shbamac
293 posts
Apr 04, 2013
7:55 PM
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How do you figure out how much voltage is running through the speaker wires?
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Greg Heumann
2088 posts
Apr 04, 2013
8:17 PM
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With a volt meter. And a speaker, connected. That will give you an average. A better measure is RMS. An even better measure of what's really going on is to use an oscilloscope.
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/Greg
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shbamac
294 posts
Apr 04, 2013
8:38 PM
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Thanks captain obvious... Just kidding!
Volt meter is busted and I haven't the time to go buy a new one. RMS, no idea how to measure. Everyone has a oscilloscope lying around and knows how to use it.
Is there an easy way to ball park it?
Last Edited by shbamac on Apr 04, 2013 8:39 PM
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ReedSqueal
401 posts
Apr 04, 2013
8:52 PM
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Ball park it? Yeah, just like when you were a kid and touched a 9 volt battery to your tongue. >;-)
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Go ahead and play the blues if it'll make you happy.
-Dan Castellaneta
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STME58
402 posts
Apr 04, 2013
9:58 PM
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There are software programs that allow you to convert you PC into and oscilloscope using input into the sound card. I have not used them but I don't see why it couldn't work. I don;t know what kind of input to the sound card you need to have it work and not overload the sound card.
I have an Oscope lying around if I need it, so I haven't tried the software. Has anyone used such a tool?
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lumpy wafflesquirt
702 posts
Apr 05, 2013
10:04 AM
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Is American electricity different to UK electricity?
We have a current running through wires measured in amps.
Voltages are measured as a potential difference between two points in a circuit.
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"Come on Brackett let's get changed"
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nacoran
6656 posts
Apr 05, 2013
2:15 PM
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Lumpy, in the U.S. our current drives on the right side of the wire.
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Nate
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lumpy wafflesquirt
703 posts
Apr 06, 2013
1:37 AM
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That'll be the difference :^)
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"Come on Brackett let's get changed"
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5F6H
1602 posts
Apr 07, 2013
3:26 AM
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Rule of thumb, working from manufacturer's supplied figures...
Speaker cab ohms*W RMS
Square root the answer.
Divide by speaker cab ohms.
So a tweed bassman/4x10 concert/Super Reverb/HG50:
2ohms*50W = 100
Sq rt 100 = 10 volts
10volts/2ohms = 5A.
100W Marshall with a 16ohm cab:
16ohms*100W = 1600
Sq root 1600 = 40 volts
40volts/16ohms = 2.5A
VHT 5W/16ohm amp:
5*16=80
sq rt 80=9 (near enough)
9volts/16ohms= 0.5A (near enough)
It's the Amps that are most important, good idea to double the A rating for safety, though in reality most speaker wire installed at the factory is overrated by both v & A.
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Last Edited by 5F6H on Apr 07, 2013 3:30 AM
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shbamac
295 posts
Apr 07, 2013
4:44 PM
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Perfect, thanks!
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