What is the science behind audiophile fuses?

Is it too early to bring up double-blind testing?

Cans have been opened, worms are out, let the games begin…

@noromance 

Visiting Chuck Miller's Millercarbon room at PAF gave me the opportunity to check in on Townshend Audio, a quirky British manufacturer of audio gear best known for its well-engineered and very effective isolation products.

Not entirely clear whether MC had a room with his personal kit that happens to use Townshend products, or whether his was actually a room representing Townshend. 
It seems Townshend would want to have a say in the gear used to display their products since the resulting SQ would represent the brand - maybe they did?

BTW, back to fuses, I have done the Teflon tape thing, and also used small orthodontic rubber bands across the tops of the fuse holder tynes to insure a secure connection, after first treating the end caps with a conductive material (i.e., ProGold, etc.).

Doesn’t the power supply include capacitors that store electrical power used by the device, including the capability to supply power for peak demands?  Shouldn’t the power supply be designed so that the current draw through the fuse should never exceed the rated value under normal use?  Otherwise, it would seem the power supply is under designed.  I believe some may be putting too much emphasis on the role of the fuse in the power supply chain.  Obviously, it is essential but, as long as it works properly, perhaps not a direct influence on the sonic end result?

@curiousjim

Ok, here goes:

How can a fuse have an audible influence on the signal, when the signal does not even pass through it?

I don’t believe that a fuse does have an audible influence on an audio signal, for the reasons presented in my previous post, among others.

How can a fuse be "directional" when it deals with alternate current?

I don’t believe that an input fuse subject to alternating current would display any different properties or sonic signature regardless of which way it is oriented. While electric current flows from higher electric potential to lower electric potential, in the case of alternating current, the flow of electrons is bidirectional, i.e. electrons flow in both forward and backward direction.

In case of direct current, flow of electrons takes place in only the forward direction so the flow of electrons is unidirectional. Therefore, if there were directional differences in fuses, they would likely only show up when used in a direct current application, IMO.

@reimarc also asked about our experiences. Although I hear differences in a variety of different equipment, all speakers, and, to a lesser extent, cables, I have yet to hear what I consider a meaningful sonic difference between fuses after trying many including SR, Furutech, ACME, several from HiFi Tuning, and others.

Also, I have yet to read a comprehensive explanation of how a power line fuse should change the sound of an audio component given that regardless of the materials used, it’s job is to pass current up to a given amperage to a power supply consisting of a variety of other parts. I have also never read about any listening tests where the listener reliably identified different fuses without knowing which they were listening to.

Finally, you asked for opinions and I gave you mine. My system is posted (but not quite up-to-date) so you can see the gear I am using to develop my opinions. I do not care what others here believe or how they spend their money, so for those here like @rodman99999 who want to turn this into a contest or dispute of one side against another, I simply don’t care.

"And even that is necked down just at one end."

Maybe from the heat of the solder used to connect that end of the wire to the end cap?  The other end was probably connected prior to installing the heat shrink tubing.

Don't know what prompted the resurgence of this old thread, but it got me thinking about power, fuses, and AC connectors, and especially the comments by @carlsbad2 about getting rid of fuses and using slugs.

What if I installed a suitably sized in-wall magnetic breaker in the same box as the dedicated duplex feeding my monoblock amplifiers, shouldn't I then be safe removing the fuses from the amplifiers, replacing them with slugs, and relying on the magnetic breaker as if it were a fuse?   I think I will look into the viability of that option since it would be a relatively inexpensive approach to remove the constraint of fuses from those amplifiers, and doesn't seem much different from using the Swiss Digital Fuse Box.  The only issue I see is that I would probably need a breaker for each of the monoblocks. Have any of you done something similar?

@thecarpathian - No worries at all, it is a legitimate question. Aside from code issues, one reason is that a line from the panel is in most cases powering multiple components/devices all of which are probably rated for less than the 20 or 15 amps that trip the breaker, where the magnetic switch/breaker would be rated for the individual piece of equipment.

What I didn’t say is that my amps do not have on/off switches so I actually operate as you suggest, when I want to power down the amps, I walk over two rooms to the panel and throw the breaker or, I can simply unplug them. They probably get powered down about once/month, on average for storms, vacation, etc. They do however have 8 amp (I believe) fuses.

The reasons to consider a magnetic switch/breaker instead of a fuse are reliability, longevity, and supposedly improved sound quality. In the case of my amps, I would need a triple box with spots for two separate magnetic switches, one for each amp, and the duplex that I plug them into. Of course, I would need to split the dedicated 20A line in and then each of the two outlets in the duplex would have to be fed separately from one of the magnetic switches so the amps could individually trip their dedicated switch.

BTW, SMc audio has started using magnetic switches instead of fuses, and they did so on the DAC-2 I received from them last year.

"What is the science behind audiophile fuses?"

Going back over this entire year and a half old thread, I cannot find where the OP’s original question has been answered.

Since, I do not plan on going sluggo commando, or paying hundreds of dollars for colored fuses, it seems I either live with the normal ceramic fuses I currently have in my equipment, add some Swiss Digital Fuse Boxes, or figure out how to install magnetic breakers.

Assuming the SDFB performs as well as described by @carlsbad2, it doesn’t seem too bad a deal, at least in the audiophile world. One for each monoblock would be $800 for two, which is about par for the course for audiophile tweaks. However, I can’t help but think they may be nothing more than self-resetting magnetic breakers, which is not surprising since many audiophile tweaks seem to be relatively normal stuff dressed up. This magnetic breaker appears similar to what SMc Audio put in my DAC-2. Maybe I will try making my own electrical box with a magnetic breaker and a captive short power cord pigtail.

@carlsbad2

"So SDFB, designed and built one and did a very nice job."

In our world, $400 for "a very nice job" on something that is actually useful should probably be considered a bargain.

Even if I find the right breaker, finding/buying a suitable box and putting it all together would take hours and even more money. In the end, it still would not have the self-resetting capability of the SDFB. I will probably break down and buy a couple of them for my monoblocks. I would like to consider removing the IEC from one end and hard-wiring a decent power cord pigtail, if that is possible.

@carlsbad2 - Have you experimented with whether different fuse replacement slugs make a sonic difference? I ask because I have a solution coming that will allow me to replace the 10A fuses in my monoblocks, so I was looking at options to replace the fuses. I have a hard time believing the $200-300 Graphene Sluggo offered by Underwood should make any difference at all compared to copper. In fact, I have 6.5 mm (~1/4 inch) OD copper tubing with 0.5 wall thickness here and I suspect that would work just fine. The resulting area would be equivalent to greater than 5 awg, which is far larger than the connecting AC wires inside of the amp. Any experience?

When my amps were finished in 2020, SMc Audio had begun doing away with power switches (mine have none) but it wasn’t until a year or two later that they found magnetic breakers that they were comfortable with using to replace fuses.  Apparently they ruled out more than a few manufacturers/models that didn’t sound so good, until they found one they liked.  The magnetic switches they use, like in my SMc DAC-2, serve three roles:

1. Over-current protection for the equipment
2. On/off switch (although less conveniently located on the back)
3. Delay to resist blowing due to in-rush current upon power-up

Their source is proprietary but I am going to receive two of them (10A) that I plan to use for a solution external to the amp chassis, but that will not require an extra power cord like the SDFB.

@devinplombier 

I for one am curious to find out how his experiment turns out

I will be happy to share how my installation of the breakers turns out, but I probably wouldn't categorize this as an "experiment" since SMc Audio are currently and successfully using these breakers in the amplifiers they construct and also in the amps that they upgrade.  In fact, I have the same type of breaker (in a lower 1A rating) in my SMc DAC-2, that I received from them last year.  Pics posted on my system page.

The only difference with the install for my amplifiers is that we decided it would be a cleaner and equally beneficial application for me to use the breakers outside of the amplifiers while replacing the fuses with slugs.  Even though I am fairly comfortable self-performing such things, installing the breaker internally is much better accomplished as part of a new amp build, or an upgrade (a process that involves SMc removing all the inside components anyway) than as a customer-installed retrofit.  After discussing what was involved with SMc, I decided not to fiddle around inside of the amp and especially if I can achieve pretty much the same result with an outside installation mounted in a box adjacent to my wall duplex. 

I will share here in advance that, unfortunately, the breakers used are proprietary as SMc Audio spent quite a bit of time figuring out which breakers worked well and sounded best with their equipment.  Therefore, I will not be sharing the manufacturer or model, although it is a 10A magnetic breaker.  I suspect a similar type of breaker is used inside of the SDFB, and it is probably not that much different from breakers that other manufacturers may use currently.  I remember my first experience with a breaker on/off switch was the thermal circuit breaker in the BPT 2.5 power conditioner I formerly owned.

Thanks @tksteingraber - the SDFB looks well made with heavy wire where necessary (except to the LED).  It appears to be a breaker with a small control board, likely for the automatic reset.

If I were to use one, I might hard wire a pig tail power cord to get rid of one IEC, but I make PCs so one more short cord is really no problem. 

If you have a dedicated line to your amp, and your amp has say 6.3 amp fast blow fuses in it, would putting a low current 6 amp breaker in your panel do the same thing?

Panel mount: The issue is that a magnetic breaker replacing a fuse needs to be dedicated to a single the component, just like a fuse protects the component. OTOH, the breakers in your panel protect the line - i.e., a 20A breaker breaks when current on the line exceeds 20A at which point a single component might already be fried.

Fuse holder mount: The magnetic breaker is quite a bit larger than a fuse holder. If you are asking about retrofitting existing equipment the easiest method would be to use something like the SDFB. In looking at retrofitting my SMc amps, it would have required cutting a hole in the back plate of the metal case and then rewiring the fuse holder and IEC, all of which I was comfortable doing myself. The problem was having to move the main board and disconnect several parts to make room to perform the work and at that point it became easier, less invasive, and less risky to incorporate a solution that was exterior to the amp. SMc uses the breaker to replace a fuse in their new equipment, and in their upgrade work. However, the breaker requires a larger hole in the case than a fuse holder. The breaker can also take the place of an on/off switch as it does in my SMc DAC-2.

Exterior box mount: I believe the easiest DIY opportunities for existing equipment are either a separate external box (like SDFB) or perhaps mounting the magnetic breaker in a gang box or separate small breaker box wired directly to the power line feeding the duplex where the equipment is connected, which is what I plan to do. The key is providing one breaker for each piece of gear so every outlet would need to have its own breaker. My two amps are fed from a single dedicated 30A line and each have a 10A fuse. I plan to mount the two 10A breakers just in front of the duplex, with each breaker feeding one of the two outlets in the duplex. Each outlet will have its own dedicated breaker. The outlets in my Furutech duplex will need to be separated from each other by cutting the tabs on the outlet and then each outlet will need to be individually wired. The breakers are basically an in-line switch wired on the hot side.

I wonder if this ABC-30-R fuse would be just as effective as a slug operationally and sonically?  This ceramic case fuse is 3x the capacity of the big 10A fuses in my amps and I suspect would be no more restrictive than the wiring connected to the IEC inside of the amp.

I would have used the 30A fuse in conjunction with the 10A magnetic breakers I just received and am working on installing.  Instead, I ordered 1/4 inch solid copper rod today, that I will cut in 7/8 inch lengths to replace my fuses for when I get the breakers installed.

@carlsbad2 - I can’t for two reasons.

First, the manufacturer and model are being held close to the vest by SMc. They apparently tried more than a few before finding the one they believed sounded best with their equipment.

Second, in addition to their request for confidentiality, there are no manufacturer’s markings of any kind on the two breakers they sent to me. There is a T10A sticker that appears to be something the SMc folks use to label their stock and a "QC passed" sticker and that is it.

What I can show you is that the breakers look very similar to this, but they were much more expensive to me than the Amazon price indicated in the link. I had to give the installation some thought before deciding how to configure them, and I am now very close to doing the work (hopefully this weekend).

I hear you on trying to figure out what works. I am wiring them to the hot wire of the incoming 20A line with the two separate load side wires going one to each half of a duplex, that I will separate by cutting the tab between the two hot sides. The neutral and ground should be fine as-is since this is basically the same as wiring a switch.

If I decide to do something for the remainder of my gear, I will likely try the SDFB, and especially if I end up going the Grimm MU2 route since that will take the place of three different components for me and only require one SDFB. However, I am struggling to get around Grimm’s omission of a remote volume control and the inability of at least one reviewer to read the numerical volume level from their listening chair. I am far from lazy but not making it easy to change volume and read it while seated seems a huge oversight on an $18K component that is expected to serve as a preamp, unless there is an easy app intended for that purpose. I need to dig deeper.

@devinplombier - Thanks.  I believe the Grimm MU2 offers a jack for an IR sensor but not the actual sensor.  It just seems like a clunky solution for an $18K piece of electronics, in this era.  I will have to check out the Roon app volume control as I have never used it.  Still wish there was a regular remote control.  I wouldn't need one if it were just a streamer/DAC but since there is a preamp, it seems like a stupid omission.

@carlsbad2 - I finally finished installing the two magnetic breakers/switches that SMc Audio sent me to replace the fuses in my SMc amplifiers.  Each switch powers one of the two outlets on the duplex that the monoblocks are plugged into.  See pics right after the first picture on my system page.

Had I known how much work that was going to be, I might have simply purchased two SDFBs.  My 1/4-inch copper rod arrived yesterday so just in time to make two slugs to replace the fancy SR fuses that SMc Audio had in those amps - 2@ T10A.  I am giving it a run in right now and it sounds pretty good, but it did before too.  Certainly didn't make anything sound worse.