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Hello, previously I probably posted this message on the wrong forum.My power amplifier has a slow blow fuse of 6.3A (220 V). Why should I use thick wiring for its mains cable if there is a limit of 6.3A? Would standard cable suffice?
I understand the importance of shielded cables. But I would like to understand why a wiring able to handle, say 10A, would help with such a limitation of 6.3A on the fuse.
Follow Ups:
OK, I'll buy your tips, thanks. I'm going to use a DIY cable with large wiring. Your arguments are convincing. See also my other post
http://www.audioasylum.com/audio/tweaks/messages/142628.html
If your equipment draws sinusoidal current, then the power cord impedance is not a problem.However, if your equipment draws current in short spikes, then the power cord resistance may affect its performance, even though the RMS current is modest. The current rating is the square-root of the time average over the square of the current (this is what 'RMS' means), so the spikes can be very short and very large and give a modest RMS value. The fuse value reflects the RMS current, not the instantaneous current.
Power supplies that consist of large transformers that feed rectifiers that feed capacitor filters will draw current in short, large spikes. Power supplies that have chokes as the filter input elements will draw close to a sinusoidal current. Switching power supplies will draw close to sinusoidal current if examined only at low frequencies, but create a lot of high frequency noise. I suspect your Quad amps use capacitor-input filters and would benefit from very low power cord impedance.
Hi.But in practice, the smallest cheapie stock 2-wired power cord, say SJT #18/2, carries 10A. It only costs you a few bucks. So why you should worry about using smaller cords which I doubt would be available off the shelf unless you custom order one or DIY it?
Also don't overlook the length of the power cord needed for your situation. Longer the length of the power cable needed from your audio gears to the wall outlet, more would be the voltage drop across
the cord (Ohm's law: voltage drop=loading current x DCR of the cord).That's why ALL stock power cords are made a metre or so short lengths
to mininimize voltage drop.Generally, the power cord of any audio equipment carries more than it can consume. But it is up the fuse used inside that gear to limit the largest safety current designed for it.
FYI since you seem got lost, for any household AC mains supply which involves long long runs of cables from the fuse or breaker panel to the wall outlets, the mininum gauge size of the cable is specified
to maintain 2% maximum voltage drop, which all electrical contractors should oblige.Say, the wall outlet (15A) is located 25ft from the breaker panel, the minimum gauge size of house wires needed for 2 singe phase & 3 electrical conductors run in conduit (75C ambient temp & power factor 45% - 100%), will be AWG #14. But for longer run, say
50ft from the breaker panel, the gauge size of the house wires must be increased to #10 to have same 2% minimum voltage drop.You don't want fire caused by overloading the power cables, right?
c-J
PS: I used mininum #16 gauge 3-wire 4N silver wires for building my audiophile grade power cords, for one metre length only. It can handle up to 13A rms current load or up to 1,560VA AC power. Yet, it is now powering my 35W+35W tube power amp which only needs max 190W power supply. The AC fuse inside the is specified for 3A which is far far larger than its max current requirement of 1.623A (190W/117V) !! Trust me, larger the power cable, it sounds better.
Good tip....always best to use a voltage drop calculator when matching power cord AWG to power supply draw.
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