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Thread: What Amp fuse do you have in the plugs of your kit ?

  1. #11
    Join Date: Jul 2016

    Location: West Wales

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    I'm Jonathan.

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    Am I right in understanding that the fuse is there to protect the cable against fire in the case of equipment faults, since UK rings have a larger current capability (depending on the circuit rating) than say EU star systems that may have lower ratings. If the cable is capable of high current as in most specialised cables, then it does not matter that the fuse is 13A. If however you have a dedicated lead for equipment that only generates a few watts, for example my TT PSU then the fuse should match the cable so in this case 3A.

  2. #12
    Join Date: Mar 2017

    Location: Seaford UK

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    I'm Dennis.

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    I have to congratulate you on bothering with all the AC theory calcs, I just could not bother even if I had the raw data because instinctually alone, it is apparent that the fuse is a relatively small factor.

  3. #13
    Join Date: Aug 2009

    Location: Staffordshire, England

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    I'm Martin.

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    Quote Originally Posted by bosa View Post
    Am I right in understanding that the fuse is there to protect the cable against fire in the case of equipment faults, since UK rings have a larger current capability (depending on the circuit rating) than say EU star systems that may have lower ratings. If the cable is capable of high current as in most specialised cables, then it does not matter that the fuse is 13A. If however you have a dedicated lead for equipment that only generates a few watts, for example my TT PSU then the fuse should match the cable so in this case 3A.
    Yes the plug fuse is there to stop the cable from catching fire in the event of a fault. It serves no other purpose except to - allegedly- ruin sound quality.
    Martin



    Current Lash Up:

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  4. #14
    Join Date: Feb 2013

    Location: W Lothian

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    I'm Grant.

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    Quote Originally Posted by Barry View Post
    Agreed, it's what I use.



    Also agree.

    Apropos the additional series impedance imposed by a 3A fuse, it is easily calculated.

    BS1362 cartridge fuses are 1" long, and for a 3A rated fuse contain a copper wire 0.15mm in diameter. The series resistance is thus 0.025 Ω.

    At 50Hz, the skin depth in copper is 9.33mm, so since the wire has a radius of 0.075mm, the current density in the wire is uniform over the cross section of the wire. The inductance is thus μ0/8π = 5.10-8 Hm-1, or 1.27nH. At 50Hz the inductive reactance will be 0.4μΩ.

    Thus the series impedance at 50Hz is 0.025 + j4.10-7Ω. This to be compared with the typical source impedance of the UK mains supply at the wall socket of 0.25 + j0.23 Ω (IEC 725:1981 assumes 0.4 + j0.25Ω, so the UK mains supply is a little better in this regard).

    Of course with current surges the effective frequency will momentarily be much higher, but even at 1000Hz, the series impedance of the fuse will still be small relative to the source impedance.

    Therefore the series impedance of a 3A BS1362 fuse is normally less than one tenth of the mains source impedance, and thus should have absolutely no audible consequences; though some might dispute that.
    took the words out of my mind Barry
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  5. #15
    Join Date: Oct 2012

    Location: NE England

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    I'm Jez.

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    Quote Originally Posted by Barry View Post
    Agreed, it's what I use.



    Also agree.

    Apropos the additional series impedance imposed by a 3A fuse, it is easily calculated.

    BS1362 cartridge fuses are 1" long, and for a 3A rated fuse contain a copper wire 0.15mm in diameter. The series resistance is thus 0.025 Ω.

    At 50Hz, the skin depth in copper is 9.33mm, so since the wire has a radius of 0.075mm, the current density in the wire is uniform over the cross section of the wire. The inductance is thus μ0/8π = 5.10-8 Hm-1, or 1.27nH. At 50Hz the inductive reactance will be 0.4μΩ.

    Thus the series impedance at 50Hz is 0.025 + j4.10-7Ω. This to be compared with the typical source impedance of the UK mains supply at the wall socket of 0.25 + j0.23 Ω (IEC 725:1981 assumes 0.4 + j0.25Ω, so the UK mains supply is a little better in this regard).

    Of course with current surges the effective frequency will momentarily be much higher, but even at 1000Hz, the series impedance of the fuse will still be small relative to the source impedance.

    Therefore the series impedance of a 3A BS1362 fuse is normally less than one tenth of the mains source impedance, and thus should have absolutely no audible consequences; though some might dispute that.
    Yep spot on.

    It needs saying that initial surge current for many items is so large that it makes a mockery of any attempt to specify "correct" fuse ratings. Toroidal transformers are the big culprit here and it is quite normal to need say a 10A fuse for something which draws only half an Amp continuously if the fuse is not to blow due to the switch on current drawn In the case of high power amplifiers using toroidal transformers (500W +), and which don't have soft start built in, I have known the switch on surge be enough to cause nuisance tripping of 20 and 32 A circuit breakers at the consumer unit!

  6. #16
    Join Date: Jan 2009

    Location: Essex

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    I'm openingabottleofwine.

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    Circuit breakers are much faster acting than fuses - typically acting within a couple of cycles.

    Fuses will pass their rated current indefinitely. At 10x that current, the fuse becomes weakened so will melt and break after a short time (seconds) . To 'blow', fuses need at least 100x the rated current.

    http://www.specialtycontrolsystems.c...ent_curves.php



    As an aside, are there audible differences to be heard between circuit breakers and fuses?
    Have you listened to this month's choice in the Album Club?

    Barry

  7. #17
    Join Date: Apr 2012

    Location: Southall, West London

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    I'm Geoff.

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    I thought the fuse was there to stop the plug melting
    Mr. Tact!

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  8. #18
    Join Date: Oct 2012

    Location: NE England

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    I'm Jez.

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    Quote Originally Posted by Barry View Post
    Circuit breakers are much faster acting than fuses - typically acting within a couple of cycles.

    Fuses will pass their rated current indefinitely. At 10x that current, the fuse becomes weakened so will melt and break after a short time (seconds) . To 'blow', fuses need at least 100x the rated current.

    http://www.specialtycontrolsystems.c...ent_curves.php



    As an aside, are there audible differences to be heard between circuit breakers and fuses?
    Indeed yes.

    As to the last sentence well obviously we need a 30 page thread to debate circuit breakers V fuses for sound quality.... What's the betting some tosser will start making "audio grade circuit breakers" next... sad thing is some would buy them!! Absolutely anything where the original can be simply unplugged/disconnected and the replacement is equally easy to fit seems game for exploitation....
    I should copyright it before Russ Andrews sees this

  9. #19
    Join Date: Mar 2008

    Location: Dunfermline, Scotland, UK

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    I'm inthescottishmafia.

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    They already make them Jez.
    There are times when you canít do the sensible thing, when you canít act like a responsible adult at all; you just have to do whatever insane thing comes into your head. When bad people do it they end up murderers, when good people do it they end up heroes, and when the rest of us do it we end up looking like total idiots. But whenís that ever stopped us?

  10. #20
    Join Date: Aug 2009

    Location: Staffordshire, England

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    I'm Martin.

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    Quote Originally Posted by Ali Tait View Post
    They already make them Jez.
    Give it up Jez. It's over. They won.
    Martin



    Current Lash Up:

    Sony X505ES CD Player * NVA P90SA passive pre / NVA A30 Power amp * JM Lab Electra 926 loudspeakers *



    "I hate to advocate drugs, alcohol, violence, or insanity to anyone, but they've always worked for me." - Hunter S Thompson

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