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  1. #1
    kriskig's Avatar
    kriskig is offline Junior Member



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    fuse on power connestion

    I have an amplifier JBL LC-A 504 (RMS 4 x 50 W, in 4 ohms).
    The amplifier has 2 fuses (2 x 20 A), so my problem is, the power
    cable I got has a fuse holder but I dont know what fuse to use
    (20 A or 40 A).



    Kris




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    Wizard9056's Avatar
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    40A




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    n2audio's Avatar
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    the fuses on the amp really aren't important. What size is the wire and about how long is it?




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    n2audio is correct. The fuses on the amp are not "AS" important.

    In the manual for you amplifier, you will see a max input current (AMPERES) and a recomended fuse size for the input for your amp. That specified fuse size is the one you should use. However, the gauge of wire used and length are not "AS" important either.

    Fact of the matter is, I you wish to protect the device used, the fusing should match the specs. If you increase the fuse size larger than the specified size, you risk damaging the component that it is protecting, by allowing it to draw to much current.

    I have seen people put a XX Amp fuse on the line by matching what the gage of the wire is. By doing so, and not having the proper fuses on the amp, they ruined their entire system.

    The wire Gage and length only plays a part in this equation if you are using a wire to small for the application. If this is the case, you run the risk of a fire hazard due to heating up the wire, so then the fuse doesn't mater anyway.

    You do not fuse an application dependant on the gauge of the wire!!!!!

    Sure a wire is capable of carrying X amps at a certian voltage, but that doesn't protect the equipment that can only handle less than X amps at a certian voltage.

    This, of course, becomes a little more intricate when dealing with multiple devices being powered off the same line. Then the Main fuse, next to the battery, must be large enough to handle the max current draw of the system (X amps + Y amps + Z amps) and/or use a larger Main fuse and smaller individual fuses for the power distribution to each device.

    If there are any further questions, or I need to clarify, please feel free to reply!




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    n2audio's Avatar
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    Originally posted by Wizard9056
    n2audio is correct. The fuses on the amp are not "AS" important.

    In the manual for you amplifier, you will see a max input current (AMPERES) and a recomended fuse size for the input for your amp. That specified fuse size is the one you should use. However, the gauge of wire used and length are not "AS" important either.

    Fact of the matter is, I you wish to protect the device used, the fusing should match the specs. If you increase the fuse size larger than the specified size, you risk damaging the component that it is protecting, by allowing it to draw to much current.

    I have seen people put a XX Amp fuse on the line by matching what the gage of the wire is. By doing so, and not having the proper fuses on the amp, they ruined their entire system.

    The wire Gage and length only plays a part in this equation if you are using a wire to small for the application. If this is the case, you run the risk of a fire hazard due to heating up the wire, so then the fuse doesn't mater anyway.

    You do not fuse an application dependant on the gauge of the wire!!!!!

    Sure a wire is capable of carrying X amps at a certian voltage, but that doesn't protect the equipment that can only handle less than X amps at a certian voltage.

    This, of course, becomes a little more intricate when dealing with multiple devices being powered off the same line. Then the Main fuse, next to the battery, must be large enough to handle the max current draw of the system (X amps + Y amps + Z amps) and/or use a larger Main fuse and smaller individual fuses for the power distribution to each device.

    If there are any further questions, or I need to clarify, please feel free to reply!
    Now I'm no electrical know-it-all, but appearently, Wizard, you're trying to come across as though you know exactly what you're talking about...sorry, but you're just plain wrong. I would like to know where you gained your mastery on the subject. I could try to dissect this comment by comment but there is a huge amount of misinformation and I don't have the time, and to be perfectly honest, I don't have the expertise.

    Kris, please don't take Wizard's advice, hopefully zane and some of the other halfway respected people on the forum can lay down the law for you.

    Just do this and you'll be fine.

    Add the total rms of your system.
    Double it.
    Divide by 13.8
    That is your current requirement.
    Use this chart to pick your wire ga. requirement.
    http://www.crutchfield.com/S-B3wf08j...e-length-image
    Use as small a fuse possible, if the wire will carry, for example, 100-125 amps, use a 100 amp fuse.
    Or if your system only requires 80 amps but your wire is capable of carrying 100, then fuse with 80A, it's just a safety factor and there's no reason to have a surplus b/c fuses already allow for short bursts of high current.

    The fuse on your power wire is ONLY there in case your wire accidentally comes in contact with ground. It DOES NOT and CAN NOT protect your equipment, except for the fact that it will keep your car from going up in flames in case of a dead short.




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    mrray13's Avatar
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    so zane??

    so zane is only halfway respected? dang, he must of pissed you off in a previous life! seeing how him and ramos are probably the 2 MOST respected people here!! anyway, just messin with ya!!

    kriskeg, i believe you should follow n2audio's advice. the fuse on the power wire is just the first step in the protection system. you want it to be just enuff to supply what you need, without to much "lee-way" to allow a surge or something damaging to get into the rest of the system.



    Quote Originally Posted by lilmaniac2
    Your circles look like something a HMO doctor would do to a **** job ....
    ^^^ speaking about cbfryman's jigsaw ability




    owner of Thread posts 11111 & 12345

    wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee

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    Um... My bad

    Sorry for the mis-information.

    I allow my younger brother use this Computer while he is living with me....

    Nuff Said. I broke both of his arms...No Worries!

    I Myself am an Electrical Engineer... Reguardless, This shouldn't have happened, and won't again. I am not interested in anyone's help in specing amps or speakers or what ever... I again appologize and would like to add that I agree with n2audio, and would also like some of the Senior VIP Members to back his point...

    This will not happen again....

    Thank you and sorry for the inconvenience. I have disabled all passwords on this PC.

    I am also very embarrased that this has transpired. Hope no problems have occured...

    Wizard9056. (The Real McCoy)




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