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Direction of aftermarket fuses (only for believers!)

It is with reluctance that I start another thread on this topic with the ONLY GOAL for believers to share their experience about aftermarket fuses.
To others: you can call us snobs, emperors w/o clothes,... etc but I hope you refrain posting just your opinion here. If you did not hear any difference, great, maybe there isn’t.

The main driver for this new post is that I am starting a project to mod my NAD M25 7 ch amp for my home theater. It has 19 fuses (2 per channel, 4 on the power supply board, 1 main AC) and I will try a mix of AMR Gold, SR Black and Audio Magic Platinum (anyway that is the plan, I may try out some other brands/models). As it is reasonably difficult to change them, esp the ones on each channel module that requires complete disassembly, I would like to know what the direction is for these models mentioned and of course, others who HAVE HEARD there is a difference please share your experience on any fuse model you have tried.

Fuses are IME directional:
Isoclean is one of the first to indicate the direction (2008/2009) on their fuses. Users of HiFi Tuning (when the awareness rose quite a bit amongst audiophiles) have mostly heard the difference.

As an IEEE engineer, I was highly skeptical of cabling decades ago (I like the speaker design of John Dunlavy but he said on many occasions that cables nor footers matter at all, WRONG!). Luckily, my curiosity proved me wrong as well. I see the same skepticism that I and many others had about the need for aftermarket cables many, many years ago now on fuses and esp on the direction on fuses.

Another example is the direction of capacitors (I do not mean electrolytic types). Even some manufacturers now and certainly many in the past did not believe it can make a difference sonically. Maybe some do but it takes time in the assembly to sort and put them in the right direction/order (esp as some of the cap manufacturers still do not indicate "polarity") so that maybe is one argument why this is not universally implemented.








128x128jazzonthehudson
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jea48
4,281 posts
 

atmashere said:

In one of our preamps I measured a 158mV (0.158V) drop; in one of our amps I’ve seen a 2 volt drop cause a loss of 40 watts at the output of the amp.


A fuse is one of those spots in that set of connections from the wall (AC power connectors, power cord and the fuse and holder) that is likely the ’softest’ which is to say that the sag occurs easier at that point, due to contact area and conductor size (the effects being limited by the fuse being so small). Part of this is due to the nature of the fuse itself, the other part due to its connection into the system.

When you said you measured a 2V VD (Voltage Drop) on an amp, I assume you are still talking across the line side and load side of the fuse clips of the fuse. Not across the actual fuse itself. I just want to make sure everybody here is on the same page.

As you know that is a perfect example of poor contact pressure and or corrosion buildup between the fuse end caps and the fuse holder contacts.

The greater the load on the poor connection can cause heat between the poor connection/s due to the resistance of the poor connection. More heat, more corrosion, more resistance, less contact surface area, more VD, when measured across the line-in fuse clip, and the load-out fuse clip connection....

Jim






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almarg
9,670 posts
 
Jim, I believe that Ralph was saying that he has observed a 2 volt difference in line voltage, as received by the circuitry in one of his amplifiers, to result in a 40 watt difference in the amplifier’s power capability. Not that any of his measurements across fuseholders were ever that large. And as I read his post he was providing those numbers for the purpose of illustrating how sensitive the performance of some components can be to variations in the voltage they receive.

Note that that reference was immediately preceded by this quote from one of your posts:
Millivolts...... If that was the reason, wouldn’t the same reasoning hold true for the AC mains line voltage feeding the fuse? In other words a small VD in millivolts on the mains feeding a piece of equipment could/would have an impact on the SQ of the piece of equipment. Not hardly....
And his response began with:
You are correct in your first statement of this paragraph.
Also, I recall him mentioning the 2 volt 40 watt figures, or numbers that were very similar, in a thread a few years ago that involved voltage drops across power cords.

I of course agree with the rest of your post just above. I would also point out that the greater the amount of current drawn by a particular component, the greater the effects mentioned in your last paragraph will be, everything else being equal. And of course different components will have differing sensitivities to those effects, as Ralph stated.

Best regards,
-- Al

jea48
4,281 posts
 

Al,

Thanks for the clarification.

Jim

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bdp24
9,437 posts
 
I’d like to hear from AC power cord designers/manufacturers. Do any of them test the wire they make their cords with for directionality? They can't simply be reversed by the user though, of course.
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