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Just to add to the head-scratching questions regarding fuses, specifically fuse ratings and reliability mentioned in several posts below this one, I thought I'd post something I read last night on the Acme Audio Labs web site.
I was on their site, double-checking an IEC jack I bought a long time ago, when I read the following about fuses:
"Ceramic Fuse Compatibility
We have found that some equipment with no inrush protection will destroy Ceramic body fuses. It is recommended that a potential fuse customer first try a stock ceramic body fuse before ordering the Acme Fuses."
So their experience has been that a ceramic fuse, even ones from UL rated companies like Buss, Littelfuse, etc. will open more often than a glass fuse of the same rating.
That doesn't make any sense to me, and their observation is purely anecdotal, but I did find it interesting, so I thought I'd pass it along.
Edit: Please note, my post isn't intended to imply anything negative towards Acme Audio Labs. I use their AC duplex outlet and several of their IEC jacks, and have nothing but good to say about Acme. I posted simply to pass along their experience with glass vs. ceramic fuses.
Edits: 05/04/17Follow Ups:
with my FW amps.
Ceramic fuses WITH the Pass installed thermistors would blow when of the same rating as the glass tube fuse.
Took me by surprise.
Endlessly repeating, "But why? But why?"
Again, not doubting your experience in the least, nor Acme's. I'm simply thinking that Bussmann or Littelfuse would say, "If changing to a ceramic fuse, use a 0.5A higher rating than with a glass fuse" if it's a characteristic of the design.
And if any of you decide to call either of the above mentioned companies to ask them, please also ask them which version sounds better. Oh, and please record the conversation. I'd love to listen to that one!
Another fellow at DIYaudio had the same experience.
I did have a higher rated ceramic fuse (either 0.25 or 0.5 A greater) and it does fine.
My first thought would have to do with heating. I am guessing air has less heating "stiction" than the ceramic, just enough to keep the thing alive. No question, if there was a long term heating question I would tend to think the ceramic body would offer more long term cooling than glass if that was a real concern.
One would think the stability added by the ceramic body would be an advantage. For some reason I have never opened one up so I do not know whether the wire is in intimate contact with the ceramic or is just as unsupported as the wire in the glass tube? In that case there would not be much of a difference if any at all.
One would think that the amount of air surrounding the wire could make a difference. No question there is a good distance between the wire and the glass case with "standard" resistors.
Could there be a quality of capacitance factor in fuse design?
I suspect most of us at one time have listened to a component without a fuse. I have not done it in decades. But I remember there was a difference. It is very frustrating.
It may be the silica in the ceramic fuses causing the element to more poorly dissipate the heat generated at turn on.
I've never tried any of my equipment with the fuse bypassed, so I guess I don't know what I'm missing.
at turn-on or otherwise, is what makes for the rating of the fuse. If a ceramic fuse blows at some current draw below its rating, then it would need to be re-rated, if the UL had anything to say about it. Which is the question, when it comes to boutique fuses.
If you read my original post, it has been the experience of Mike from Acme Audio Labs that standard, UL rated ceramic fuses of the same rating as their glass counterparts tend to open sooner than the glass variety. Rick then posted that some guy over on DIYaudio had a similar experience.
I was trying to wrap my mind around that, because honestly, it still doesn't make any sense to me, which was the reason for my post.
It's not only odd, it's against "the law". Sorry for misunderstanding your reference points.
I figured you just missed my point, and that's OK, 'cause the whole subject is rather confusing.
"Suddenly, I'm not half the man I used to be. 'Cause now I'm an amputee" J. Lennon
Inrush Limiters prevent transient current or voltage overload. Their use is common on the primaries or secondaries of transformers in good quality circuits. Could be that a ceramic fuse is more likely to exhibit a fast-blo characteristic under very short duration stress. No big deal.
PS. I use Acme fuses, my soul concession to fuse obsession. They're relatively cheap and good.
Have you tried the "special sauce" version and, if so, do you find them to be worth the additional 33% it adds to the cost?
My OTL tube amplifiers require fuses directly in the output stage, where a fuse might logically make an audible difference. So, if anything, I may have bought some "special sauce" fuses for those positions (six needed per monoblock). But did I make any effort to figure out whether I can hear a difference? Nope. I also bought and installed Acme silver fuse holders for each position in the output stage. All I can say is that the amplifiers sound their best ever, albeit I made several other changes at the same time as installing the fuse holders and special sauce fuses. Throwback heard the amplifiers in their current state of tweak, I think.
I DID hear Lew's system in its current state of tweak and it sounds fantastic (fantastically GOOD, that is). In fact, it is one of the best systems I have ever heard. But Lew has done many things to make that happen so even with my highly burnished, platinum ears (hah!) I can't begin to attribute his excellent sound to any one thing or group of things. I am reminded of Salieri's comment about Mozart's music in the film, Amadeus: "Take away one note and there would be diminishment."
Thx. You're absolutely right; a good system is a complex soup of matched bits and pieces. Hard to say what in particular is the contribution of one item or another. I'm sure the fuses are a subtle part of the mix.
By the way, Chuck, I recently acquired a ZYX Universe (the original version) with very low hours and mounted it on the Reed tonearm on the SP10 MK3. Wow! A huge upgrade. I may have to admit that expensive cartridges make a difference, at least sometimes.
Did you mean sole concession? You using the Acme's with the special sole food sauce?
"The Borg is the ultimate user. They're unlike any threat your Federation has ever faced."
- Q, 2365
I realized the moment that I clicked on "Post Message" that I had made that error, but I had to hit the john. Some needs over-ride others. I knew you'd know what I meant.
Considering how often I have been crucified for my spelling mistakes (not by you) just thought I'd get my licks in. You call that an excuse? I feel much better now. For some it's getting even, for others it's a toilet run. Yes, by golly, I did know what you meant.
"The Borg is the ultimate user. They're unlike any threat your Federation has ever faced."
- Q, 2365
Lew, I hope you made your toilet run "solo."
At least I have a shred of dignity remaining.
I am enjoying TL's LPs immensely. But organizing my swollen collection is something to do in retirement, if and when.
I will pipe in since I wrote the warning. I still own a pair of Quicksilver Silver Mono tube amps. I was using them at the time I started doing fuses. I replaced the stock glass fuse with the same value Littelfuse ceramic. It blew it on startup. I repeated it a couple more times. No inrush current protection on these amps and a number of others. I communicated with the owner of Response Audio back then about it. He had run into the same problem. Thus the warning.
I currently use a ARC VT100 mark III. It has startup surge protection. No problems with ceramics.
I ended up going one amp bigger on the fuses in the Quickies and there were no more problems with blowing them.
I'm still trying to understand the "why" of your results, which was the reason for my post. Not that the cause really matters, but it was something I simply found curious.
Also, thanks for posting the precautionary test on your site. I've never tried "boutique" fuses of any sort, and pre-testing with a standard ceramic could potentially save someone a lot of money if they're putting their toe into that water for the first time.
To be honest, I didn't do any extensive tests that could backup the basic idea of Ceramics VS glass fuses. I added that info early on to protect my customers. For years I also asked if they had big amps with not current inrush protection, but have let that practice slip since sales have dropped off. A better statement might be that not all fuses react to inrush current the same way. They might have less threshold before blowing. In my experience, fuses usually blow due to much higher amperage draws than their rated value. I don't understand why designers don't implement inrush protection. It can be done easily with relays, thermistors, and inrush current limiters. DIY people can see easy implementations in Nelson Pass DIY class A designs.
And that was the intent of my original post, to try and get a better understanding of "why".
I once posted an observation on the Asylum about the element of a 0.25A fast-blo glass fuse glowing bright orange when I first apply 24 VDC to one of my phono stages, which has a quiescent current draw of about 30mA. It does it every time I've switched the power on. The glow lasts for about a second and then looks normal, and yet the fuse has never opened (i.e. "blown").
According to Neolith in his reply to my post, ceramic fuses contain silica. Pure speculation on my part, but I wonder if that silica doesn't allow the resulting heat of a "glowing orange" fuse element to dissipate as quickly as an element in the open air of a glass fuse would, causing the fuse to blow. Still, you'd think that if that were the case, manufacturers like Buss, etc. would take that into account when assigning their fuses over-current protection ratings.
My Nelson Pass First Watt F1J (not a DIY amp) has thermistors in the power supply, and I've never had its fuse open, so your point regarding inrush current is well taken. The schematic calls for a "4A slow", and I got curious while typing this to see if the fuse was glass or ceramic. It turns out it's a 2.5A slow blow glass fuse, 1.5A under spec, and yet has never blown. I guess those thermistors do their job!
Many electronic products now use a power-on sequence control (i.e., soft start) circuit to prevent damage that might be caused by an initial power inrush, or surge. Not sure why the ceramic body fuses would be more susceptible to blowing in the absence of a soft start sequence, or what any of that has to do with sound quality, but I believe they are more often used as "audiophile" fuses (by folks like Acme and others) because of the assumed superior damping properties of the ceramic (compared to glass) body and the silica filling. If you believe something more exotic like beeswax filling would be even better, then you can purchase those at about 50 times the price of the ceramic body Bussmann fuses, or about $175 each.
The thread titled, "Synergistic Red Fuse ..." over on A'gon provides more than you may ever care to read about fuses.
Ceramic and glass fuses will "blow" at the same current but in cases of very high over current there may be arcing across the gap allowing current to continue to flow. Ceramic fuses have silica inside that melts and blocks the arcing. They are recommended for situations that involve potential for explosion - for example, a hospital OR with anesthesia gas - or where high over current may be expected. Typically multimeters specify the use of ceramic fuses. Otherwise the characteristics of similarly rated ceramic and glass fuses are the same.
In situations where there is a high in-rush current (such as charging the power supply caps) causing nuisance blowing, a slow blow fuse is used. This can be glass or ceramic depending on the situation.
I married the perfect woman. The downside is everything that goes wrong is my fault.
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