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Old 8th April 2008, 05:08 AM   #1
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Default PTC instead of Fuse?

Has anyone experimented using a PTC instead of a fuse? I was thinking it may be a simple method to protect against short-circuit at the speaker terminal. But I'm wondering about sonic quality? Those things have some finite impedance, and they get worse every time they trip. I don't remember the details, but the resitance will be in tens of milli-ohms, maybe?


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gene
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Old 8th April 2008, 05:46 AM   #2
luka is offline luka  Slovenia
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Hi

So what you are trying to do is, when 1000A will go when short circuit, you would use PTC that take time to heat, or in this case they would explode...they are just way too slow, fuse is made to overheat then overloaded, and bigger the overload faster it cuts current
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Old 8th April 2008, 10:08 AM   #3
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Looks like you are right. I just checked, although only 1 device from 1 manufacturer, and the trip time is 3 seconds! Yeah, I think a lot of smoke would come out of the circuit by then.
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Old 8th April 2008, 10:37 AM   #4
luka is offline luka  Slovenia
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Hi

I think you can't do anything wrong by using cheap and siple stuff like fuses, whey work and you can choose many different ratings
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Old 8th April 2008, 03:42 PM   #5
Corax is offline Corax  Germany
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PTC are used often in (expensive) loudspeakers to protect the tweeters from overload conditions. Once in a while you also find simple light buls (i.e. tubular lamps).
Both are effectively when protecting something that can widthstand an overload condition for a few seconds. A moving coil of a loadspeaker for instance wouldn't immediately burn when overloaded. And basically tweeters need a protection only when the input signal (what's coming from the amp) is clipped.

For any protection of electronic circuits this device wouldn't do any good at all. The voltage drop, when not triggered, is often too high, and of course the reaction time for sensitive electronic is absolutely insufficient.
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