rantan Posted January 26, 2023 Posted January 26, 2023 59 minutes ago, BugPowderDust said: at what point will ordinary people stare at nonsense like this and realise someone is pulling their chain? The problem is that they really don't want to know the truth as they wish to preserve their fantasy. Also, please don't get me started on audiophile fuses. Seemingly, there is some pre conceived notion of nobility and sufferance for the cause if they have to endure something sounding like schit ( a technical term ) for weeks ,or even years in some instances, always in the hope that one day they will arrive in an audio Nirvana. 7
The Mad Scientist Posted January 26, 2023 Posted January 26, 2023 (edited) 1 hour ago, rantan said: Also, please don't get me started on audiophile fuses. I'd really like to see some scientific evidence to support the claimed mystical properties of audiophile fuses. It's a sacrificial piece of wire and it has to have the necessary I²R heating and rupture requirements (so it can't have lower resistance, for example) to fail at the appropriate fault current so as to avoid burning your house down. I'd also really like to know if any of them have actually been certified to meet the legislative electrical safety standards (BS 1362 over here in the UK) that every developed country requires. I also wonder what a home insurance underwriter would make of them in the event of a claim? I can only guess that there exists some magical, hitherto undiscovered property, which enables audiophile mains fuses to somehow calm, reorder and smooth the sinusoidal waveforms of the angry wall-pixies that your mains powered audio devices rely on...... Edited January 26, 2023 by The Mad Scientist 2 3
MLXXX Posted January 28, 2023 Posted January 28, 2023 (edited) On 26/01/2023 at 5:44 PM, The Mad Scientist said: I can only guess that there exists some magical, hitherto undiscovered property, which enables audiophile mains fuses to somehow calm, reorder and smooth the sinusoidal waveforms of the angry wall-pixies that your mains powered audio devices rely on...... A tongue in cheek guess, no doubt! * * * Fuses may be used in audio equipment in different ways: 1. As "mains fuses", in series with a power supply transformer primary winding. This is a common application. 2. As DC power supply fuses after the mains has been converted to DC. 3. In the output stage in series with the output semiconductors or directly in series with the output terminal for the speakers. In application 1, the resistance of the fuse under normal operating conditions is negligible compared with the resistance of the transformer primary winding. Directionality has no meaning, as the current through the fuse alternates its polarity at 50Hz. The suggestion there could be an audible effect on sound quality is far-fetched. In application 2, the resistance of the fuse under normal operating conditions should be small compared with the DC power supply source impedance. Current will flow through the fuse exclusively or predominantly in one direction. However fuses have the same resistance whether measured in one direction or the other.* Commonly, filtering and/or decoupling capacitors would follow such a fuse. The likelihood of any audible effect is remote. In application 3, the fuse is in series with the audio output signal, and so conceivably could alter that signal through non-linearity of some kind. This is the only application where I would have a degree of concern over the audio being affected. However it would be a small degree of concern because the fuse resistance would only become an issue at high output currents, with the amplifier approaching clipping or with an abnormally low impedance load connected. Even here though, it would be surprising if fuses of a particular class and rating differed much in their performance.** If a manufacturer wants to claim that their fuse maintains a particularly low resistance right up to the rated rupture current, let them provide graphs of the resistance as a function of current for different ambient temperatures, thus supporting their claim. Flowery marketing spiel carries no weight. It is dreamt up by the marketing team. __________________ * Regarding directionality:- If a measurement is taken at a high current it is possible that a thickness variation in the fuse wire will cause one end of the fuse to heat up appreciably more than the other. It will then depend on convection currents in the surrounding air and on the thermal conductivity of measurement clips or the fuse holder as to whether that asymmetrical heating of the fuse itself will be transferred away by conduction and convection in an identical manner depending on the physical orientation of the fuse for the two tests. A way around that issue is to leave the fuse in situ for both tests of current flow direction and merely change the polarity of the test current. This also eliminates as a confounding issue slight random variations in contact resistance between a fuse and a fuse holder each time a fuse is inserted into the holder. ** Regarding resistance and voltage drop:- If a fuse is tested with a sustained current at, or just below, its rated current, it will be on the point of blowing or rupturing and the resistance and voltage drop will be unusually high. Such a measurement would not be particularly helpful or representative, as in normal operation the sustained current through the fuse will be much less. Edited January 29, 2023 by MLXXX Footnotes added 1 1
MLXXX Posted January 29, 2023 Posted January 29, 2023 18 hours ago, MLXXX said: Fuses may be used in audio equipment in different ways: 1. As "mains fuses", in series with a power supply transformer primary winding. This is a common application. 2. As DC power supply fuses after the mains has been converted to DC. 3. In the output stage in series with the output semiconductors or directly in series with the output terminal for the speakers. Is there much use these days of fuses at the output of an audio amplifier, as described at 3 above?
The Mad Scientist Posted January 29, 2023 Posted January 29, 2023 (edited) 5 hours ago, MLXXX said: Is there much use these days of fuses at the output of an audio amplifier, as described at 3 above? They were much more common in older designs. Modern amps' protection circuitry is much more effective than fuses. Edited January 29, 2023 by The Mad Scientist 1
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