Anyone got any opinions on this?

[fdegrove]

Hi,

Obviously this only applies to AC-heated filaments, although some noise from a regulated DC supply could be transferred. In the case of overall noise figure, a magnetized cathode could cause a greater randomization of shot noise, thus increasing RMS values.

Exactly.
While I've said it before, on simple IDHTs it's pretty easy to actually measure and listen to the coupling effect of cathode to heater and vice versa.
Snubbing across heater pins can be effective in reducing this effect, demagnetizing the tube helps as well.

Cheers,

 

[georgehifi]

The fact remains that the results of demagnetization are MEASUREABLE

Now that the discusion has got down to a scientific level and all the testosterone has faded, can anyone measure this and give some before and after figures.

Cheers George

 

[georgehifi]

Sorry to bring this de-magnetizing topic back up again, but over at AA some one has finaly done viewable measurements to prove that de-magnetizting tubes has a measrurable advantage.

http://db.audioasylum.com/cgi/m.mpl?forum=tubediy&n=57559&highlight=BDT&r=&session=

Cheers George

 

[philipbarrett]

my 2 cents...back in the good old days of de-maging big ol' 16 & 24 track headstacks we were always taught to keep the demagnetizer rotating as we pulled it away from the head. BTW, about 20% of the time we managed to magnetize the head rather than de-mag it and this procedure was always seen as a fix of last resort! In other words, be careful.

 

[serengetiplains]

In other words, be careful.

That is, be careful only if you "believe" in demagnetising.

Could someone not pass the entire set of DIYAudio posts through a demoronicizer? I mean, the dross is considerable, and building.