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Thread: Fuse on each AC wire of component when fed by Balanced Power Transformer?

  1. #1
    Join Date: Mar 2012

    Location: West Yorkshire

    Posts: 172
    I'm Bruce.

    Default Fuse on each AC wire of component when fed by Balanced Power Transformer?

    I've been feeding my HiFi with a balanced power transformer the last few months to good effect. But lately I've been considering internal fusing on the components. Since there is no Neutral & Live wire anymore, just two Live wires, if the internal fuse blows it only affects the wire that has always been Live. The formerly Neutral unfused wire is still Live in a balanced system, I think. So if I have the opportunity, especially on the amplifier, it seems good to fuse the second Live wire, right?
    Bruce

    Theories are not so much answers as questions, to be supported or undermined by experience & testing.

    Source: Calyx 24/192 DAC, Laptop w/JRMC. Amplification: Classe Audio 30/70 balanced. Loudspeakers: Proac Response 1sc. Cables/stands: spkr MIT MH-750 / HT Truthlink XLR, Vampire AI2, RFC Pluto, heavy sand-filled Target stands for speakers and Hi-Fi. Bass traps in corners, acoustic panels at first reflection points. Isolation: Roller bearings & cups, inner tubes. Mains: Balanced power transformer feeding hydra mains block.

  2. #2
    Join Date: Jan 2009

    Location: Essex

    Posts: 15,680
    I'm openingabottleofwine.

    Default

    No - what you should have is a double-pole RCB in the output from the secondary winding, so if there is a leakage to earth by whatever means, the current imbalance will cause the RCB to trip.

    If you use double-pole fusing, should one fuse blow, the mains will not be fully disconnected and there will be 120V on the line with the intact fuse.
    Have you listened to this month's choice in the Album Club?

    Barry

  3. #3
    Join Date: Mar 2012

    Location: West Yorkshire

    Posts: 172
    I'm Bruce.

    Default

    I already have a double pole rcb on the balanced transformer output. I'm talking about the additional internal fusing once we get just inside the amp.

    Sent from my GT-I9505 using Tapatalk
    Bruce

    Theories are not so much answers as questions, to be supported or undermined by experience & testing.

    Source: Calyx 24/192 DAC, Laptop w/JRMC. Amplification: Classe Audio 30/70 balanced. Loudspeakers: Proac Response 1sc. Cables/stands: spkr MIT MH-750 / HT Truthlink XLR, Vampire AI2, RFC Pluto, heavy sand-filled Target stands for speakers and Hi-Fi. Bass traps in corners, acoustic panels at first reflection points. Isolation: Roller bearings & cups, inner tubes. Mains: Balanced power transformer feeding hydra mains block.

  4. #4
    Join Date: Jan 2009

    Location: Essex

    Posts: 15,680
    I'm openingabottleofwine.

    Default

    The same argument applies: if there is an overcurrent, owing to fuse tolerances, it is unlikely that both fuses will blow, so one leg or the other could still have 120V on it.

    I would leave the single fuse in place. After all, if it were to blow you would of course unplug the amp from your BMU before investigating the fault.
    Have you listened to this month's choice in the Album Club?

    Barry

  5. #5
    Join Date: Mar 2012

    Location: West Yorkshire

    Posts: 172
    I'm Bruce.

    Default

    If I understand correctly, the internal fuse does two things: 1) it protects me if a fault puts voltage on the enclosure; 2) it protects the amp's circuitry in case of a fault. Right?

    Unplugging the amp protects me. But if a fault was dangerous to the circuitry, the internal fuse only protected one leg, right?

    Sent from my GT-I9505 using Tapatalk
    Bruce

    Theories are not so much answers as questions, to be supported or undermined by experience & testing.

    Source: Calyx 24/192 DAC, Laptop w/JRMC. Amplification: Classe Audio 30/70 balanced. Loudspeakers: Proac Response 1sc. Cables/stands: spkr MIT MH-750 / HT Truthlink XLR, Vampire AI2, RFC Pluto, heavy sand-filled Target stands for speakers and Hi-Fi. Bass traps in corners, acoustic panels at first reflection points. Isolation: Roller bearings & cups, inner tubes. Mains: Balanced power transformer feeding hydra mains block.

  6. #6
    Join Date: Jan 2009

    Location: Essex

    Posts: 15,680
    I'm openingabottleofwine.

    Default

    If the internal fuse blows, current is cut off from the amp's internal transformer and no harm will be done to the circuitry.
    Have you listened to this month's choice in the Album Club?

    Barry

  7. #7
    Join Date: Mar 2012

    Location: West Yorkshire

    Posts: 172
    I'm Bruce.

    Default

    Ah yes, that. Thank you

    Sent from my GT-I9505 using Tapatalk
    Bruce

    Theories are not so much answers as questions, to be supported or undermined by experience & testing.

    Source: Calyx 24/192 DAC, Laptop w/JRMC. Amplification: Classe Audio 30/70 balanced. Loudspeakers: Proac Response 1sc. Cables/stands: spkr MIT MH-750 / HT Truthlink XLR, Vampire AI2, RFC Pluto, heavy sand-filled Target stands for speakers and Hi-Fi. Bass traps in corners, acoustic panels at first reflection points. Isolation: Roller bearings & cups, inner tubes. Mains: Balanced power transformer feeding hydra mains block.

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