2. amps-preamps
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New Fuse Thread . . .

So the talk about the sonic effects of fuses got way out of hand, and I would like to know some details from those who have actually tried the boutique audio fuses. So if you have, please let us know any of the following:

1. What value (ampere rating) were you using, and was it fast or slow-blow (time delay)? Time-delay fuses usually have a letter 'T' in their rating, like "T2.5A" is a 2.5 ampere, slow-blow fuse.

2. Does anybody have a reasonably decent ohmmeter, and could you measure the difference in resistance between the boutique fuse and the standard one? If you measure, be sure to subtract the resistance of your test leads. Of course, if somebody has an impedance analyzer, I'd love to see that data . . .

3. What position is this used in? That is, on the AC line, or after the transformer, after the rectifier, etc.?

4. Has anybody had occasional fuse-blowing with the stock fuse, and replaced it with a boutique fuse, and had the boutique fuse blow? Did the failure patterns seem similar to both types?

5. Has anybody made any performance measurements on their equipment with various types of fuses?

So I'm hypothesizing about some ways in which fuses could affect circuit performance, and there are two things I can think of. First, if silver wire is used, then since silver has a lower melting point than copper, the fuse resistance *could* possibly be lower for a given rating. Also, many slow-blow fuses seem to have a resistive element wound around a central core, so it's possible that these could be inductive as well. So what could that mean in a circuit?

First, for a slow-blow line-fuse application, where there is an AC input filter, adding/changing resistance/reactance in the AC line could affect the Q of the input filter, and if this unit was RF suceptible or had a switch-mode power supply, the fuse could therefore affect RF emisions or suceptibility.

Second, many power amplifiers have no snubber capacitors on their rectifiers, and also use fuses for the power-transformer secondary. It's possible here that changing the reactive/resistive characteristics of the fuse could slightly change the switching speed of the rectifier diodes, and affect the diodes' RF emissions.

Third, some power amplifiers use fuses on the DC rails, after the filter capacitors. In this case, it's easy to see how fuse resistance could influence the amplifier performance.

Fourth, if a fuse was placed between a low-voltage linear regulator (like the ubiquitous 78XX or LM317) and its local input filter capacitor, the characteristics of the fuse could affect the regulator's stability, and cause it to oscillate.

And finally, there's the UL rating issue . . . it's important to have confidence that a fuse will blow when its supposed to, and without any certifications, who's to say? At $40 a pop [sic], testing their tolerance and production consistency is a very expensive proposition indeed.

Now I'm not claiming that fuses make a difference, or don't make a difference, I honestly haven't tried, and I'm too cheap to conduct an exhaustive study into the matter. But if anybody has some good data (even if incomplete) on their experiments, please share it.
kirkus

Showing 3 responses by kirkus

kirkus OP
502 posts
 
Dave, let me put it this way. The best way to get repeatable results is to understand what you're doing and what you're changing. And it's obvious to me that if I wanted to duplicate the results of those who have heard audible improvements . . . then a great place to start would be by gathering information on what has been observed by others, no?

As far as the price thing goes, I don't think $39 for a big improvement is outrageous. But should your technical skills ever progress beyond mere fuse-swapping, you will see that there are literally thousands of tiny details in your equipment where you can apply a "cash infusion" . . . and if you like to dork around swapping parts inside your electronic equipment, guided only by your whimsey and credo, without any real knowledge of what you're doing . . . my friend, it is YOU who is the "techno weenie".

But I'm still interested in knowing details from those who have heard improvements, and that aren't too dogmatic to coherently describe their experiences.
kirkus OP
502 posts
 
Gentlemen, please. The other fuse thread was a fine place to argue about these generalities . . .

Rodman and Albert, I'm glad you're happy with the improvements the fuses have made; if you please, I'd be interested in knowing the values and circuit positions of the fuses where you've found the improvements, if you recall.

Magfan, I'd postulate that your loudspeaker fuses are a great place to see if there's a difference - they're directly in the signal path, they're a low amperage fast-blow variety (hence higher resistance), and the Maggies can draw significant current peaks, which could aggrevate any temperature-dependent characteristics in the fuses.

Remember, more and better data helps all of us! I have 14 glass fuses total in all of my components, and if I am going to try it like many of you suggest . . . $546 for all of them is a lot of Jack! Simply choosing one at random, or just switching out the easiest ones to reach . . . pretty lame approach. If we were that haphazard in our methodology for speaker placement, or tonearm setup, well, you get the picture.
kirkus OP
502 posts
 
Rodman, he doesn't want that answer.
Ooooo, baby! Why don't YOU tell me what I WANT to hear . . . that's soooo hot . . .

Anyway, I'm taking you up on this, Rodman . . . I ordered two Hi-Fi Tuning 2A slow-blow fuses from Acoustic Sounds, they have them at $34.95 (still made me wince a bit). I will do as you suggest, and use them in the AC line of my Marantz Model 2s. I'm thankful that your suggestion is for the easiest fuses to get at - gotta love external fuseholders right on the front ;)

I'm curious, did you change all of your power-amp fuses at once, or did you try it in one place, first? From what you described, the driver-rail fuses in the Hafler are the main suspect in an engineering sense, especially if these rails are taken directly from the main supply rails, and shared between both channels. I have personally seen (in solid-state amps) driver-rail bypass capacitors that "seem to be" fine and measure OK, but inexplicably cause an increase in measured THD. Same goes for cold solder joints on connectors that feed these rails.

If you were interested, you could change only these fuses back to the stock types, and see if that accounts for the bulk of the change in performance . . . but if you'd rather leave well enough alone, I understand.
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