Mine, stock, was 5 amp. I have tried 6.3 amps, but liked 5s best when I was carefully testing them. Have not put in a 3.1, but if it has been working, it would seem to be even safer...right?

I tried a couple audio fuses from another MKIII user that were his preferred (sound-wise) 6.3 amp. Though not the same makes, I thought two 6.3s sounded denser than a couple audio 5 amp fuses. The 6.3s were a furutech and a hifi tuning gold, nice, but a little too thick for my system and tastes at the time compared to 5 amp hifi tuning supreme and a hifi tuning silver. Each audio fuse I have tried sounds different, so not a perfect test, but I heard the general difference between the 5 and 6.3 that was consistent.

So it may be worth a test. Just put in a 5 amp of the same type and see if it sounds different. Those normal fuses from parts stores are dirt cheap, so could be an interesting test.

I recall Steve saying fast or slow both work. I have been using slow blow.

I agree, but I checked out the 6.3 with the "source" and at the time, he thought is would be fine. Also checked it out with PSAudio for my P5 since I had a 6.3 around, and they said it was fine for the stock 5 amp fuse position. Can't say what Steve might say today though so a good caution Core. I like 5 better sound-wise.

I'll try not act like an expert...  ;D  Because I am not.
But the voltage rating on a fuse is not the same as say a cap or resistor.
If the rating is 250V it is ok to use up to 250V.
The amperage rating does not change with voltage.
So a 3A fuse is 3A at 125V and 250V.

Written in a better way:
Quote:

Core32 is correct....

OK.... here's the deal, direct from "two" horses mouths.

My commercial electrician son-in-law says the voltage rating of a fuse only comes into play "after" the fusing element(wire) blows/melts.  
After the fuse blows, it then becomes the responsibility of the outer case of the fuse to prevent the voltage from arcing over from one end of the fuse to the other, thus bypassing the purpose of the fuse in the first place.  
So a higher voltage rated fuse is better at preventing this than a lower voltage rated one.
It is recommended and common practice to use a fuse with a voltage rating at least 2x the voltage of the circuit the fuse will be used in.

Per Zenmaster Steve... Torii should have a 5 amp fuse... only because if you turn on both sides of the amp at the same time, a 3.15 amp fuse may blow.  It does not need a 3 amp fuse at operational current draw.  He said, if you turn on one side of your amp at a time, a 3 amp fuse will protect it better and will not blow at turn on.

I unplugged everything from my PS Audio P5 regenerator and monitored the Torii's wattage draw at initial turn on, when the slow start mute circuit turns the music on and its steady state after the amp has warmed up.
The power fluctuation happens too fast to get a steady state read at
initial turn on, and when the mute circuit un-mutes.
But I can see something like 250-270 watts at turn on.  Then it drops quickly back to 150-170ish watts until it un-mutes.  When it un-mutes, it jumps up again very quickly for just a split-second to something over 200 watts and then settles back down.
After the amp has reached thermal stability, my Torii draws 153 watts steady as a rock per the P5.

I have my P5 set to output 118 volts, it's reducing not boosting, as we typically have voltage at our house over 120 volts, and it is not uncommon to see 125-126 volts.
So if we take the 153 watts draw of the Torii at 118 volts and assume a .9 power factor of the Torii's power supply(a guess on my part)... that equates to about a 1.4 - 1.5 amp steady state current draw.  
The Torii, being a class A design, does not draw more current as the volume goes up.  Idling or at ear-bleed levels, it draws the same current according to the meter on my P5.

I have never turned on both sides of my Torii at the same time in over 3 years... and thus I have never had a problem with the 3.15 amp fuses in it.

Now... let's talk "type" of fuse.  Ceramic fuses have a much better rating at stopping voltage arcing than glass cased fuses.  
So... if you really want to protect your investment... put a 3.15 amp 250 volt, fast-blo, ceramic fuse in it and turn on one channel at a time....

Yes I've tried boutique fuses... I "thought" they may have made a small improvement in a huge solid-state class A/B amp I once had, that actually had 4 fuses in it.  Two in each channel.  One fuse each on each leg of the power rails, positive and negative for each channel.  It had 12 amp fuses in these places.  When I was studying boutique fuses, I pulled the top off the case of this amp while it was operational and music was playing.. NO BS... I observed the fuse wire element of the glass cased fuses twitching/flexing to the beat of the music..!!!!  My audiofool pshyche simply could not accept this!!!!  So I bought some ceramic cased fuses, which are filled with silica, and thus the fuse wire is "damped" and should not be able to jump around - but you can't see into a ceramic fuse, so who knows - but it sure made me feel better and I was once again able to sleep at night.
Shortly after that I bought some boutique fuses... I thought they had a slight positive effect on the sonics of the amp.  If they really did or not - no one can say.  But since hearing is an "individual perception" and if you think you hear it - then you do - doesn't matter what anybody else thinks they hear, nor that nobody knows how to measure some characteristic of the sound.
That said... I have never even "thought" that I heard a boutique fuse make a difference in the sound of a component, if the fuse was simply in series with the IEC power cord socket, before the transformer or any other circuitry.  I don't even see, logically, how a fuse at the power cord input, before the power transformer possibly could have an effect on the sound.  I once heard the Zenmaster share this same opinion on boutique fuses.... And I tend to agree with him.  But there are those that would swear otherwise....  :)

I agree that it really makes no sense that a power cord or a power fuse would make a sonice difference at all.

But my own experience tells me they do. To varying degrees. And it may be that it is actually "the creating silence" part that seems to be the only real logical benefit. That and assisting current flow seem to be the obvious benefits. Tiny improvements in either may well be creating quite audible results in the final waves emanating from the speakers. Don't know. Just know I hear differences. Are they worth the cost? That is a totally different and more personal question.

Yes. Audio-acoustic psychology is an interesting phenomenon. I usually look to other things when folks don't hear what I hear in my system/room (and my wife easily corroborates without even knowing what I am changing). Though there are cases when I can hear little difference testing things, this is a rarity, so I tend to find the placebo effect lacking in real merit from my personal experience. So I often wonder what would cause one not to hear what is clear in my system. The following come to mind:

Obviously, to hear subtle changes (that in my system can be sort of bigtime in terms of fleshing out the realness of music from a recording) the system/room has to be tuned to be very accurate and revealing. If the balance is off, or the information not there, it will make some things inaudible. That musical accuracy, complete in every way, requires a highly revealing system/room has been proven here countless times. And that it can and does continue to get better from a given point of amazing beauty also proves that we can be missing musical revelation without knowing it.

In any system, an IC, speaker cable, power cord, vibration, one tube of many, room reflection and resonance issues...any part or group of parts in a system/room can throw the balance, masking or truncating fine detail and other important information that exists in the recording but the system/room can't reveal fully and musically..... And here, if everything is not tuned together as a whole to this end, I absolutely will not hear all the musical information in balance, eliminating to various degrees the possibilities of natural and complete presentation.

Since I am often playing with tubes, I consistently experience the very same tube cutting or enhancing fine musical information depending on the other tubes it is with. The same input tubes with a darker/bassier tube set can easily throw the whole into a less revealing, off-balance presentation. Or the same tube with a strategically more open tube set can contribute to great beauty and revelation. And none of my tubes are not considered...all working together in synergy critical to the complete sound. I use no stock tubes at the moment, each one of the 8 positions I have tubes in being better for my system/room in their own ways, and having logarithmic effects as a whole.

In my constant explorations, in fine tuning and synergistically "waking up" a system/room, all feet, fuses, ICs, tubes, power cords, regenerator settings, amp settings, shelves and on and on.....all these have sound effects that can help or hurt revealing all that the system is capable of.

And this is not to mention the main things. If the info is not revealed by the source, or the amp or speakers can't reveal it, it is just not there!

If we do hear dedicated circuits, receptacles, power cords, power filters or regenerators making differences, is it not a disconnect to conceptually believe a fuse can make a difference with every bit of the power the amp receives coming through it?

Another obvious issue in hearing the recording fully could be that one just does not have the physical ability to hear fully for various reasons. And not hearing as well can make it really hard to tune a system/room to be able to reveal musical information fully.

Equally, if we have not tuned/trained ourselves fully to discern all the information with differentiation and accuracy, the information is less perceptible, making fine tuning a system/room fully a real crap shoot. If we can't discern what is not revealed in a system, it is hard to find it.... especially with bias/belief against whatever it is.

And this leads back to psycho acoustic stuff....With the devotion that denial of what others can hear so strong for many (often without ever having tried this or that in a revealing system and room) I guess I have to admit that Audio psych is a potential issue...But logically, that it only goes only one way makes little sense.

Whatever the reasons, my experience is that it is way harder to get a system/room to work together to be revealing of full musical potential than not! And if not, something is missing, perhaps something that makes fuses less audible.

Interesting thoughts Archie.

I guess I think most people with the desire and OK ears can learn to "listen" while "hearing." And for most it takes practice to get deep, but even more, it takes confidence to refine our skills.

At the same time, as I pointed to above, if something is in the way of a complete presentation, you or I won't be able to hear things in one system/room that we will be able to hear is a more revealing system/room!

Before getting in a disabling car wreck, I made pots for 35 years and we taught workshops a couple times a year. I think what made us pretty good teachers was that we were so excited about pots ourselves, the students "caught" our need to explore beauty. Then the methods we taught were useful to the end of creative discovery rather than as a technical means to an end. Like we see in audio circles, we can chase technical stuff forever and never really get there unless we are really lucky! Technical knowledge alone is not enough for art making or experience!

Over time it became clear that the most important teaching was helping to empower folks to trust, follow and refine their own perceptions and preferences. Then as creative process unfolds, honing preferences naturally enlivens what we make while our perceptive abilities come along for the ride. Repeat it over and over, and before we know it, we are gifted and skilled at the expression, but also the experience of beauty.

I think audio exploration is the same. Every listen is a chance to refine perceptive abilities, thus refining the musical experience. Sometimes articulate, and sometimes broader impressions, the gorgeous complexity of musical experience unfolds. In this we are more open and able to exploring tools to make our system/room better. And once we figure out how to trust this creative path, each new perception or improvement creates a new beginning, a new place to explore further from.

Digging in, we notice more, aspects that sound amazing, or a little off in the tone, timbre, detail layers, balance......We look at what we might be able to do to shift the musical experience to a better baseline....a tube, a wire, speaker placement, traps/diffusion, power cleaners, etc....

We continue the creative process by checking out what trusted sources have found to work that might help what we notice as needing attention. We experiment, shifting things around, or we get a new tool to try. Then whether it works or not toward "fixing" what we thought was the problem, we learn. And if it was a good tool, we often add layers and dimension to the music, creating another new baseline.

I think this is a fun way to refine a system/room while naturally training our listening discernment, confidence in our abilities, and pleasure. With enough desire and trust in our perception and discernment to get in the path, refining as we get better at it is inevitable.

But back to the other part...If there is something trusted ears can hear in their systems, but can't be heard in ours via honest, unbiased effort, there is probably something in the way...something limiting the potential of our system and room.

Personally, I don't keep things that do not make sense in value versus improvement. But at the same time, the less impediments to the system/room revealing all that is there, the more we hear. Beyond any psychology or subjectivity, this makes the same tools worth it in one system, and not it in another. Though enhanced abilities to hear will help us define the most efficient path to musical refinement, the system being better at getting out the music makes us hear more!

Dang Will!!!! You are sooooo good at expressing all this stuff. I copied these last 2 posts of yours and sent them  friends. Absolutely brilliant. I'm humbled.

marcocolo said:  Dang Will!!!! You are sooooo good at expressing all this stuff. I copied these last 2 posts of yours and sent them  friends. Absolutely brilliant. I'm humbled.

I'm in total agreement. I relish all that will contributes to this board (and off the board privately).