Here's something interesting. It doesn't have to do directly with fuses, but adds to the side topic conversation about power filtration.
If I understand how these filters work, which Blue Circle and I believe Audience have been making for quite a long time in their power conditioners (Blue Circle especially), they use (guess what?) a bunch of capacitors. What else uses a bunch of capacitors (or a few large caps) in the power supply in an audio system? If you answered, "Amplifiers," you are correct.
Where these Blue Circle and Audience filters are somewhat unique is that they contain capacitors of various sizes / values to filter a range of noises coming from the wall. While the efficacy of these types of power filters may be limited when used with power amplifiers, especially those with large power supplies, I think their effect could be more pronounced with equipment that have much smaller power supplies (ie source / front end components).
Regarding how this relates to fuses (and Roger please correct me if my thinking is way out of wack): Unless the fuse is acting as a capacitor, then the fuse can't be acting as a filter to reduce power line noise.
RD, Thanks you for an amusing video. The only thing that could be in the Sillycone filter is some capacitors. The demo is very clever as it has a long shop cord coiled up for a supply point and another 15 foot extension cord, also coiled to the end test point. He uses an amplified speaker that lets us hear what is on the line while rejecting the 60Hz AC that dominates. Just a speaker and series capacitor connected directly across the line might have enough sensitivity. For all we know there is a blender or some motor running elsewhere putting a lot of noise on the line.
It is a very convincing demo, however note a few things. The 15 ft extension cord provides some series inductance resistance so that the Sillycone filter (capacitors) can shunt it. When you go to the other end of the 15 ft cord the noise is still there because the shunt is on the other end.
What is in the Sillycone for $850. A few capacitors that cost a few dollars. BTW there is no need for different size caps to filter different frequencies, Good caps dont work that way. One proper cap can do the job, but hey why not stack some up, makes a better story. The truth about paralleled caps of various sizes is they often cause ringing at certain frequencies that are worse than a single cap.
The electrical point I would like to make is this. Capacitors across the power line are presented with 120 Volts AC. The current through them can be calculated by a reactance calculator and ohms law. http://www.sengpielaudio.com/calculator-XLC.htm
A 10 uf cap at 60 Hz is 265 ohms and 120V/265 ohms is about 1/2 amp. That is about as big a cap as you can put on the line without some problems. By comparison the cap in a tube amp power supply might be 1000 uF (it's not conducting any large AC so it can be of unlimited size). In a solid state amp they might be 100,000 uF. So you can see the caps in the power supply do the majority of the work. In addition they are on the good side of the best series inductor, you power transformer.
If you really want a good, inexpensive power filter get a 1 KW isolation transformer and drive your electronics through that. It can be placed anywhere in the line, at the fuse panel, in a closet, in the garage just so the power goes through it. It will do several things. It will eliminate any DC on the line and is a very effective low pass filter as the leakage inductance is larger than most series chokes in power conditioners,
It is becoming more and more apparent to me how the modification business (tweaks) works. A guy who may not understand electronics cooks up something, sends it to a reviewer who doesn't understand electronics either who then writes about the glories he hears and that is what you buy. (well you don't, but the believers do).
This is where we are in the state of Hi Fi add-ons (modifications, tweaks, call them what you will). I happen to think there are more useful things we could do with out time, money and effort. Those are things I speak about here and teach in my school.