Give the Purple some time, I felt they didn’t “be all they can be” for 300 hours or so, and I was surprised when I reversed the direction of a few with subtler better sound. They are quite interesting pieces–I preferred them to Audio Magics, albeit not the Ultimate but the “Super” that I loved before.
But we are talking about AC. The current change direction 60 times/second, right?
It sure would be nice to see such noise measurements results, though.
In the case of my amps, Nagra not only uses stock fuses, but strongly advises against using any boutique ones. So I never had the nerves to go down that road.
When I used Audio Research, they also advised against swapping fuses. And in their ref160m there is one main fuse + one per tube (that sums up to 11 fuses per channel). I will see if I can recover a photo I took from the inside of the amp.
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I don’t think it is the noise but rather conductivity of
the fuse element…
All the fuses I have tried have yielded very nice desireable
improvements to sound quality for me.
Best wishes
PM sent.
But being in conductivity, this would be very much measureable, right? Just like Ted stated before.
And I cannot explain the manufacturers strong position against swapping fuses. I find it hard to believe in the cost argument alone, specially for the top tier gear: they all go about caps, wiring, exotic materials, special types of transistors. And sell for thousands (audio research sells for almost USD30k; Nagra sells for almost USD90k, same goes for dagostino, dartzeel, ch precision and so many others). Should there be a clear advantage in sound quality in using such kind of fuses, wouldnt that be an opportunity to differentiate from other amps?
The conductivity should be measureable…someone here might
be able to provide a comparison vs stock…
Amazing isn’t it? Even McIntosh doesn’t approve specialty fuses.
Sometime back I was interested in Mac C49 preamp…when I inquired about the fuse value and location…the reply was evasive and never answered my simple question…Imagine that…
Best wishes
Ah…so what do I know…ha ha 
Best wishes
However…SR’s use of graphene which is a very efficient
conductor…would suggest lowered resistance
Take a look from Bosch
Result: Macroscopic graphene is able to outperform copper in electrical conductivity
Our results show that there are two main parameters to obtain a high electrical conductivity for macroscopic graphene. It is crucial to have a high in-plane electrical conductivity in most of the graphene flakes. The value for the in-plane electrical conductivity determines the maximum possible conductivity. Of course, it is also necessary to reach a reasonable out-of-plane electrical conductivity. Nevertheless, the lateral size of graphene flakes compensates a lower out-of-plane conductivity to a certain extent due to the larger overlap area and the lower contact resistance as shown in the diagram below. The assumed in-plane conductivity used in the calculations of the diagram is 100 MS/m.
Diagram shows the dependencies between the lateral flake size, the out-of-plane conductivity and the total electrical conductivity.
Diagram shows the dependencies between the lateral flake size, the out-of-plane conductivity and the total electrical conductivity.
Appropriate tuning of these three major parameters will allow outperforming all metal-based conductors.
The experimental validation in the range of low electrical conductivity shows good agreement to the results from the simulation as seen in the diagram below. The lines represent the results of the simulation and the circles represent the experimental results.
Diagram shows experimental validation in the range of low electrical conductivity. The lines represent the results of the simulation and the circles represent the experimental results.
Diagram shows experimental validation in the range of low electrical conductivity. The lines represent the results of the simulation and the circles represent the experimental results. (Rizzi, L., Wijaya, A. F., Palanisamy, L. V., Schuster, J., Köhne, M., & Schulz, S. E. (2020). Quantifying the influence of graphene film nanostructure on the macroscopic electrical conductivity. Nano Express, 1(2), 020035, DOI:10.1088/2632-959x/abb37a)
Conclusion:
Given as appropriate doping enables an in-plane conductivity of 100 MS/m for the graphene flakes with a flake size in the tens of micrometers, the macroscopic graphene can reach an electrical conductivity of up to 80 MS/m. A graphene-based conductor with 80 MS/m in electrical conductivity allows enormous efficiency gains, weight as well as volume savings and enables new designs for the powertrain in e-mobility.
The whole article:
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And…according to this article graphene conductivity is
3000 times higher than copper.
https://onlinelibrary.wiley.com/doi/abs/10.1002/adfm.201806792
This their abstract: From 
Abstract
Highly efficient conductors are strongly desired because they can lead to higher working performance and less energy consumption in their wide range applications. However, the improvements on the electrical conductivities of conventional conductors are limited, such as purification and growing single crystal of metals. Here, by embedding graphene in metals (Cu, Al, and Ag), the trade-off between carrier mobility and carrier density is surmount in graphene, and realize high electron mobility and high electron density simultaneously through elaborate interface design and morphology control. As a result, a maximum electrical conductivity three orders of magnitude higher than the highest on record (more than 3,000 times higher than that of Cu) is obtained in such embedded graphene. As a result, using the graphene as reinforcement, an electrical conductivity as high as ≈117% of the International Annealed Copper Standard and significantly higher than that of Ag is achieved in bulk graphene/Cu composites with an extremely low graphene volume fraction of only 0.008%. The results are of significance when enhancing efficiency and saving energy in electrical and electronic applications of metals, and also of interest for fundamental researches on electron behaviors in graphene.
Happy reading
Best wishes
I had a friend do my transformer upgrade in DSD DAC and he was surprised at the quality of the fuse they put in the from the start. One of the reasons I respect PS Audio, they don’t cut corners.
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A lot of the top tier solid state amps don’t use fuses, they use a breaker and other forms of protection for the power rails.
But then it is another whole can of worms, aint it? What breaker to use? Standard, or “audio grade”? and so it goes.
@joe-appierto was so kind to share with me some fuse measurements done by hifi-tuning, one german fuse boutique.
They indeed measure differences in direction. But it is on the order of milliohm (see below).
HiFi-Tuning US-Ultimate3 (Silver Star) 44,47 - Direction 1(mOhms) 44,57 - Direction 2(mOhms)
HiFi-Tuning US-Gold2 45,02 -Direction 1(mOhms) 45,14 - Direction 2(mOhms)
Iso Clean 155,8 - Direction 1(mOhms) 155,9 - Direction 2(mOhms)
They also measure differences in noise. But the differences between fuses are less than 1dB.
HiFi-Tuning US-Gold2 Cryo 1,6 dB
Standard Ceramic 1,9 dB
Iso Clean 1,1 dB
They also measured the voltage drop. It is on millivolt range
HiFi-Tuning Ultimate2 Cryo 28,180mV
AMR 29,452mV
HiFi-Tuning Ultimate3 Cryo 29,730mV
Iso Clean 34,697mV
Solder Fuse 44,083mV
SinnOxx Germany 54,971mV
AHP 68,461mV
Super Cryo (LF) 99,635mV
And then they reach the following conclusion (and I am quoting their own text). It seems to me pretty straightforward and honest ones:
- better conductivity results in audible benefits for DC applications - “For DC applications it ́s recommended to use the solder type fuse or the cryogenically treated fuses from HiFi-Tuning Germany. The drop in resistance up to the factor of 8 is clearly measurable and also could be detected in listening test.”
- for AC application, better conductivity is negligible - “In that case a power of 0,113 VA is dissipated in the worst case (glass tubed fuse with spiral shaped melting wire) or of 0.060 VA (cryogenically treated fuse by HiFi-Tuning) by the fuse. This power loss of a maximum of 0,25% is very small in comparison to typical variations in line voltage of average 3%.”
- fuses that are in line with the music signal are more critical than those that are in line with the power supply, due to different resistance accross the frequency range - “So all components direct or indirect
in the signal pass, should be able to handle that pulses. Fuses with a rising AC-Resistance
will limit that pulses to some degree.”
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Being my pedantic self, that’s not what I recommended, or at least the numbers given aren’t the measurements I was suggesting. I suggested that there be two voltage measurements at two different currents and then compare the differences in ohmage to see how non-linear they are over the normal operating range. The hypothesis is that more non-linearity is bad.
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Depending on type, manufacturer and intended use, fuses can vary in resistance. The question I always ask, is the fuse UL or CSA certified and approved? If not, it won’t be used in my equipment. Aftermarket “audio” fuse companies hope you don’t ask them that question…
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Thanks for the clarification. I am sorry I misunderstood your recommendation (and I will edit my post). And I did not see this test on their papers.
A point I’d like to make that could be considered anecdotal.
I’ve used aftermarket fuses in two different types of applications. In one the electrical draw was miniscule: the IEC connection fuse on QUAD 989 speakers that probably consumed about 5 watts. The other were the plate fuses for a 140 wpc tubed amplifier and a 185 wpc solid state integrated on the B+/B- rails and the IEC connection.
They were and have been used for years without any damage resulting to the equipment. My experience has been that, if anything, aftermarket fuses are built to tighter tolerances than the stock OEM fuses that come standard. In other words, if there’s an anomalous situation the aftermarket fuse will blow while the OEM fuse doesn’t. The more cynical might conjecture this tighter tolerance is intentional in that a fuse blown is a fuse that needs to be replaced and therefore another sale. My perhaps naive thinking is that the aftermarket fuses are better built and protect the equipment to a greater degree than the stock fuses.
@joe-appierto Speaker fuses and those used to protect equipment that is FCC Part 15 consumer devices fall under very different umbrellas. Your claim of “tighter tolerances” is only your conjecture. If you have a fire and the fire inspector finds a non-UL approved device for protection and that device was determined in part at fault, they can and more than likely will deny your claim. (and they will look) Just sayin’
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Point taken.
Insurance companies exist for two reasons - to collect money and deny claims. Well, three if you count making commercials.
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In a consumer context, carriers typically pay the claim and then subrogate.