated the rather large chunk of getter and support structures on top of a 6BM8 to approx. 1500řF. With a better coil and more power I can do sides.)

Since this is inductive (strong AC magnetic field), it also demagnetizes things...so it's on topic mmmmm'k.

Tim

P.S. FWIW, I didn't notice any change in the getter on the glass after doing this.
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