I don't know if its common practise but Rotel used to do this and in my experience it worked well in terms of protecting the speakers. I've had a few of these amps fail and if one rail fuse blows and the other rail shorts to the speakers the other rail fuse blows as well.
It causes one rail voltage to be at the output and if there is no DC protection circuit and if the filter caps are large value it will possibly cost a woofer. One rarely see the other fuse blow as well so the caps discharge in the loudspeaker with full rail voltage and as the current goes down relatively fast the voice coil overheats/melts instead of the fuse. Of course it will never occur that both fuses of both rails blow simultaneously. IMHO it is only to protect against fire etc. but so does a primary fuse. When a primary fuse blows both rails will go down. I used to repair British cottage brand amplifiers that had no loudspeaker protection but they usually did have the fuses. Defective amplifier practically always meant a defective loudspeaker.
Some try to prevent all possible horror that may possibly happen but doing so may have some drawbacks... just don't leave stuff powered on unattended so when leaving the home, sleeping, holidays etc just switch off stuff with real mains switches or by switching off the audio power distributor. It won't prevent stuff breaking down but it will prevent stuff breaking down when no one is around to notice it.
I am into low power amplifiers myself as one really does not need much power in the majority of cases but I did not realize until recently that some are so light they can not even damage loudspeakers unlike 2 x 400W amplifiers.
Some try to prevent all possible horror that may possibly happen but doing so may have some drawbacks... just don't leave stuff powered on unattended so when leaving the home, sleeping, holidays etc just switch off stuff with real mains switches or by switching off the audio power distributor. It won't prevent stuff breaking down but it will prevent stuff breaking down when no one is around to notice it.
I am into low power amplifiers myself as one really does not need much power in the majority of cases but I did not realize until recently that some are so light they can not even damage loudspeakers unlike 2 x 400W amplifiers.
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Well I've seen it work and obviously the fuses are after the caps so the situation is identical for each rail fuse independant of the cause. It is also true that the speaker will fry if its power capability is not matched by the fuse rating and type but that is obvious.
I am not advocating rail fuses in general just stating that they can offer some speaker protection in a simple and low-cost manner. Or putting it another way, its a better way to protect your speakers than just the mains fuse.
I am not advocating rail fuses in general just stating that they can offer some speaker protection in a simple and low-cost manner. Or putting it another way, its a better way to protect your speakers than just the mains fuse.
Best is a DC detection/loudspeaker protection circuit. No fuse will protect a loudspeaker reliably enough. Rail fuses are an extra risk to the loudspeaker IMHO a they now offer a full rail voltage when one blows.
Fuses in general are there to prevent fire and secondary damage to cabling. They are not there to protect a load.
Fuses in general are there to prevent fire and secondary damage to cabling. They are not there to protect a load.
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