fuses - the $39 ones or the 85 cent ones

Theaudiotweak..."Tube" preamp you say. Perhaps you should be concerned about the effect of a magnet on the electron beams in your tubes.

At work, when testing a vidicon to calibrate it we found that the results varied depending on which way the device was pointed. (A vidicon is a vacuum tube imaging device, once used for TV). Turns out that the earth's magnetic field was deflecting the electron beam. Of course we all know what a speaker magnet does to a CRT. However, the good news is that, unlike transistors, tubes are not damaged by radiation.

Eldartford,

I am concerned about that issue of bending the beams. I think the sound advantage that I gained with the use of the magnet may be further enhanced with the addition of a Faraday shield. Any disruption depends on where the magnet is relative to the tubes or other critical circuits. In each case so far whether on the ac or dc side of things there has been an increase in audible performance. From the visual side I really think the display of my transport became slightly brighter and easier to read off axis with the use of a magnet instead of line fuse. The fuse holder is internal otherwise I would do a quick swap out for comparison,to be sure.

Some one here said that a fuse element vibrates. Well of course everything vibrates or resonates. So maybe these fine resonances within the fuse line itself is an influence on purity of the ac or dc line voltages even after the filter stage. If this is true then to me it seems like the filament of a vacuum tube would also be at risk for these same self generated resonaces. Same tube type different material structure of the filament would generate a different resonant structure while conducting. Tom

Theaudiotweak, vibrations are why I think tubes whether from within or without are improved with resonance control devices, such as the Acoustic Revive QR-8 and especially AVM painting.

What is of interest to me with using magnets to replace fuses is what does the magnetic field do? Does it shape the ac fields but also does it influence those components that are nearby? This entire idea seems to come from out of the blue, but maybe it is my deficiencies in understanding electro-magnetic interactions.

If a fuse element (wire) is 1 inch long, an electron is in that said element for about 8.5e-11 seconds. I simply can not see how that could effect an electron enough to be audible.
Also, If fuse elements DID vibrate you would see more failure of these wires, due to metal fatigue.

Now, a Faraday Cage? Where? Around your house? Around your amps or low level equipment? Bad stuff in whatever form will still sneak in on your power lines. Maybe a huge isolation transformer for your house?

Magfan, well your theory fails to conform to the reality, so you need a new theory.

I heard a lecture once at the VSAC in Washington by John Camille about designs that it took to get to 90db signal to noise and higher, which he admitted was God's country. A Faraday cage is totally insufficient. Grounded 1/2" thick mild steel totally encompassing the component with no access for cables or controls and very careful circuit paths, in particular up to caps was what it would take. I went away feeling that our goals are beyond us.