Corduroy clothing - I miss that stuff, on the rare occasions I go to a “posh” event (i.e. one where I have to wear “sensible” clothes and be polite), I break out my corduroy jacket to show I can wear fine clothes too 
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It would be nice if you can quantify “A LOT” this will give the consumer more confidence in your development, testing, part selection, reliability, and especially compromises of the product.
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Fair Question falling_leaves
We built more than 30 design prototypes
We also test critical parts like MicroP’s and Relays - many were considered inferior
That all said - the Dev Time and iterations of the software was the real issue. Programming for In Rush was quite important, etc.
We like and feel confident in the Finished Product.
There is more - but I don’t want to bore - instead just informally “inform”.
Thanks - Mark
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You say on your site about this product:
“By design, the current flowing through it causes the fuse filament to get warm because it is, in fact, a small value resistor. It uses Ohms Law and the concept of resistance heating (just like your toaster) to protect you. As the current through it increases, the heating of the element increases, until the conducted current exceeds its current rating, when, ultimately, it burns through and opens the circuit … As current flows and the element heats, its resistance increases, up to the point of failure.”
Are you suggesting some sort of linear relationship between current and heat?
I understand that fuses are made from low resistance alloy with a high temperature coefficient so that when heating begins, the wires resistance increases causing a runaway condition where the wire melts rapidly. The wire is produced so that it will carry the rated current without appreciable heating.
If you look at a data sheet for what looks like standard domestic type fuses, a 250v 5A fuse operating at its rated current drops only 0.1V. Am I reading this correctly? Given my amplifier has a 13A fuse and draws 0.5A, the voltage drop is going to be nothing.
So if fuses don’t actually cause a voltage drop at their rated current, what’s the problem with them?
P.s. PS Audio BHK 300 amplifier fuse specification is 10A, so at full current rating the drop in voltage will be close to nothing.
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Awaiting your reply.
More on regular fuses.
If a circuit used at normal domestic temperature draws 2A, it should be fitted with a 3A fuse. 10A should be fitted with 15A. So the fuse will never likely be operating at full current value, and is designed to operate 60% higher for about 30 minutes.
So the proper fuse in normal operation is never even going to suffer the voltage drop if operated at full rating, because the device will never draw that much current.
Everything I read leads to the conclusion that a correctly rated fuse in the correct environment will not increase in resistance and cause any voltage drop.
Before that happens, your component must have been drawing so much current that it would likely have exploded and set your house on fire, so any additional fuse resistance would be the least of your worries.
I personally did not feel like I was qualified “enough” to answer your very good questions and offer comment on your opinions
I asked for the team to review your post.
There are a few Teams involved - We are a small group and there will be times when we will be behind. Apologies for being a bit tardy. We have Dev work going on for LSA, Vera-Fi and Bob Carver Corp all this week.
Below please -
Mark:
Your customer makes a fair and intelligent argument, and is correct, at least as viewed from a macro perspective.
When viewed on the micro scale, there are resistance parameters that do change with heat on an instantaneous basis and these changes do matter. It is likely the reason for why any improved fuse sounds different. We know from our own testing that placing a grossly oversized fuse in a product needing only a much smaller value results in an audible improvement. The larger the replacement fuse, the better, all the way up to what you call “sluggo”, which is universally best.
To what would you attribute these differences? To us it is the result of micro-heating limiting the power supply’s access to transient current. There could also be the possibility that fuse element vibration is at play as well, but resistance is the only measurable phenomenon we can point to. That, however, does not mean it is the only difference.
Such is the nature of measurements and hifi.
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Interesting…but I am not sure I understand how the “mechanicals” being written about here impact the “audibles”…
I do understand that a discernible difference in sound was heard when I removed the fuse from the P10 Regenerator, replaced it with a copper “Sluggo” and placed the SDFB in the power supply path. The difference was for the “better” to my ears, so the SDFB is staying right where it is.
I hope others chime in with commentary about why they believe fuses can make a difference and what those differences are in their systems because I am surmising the electrical properties of the “Sluggo” vs. the fuse that was replaced are related to what others report regarding fuse “upgrades”.
FWIW.
First things first, fuses are not bad. They have been a compulsory part of electrical regulations in the UK for 140 years and I reckon that if they were bad, someone would have noticed. In fact the opposite is the case. Different fuse designs and performances have been developed for a vast array of applications. In my humble house, the power that reaches my amplifier passes through 6 different fuses, each serving its own specific purpose.
So on the “macro” scale, it is accepted that at or below full current rating of the fuse, there is no heat/resistance/voltage drop issue?
A good example is the PS Audio BHK 600 amplifier. The fuse compliment and types are included in here, on pages 21 and 26:
The 8A fuse specification is in the link below (S506-8-R). In 250v money that’s 2,000W at the fuse rating, which will result in a 0.055V voltage drop - nothing. That is already well over the specification of the amplifier. The specified fuse can actually permit 25A of current draw or 6,000W for a whole second before arcing, and just over 50A for 0.1 seconds. This isn’t going to happen unless the device is broken and I presume would blow the consumer unit (mine has a reaction time of about 20 milliseconds). What little I know is that the amplifier has a huge bank of reservoir capacitors to ensure transient power delivery. That’s what you pay for.
https://www.mouser.co.uk/datasheet/2/87/eaton_s506_time_delay_glass_tube_fuses_data_sheet-1608792.pdf
The vibration theory is the “ah, but”, or what we in the UK call moving the goal posts.
We do seem to have moved away from the description of the problem on your website.
Perhaps a good thing to do would be to demonstrate the problem you are trying to fix. Get hold of a couple of BHK 600 fuses (I’m sure they will send you a few, or from the link above), draw an increasing current through and measure the resistance. Do this up to the amplifier spec and then to the fuse breaking point. then we’ll know what this is all about.
p.s. If you get to levels of current draw in excess of the fuse rating that cause heating, which you call transient current, surely your device is designed to trip at that point? If it doesn’t trip, why not?
How did you decide how much above the fuse rating and for how long your device will remain operational for this transient current before tripping?
This is why PS Audio use H-rated fuses, they are very clever and allow overcurrent, within reason.
How does your device mimic the profile of the different types of fuses that are specified for audio components?
With all due respect, what in the world does this opening statement have to do with the subject at hand? It reads like a classic, beside the point, straw man. Where has anyone on this thread directly or indirectly stated or implied that fuses are inherently “bad”.
The premise (and I would suggest subject-matter being discussed here) is fuses may have a discernible, negative impact on the subjective sound quality of certain Hi-Fi kit and that “better” fuses (however defined) and the subject product, the Swiss Digital Fuse Box, may have a discernible, positive impact on the subjective sound quality of certain Hi-Fi kit when it replaces the specified fuse for that kit.
Do you have any opinions or suggestions regarding these premises and why they might or might not be subjectively or objectively supported? In the interest of furthering the discussion and my understanding of the matter, I would truly like to read anything relevant you might like to share.
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They are not bad because they only offer significant resistance when they have to. The 8A BHK fuse has resistance of 0.0044 ohms with 8A going through it, which is more than the product would ever demand. The Swiss product website says it’s bad because it heats up and resistance increases, which could have negative implications (probably doesn’t, depending on the rating). We have now moved away from that to extreme operating conditions, which I’m suggesting don’t arise.
I bought one after-market SR fuse. It is a 3.15A slow blow fuse for my Innuos streamer. Subjectively, it makes absolutely no difference at all. I’ve just bought today a replacement - I had to buy 20, about 30c each.
Most of the fuses we use in the UK are in plug sockets and consumer units and are heavily regulated in UK and EU law, because they are overcurrent safety devices. Getting compliance certification costs a fortune, so there are relatively few manufacturers selling millions of them. Those fuses (3A, 5A 13A) are sold after-market by more than one supplier. It is illegal to import and distribute a non-compliant fuse. I have something ongoing there as well.
One of those after-market companies starts with a £1 Bussmann fuse and “treats” them. One of the treated fuses is listed for £8,000. That’s $10,000. The £1 fuse is fully compliant and legal and they rely on that certification. So how can you modify a fuse to make it better, but not have to get new certification because you’ve changed its performance?
PS Audio put fuses in their devices for a reason, and their performance is based on those fuses. They have safety and protective functions. If those functions were not needed, there would be no fuse.
You could equally argue that skydiving is more fun without having a parachute strapped to your back, so I won’t bother with one and just hope I land somewhere soft.
The BHK 600 uses what’s far from a standard fuse. How does the Swiss thing replicate its required performance?
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Again (just quoting the above as the most recent example), another completely factual, but arguably unrelated point of fact/observation…
I’ll jump out of this particular back and forth now and look forward to you and others providing additional, informative (and hopefully relevant 
) information.
Cheers.
The relevant information would be how resistance of a fuse increases under increasing current draw, because the sole purpose of this device is to reduce resistance where the fuse was to zero.
Hopefully Mark can provide this data, it will explain why he and his team came up with this product.
PS Audio Land – hello
As some of you know, Paul was my partner for more than 4 years at Genesis. I am a guest here and I want to honor my old friend by acting NOT like I know everything there is to know – but instead, be a good Ambassador of the brands that I have a personal stake and those as well that I lead a Development Team(s).
I have decided to be a “quiet cheerleader” and not try to PROVE that my widget is The Best. Instead, as some of you know… I will do everything to help YOU discover my products and the passion I still have for Audio 54 years later.
I will never have enough time or temerity to “engage” in a place that’s not my home. I’m a guest – if someone wants me to prove out my widget – then call me or write me and I’ll engage until the cows come home.
Lets just say I’m a big proponent of FUSE BOX, Puron and others. I need not spend my time arm twisting or jousting with those that clearly have way more time than I do.
BTW – FUSE BOX is NOT available in the U.K. – enough said.
Thanks for the nice time – you now know where to find me
Mark
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Mark
I am surprised you engaged with for that long. As the product is not relevant in his country was nothing more than an argument for arguments sake which we are familiar with.
This is unfortunate, Mark; but I completely understand.
It would have been nice for others here to have been able to learn more from you and your partners.
Regards.
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It must be a British “idiosyncrasy” * regarding our electrical standards
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* it’s not an idiosyncrasy - a number of people were maimed or killed by unsafe electrical installations in the 40s 50s and 60s, and the answer was fuses, followed later by RCDs to catch the edge cases, and they have served us well.
I wish anyone well who wants to experiment with alternatives to standard fuses, or alternative lifestyles come to that, but as with alternative lifestyles, it is important to know the risks, and they should be acknowledged by the seller.
Your (and everyone’s) good temper has been appreciated in this debate which could easily have turned nasty (and then I would have felt bad since I think I started the nay-saying).
As they say on Dragon’s Den - folks, I’m out (i.e. I shall not be buying a digital fuse).
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Mark, it has been great to have you participating in this forum.
I hope we hear from you again!
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@o2audio, I second that and hope you stick around and check back in from time to time.
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And no regular here should be surprised at Steven’s “performance” as it’s commonplace when he has time on his hands.
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