On **numerous** occasions earlier in this thread and in several other fuse-related threads I as well as several respected designers of highly regarded audio electronics have explained why the measurements reported in the HiFi Tuning paper are not supportive of claims that fuses are inherently directional. One of many such statements was this one by Roger Modjeski of Music Reference and RAM Tube Works, which I quoted in this thread on 10-28-2016:
Has anyone considered what portion of the total resistance the fuse contributes to the whole of the circuit in which it is inserted?
From the Tuning Fuse data sheet their 2 amp slow blow 5x20 fuse has a resistance of 24.077 milliohms in one direction and 24.115 in the other direction and 26.257 in the holder. If a butterfly flew by while the measurements were taking place we might see a bigger difference than the 0.038 milliohm difference in direction. Of course it might depend on which direction the butterfly was flying. But never mind, the direction measurements were made with DC and we are using these fuses in AC circuits. Perhaps if the butterfly flies clockwise vs counterclockwise there will be a difference.
Sorry I just had to put that in to keep up with all the humor that has been presented here.
[Note: 0.038 milliohms is 0.000038 ohms]
In another post in this thread, dated 10-7-2016, I said as follows:
Regarding the measurements described in the HFT paper ... which purport to support the notion of fuse directionality:
IMO those numbers are so miniscule as to be:
(a)Laughable.
(b)Very possibly attributable to changes in the voltage of the battery in the measurement meter, from measurement to measurement (each measurement imposing a slight drain on the battery), and from minute to minute. Or if the meter was AC powered, to the very slight differences in AC line voltage that may occur from minute to minute, as various loads are turned on and off at nearby locations.
(c)Very possibly attributable to differences in contact pressure and contact area between the meter’s probe tips and the contacts on the fuse. The paper presents separate measurements of fuse resistance as measured in a fuseholder (for just one direction), indicating that the direction-related measurements were performed by touching the meter leads directly to the contacts on the fuse.
(d)Perhaps even contributed to by differences in the resistance of the measurer’s body, that would have been paralleled with the resistance of the fuse if he or she had fingers on the probe tips and/or the fuse contacts while the measurements were being taken.
(e)If Geoff’s comments about all wires being significantly directional are to be believed, then these differences would be totally swamped by both the resistances and the alleged direction-related resistance differences of the vastly longer associated wiring. In the case of mains fuses, that would include the power transformer and the power wiring in the component, as well as the power cord and the AC wiring in and outside of the house.
All of which is NOT to say that the direction-related sonic differences which many have reported are the result of extraneous variables such as differences in equipment warmup state, or misperception, expectation bias, etc. I don’t doubt that many of the reports are accurate. But another distinguished designer, Ralph Karsten of Atma-Sphere, has explained why those differences would have occurred, and has indicated that he has verified his claims with experimental measurements. In a post in this thread dated 10-28-2016 I quoted the following comment he had made in a different fuse-related thread:
Ralph Karsten of Atma-Sphere:
… Fuses are inherently incapable of having directionality in any way whatsoever.
… I joined this thread recently with some results on testing. Those results are that the directionality appears out of coincidence and that actually greater improvement can be had by rotating the fuse in the holder for best contact…. Reversal is improving the contact area because fuse and holder are not dimensionally perfect and the fuse might sit better in the holder in one direction. By rotating the fuse in the holder without reversing it gets the same effect only more profoundly.
Yet despite all that, and despite similar comments about the HiFi Tuning measurements that have been provided in numerous other posts going all the way back to the "Fuses that Matter" thread that began in 2012, Geoff continues to assert that the HiFi Tuning measurements support the notion that fuses are inherently directional.
Regards,
-- Al