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Source Impedance [message #44355] Fri, 09 April 2004 23:57 Go to next message
Adrian Mack is currently offline  Adrian Mack
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Registered: May 2009
Illuminati (1st Degree)
Just wondering if theres an easy way to measure the output impedance of an amplifier?

Re: Source Impedance [message #44356 is a reply to message #44355] Sat, 10 April 2004 01:19 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18726
Registered: January 2001
Illuminati (33rd Degree)
I think the easiest way would be with a test resistor, oscilloscope and signal generator. You could measure current using the voltage drop and compare with open circuit output. While you're there you could find bandwidth and other specs.

Re: Source Impedance [message #44362 is a reply to message #44356] Sat, 10 April 2004 21:42 Go to previous messageGo to next message
Adrian Mack is currently offline  Adrian Mack
Messages: 568
Registered: May 2009
Illuminati (1st Degree)
Hmmm, I dont have an oscilloscope, I guess I cant do it then. I just thought there may be an easy to to do it with stuff I already got, like a multimeter and some sort of computer programs like speakerworkshop or winMLS. Anyway, thanks for the info.

Re: Source Impedance [message #44363 is a reply to message #44362] Sat, 10 April 2004 22:45 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18726
Registered: January 2001
Illuminati (33rd Degree)
You could probably do it with a DVM too. Just use a low value, high power test resistor and generate a 50Hz to 100Hz sine wave with your PC for an amplifier input source.

Re: Source Impedance [message #44364 is a reply to message #44363] Sat, 10 April 2004 22:51 Go to previous messageGo to next message
Adrian Mack is currently offline  Adrian Mack
Messages: 568
Registered: May 2009
Illuminati (1st Degree)
Where abouts would I actually measure the resistance? Just accross the speaker output terminals on the amplifier?

Re: Source Impedance [message #44365 is a reply to message #44364] Sun, 11 April 2004 01:37 Go to previous message
Wayne Parham is currently offline  Wayne Parham
Messages: 18726
Registered: January 2001
Illuminati (33rd Degree)
I'd measure the amplifier voltage output with no load, and then connect a low value resistor across it to see how much that dropped the voltage. Monitor the voltage across the amplifier's output terminals.

You can either measure current directly or you can measure the voltage drop across the resistor and calculate current. Then, knowing how much reduction in voltage on the output will tell you what the output impedance is. Divide this amount of voltage drop by the current flowing to find output impedance.

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