Although like several of the others I have nothing constructive to say in response to the specific question that was asked, I can't help but question the wisdom of spending what figures to be $1000 to $2000, or possibly even more, on fuse upgrades for a 7-channel amplifier that sold for $2500 to $3000 ten years ago.
Many of those who have extolled the virtues of the fuse upgrades that have been discussed in the other recent threads have expressed the opinion that the higher the resolution and the quality of the components that are involved, the greater the benefits fuse upgrades are likely to provide.
My suggestion is that you initially just replace the mains fuse, which of course you can easily try in both directions, and assess that result before embarking on anything more ambitious (and expensive) internal to the unit.
Regards,
-- Al
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JazzontheHudson, while you're probably already aware of this you can download a pdf of the service manual for the M25 via the following link, if you first complete a simple registration process at hifiengine.com: http://www.hifiengine.com/manual_library/nad/m25.shtmlIn addition to the schematic you mentioned having, the manual includes printed circuit board layout diagrams and other information that might be helpful. Thanks very much, btw, to you and Charles for the nice words. Good luck as you proceed. Best regards, -- Al |
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Jazzonthehudson 4-29-2016
Al, have I fallen for a SR marketing trick? Their website states
repetitively "... By applying a two million volt signal to a cable at a
specific pulse modulation, and ultra high frequency for an exact
duration of time, we transform the entire cable at a molecular level
through a process we call Quantum Tunneling...."
Well, it seems safe to say that he is using the terminology in, um, a creative manner.
FYI I was part of the AP/MTT chapter and worked for a large telecom
equipment manufacturer so no high voltage experience. I did had fun with
Microwave oven trafo powered arcing in labs though...
Cool! To clarify for others, AP/MTT refers to an IEEE Chapter on Antennas & Propagation/Microwave Theory & Techniques. I was never active in any IEEE Chapters; never had the time. Best regards, -- Al |
Infection 5-12-2016
Geoff, the statement I quoted is from almarg.
Although you omitted the first part of my sentence that you quoted. The full sentence (see my post dated 4-28-2016 on page 1 of this thread) was: Many of those who have extolled the virtues of the fuse upgrades that have been discussed in the other recent threads have expressed the opinion that the higher the resolution and the quality of the components that are involved, the greater the benefits fuse upgrades are likely to provide.
So I was citing the opinions of others, who are experienced with fuse upgrades, which I am not. Also, I have pointed out in many prior threads on various topics that the sonic quality of a system, and its ability to resolve musical detail, do not necessarily go hand in hand with the ability of the system to resolve hardware differences, contrary to what many audiophiles seem to believe. Just to mention one example among countless others that could be cited, lower speaker impedance will tend to make a speaker more resolving of amplifier differences and speaker cable differences, while not necessarily resulting in the speaker being an intrinsically better sonic performer than one having higher impedance. In this particular case, however, and despite the additional fact that I have often emphasized the considerably less than perfect correlation between price and performance in audio, I did feel that there was a substantial chance that the cited opinions could be applicable. As what was being considered was a relatively expensive upgrade of 19 fuses in an amplifier providing **seven** channels of fairly high powered amplification, but which cost just $2500 to $3000 ten years ago. I hope that clarifies the thinking behind my comment that you quoted. Regards, -- Al |
Sounds right to me, Ralph (Atmasphere). I’ve made similar points in some of the other fuse-related threads. I’ve also suggested at times that before reaching conclusions about the matter that people reverse and re-reverse the direction of the fuse a couple of times or more, to verify that their findings are repeatable. While also assuring that the equipment is in equal states of warmup as the comparisons are made.
Not sure if anyone here has been that thorough, but it seems to me that the less likely and the less explainable a perceived effect would seem to be, the greater the degree of thoroughness that is called for before reaching a conclusion as to its cause.
One additional point that occurs to me, though, is that if the AC voltage at a particular location is significantly on the high side, and therefore presumably higher than the voltage that was assumed and used in the design and test of a component, minimum voltage drop across the fuse holder could conceivably degrade the sound to a slight degree, rather than enhancing it. Depending on the specific design, of course.
Best regards,
-- Al
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Are you suggesting that you have done the experiment with the same "thoroughness" you demand of others?
No, Geoff, I’m not. I didn’t say that, and I didn’t mean that. As you probably realize I haven’t done the experiment at all. But if I did choose to do it, I would do it with the thoroughness I described. Regards, -- Al |
Would the imprint on the side of the cap diminish the contact area enough to degrade the sound and could it be that by rotating or reversing the fuse has the potential to align things in the most desirable manner? Hi Nonoise, I suspect that the significance, if any, of the positioning of the imprint on the sonics of a component could only be determined experimentally. And I would expect that significance, if any, to certainly vary widely among components that perform different functions and that are different specific designs. Just as different designs will vary in their sensitivity to the much larger differences in line voltage that occur from location to location, and in many cases from time to time at a given location. The presence or absence of internal voltage regulation (most power amp designs have unregulated power supplies, in contrast to most line-level components), and the efficacy of that regulation if present, being just one of a great many design-related factors contributing to that variation. Also, would this be akin to the "eddy effect" that connectors encounter? What I am envisioning, and what I believe Ralph was referring to, are simply differences in the very small amounts of resistance that may exist between a fuse and the contacts on its holder. Not sure that eddy currents have relevance in this context. Best regards, -- Al |
I would think that it is not necessary to start modifying hardware and perhaps invalidating warranties in the process of getting to the bottom of the fuse directionality issue. IMO the methodology I suggested earlier should suffice, if done in an honest and careful manner.
Furthermore, if you are suggesting soldering wires directly to fuses in lieu of using holders I would wonder if the heat that is applied to the two ends of the fuses during the soldering process might change their characteristics sufficiently to invalidate the results, and/or might shorten the lifespan of these often expensive fuses.
Finally, my suspicion is that underlying your response to my suggestion is the goal of attacking my advocacy of thoroughness in the investigation of the causes of seemingly implausible and/or unexplainable tweaks by suggesting that the rationale underlying my proposed methodology suggests going to extremes, extremes that I however would consider unnecessary. It comes down to a matter of judgment, judgment that is hopefully as informed as possible, and as I say I would draw the line at what I originally suggested. I’m sure, though, that YMWV ("Your Mileage Will Vary").
I have nothing further to say on the subject.
Regards,
-- Al
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Atmasphere 5-26-2016 12:31pm EDT
... 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. The improvement is measurable and audible;
descriptions others have made on this thread of what happens when you
get the direction right accurately describe what happens when the
contact area is maximized.
Occam’s Razor has something to say
here! Given that a fuse has to be used in AC circuits and given that
people report differences by reversing the fuse, and also understanding
how fuses are inherently incapable of having directionality in any way
whatsoever, the explanation that they somehow have an effect by
reversing them in the holder is a fairly complex explanation: some sort
of unknowable, unmeasurable quality of the fuse itself.
A simpler explanation is that the 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.
Thank you, Ralph. I for one cannot envision a more persuasive case being provided on either side of the issue. And thanks also for the compliments you extended in my direction in some of your other recent posts. Best regards, -- Al |
Gs5556, well said IMO. I've had occasion to make similar comments about those measurements in a number of other fuse-related threads, such as in a post dated 4-8-2016 in this thread. An excerpt:
Regarding the measurements described in the HFT paper ... which purport to support
the notion of fuse directionality:
1)Resistance measurements
related to directionality were provided for 16 different HFT fuses,
having current ratings ranging from 1.6 amps to 20 amps, as well as for a
few competitive fuses and standard glass and ceramic fuses (the
specific make of the "standard" fuses being unspecified). The
differences in resistance for the HFT fuses in the two directions ranged
from 0.000002 ohms to 0.000120 ohms. The differences in resistance for
the competitive fuses were a bit greater in some cases, with the worst
cases generally being the standard fuses, for which there was one
isolated case having a measured difference of 0.005200 ohms.
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.
Best regards, -- Al |
Atmasphere 5-27-2016 12:57 pm EDT
I was not at any time suggesting that the holder was directional.
Yes, that was very clear in your post, Ralph. It was also clear to me that Geoff's response represented a complete misreading of what you said. Jea48 5-27-2016 9:17 am EDT
Your explanation makes more sense, at least to me, that the
directionality of the fuse has to do with a VD, voltage drop, across the
fuse element itself. That assumes the VD across the fuse would be measured in
millivolts.
Jim, I believe that you inadvertently omitted the word "than" in the first line quoted above, and that you were intending to say:
Your explanation makes more sense, at least to me, THAN that the
directionality of the fuse has to do with a VD, voltage drop, across the
fuse element itself. That assumes the VD across the fuse would be measured in
millivolts.
I wouldn't normally point out a seemingly minor omission like that, but with that word not included it took me a while to interpret your comment (with which I of course agree). Best regards, -- Al |
Great post and great insights, Ralph. Thanks!
Best regards,
-- Al
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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 |
Some PC w/o shrink sleeves on plugs/IEC and thin threads like NordOst Valhalla can be tested, simply swap the ends. I may try that on my remaining Valhallas. Although if that is done and a difference is heard, it by no means proves that directionality of the wires is responsible. For example, the act of simply removing and reattaching the connectors would seem to me to have a greater chance of being responsible. Assuming, of course, that care has been taken to eliminate other possible extraneous variables, such as differences in warmup state (many here have asserted that days of warmup may be required for some solid state equipment to achieve optimum performance), or the re-initialization that occurs in some designs (especially those which include digital circuitry) when power is removed and re-applied, or even (as some members here have asserted in other threads) the act of physically manipulating the cord, allegedly necessitating significant time for it to "settle." Best regards, -- Al |
