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Thread: Hi fi fuse ? Tweek !

  1. #11
    Join Date: Jun 2017

    Location: Co Antrim,Northern Ireland

    Posts: 115
    I'm Norman.

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    Just to bring post back on track, what I was actually doing back in the 80's was removing an unnecessary extra layer for the electrons to be conducted through

    Norman
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  2. #12
    Join Date: Oct 2011

    Location: Bacup

    Posts: 502
    I'm Andrew.

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    Here is a question for the physicists on the board. If you have a ‘noisy’ mains supply as many have complained about. Would a polished fuse allow the ‘noise’ through more effectively?

  3. #13
    Join Date: Jan 2009

    Location: Essex

    Posts: 31,846
    I'm openingabottleofwine.

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    Quote Originally Posted by RMutt View Post
    Here is a question for the physicists on the board. If you have a ‘noisy’ mains supply as many have complained about. Would a polished fuse allow the ‘noise’ through more effectively?
    No, it would make no difference.
    Barry

  4. #14
    Join Date: Oct 2011

    Location: Bacup

    Posts: 502
    I'm Andrew.

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    Thanks Barry.

  5. #15
    Join Date: Mar 2017

    Location: Seaford UK

    Posts: 1,861
    I'm Dennis.

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    IMO Grant is spot on, a fuse of the lowest value which works and does not blow on surges, best protects everything.
    It will have a higher resistance, but I challenge anyone to even measure it, and it will be very small in comparison with all the other resistances in the cct, even though it may be much thinner than the cables or transformer wire.

    Polishing is sensible, but not to remove any protective plating, just the oxide and dirt.

    In the 70s my Nelson Jones power amp was fed from a Quad 33 pre, and I used Belling-Lee coax (aerial) plugs and sockets to connect the two. One day I polished all the interfering surfaces, and the sound improved quite considerably, and my friend, then an ITN engineer laughed that such a thing needed to be done to get better sound.

    Of course since that time a whole can of worms about all this has been opened.

    FWIW the BBC used to use 'nose grease' on fader studs to reduce 'wiping noise', and I do the same with mains fuses, it is acidic, I believe like the battery grease used on car battery terminals. (From the side of one's nose).

  6. #16
    Join Date: Jun 2017

    Location: Co Antrim,Northern Ireland

    Posts: 115
    I'm Norman.

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    Agreed that the resistance is of little consequence but the "protective" plating deteriorates as it's not gold in this case, common fuse, and also introduces an extra layer which removing will not so much improve the sound as remove another source of "interference". Back when I first did this I was able to discern an improvement maybe not so much today, I'm 65 and been exposed to noisy work environments.
    Now that I think about it when Chris substituted same rating exotic fuses his sound deteriorated, as gold /silver fuse wire is more conductive it occurs to me it would probably be thinner gauge having an effect.
    Did I mention that the plugs didn't have partially insulated prongs and also sounded better than the ones we use today ��

  7. #17
    Join Date: May 2018

    Location: Woking

    Posts: 803
    I'm Chris.

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    Grant - usually spot on to be fair!

    I'm working on condensing my replies into simple concise answers like the aforementioned mod. I do tend to ramble around the point a bit . . .

    Doing a bit more research its interesting to see the construction of slow vs quick blow fuses. Slow blow tend to look slightly thicker gauge or at least have more material and a "wound" construction. Presumably requiring a longer exposure to the given current to blow.

    Considering all points made I'm just going to try ceramic fuses in place of glass ones with all identical values where required. Not expecting much change but worth finding out for less than a fiver.

    Back to the thread (apologies for deviation Norman!) - I reckon any electrical contact surface be it plug, cable, pin connection, fuse holder etc will benefit from a de-oxit and (gentle) polishing treatment every once in a while.

    Just add up the amount of those in your system though, would be a real PITA . . .

  8. #18
    Join Date: Jun 2017

    Location: Co Antrim,Northern Ireland

    Posts: 115
    I'm Norman.

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    There is no such thing as 'Too Much Information' so need for apologies, its all relevant. Looking forward to results of your trial plus observations of everyone that is willing to polish standard fuses and post their results. Glass fuses are possibly more affected by vibration than ceramics

  9. #19
    Join Date: Mar 2017

    Location: Seaford UK

    Posts: 1,861
    I'm Dennis.

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    The benefits of the 'protective layer' are questionable; +'s and -'s, and I doubt that so much scrutiny has ever been dedicated to them in design - until we audiophiles started to question them, and became rich pickings for foo salesmen.

    Yes the "Too much information" and IMO the "Over analysing" are both mythical; both produce more and probably useful information which may be excessive at any given moment, but could be useful in the future.

    However time may be important in a situation, for eg., the Hudson river air crash, where it was stated that to go through the manual to determine the correct sequence in a protocol would have taken more time than was available before crashing. Similarly, whilst potentially useful in the future, info can be irrelevant to and hence impede immediacy of needed actions.

  10. #20
    Join Date: Jan 2009

    Location: Essex

    Posts: 31,846
    I'm openingabottleofwine.

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    In general for a mechanical connection, such as a fuse in a fuse carrier, the effective contact surface area through which the current passes, is about 15% of the actual physical area. This is because the two surfaces are never completely smooth, so current only flows via the surface asperities of the two metals. Mechanical polishing will do little to reduce the already low surface roughness and even this small effect will only be of benefit if both contacting surfaces are polished. Increased contact pressure will help to 'crush' the asperities, though to have any real effect the contact pressure needs to be very high: far higher than that achieved in a simple fuse clip.

    It is more likely that 'polishing' the end caps of a fuse removes any tarnish due to atmospheric reaction as well as organic monolayer oils (such as finger grease).

    Regarding the resistance of a BS1362 fuse, the specification is that the fuse itself (regardless of rating) must dissipate no more than 1 Watt. In practice the resistance is very low, and the reactive inductance negligible. For example a 3A rated fuse consists of a 0.15mm diameter copper wire 25.4mm long. Its resistance is thus 0.025 Ohm.

    At 50Hz the skin depth in copper is 9.33mm, so since this is very much larger than the wire radius, the current surface density through the wire is constant. The inductance per unit length is thus the (permeability of free space)/(8 * pi) = 5. 10-8 H/m, so an overall inductance of 1.27 10-9H creating an inductive reactance at 50Hz of 0.4 micro Ohm.

    Thus the impedance at 50Hz of a 3A rated BS1362 fuse is 0.025 + j 4 .10-7 Ohm. Comparing this with the typical mains source impedance in the UK (as measured at a wall socket) of 0.25 + j 0.23 Ohm, the additional series impedance of the fuse is negligible.

    The above calculations have been done assuming the conductor is at room temperature. Of course, in use the wire in the fuse will heat up so the resistance will increase, but even so the resistance will still be negligible compared with the mains supply source impedance.
    Last edited by Barry; 22-06-2019 at 12:47. Reason: Clarification and addition
    Barry

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