Originally Posted by
Barry
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!
Arkless Electronics-Engineered to be better. Tel. 01670 530674 (after 1pm)
Modded Thorens TD150, Audio Technica AT-1005 MkII, Technics EPC-300MC, Arkless Hybrid MC phono stage, Arkless passive pre, Arkless 50WPC Class A SS power amp, (or) Arkless modded Leak Stereo 20, Modded Kef Reference 105/3's
ReVox PR99, Studer B62, Ferrograph Series 7, Tandberg TCD440, Hitachi FT-5500MkI, also FT-5500MkII
Digital: Yamaha CDR-HD1500 (Digital Swiss army knife-CD recorder, player, hard drive, DAC and ADC in one), PC files via 24/96 sound card and SPDIF, modded Philips CD850, modded Philips CD104, modded DPA Little Bit DAC. Sennheiser HD580 cans with Arkless Headphone amp.
Cables- free interconnects that come with CD players, mains leads from B&Q, dead kettles etc, extension leads from Tesco