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Old 6th March 2005, 05:26 AM   #21
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What i was getting at with my last post was how do you know they were'nt magnetized to begin with?
I think the only way to tell now is that it be demagnetized using a demagetizer and re-measured.

Cheers George
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Old 6th March 2005, 11:53 AM   #22
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The point is that any magnetic field that a demag gets rid of is a static field. So my question is, does a static field have any discernable effect on a tube's performance (no reason physically to belive it does for "normal" tubes)?

The applied magnetic field in my experiment is huge, much greater than any possible static magnetism in the tube. So if it doesn't have any effect, why worry about the piddly little fields that a wimpy demagnetizer might clean out? I note that in JS's experiment, he did not have any indication of the effect of his homebrew demagnetizer on the internal magnetism- this was never measured on a before-and-after basis- so he really doesn't know if there was any magnetism in there to begin with and, if so, how much less there was after his treatment.

In my own mind, the case for effects of static magnetism on certain types of beam tubes is "possible but not proved." The case for these effects on common triodes is extremely dubious. Assertions of sonic improvements from demagnetizing triodes should probably be regarded as the typical audiophile useless noise unless accompanied by either controlled listening tests or by solid measurements.
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Old 6th March 2005, 01:18 PM   #23
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I'm late on this one but, with respect to the noise difference, is there even an attempt anywhere to postulate a physical mechanism for this effect. I have studied noise for 30yr. and can't think of anything that could even begin to explain the results. In fact _excess_ noise phenomena that are fairly broad and flat in spectra are unknown (to me at least). Further, if the second plot is supposed to show noise below that from the tubes gm then first principles are violated and I consider it an 'extraordinary claim'.
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Old 6th March 2005, 04:55 PM   #24
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Hey SY, while you've still got your rig set up, care to pop over to the battery thread and see if you can duplicate ALW's results with regard to noise and SLAs?

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