Fuses that matter.

Hi Vance,

I don't doubt that these companies COULD replicate the protection characteristics of the stock fuse. However, different designs of just about any electronic product differ in terms of their design goals and philosophies, and how the tradeoffs that inevitably must be made between many different parameters are prioritized.

As you've seen in the datasheet, even something as simple as a fuse has a great many different specifiable parameters. In addition, earlier in this thread links were provided to papers prepared by HiFiTuning which presented several pages of comparisons between various measurements of various makes of fuses. The data differed widely among the different fuses. (Although I commented that IMO none of the differences appeared likely to be quantitatively significant, and even if some of them were quantitatively significant in some applications, I saw no reason to expect the resulting sonic effects to be consistent among different component designs, and among different AC line voltages).

So given the many parameters that are involved, and the diversity of measured data for different fuses having similar current ratings, it seems to me that while the aftermarket fuse manufacturers COULD replicate the protection characteristics of this particular Littelfuse, I would have my doubts that they DO closely replicate them. But as we said earlier, it will be interesting to see what they provide in response to an inquiry asking for breaking capacity and nominal melting numbers.

Here's another thought, though, that is suggested by the numbers in the Littelfuse datasheet. On the first page, take a look at the numbers in the table of "opening times" (i.e., the amount of time required to blow) that are shown at the lower right. Note in the entries for 275%, 400%, and 1000% that the range of specified opening times for a given fuse and a given overload is huge. For example, for fuses rated between 8 and 20 amps, and overloaded to 400% of their rating, the blow time can be anywhere from 0.15 seconds to 5 seconds. That is a huge possible variation from fuse to fuse. Which suggests the likelihood that many other parameters, for which only a nominal value and not a range of possible values are specified, could also have wide fuse-to-fuse variations.

So it seems to me that a useful experiment may be to simply buy a bunch of fuses that are the same make and model as the stock Littelfuse, and compare sonics between them. Who knows, maybe you'll find significant sonic differences between them, and perhaps one or more of them will provide sonics comparable to what the aftermarket fuses would provide.

If you do that, btw, it might be best to split the order among multiple distributors (e.g., Digikey, Mouser, Newark, etc.), which may increase the likelihood that the fuses you try come from different production runs.

Regards,
-- Al

Al,

That's quite a can of worms you just opened. ;-)

I have sent an email to the owner of Hifi Tuning. I'll post if I get a response.

V.

Almarg, i wonder if any manufacture has ever gone about choosing a fuse value this way. I know with certainty two who went to a different value when the first was blowing too often. I think it is more like civil engineering with a big safety factor. After all why not start low and work your way up?

This might be a good time to remind folks that quite a lift in sound quality can be achieved without buying ANY new fuses at all. What are the odds that the existing stock fuses in any given amp or speaker were originally inserted in the correct orientation? If you guess 50% you're correct. So, the trick is to make all the fuses in the system be the correct orientation. The way to do this is reverse the direction of fuses one at a time, listening each time. Reverse the first fuse direction - If the sound gets more harsh and unnatural sounding put the fuse back in the way it was. If you are uncertain which direction is correct by ear, leave as it is for the time being and proceed to the next fuse. Reverse the direction of the second fuse and evaluate the sound. When all fuses have been evaluated, you should observe the system sounds more natural and less distorted and harsh than before you started to change fuse directions. There still might be some fuses that are not in the correct orientation due to uncertainty during evaluation. Repeating the whole procedure should uncover any fuses that still remain incorrectly oriented.

The following is my experience replacing the standard fuses in my integrated amplifier with Hifi Supreme Tuning Fuses. The amp is an ARS-Sonum Filarmonia. It has maximum output power of 30 watts RMS per channel at 8 ohms. Its output stage uses a pair of E34L pentodes per channel, in push-pull configuration. It is an outstanding amp paired with Merlin Master VSM's.

There are three fuses. The main power fuse is a slow-blow 4 amp, and the two internal fuses are also slow-blow rated at 500 mA.

I initially purchased only the main power fuse, as I had heard that it has the most dramatic impact. From the moment I replaced the stock fuse, the improvement was clear and continued to improve over the next week. With that success, I decided to spring for the two internal fuses. Unlike the immediate improvement with the power fuse, my initial response to the new internal fuses was, "Wretched!" It was so bad that I immediately shut the amp down, took the tubes out, disconnected all cables, opened up the amp and switched the direction of the fuses. I believe that this improved things slightly. But still it was virtually unlistenable for the first ten hours. By 15 hours, it had started to relax a little, although still extremely congested. By 20 hours it was just barely starting to sing.

I've now got about 30 hours on these new fuses and they're sounding pretty darn good. At this point I would say that they are a definite improvement over the stock fuses. Primarily, the soundstage seems to be more clearly defined. I have more of a sense of the depth and boundaries of the original recording environment. Instruments are also more realistically "shaped."

This is perhaps the most dramatic burn-in phase of any new component I've added to my system: from wretched to pretty spectacular. Maybe it's the 99% silver wire. I am expecting continued improvement through 100 hrs. based on what I've read.

I'm writing this for anyone who has purchased these and have not had the patience to let them burn in. I was tempted to give up at 10 hours, given my experience with the immediate improvement with the main power fuse. I suppose, however, this makes some sense. I have very little technical knowledge, but the current running through the signal path must be much lower than the current running through the main power fuse, hence the longer burn-in time??

It always amazes me that manufacturers do not state clearly and unequivocally that their product WILL sound inferior until after XX hours of playing time. I bet that plenty of "non-believers" in the burn-in phenomenon have judged products inferior before giving them a fighting chance.