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Tweeks on tubes - bring out the demagnetiserss

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#21
What's all this electron and magnet stuff, anyway?? Why would an electron care??
I have lots of luck with refrigerator magnets...they stick rather well..unfortunately, it does tend to attract those excess charges...perhaps using a van de graf generator in reverse will help...

(note: I don't know if south of the equator changes the van de graf polarity, maybe you have to put it upside down.?

John
 
#22
If in doubt, read this:

http://www.audioasylum.com/forums/tubediy/messages/57559.html

and this

http://www.audioasylum.com/forums/bottlehead/messages/83595.html


Here's what I did (and many others followed, confirmed results)

Turn off the tube amp and remove tubes

take a demagnetizer (I use an old Nakamichi tape head demagnetizer) and treat the tube. I spend about one minute exposing the tube from all angles to the Nak demagnetizer.

put tube back into gear

power up, warm up, listen

It works, it can be measured, and it clearly can be heard. The tubes sound better after such a treatment.

I did this to a pair of Telefunken ECC802S - the treatment seems to last quite a long time, since a second treatment about a week after my initial demagnetizing didn't seem to deliver much of a noticable improvement.

Peter
 
#24
Sch3mat1c said:


Because an electron is a charged particle. But as I said, it won't do anything good for a tube.

Tim
Click to expand...

Are you sure it's a charged particle? or, just a probability?😉

What specifically, is the Curie temp for the materials of typical tubes? Once exceeded, is there any residual left? Curious minds want to know...

The first link provided by pburk shows an interesting difference..but, I wonder...did the person re-magnetize the tube to cause more distortion? Is the result repeatable, or did he simply do it once? Was it just contact resistance?

Is the residual magnetism of a tube structure sufficient to actually spiral the electrons? Magnetrons usually have some decent fields...small in the scheme of things, always less than 1.5 to 2 Tesla, but certainly much larger than tube residuals...I don't think the voltage gradient in regular tubes is that much lower than a mag..

Repeatability of those harmonic graphs would be nice..

Cheers, John
 
#25
Repeatability of those harmonic graphs would be nice..
Click to expand...

Yes, indeed. Contacts and time of warmup were the first two things that came to my mind when I saw those graphs. Doing this in a controlled way is a PITA, but necessary if you want to demonstrate the phenomenon (if such actually exists).

I'd also be interested to use a magnetometer on a tube before and after "treatment" and see if there is a change in magnetism, and if so, in which direction- the methods described here might actually increase remnant magnetism.
 
#26
SY said:


Yes, indeed. Contacts and time of warmup were the first two things that came to my mind when I saw those graphs. Doing this in a controlled way is a PITA, but necessary if you want to demonstrate the phenomenon (if such actually exists).

I'd also be interested to use a magnetometer on a tube before and after "treatment" and see if there is a change in magnetism, and if so, in which direction- the methods described here might actually increase remnant magnetism.
Click to expand...

Geeze, I forgot about warmup....:xeye:

It'd also be interesting to see the magnetometer while the tube is actually operating...I make the assumption the elements are too hot to retain magnetism...

Cheers, John
 
#28
SY said:


This may not be the case. Certainly things like lead outs and the support structures don't get hot enough to exceed their Curie temperature.
Click to expand...

Agreed..but if they are cool enough to be below curie, aren't they also far enough from the e stream that they don't make a diff?

Ah yes, I remember my 6L6/12AX7 days.....almost as if it was 35 years ago...

Cheers, John
 
#30
SY said:


This is a tweak. No logic or physics allowed. You've been warned!
Click to expand...

OH NO!!:bawling: I seem to always be getting doze warnings....

I knew that e/m physics background would lead me to a life of crime against tweak-manity..:dead:



Anyway, I don't think the plate or grid get hot enough, either. Not that they're normally magnetic material in the first place...
Click to expand...

hmmm..you've never seem my tube contraptions, have you....if it ain't cherry red, it just....aint..:devilr:

OH, btw, Sy?? twas a dark day when you removed that chick pic from your profile....I really liked her...da guy...he's not my type...:xeye:

Cheers, John
 
#32
Hello all, I'm the one that started this whole mess with my beam deflection tube preamp. After I posted information on it, one of the other members mentioned that these tubes are very sensitive to magnetic fields and that sometimes they get magnetized which can cause performance effects. I decided to try this out. I made a demagnetizer out of a spool of wire and a 6.3V transformer and attached the tubes to a plastic tube and slowly moved them through the field.

The spectrums I posted were two representave ones out of many that I did. By the time these were made the tubes had been in and out of the sockets at least 4 times so it was not initial "pin cleaning". They had been "burning in" for several days. Every time I do a spectrum I turn on the tubes and let them sit for 15 minutes to have some form of standardization. For both before and after demagnetization I ran several spectrums over a period of an hour. Of course there were small differences between runs but they were much less than the differences between pre and post demagnetization.

I perfromed this on the two tubes I had and got similar results for both. Not identical but similar.

Note, the spectrums were for BEAM DEFLECTION TUBES, not regular triodes or pentodes. I am NOT saying the same thing is going to happen with a 12AX7.

Other people have decided to try this demagnetizing thing on "normal" tubes and some have found a sonic difference. I myself have not tried this so I can't comment on what effect it has.

Since the Initial trials I have done the demagnetizing thing on 4 more BDTs, on two of them there was a significant change, on the others there was not very much of a change. All 4 of these tubes were GE, but two of them were in slightly shorter boxes than the others and had nice clear markings, the other two had somewhat deteriorated markings. I got the impression that two of them were much newer than the other two, so either manufacturing changes had taken place or the two older ones had been magnetized more by sitting around in the same location for a longer period of time. I did not perform exhaustive tests on these, that wasn't the goal, I'm trying to get good sound not a thesis.

Given that I can clearly hear a difference when demagnetizing on some tubes I'm going going to continue doing this when I get new tubes. So far the sample is pretty small (6 tubes) so I have not come up with any way to know in advance which will benefit from the procedure so I'm going to continue performing it on any new BDT tubes I get. It takes only a minute to perform and CAN make a big difference.

John S.

John S.
 
#34
John Swenson said:
Hello all, I'm the one that started this whole mess with my beam deflection tube preamp.
John S.
Click to expand...

And a fine mess you've gotten us into....thanks a lot, John...😉

Um, John? what is a beam deflection tube? Sounds like it relies on beam steering for amplification, instead of the pinching of the stream... (I know, I know..simple question...problem is, I lost my near and dear RCA tube manual back in, I think, '74..I'm lost without it..):bawling:

In all your trials, did you try magnetizing any tubes to see if you could make it worse?

Cheers, John (oh no..not another one..)
 
#36
Sch3mat1c said:
Beam deflection tubes use electrostatic deflection, 7360 I think is one of them (among other types in the 6V heater range). Popular among shortwave radios because you can modulate/demodulate SSB with them.

Tim
Click to expand...

Thanks Tim...those things can certainly be altered by magnetic fields...

I figured only my tv set worked like that...well, ok...that and the particle collider rings I build magnets for..

Cheers, John
 
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