A couple of noob questions on REW impedance rig

roger2

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Jul 21, 2019
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Hi everyone. Great forum!

1) I am confused by the circle symbols from the diagram in REW help.. Do those circles represent the sleeve of a TRS connector?

2) How much power might the sense resistor need to dissipate? And just how "non-inductive" does it need to be?

I have 100 ohm carbon film .5 watt resistors on hand, and a B&K LCR meter to get a precise reading to enter into REW. Would the 1/2 watt carbon film be a good choice or would a different type of (or higher power rated) resistor be better?



~~~Just a quick thank you to Mr Mulcahy for providing the DIY community with such a useful and powerful tool~~~



impedancesetup.jpg
 
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John Mulcahy

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Apr 3, 2017
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7,212
The rings represent the ground terminals of the connectors. When using a soundcard the power dissipation in the sense resistor is low - at 2V rms out into a shorted load 100 ohm would dissipate about 40 mW. If you were to use a power amp and a lower sense resistor power would be commensurately higher, but soundcard measurements are pretty benign. As long as the resistor isn't a helical wirewound it should be OK, film resistors typically have very low inductance.
 
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