fuses - the $39 ones or the 85 cent ones

I was curious about the theory that vibration applied to wires and/or electronics would generate some kind of signal. So...I put a high gain phono preamp into a closed box with a speaker system, and blasted it with very high volume sound... much higher than it would experience with a normal setup. What came out of the preamp was absolutely nothing. No measurable voltage and no audible signal.

Vibration is certainly bad news for turntables, for tube electronincs, and, at very high levels, for disc players and maybe tape decks. But otherwise I don't believe there is an effect.

I was curious about the theory that vibration applied to wires and/or electronics would generate some kind of signal.

Try this. Get a male XLR connector, and solder a 50-100 ohm resistor between pins 2 and 3, and connect pin 1 to the XLR shell - this emulates the source impedance of a microphone. Connect this through a typical cheap guitar-store microphone cable to any reasonably low-noise, high-gain mic preamp, and crank it up to full gain and listen.

Now slap the microphone cable around, and you will hear the effects of cable microphonics - they're obvious. Substitute a typical pro-grade cable (i.e. Belden 8412), and you will hear a significant difference. You might actually be able to repeat this with your phono-cable leads - it's just that the cartridge itself is microphonic as well, so it's less definitive.

But that's of course NOT the reason that some fuses have sand in them. The sand keeps the fuse filament from failing for mechanical reasons (i.e. shock, mounting position) when the fuse is operated continuously near its rated current, and the filament softens.

Pubul57,

The ones I have are Bussmann's ABC. Below are the specs for the 4Amp fuse I use for the mid-range driver that I got from Master-Carr. It doesn't mention whether it is sand-filled or not. I also have the 2.5Amp fuse for the tweeter, and that one is also sand-filled.

Part Number: 71385K29

UL Specification :: Listed
Bussmann Type :: ABC
Littelfuse Type :: 314
Ferraz Shawmut Type :: GAB
Available Amps :: 4
AC Voltage Rating (VAC) :: 250
Fuse Type :: Fast-Acting Fuse
Ceramic-Tube Fuse Type :: Fast Acting
Fast-Acting Fuse Type :: Ceramic-Tube Fuse
Visual Indicator :: Without Visual Indicator
AC Interrupt-Current Rating :: 10,000 @ 125 VAC
DC Interrupt-Current Rating :: 10,000 @ 125 VDC
Diameter :: 1/4"
Overall Length :: 1-1/4"
Specifications Met :: Underwriters Laboratories (UL)

Thank you.

Kirkus...OK. I will try your kind of experiment. The easiest way to do it would be to simply "slap the mic cable around" which goes from an actual mic to my Behringer DEQ2496 spectrum analyser. The analyser is very sensitive and will show sound levels below what is audible when I play my system. I will stuff the mic under a cushon so that the slaps won't be picked up acousticly.

And about the sand, another reason is to prevent violent destruction of the fuse body if it blows. Safety issue.